Tropical Storm Katia: August 30, Update A

I'm on another planet so not much time to dilly dally today either, alas.

 

Tropical Storm Katia is cooking nicely. Officially she has winds of 60mph (TS range: 39-73mph), so she is a mid-size Tropical Storm, central pressure 997mb. SHe is at 12.7N, 35.4W, heading WNW at 20mph. Her track has shifted slightly southwards since yesterday, and I think it will continue in that vein for now and of course if this pans out, it means she will be closer to the VIs than initially forecast.

 

The NHC have her as a hurricane by tomorrow afternoon. I am not 100% sure of this yet. Although she has good circulation in the lowest half of the troposphere, I do not see any sign of circulation in the upper troposphere. Also, her lower level convergence (inflow) and upper level divergence (outflow) are not very well developed. Both of these indicate that she doesn't have a good structure (at the moment). However, wind shear is low and will remain low for at least a day if not longer. Also, she is in the tropics, so sea surface temperatures are warm. She certainly has the buffet she needs to put on a few pounds.

 

More later tomorrow.

Ciao for now!

J.

 

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Tropical Depressions Jose and 12: August 29, Update A

"A distressingly busy day with little time for sloth or idleness" (Oscar Wilde)... fortunately we don't have much going on out there. It's all depression this, depression that.

Jose was downgraded to a Tropical Depression this morning and is just a cloud in the minds eye now. Somewhere way up there in the North Atlantic. The NHC issued their last advisory on him at 11am this morning, when he was at 39.5N, 63.1W, moving NNE at 29mph. Winds were 30mph, central pressure 1009mb.

The Atlantic Blobette is now Tropical Depression 12 (it was upgraded yesterday). It has remained as a TD all day today, and doesn't look like it's going anywhere fast. Convection is really super weak. It is currently at 10.2N, 29.4W, moving W at 14mph. Winds are 35mph, central pressure is 1008mb. They do forecast this to be a hurricane by Thursday afternoon. It is a bit far on the eastern side of the Atlantic for me to get a good reading on, but it looks like wind shear is a little strong so the convection is all to the west of the center of circulation. The circulation is much improved in the lower troposphere today, so once that convection gets itself sorted out, I expect this to be a Tropical Storm at least. The current forecast track takes it in a WNW and NW direction, so it is east of the VIs (by a few hundred miles) on Saturday afternoon. I think that it will carry on in a more westward direction for longer than the forecast tracks show, so it will be south of there.

That's it for today. I'll return when we have another TS on our hands.
Ciao!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Tropical Storms Irene and Jose, and an Atlantic Blobette: August 28, Update A

Oh Great Googliemooglies! Really? Another storm that is named as it is practically on top of land? Really? Well, we’ll get to that later. First, that other one…

Tropical Storm Irene
As expected, she was a Tropical Storm by the time she got to New York, and was mostly a water event rather than a wind event. I hear the levels in the Hudson River rose, so downtown Manhattan experienced a ~5ft rise in water levels (above the high tide they were expecting anyway) so a part of Manhattan got slightly submerged. Don’t worry, the NY Stock Exchange is ok…. I’m sure your stocks and shares will be worth just as much as they usually are.

Irene is currently visiting northern New England, and is about 60 miles south of Rutland, Vermont, around 43.5N, 72.5W. Winds are officially 50mph, so she’s a weak-to-mid-level Tropical Storm (range: 39-73mph), central pressure is 975mb (which is rather low for a storm with these winds!). She continues to move NNE at a whopping 26mph (an indication that she’s not a tropical storm really, but an extratropical storm now). Convection is greatly reduced, although she still has some circulation, so I expect places to the north will get a bit breezy but nothing too bad.

In my excitement about Tides Online yesterday, forgot to mention what the other graphs were on the water level figure in yesterday’s entry, although they cleverly use these things called words to label them so I’m pretty sure everyone figured it out. J But just in case you had your eyes closed, the remaining graphs showed the wind speed (and direction), the air pressure (it is quite cool to see the drop and then subsequent rise as the storm passes the sensor), and in the example I showed yesterday, air and water temperatures. Not all sites have all this yummy data, but the main reason I go to the Tides Online is to see the water levels.

Reports from in the field:

Chris in Maryland wrote at 5am (!!!): "Large sections of Silver Spring are without power (hopefully I will get this out and not lose power here).  Sounds like that is the major issue.  The power lines here are weak and they don't trim the trees, so every little gust knocks out power for a day or so.

At 05:00, winds are steady at 26 kts from the NNW and gusting to 39 kts.  The main problem here (DC and north or west cities) will be downed power lines and residential flooding.  It has been coming down steady for hours and all the local streams are flooding.  No big news there.  The forecast is for the rain to really start to let up in the next 3-5 hrs with basically no rain by noon, but still have winds of 25 kts.  The morning buses are running but all the traffic lights in my area are out."

(Ed. Notes: 1kt = 1.15mph, I’ll let you all work out the conversion)

Shalini in Massachussettes wrote at 9am: "The weather is getting windy here..lots of rain, dark cloudy skis and hte wind is starting to pick up..not bad but definitely ugly weather."

Sameer in New York said at 11am: "Wow. No event mostly. Things seemed to have passed."

It is unfortunate that a number of deaths have been caused by Irene. I don’t know the details of all of them, but I know that at least one was from a tree that fell on a house. It’s very sad. L The major damage seems to be from falling trees, including the power lines that have been downed. I hear that about 3 million people are without power. I’m glad she wasn’t as bad as the earlier forecasts suggested – she has caused enough problems. I expect they will retire the name ‘Irene’ from the list.

There is not much more to say on Irene really, so this is my last post on her unless I get more Reports from in the field. 

Tropical Storm Jose
I can’t believe they named this one! What another waste of a name this season. I actually know a Jose, and was lining up to have all sorts of fun with this named storm. What a nuisance! ;-)

Jose apparently has winds of 45mph, central pressure is 1007mb. He is at around 33.9N, 65.5W. Northwest of Bermuda, and moving NNE at some rapid speed.

Jose has some circulation in the lower troposphere, and not very much convection, as you can see (in case you are wondering, the convection associated with this storm is that little blob just west of Bermuda, not the larger blob to the south).



He was named about 12 hours ago, and according to the official forecast, he’ll be gone by tomorrow (because he is experiencing wind shear). He was almost on top of Bermuda when he was named and is zipping past on the western side… If you took a lovely 5 minute afternoon nap, the chances are you probably missed it anyway. Bermuda is under a Tropical Storm Warning and according to the NHC some parts of Bermuda are already experiencing Tropical Storm conditions. Maybe a couple of drops of rain or you might be adjusting your swing to allow for a slight breeze during your golf game. Let me know how you fare!

Atlantic Blobette
This one came off Africa not very long ago. They have currently given it a 70% chance of developing, but it looks a bit more wishy washy than that to me. It has some circulation in the lower troposphere and some convection, but neither is very well developed. I’ll be back with more if this one gets any better. Probably tomorrow the way things are going! Next name is Katia.

That is all I have for today. Maybe tomorrow I’ll have next to nothing to say. That’ll make a nice change for you, won’t it? ;-)
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene and the last on TD10: August 27, Update A

Hello my friends! I've been watching Irene as she moved on shore in North Carolina mid-morning. I'm glad they downgraded her winds further, so she was a mid-level cat 1 storm at that time with winds of 85mph (cat 1 range: 74-95mph).

She is currently at 35.5N, 76.3W moving NNE at 13mph. Winds are still officially 85mph, with a central pressure of 950mb. The main thing as she weakens will be the water impact rather than the wind - rain (including river flooding from rain) and storm surge if you live along the coast. Just before she got to North Carolina she did pick up some moisture because she was over the Gulf Stream, so they have had a lot of rain methinks (in some parts). However, as she moves farther north, that should diminish a bit - and it looks like it is already diminishing. I think she's probably now barely a cat 1 storm, and if you look at the IR satellite image, you'll see that although she covers a large area, most of that is clouds and light rain. There is no deep convection (no red or grey).

By the time she gets to NY and New England, I expect her to be a Tropical Storm (range: 39-73mph).

Speaking of storm surge, I don't think I've mentioned where you can monitor the water levels along the coast for yourselves yet. The National Ocean Service section of NOAA runs an excellent site called Tides Online (http://tidesonline.nos.noaa.gov/). If you go there, currently you will see on the left side of the page a list of stations that they have identified for this storm. But my preference is to click on the link on the left that says 'State Maps'. That will bring up a map of the US (and the world). Click on the state of interest (umm... how about North Carolina as a random pick?). This will bring up a map of the state with red dots (and the locations) which indicate where they have water level stations. So if I click on Wrightsville Beach, you will see some graphs:

 The top graph (water levels) has three lines on it. The blue line is the predicted water level, which includes the daily tidal variations. The red line is the actual observed water level. The green line is the difference, and will show what the actual surge component of the water level will be. So for Wrightsville, we see that storm surge peaked at 3-4ft, whereas if you go to Duck, NC, you can see it looks like it surged at about 2ft. If we look at Maryland, it looks like the water is about 0.5ft above normal in the Annapolis/Baltimore region, and moving farther north, in Montauk, Long Island, NY, it looks like at the moment the water is also just about 0.5ft higher than normal and rising. You can monitor the water levels at your leisure. 

From in the field, Jennifer in North Carolina wrote at around 12.30pm today:
"So Irene is like a bad house guest. She just doesn't know when to leave! The eye is well north of Wilmington, but the winds are still gusting up to 50+ MPH. We've has TS winds since around 10 PM last night. The power has flickered, but the longest I was without power has been about 5 minutes. The houses built along the coast are faring much worse.

Jay's family lives in Cedar Island, NC. The eye of the storm passed directly over Cedar Island around 10 AM this morning. Jay's dad didn't leave town for the storm. Jay spoke to him around 8 AM and water was starting to come into his house. We haven't heard anything since that time. We are going to try to get up there tomorrow (Sunday). We can't get up any earlier than that because: 1) roads are flooded and 2) they still have hurricane strenght winds which won't deminish to TS winds until late this evening.

All in all everything is ok at my house. Lots of limbs down in the yard and lots of standing water but that's about it."

I hope everyone is ok!

As for wimpy Tropical Depression 10, although it is hanging out in the same general vicinity there is almost no convection. Unless it does something interesting, this is my last entry on this system.

I'll be back tomorrow with more shinanigans from Irene.  Everyone stay safe!!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene and TD 10: August 26, Update B

Gotta be quick as I have about 10 minutes to do this and then I’m out of time until tomorrow.

Hurricane Irene:
I see they have progressively brought her wind speed down, so now she is a weak cat 2 with winds of 100 mph (cat 2 range: 96-110mph). I think she’s a bit weaker than this, but at least they are heading in the right direction. Central pressure is 951mb. She’s at 31.7N, 77.4W, officially still maintaining that Northward heading at 14mph. However if you look at the satellite images, she’s heading NNE, so the outer banks look very likely. No eye, and the convection has decreased so most people will get a lot of rain, but not too much in the way of thunderstorms. Should be like a normal day in the UK!

The intensity as she moves north has also been downgraded. I expect it to get lower. At the moment they have a Cat 1 (range: 74-95mph) in the New York area, and I expect a Tropical Storm (39-73mph) by the time it gets to New England. Again, they are basing this on a stronger initial intensity than I think she has, so I expect it to be a Tropical Storm sooner than that. Especially as wind shear really really picks just north of Cape Hatteras!

TD 10:
This one is now apparently at 15.6N, 34.3W, moving NW at 8mph. Winds are 35mph, central pressure 1009mb. They expect it to vanish by Monday. I still disagree, but this storm has so little oomph to it that it doesn’t look like it will amount to much. ‘So little oomph’ is a technical phrase for that you can translate to this storm hasn’t eaten it’s spinach and is therefore a wimp ;-).

Bother, I have run out of time. Well, good luck and may the force be with you all!
Back tomorrow!
Toodle pip!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene and TD10: August 26, Update A

Hurricane Irene:
They downgraded her to a cat 2 storm last night (barely) with winds officially at 110mph (cat 2 range: 96-110mph) and a central pressure of 945mb. This is ok, I know they have to be conservative and cautious and there are a lot of people getting ready. I’ll give them this (obviously I’m a much nicer person before my first cuppa tea ;-)). At least she’s in the right category now. They have changed their forecast back to her being a cat 3 at landfall in the North Carolina region, but they do acknowledge that she’s expected to be a strong cat2/weak cat 3 at landfall. I think this is an overestimate too. At the moment they are basing this on her being a border-line cat 2/cat 3 now, but I think she’s weaker than that at the moment for a number of reasons:

1. She does not have a well-developed eye, which I expect in a mid-to-strong cat 2, let alone a cat 3.
2. She is not symmetrical.
3. There is wind shear and dry air to the west side of the storm.
4. The convection is not as strong as I would expect from a strong cat 2.
5. She is interacting with land on the west side of the storm.

Here are the Visible and IR satellite images so you can see for yourselves:


If she is going to intensify (and there is a chance of this because she is still interacting with the deep warm waters of the Gulf Stream), then she will intensify from a weaker intensity rather than the stronger intensity they have her at now. However, as I said, their job is to be cautious and given the population density ahead of this system, I am glad they are doing that.

If you are in the path of the storm, then remember two things:
1.Listen to your Emergency Managers – if they say evacuate, then please evacuate. Fascinating though my words may be, you can always read them later. ;-)
2.If for whatever reason you can’t evacuate (maybe too many people on the road or something), “Hide from the wind, run from the surge.” – those areas that might get storm surge should evacuate. Those who are on higher ground/inland – unless it’s a cat 4 or 5, you can hide (and even in those two cases you can hide, but personally, I would run away if that’s what was heading towards me). It’ll be rough, but it’s possible.

She is at 30N, 77.3W, currently heading N at 14mph, with a NNE turn expected later today. Today I will be watching to make sure she carries on this track and doesn’t slow down or move towards the NNW.

For those of you north of North Carolina, her intensity will depend on how much she interacts with land before getting to you. In your favour, you don’t have a Gulf Stream. If she is going to intensity, she will do that south of the North Carolina region because the Gulf Stream heads out into the Atlantic from Cape Hatteras. Of course, if she stays away from land (North Carolina region), then there’s a chance she won’t make landfall until she gets much farther north. Despite this, you should be getting ready for a cat 2 storm (although I expect it will be a cat 1 at the most), and of course the closer you are to NC, the greater the intensity.

Surf is good on the Atlantic Coast of Florida I hear!

Tropical Depression 10:
Ok, on this one I completely disagree with the NHC. Officially they have it moving WNW at 9mph, located at 14.5N, 33.7W. I have it at around 13-14N (not a very clear storm, hard to find the center), and stationary. It has not moved since last night. I wish I’d taken a snapshot of this little thing yesterday evening. I took one this morning, and will take one later for comparison. Winds are still officially 35mph, central pressure 1009mb. I understand they are distracted with Irene, but there are people in the Caribbean who are already watching this one.

Today is a super busy day, but I’ll try and pop back later.
Ciao,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene and the TD 10: August 25, Update C

Hurricane Irene:
She’s finally cleared the Bahamas after paying Grand Abaco a visit. Here’s one of those cam thingies from Rockybay on Abaco… http://www.rockybay.com/webcam_page.htm (sent to me by Charlie in Florida). This photo was taken yesterday evening, and it looks like that they lost their internet connection early this morning. Conditions look perfect for an outdoor picnic, don’t they?

As of the last advisory she’s hanging out at around 28.3N, 77.3W, moving N at 14mph (good, she’s moving N finally!). They have kept her winds at 115mph all day, with a central pressure of 942 mb. This means she’s been a category 3 (range: 111-130mph). I still think this is an overestimate, however two aircraft found this low pressure – a NOAA plane and an Air Force plane (I completely agree with the NHC when they say that these aircraft supply very valuable data!!). Interestingly, they did not record a corresponding increase in winds, suggesting that she is not structurally as sound as she could be. The NHC say they are keeping her intensity at a cat 3 for now, but may change that if the winds do not pick up. In the IR satellite image below you can see that she’s really not symmetrical (because of wind shear and dry air), and although she has an eye, there’s not as much red and no grey meaning that cloud tops are not as high as they could be in such a storm.



Another clue that she has weakened is her upper level divergence and lower level convergence – these have both weakened since this morning as well. The other thing the satellite image shows in the large reach of this system… she’s been eating one too many donuts, hasn’t she? ;-) Her outer bands at the moment are still over the southern Bahamas to the south, and North Carolina to the north. I took a couple of photos of the outer bands over on this coast of Florida, but don’t have the time to upload them. They were obviously of award winning quality. ;-)

They have, however, downgraded her forecast intensity at landfall, with landfall as a cat 2 (range: 96-110mph) in North Carolina on Saturday.  The wind shear ahead of her will continue to increase, even though she’s over warm deep waters. It looks like at the moment she is tracking east of the forecast track actually – I hope she continues in this N and NNE (and then NE) direction tomorrow!

Tropical Depression 10:
This one now has some nice circulation in the lower half of the troposphere, but the convection isn’t quite there. Hmm… officially the NHC have this one at around 14.1N, 33.1W, moving WNW at a slightly slower 9mph. The satellite images show it at around 13.8N, 35.2W (ish – it’s night time so it’s tricky for me to see). That doesn’t match up at all. How odd. Central pressure is 1009mb, winds are 35mph (over estimate still). They have forecast this one to head NW and fizzle out in the Atlantic on Sunday at around 17N, 36W. I think it will carry on WNW for a lot longer, especially if they have it at the wrong coordinates! It is surrounded by a high pressure on all sides so I expect this to slow down a lot more, and possibly stall.

That’s it for tonight.
Adieu,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene and TD10: August 25, Update B

Quick lunchtime update on things.

Hurricane Irene:
Officially her winds are 115mph, central pressure 951mb. She’s at around 26N, 76.8W moving NNW at 13mph.

Although officially she is still a cat 3 with winds at 115mph, I don’t think she’s a cat 3 (range: 111mph- 130mph). In fact, I think she’s weakened further since this morning and may be a strong cat 1 (range: 74-95mph), possibly weak cat 2 (96-110mph). Here is the satellite IR image of Irene:


There is no eye and there hasn’t been for many hours. She is not very circular – a result of wind shear. And her convection is much weaker – very few really strong thunderstorms (not much of the red or dark gray colour means that the cloud tops are warmer – I covered that in an earlier post this season). She still has a good circulation of course, and also covers a large area, but that doesn’t make her a cat 3.

She’s moving NNW at the moment, parallel to the FL coast. Now it depends if she continues to turn to the North and then NNE soon enough… that will be tomorrow and that’s what I’ll be watching for then.  The latest pressure fields still have a gap in that Georgia/S. Carolina area, but it has shifted north a smidgen. It looks like a South or North Carolina landfall is likely so I would kinda agree now with part of the NHC forecast. In my mind I question her intensity. Currently the forecast has her as a cat 3 all the way up to landfall in North Carolina on Saturday.

I guess they are keeping her as a weak cat 3 so that everyone continues to get prepared for the worst, in case she strengthens further. However, this messes up the science because the data scientists use to study storms are things like the official wind speed, the duration that a storm was at a certain category etc. Surely it would be better to have her downgraded and tell everyone that there’s a strong chance she will become stronger (and why). Ho hum.

Tropical Depression 10:
This poor little thing is struggling to get it’s convection up to speed, it really is. The circulation looks a bit wishy-washy too at the moment. This might not even develop any further if it slows down. I’ll keep watching it of course. Central pressure is 1010mb, which is quite high for a low (!!!), with winds estimated to be 35mph (doesn’t look that strong to me).  It’s officially at 13.3N, 31.8W, moving WNW at 12mph.

Until later,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene & Tropical Depression 10: August 25, Update A

Hurricane Irene:
Well the good news is that wind shear took a bit out of her and although officially her winds are 115mph, making her a weak cat 3 storm (range: 111-130mph), I think she might be a bit weaker than that, but still in the strong cat 2-to-cat 3 range. Central pressure is 950mb, but she does not have a good eye at the moment and her outflow is not equal in all sectors. A hurricane is truly a combination of the ocean and atmosphere combined. As she gets closer to Florida and the eastern US her intensity will be a battle between good and evil… between the atmosphere and the ocean… between the wind shear (inhibit her development) and the deep warm ocean (allow her to develop). The wind shear looks like it will get stronger as she gets to that region, so we’ll see whether that is strong enough to prevent her from becoming a cat 4.

The 8am advisory has her at around 25.5N, 76.5W, heading NW at 13mph. The not so good news is that the high pressure that had started to redevelop has continued on that trend. Yesterday the turning point was around North Carolina. Today it extends a bit farther south, to the Georgia/S. Carolina region. This is a bit troublesome because if this trend continues, she might not make the forecast N & NNE turns, and instead continue NNW and then back to NW tomorrow/later today, which means she will head closer to S. Carolina/Georgia/Florida. What we are watching for today is that turn towards the north so she runs parallel to the Florida coastline and then later today/tomorrow for the turn to NNE.

Tropical Depression 10:
They have upgraded the Atlantic Blob to a Tropical Depression, which means it has closed circulation with winds greater than 17mph. Convection and circulation are both weak but still developing. It is currently heading W at around 10-15mph, but might slow down later today because it is surrounded by high pressure. The pressure at the moment extends to the southern Caribbean, so for now I would say it will continue to track west, and then follow a curve similar to Irene’s towards the Dominican Republic region – but it is far too early to say with any certainty.

More later,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene & Atlanic Blob: August 24, Update A

Hurricane Irene is a nice looking storm from the satellite images. About 5 minutes after my last update I guess she got my phone message, so since about 1am EST she’s been moving in a NW direction and picked up a bit of speed (the velocity type, not the drug type!) and has been churning forward at 12mph all day. In the last NHC advisory at 8pm EST, she had winds of 120mph which makes her a mid-sized category 3 storm (range: 111-130mph), and a major hurricane. Central pressure is 954mb.  She’s currently at around 23.5N,  75W, moving NW at 12mph. She went over Crooked Island (twice) and is going between Long Island and Rum Cay.

Intensity:
She’s had an eye on and off for most of the day so I think a strong cat 2-to-cat 3 range is about right. She also has some low level convergence (inflow near the bottom) and upper level divergence (outflow near the top) and both the convection and circulation is looking good of course.

Here is a satellite image of the water vapour over the Northwest Atlantic:
This shows how humid the atmosphere is of course, with the dry parts in brown and the humid parts range from white (cloudy) to a dark pinky-purple-blue colour for heavy rain (I’m sure there’s a name for this colour – magenta maybe?). Anyway, you can see Irene over the Bahamas. I wanted to show you this image for two reason, one of which is to show you what good outflow looks like in a satellite image. It is shown by the white clouds, especially on the northern edge of this storm where the outflow is really nice. To me, it kinda looks like the outer edge of a rotary saw blade, for those of you familiar with such tools (umm, yes, so maybe I do know my tools better than my colours. I’m a card-carrying geeky physicist-type… I like technical things and maths and stuff ;-)). In a category 4 or 5 storm, the outflow would be really nice on all sides. I’m sure you’ve all seen images of hurricanes with good outflow on all sides… well now you know what the edges are indicating.  In Irene, on the east side we have a stream of clouds instead of good outflow. This is because of wind shear… which is picking up a bit and is flowing from out of the northwest. The wind shear looks like it might continue to increase as Irene moves farther NW. This is good because it might help to curb her a bit as she gets closer to the Florida Current and then Gulf Stream, but I would not be surprised if she developed into a category 4 storm. Currently water temperatures are around 30 deg C, with water warmer than 26 deg C in the upper 75m. I think she’ll remain a Category 2 or 3 for the rest of today as she carries on through the Bahamas.

Track:
Blistering barnacles Tintin, but she’s a tricky one to keep track of (puns intended). As we expected, she took that NW turn and picked up speed because the high pressure in front her eroded yesterday. Today, unfortunately, it has started to build back up. This is not what I asked for! I am trying to figure out a way to show you this (now that I have the technical abilities of a 5 year old and can upload images to the blog site), but it would take me some time to explain what you are looking at so for now, a thousand words will have to tell a picture.

There are two things to chat about here.

First, the actual pressure fields. The edge of the Bermuda-Azores High Pressure is always fluctuating (pressure fields discussed in some much earlier in the season entry), and unfortunately it is fluctuating right along the US east coast at the moment. Yesterday it was moving out towards the Atlantic, today it is moving in towards the coast. Tomorrow I don’t know yet (time machine is on the blink). Based on these fluctuations and maps, I figure out the direction she will take. For now, it looks like she has room to carry on moving NW, but won’t turn NNW, then N and northeast into the Atlantic as quickly as I had hoped. Bother.

Second, is the forecast track which takes her to North Carolina on Saturday afternoon and then to New York (As A Hurricane) on Sunday, and then to the rest of New England and Canada for Monday. This is the other reason why I wanted to show you the vapour image. If you look to the north and find the Great Lakes, just north of that is a swirlygig. This low pressure system that has been moving east across Canada, and that is what the models are essentially incorporating into her forecast track… this is why they are taking her up along the east coast to New York and beyond (AS A HURRICANE – I hope you guys are also getting ready!).

In my head, both the high pressure and that northern low are factors in her track. What I don’t know is how much emphasis the models give to one over the other, and I don’t have enough information to be able to say what will dominate yet either. In the good old days I know they gave too much weight to these low pressures to the north, but the models have evolved over the last few years as well, so I don’t know if this is the case anymore. This will be an interesting thing to watch (from a scientific/observational point of view). I hope everyone is preparing for a pretty big storm! I’ll be looking for changes in the high pressure tomorrow and the following day.

This is a big storm – both in terms of her size and also in terms of her intensity. Please be getting ready – even if she stays offshore, at the moment category 1 or higher winds are within 60 miles of the center, and tropical storm force winds are estimated to extend out to 230 miles!

Atlantic Blob:
Meanwhile, on the eastern side of the Atlantic, there is another blob. It is beginning to look good – convection is picking up because the Saharan Air Layer is no longer a big factor (boo). It is currently at around 12.5N, 27W, moving WNW at around 10-15mph. There is some circulation in the lower half of the troposphere. There is some wind shear, but I don’t see anything that will stop this from becoming the next Tropical Storm.

That might be it for today – busy day!
More tomorrow (unless I see some amazing new data that changes things).
Ciao!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene: August 23, Update B

Strictly speaking, it’s August 24, but this was supposed to be written before midnight rolled around. Oopsie.

The NHC downgraded Hurricane Irene to a category 1 (range: 74-95mph) storm this evening, with winds of 90mph, and central pressure of 969mb. Since then I think she might have strengthened again a tad, because there’s a very clear eye in that mass of swirling clouds:



And that central pressure is rather low for a cat 1. I think she’s back at being a good cat 2 again. They had forecasted her to be a category 3 by this afternoon, but (in my humble opinion) because she lingered over/near Hispaniola for so long, it took its toll on her. She is now forecast to become a cat 3 (wind speed range: 111-130mph) overnight on wed/thurs as she reaches the northern edge of the Bahamas. This is a more reasonable forecast (again, in my humble opinion) because she will be closer to the Florida Current, which is part of the Loop Current-Gulf Stream system and runs along the east coast of <insert drumroll> Florida. The entire Loop Current (in the Gulf of Mexico) – Florida Current (in the Straits of Florida/east coast of Florida) – Gulf Stream (skirting the east coast of the US from Florida until Cape Hatteras in NC) is an area of deep warm waters, with the upper 75m (at least) being warmer than 26 deg C. Unless something happens in the atmosphere (like wind shear), there’s nowt to stop her from growing to a cat 3 as she approaches the northern end of the Bahamas.

She is currently at  around 21.3N, 72.4W and is still heading WNW at a slow(ish) 9mph (apparently no-one told her that slowing down was *so* yesterday! ;-)).

She is almost on top of the southern Bahamas/Turks and Caicos region and will, unfortunately, cause quite a bit of havoc there. There is some heavy convection over those southern islands at the moment.

Ok, tomorrow I am looking for her to move towards the NW and pick up speed. But just for something a bit different, here’s a cool photo of her taken from the International Space Station: http://www.nasa.gov/multimedia/imagegallery/image_feature_2043.html (thanks to Trent in Florida for sending that).

Regarding the natural disaster-du-jour… to Rob in Georgia: why yes, I do forecast earthquakes but no-one has ever asked me… why do you ask? ;-) Ha, I wish! Hopefully the northeast US won’t be hit by an earthquake AND a hurricane in the same week! (although, hmm… do you think this tactic will work to increase funding for the environmental sciences?) Anyway, from a state that is used to such things, Ben in California reliably informs me that they should have no problems re-building from the damage this caused…J:



More from Hurricane Irene The First tomorrow and I might mention another Atlantic Blob (far out to the east still) if I have time.

Toodle pip!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene: August23, Update A

A quick note for now: Irene did indeed slow down and has been impacting the Dominican Republic for over 24 hours now, but I have just seen what I was waiting for (phew) - the high pressure in front of her has been eroded. This means she will begin to speed up a bit in forward motion and move more rapidly towards (and through) the Bahamas. But I expect that this shift in pressure also means that she will probably stay out in the Atlantic. It looks to me like there’s a good chance she will not make landfall along the eastern seaboard of the US. I expect that track that currently takes her to the Carolinas to keep shifting to the right and I also expect her to take a more northerly turn (i.e. move NW instead of WNW). I know a lot of people all along the eastern seaboard are getting ready, and I think that’s a prudent thing to do. I don’t think she’ll manage to swing over as far as Bermuda, but you guys on Bermuda should watch her carefully just in case.

My ideal scenario now is that she takes a NW turn today, then N, then NE, so she only skirts the right side of the Bahamas, and then heads out into the Atlantic, steering clear of Bermuda as well. I’ll give her a call and see if she will oblige. ;-)

The impact with the Dominican Republic has taken a bit of steam out of her and her convection has weakened (for now). I don’t think she’s quite a category 2 (cat 2 range: 96-110ph), but is certainly a good category 1 (range: 74-95mph), and there was some doubt about the strength of her winds on the NHC site this morning as well. I see an eye beginning to develop, which suggests winds of maybe 90-100mph, so I don’t know if they will bother to downgrade her because they have her at the higher end of that envelope. She will get more intense as she gets closer to the Florida Current/Gulf Stream. The one good piece is that because she stayed closer to the Dominican Republic, the brunt of the rain was on the east side of Hispaniola and Haiti was spared.

She’s currently at around 20.7N, 71.2W, moving WNW at 10mph. Winds are 100mph, so still holding as a weak-to-mid intensity cat 2, and central pressure is 977mb.

More later!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

-------------------------------
DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene: August 22, Update B

Irene was upgraded just about 1.5 hours ago to a category 2 hurricane, based on aircraft observations. They estimate winds to be 100mph which makes her a weak-to-mid level cat 2 (Category 2 range: 96-110mph). The central pressure is 981mb. I would agree with the assessment that her winds are greater than 80mph, although I don’t know if she’s quite that strong yet. There is not eye, and usually at around 90-100mph wind speeds we begin to see an eye in the satellite images.   

However her convection has increased, and the upper tropospheric circulation slowly continues to improve. The only good news is that the worst weather is offshore from Hispaniola, although the Dominican Republic is getting a downpour and quite a few strong thunderstorms at the moment. I hope everyone is ok there (including you holiday-makers). Here's a satellite Infra-Red image of the area to show you:



If you somehow forgot or missed my amazingly wonderful and witty words of wisdom (move over Oscar Wilde ;-)), how to read IR satellite images is in this entry:   http://jyotikastorms.blogspot.com/2011/07/caribbean-blob-july-27.html.

Umm, it looks like she has slowed down a tad and her track has shifted slightly southwards, bringing her a bit closer to Hispaniola (but currently the center will still remain off-shore). Her forward speed is now 10mph (which is still fairly decent as forward speeds go) and although she’s heading WNW still, it’s a little more westward than that (for now anyway). This translates to the Dominican Republic getting wet and windy weather for over 24 hours because she has been in that area since this morning, and hasn’t yet got to the closest point to the island in her forecast track.  

Although her current track is slightly south that before, the longer range forecast still takes her northwest through the Bahamas and to the east of Florida. It looks like the forecast curve has sharpened to more of a turn really: ‘get to Cat Island and take a right turn at the golden arches’). I think this is because the computer models are focusing on a low pressure front that is moving through the US and off the North Carolina region into the Atlantic  - that’s the target she’s aiming for (in the models). I was hoping she would be making a bit more of a definite move towards the Bahamas by this evening, but with her slowing down a bit I will, instead, be looking for that tomorrow.

The forecast also makes her a category 3 storm by tomorrow afternoon. If she remains on a WNW track and moves away from Hispaniola, I agree with that. It looks like the Bahamas are going to have a bit of a  tricky time. If she is a cat 3 as she goes through the Bahamas, I would not put it past her to decide she’d like to be a cat 4 as she gets to the Florida Current/Gulf Stream region (assuming that’s the path she takes). I know the track has her making landfall probably in the Carolina’s on Saturday. Until she moves into the Bahamas, it’s a bit tricky to assess this (from my limited information) but tomorrow I will try and make the time to hop into my time machine and have a peek at the future.

Until tomorrow,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Hurricane Irene: August 22, Update A

As expected, Irene is now a hurricane and the first of the season. She was upgraded overnight as she visited Puerto Rico, where I hear she caused some damage – power loss to over a million people, trees down, flooding etc. No reports of major injuries though (phew).

From the US VIs, Tom reported in at 2.12am with:
“2:12am aug 22. Power still on and uninterrupted since around 7pm last night. raining all night long with heavy wind gusting the dickens out of the vegetation...forget the late mango season. not sure how the rest of the island is faring but the wind part of this storm is still a factor. but, as hurricane and storms go, the worst is facing all of the rain which will impact negatively when it comes 7 inches in a short period.  As a wise old British Virgin Islander was quoted (donkey years ago) as saying about hurricanes and storms..." it's the tail end that stinks"”

And at 11.12am:
“After my 2 am report we fell asleep and got up at 6am to very little wind and mostly light rain(and internet serving tower down with no power). still light rain on and off but we are not free of the systems' rain bearing clouds. Have not heard about the impact on San Juan or Puerto Rico...looks like Irene got stronger as she was leaving us”

From the British Virgin Islands, amongst other things, I read that Sir Richard Branson’s house was completely destroyed (burned) because of lightning and winds from this storm (http://www.bbc.co.uk/news/uk-14616123).

Irene has been strengthening slowly and her center is near the Dominican Republic at the moment. As of the last advisory (11am EST) she was at around 19N, 67.5W heading WNW at 13mph. From looking at the satellite images, it looks like her center is now at around 19.1N, 67.7W, but I will put my slight westward estimate down to a cloudy satellite image (puns always intended ;-)), and will quite happily duct tape yesterday’s niggling voice in my head. ;-)  

She’s a weak-to-mid-sized category 1 hurricane (Cat 1 winds range: 74-95mph). Winds are 80mph, central pressure 988mb. Tropical storm force winds extend out to about 160 nmi northeast from the center. It looks like she weakened slightly earlier this morning because both the circulation in the upper troposphere decreased a bit, and also the lower level inflow and upper level outflow (convergence/divergence – that fun & fascinating ‘bit-o-science’ over the weekend J) weakened slightly.  Although the circulation has already improved at the highest levels of the troposphere, I think she will be slow to strengthen today because her outer bands are interacting with Hispaniola.

The forecast has her going north of Hispaniola and through the Bahamas, becoming a major hurricane overnight on Weds evening/Thurs morning. A major hurricane is defined as a category 3 or higher, and has winds stronger than 111mph. Here are the latest conditions that will impact Irene’s intensity:

1. The wind shear is low, and looks like it will remain low, so this won’t inhibit her from strengthening
2. The water temperatures are 29-30 deg C. Water temperatures are warmer than 26 deg C in the upper 75m or so of the water column. That’s a small reduction since yesterday, so for now it will allow her to develop but not as quickly as she could have if she was somewhere else.<
3. She is out of the dry, dusty Saharan Air Layer, so that will no longer inhibit her development.
4. Her vertical structure is looking good, with strong circulation in the lower half of the troposphere, and slowly increasing circulation in the upper troposphere.
5. Finally, and perhaps most critically, the intensity will depend on what her track is. If she is closer to Hispaniola than the current center of cone forecast suggests, then her intensity will not increase as quickly as forecast.

The track is the key to her intensity. Once she gets over the Florida Current and Gulf Stream there will be very little to stop her from growing. The NHC have repeatedly cautioned the reliance of the 4-5 day forecasts (and I would agree with them saying this). Over the last 5 years the average error for the 4 day forecast is about 200 miles, and for the 5 day forecast it is about 250 miles.

The rain and thundery weather is over the DR at the moment, and heading towards Haiti. As usual, Haiti is the most vulnerable at the moment from flooding etc. They will get that later today, unfortunately.

Meanwhile, a small Atlantic blob is trying to develop at around 20N, 33W. Circulation is good in the lowest levels of the troposphere, and poor thing is trying valiantly to get some convection going, but it is surrounded by dry and dusty air.

Here is a satellite map of the Atlantic:



The blob to the left is what’s left of Harvey, the middle one is Irene, and the one to the right is the little Atlantic blob. Pretty cool image, huh? J

Lunchtime over. More later!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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TD Harvey & TS Irene: August 21, Update C

TD Harvey:
I thought I might as well keep going, because apparently he is still going. We are all having a difficult time finding his center (e.g. from the NHC at 11pm EST: “THE CENTER OF HARVEY HAS BEEN VERY DIFFICULT TO LOCATE THIS EVENING.”) So he’s not a very well developed system, and it’s really tricky to tell if he’s even over the Bay of Campeche, even though it did look like he might have made a move in that direction. His last estimate from the NHC was at 19N, 95W, moving WNW at 12mph. I think he’s already west of there, and has made landfall in Mexico again. Winds were weakish at 35mph, central pressure estimate 1005mb. Although convection increased during the day, it should begin to decrease again soon. So this is my last entry on this system – really this time!

TS Irene:
The latest NHC advisory has her located at 17.9N, 65.5W moving WNW at 15mph. Her winds are now at 70mph, which makes her almost at hurricane strength (TS range: 39-73mph) and her central pressure is 993mb. The track has shifted northward and eastward during the day, which would reflect the fact that the center was on the northernmost edge of their cone this morning (actually looked like it was just north of that). She has officially passed the US Virgin Islands and is about 50 miles SE of San Juan, Puerto Rico now, although the entire area is getting rainy and windy sort of weather. Hurricane watches have been posted for the entire area, including the VIs. They are telling everyone not to focus on the track at 4-5 days from now because there is a huge amount of uncertainty in this. I agree and will explain below.

Intensity: She is just about leaving the Saharan Air Layer now, so her convection has improved and will continue to improve:



I would be surprised if we didn’t wake up tomorrow to our first hurricane of the season. Wind shear is not very strong compared to the storm, so that will only have a slight impact. Water temperatures are still in the 29-30 deg C range at the surface, with waters warmer than 26 deg C in the upper 100m. The only thing that will slow down her development is the land masses of Puerto Rico and Hispaniola (and possibly Cuba if she interacts with it in the future).

Track: Her track was pretty much as I thought earlier – she hit the northeastern Caribbean islands and the forecast shows her clipping the northern side of Puerto Rico and the Dominican Republic:



At least that is what the latest center of the cone is showing. Umm… however… there’s this little niggling voice in my head that is saying that now she’s managed to visit every island up there, she might actually take a more westward track tomorrow, or she might slow down and stall. The reason I say this is because there is an area of high pressure in front of her, which means that it is like going uphill for her, which she won’t like to do (because storms are lazy ;-)). If she moves W (or even WSW), the track will shift towards the south and west again. If she slows down or stalls, that’s another scenario entirely because where she slows/stalls will impact her intensity as well. I could be completely wrong, which would be fine with me because I don’t particularly like either of those scenarios compared to her current forecast track.  

Reports from the field:
I’ve heard from Tom in St. Thomas throughout the day and I posted some of his notes earlier. The latest one was at 8.08pm:
“wind in north quadrant is very strong and must be close to 60mph. lots more rain north of this storm and it is powerwashing St. Thomas, the strangest thing of all is that the electrical power here where we live has been on more than off. with the wind as high as it has been all day just can't figure that more power lines are not down. with the bulk of the weather north of us now I figure the center will move more northward as well which may spare florida. fingers crossed!”

I also heard from Debbie, whose mum (on St. Thomas) said that they were under a curfew on the island from 6pm until 6am.

Thank you for the reports from in the field! I hope everything is ok over there and you are all safe.

More tomorrow!
Adieu,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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TS Irene: August 21, Update B

Quick update: Irene is a bit north of the NHC track (right on the northern edge of the cone), and her center is passing directly over the Virgin Islands (pretty much directly over The Virgin Island in fact) en route to Puerto Rico – so she is essentially passing over all the islands. Convection is still not too strong overall, with the worst of it being north of the center. From updates Tom in St. Thomas:

1.13pm: Just got back online as the power had been out when a brisk frontal band swept in from the east...the large orange blob is now on top of us and bringing windy rain squalls not continuous yet…the trees are dancing to brisk gusts, maybe 25mph or so. waiting for the worst of the weather. am surprised that the power is on and holding. no flooding as of yet...1:11pm

2.33pm: winds have picked up to well beyond kite flying stage. strong and heavy gusts, almost steady 30mph with higher gusts. moderate rain but nothing flooding so far. electrical power holding at 2:32

3:09pm:from the sattel. pics I am viewing I would say we are closer to the center of Irene than NHC thinks.

More later,
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

-------------------------------
DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Tropical Depression Harvey & TS Irene: August 21, Update A

Ok, I’m now armed with a new bottle of window cleaner and can see things more clearly. We have what’s left of Harvey and Irene to chat about.

TD Harvey:
Let’s just get Harvey out of the way shall we? His convection started to deteriorate yesterday evening as he moved away from the bad influence of the Caribbean waters, and he is now just a tropical depression. Currently he is at around 17N, 92.6W (a little south of the official location), heading W(ish – with a bit of a southerly direction in there) at 15mph. Winds are 30mph and central pressure is 1006mb. He’ll probably stay over land (Mexico) and the plan is that he will fizzle away there. However, I see his circulation is still very good in the lowest half of the troposphere. If his center is a little south of the official location (17.7N, 92.6W) then there is a very very small chance that he might cross over into the Pacific and decide to have another go. If the center is at the official location, there’s a very small chance he will remerge into the Gulf before hitting Mexico again. This will be my last entry on Harvey, unless he does something else.

TS Irene:
“I can see clearly now the rain has gone” (who sang that first?). It pretty much sums up Irene (well, it also helps that it is daylight now). The dry, dusty air took its toll and the convection decreased a bit – it is still not very cohesive. This is why Tom on St. Thomas reported: “as of 6am not a single drop of rain here in Peterborg… and the trees are as still as a painting.” and then again about three hours later “we had a 5 minute rain about 45 min ago...still no wind yet but I think if the NHC track is correct things should get interesting later today as the VI will be in the northeast quad where the winds should be brisk.”

The NHC center was in the wrong place last night, but not to the south as I was guessing. It ‘redeveloped’ to the north. At the last advisory they had her at 17N, 63.2W, moving WNW at 20 mph. This means her track is closer to the north-eastern islands of the Caribbean (it might actually pass over all of them and skirt the northern side of Puerto Rico and the Dominican Republic).

They currently have her as a mid-level Tropical Storm with winds at around 50mph (TS range:39-73mph) and a central pressure of 1005mb. I think the winds might be stronger than this. Her circulation is very good in the lower half of the troposphere, and there is also a signal in the upper troposphere (the first clear signal up there that I’ve seen all year)– this is an indication of her being close to hurricane strength. However, because her rainbands are not very well developed, I don’t know if they will classify her as a hurricane until she has had a chance to improve her convection as well. The forecast calls for a hurricane as she gets to the Dominican Republic, but it will be interesting to see what call the NHC will make if she doesn’t manage to get the convection going. The main convection is to the north side of the center, so I agree with Tom’s analysis that they should get something more ‘interesting’ later today. Sea surface temperatures are around 29-30 deg C in this area, the upper 100m of the water is warmer than 26 deg C, and wind shear is not too strong – these are factors that will help her to develop. But working against her is the SAL and her interactions with the islands (although they are small, they still have a bit of an impact).

Another indication that she has good bone structure is the upper level divergence and lower level convergence, which are both looking good. I hear you ask: “But what gobbly-de-gook is this that she babbling about now? It’s Sunday morning… surely too early for a glass of wine already?” ;-)

<Science Alert> (yay! J).

So, in addition to the other things I mention regularly, I also look at something called upper level divergence and lower level convergence. Although we all look at maps or satellite images of tropical storm, we know that tropical storms aren’t only 2-dimensional and on the surface but also have a structure that extends up vertically through the troposphere (the lowest level of the atmosphere – see much earlier blog for definition). At the surface (where we live), we know there is a low pressure at the center. You can imagine a low pressure being like a dip or valley and high pressure being a hill (I think I’ve mentioned this before when I talked about storm steering). When you have a fluid, like rainwater, and there’s a dip in the land, that’s where the water flows towards. Well the air is the same. Where there is low pressure, it flows towards that, and where there is high pressure, it flows away. So one indication of a strong storm is the central low pressure – the lower it is (i.e. the deeper the dip), the faster the air ‘rushes’ in and the stronger the winds are. Of course as it doesn’t just flow straight ‘in’, it spirals inwards because of the Coriolis effect (because the earth is rotating). But basically, lower level convergence is the convergence (or inflow) of this air near the surface.

Now you can’t have all this air rushing in from all directions without it going somewhere… so where does it go? It can’t go down because that’s where the earth is, so it has to flow upward. But at the top of the troposphere (called the tropopause) there is essentially a barrier in the atmosphere that divides the troposphere from the next level up (the stratosphere), which stops the air just carrying on upward all the time like we would see with smoke from a chimney or steam from a steam train (if you are into those). So there is only one way it can go when it reaches the tropopause, and that is out from the center. Because all this air is being ‘pushed’ upwards and flows outwards at the top, instead of low pressure, we have a high pressure at the top of a tropical storm. So upper level divergence is the divergence (or outflow) of this air at the top of the storm.

If the lower convergence and upper divergence are good, it means that the vertical structure of the storm is good.

<End of Science Alert>

Here are maps that show Irene’s lower convergence (left) and upper divergence (right).



You can see a nice concentric circular(ish) pattern in both images near the storm, which is what I expect to see with something that has a nice structure. If it didn’t have good structure, the pattern would not be as circular, and there would not be many concentric contours. The more contours we see, the stronger the storm.

Now that I’ve given you all something to think about, I’ll go and put my feet up. J I’ll be back later today with another update!

Oh, and with Gert, Harvey and now Irene, Kevin in Florida wants to know if these are tropical storm names or somehow we got confused with the roster for the members of a shuffleboard club. ;-) If it’s any help, the next two are Jose and Katia.

Ciao for now!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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TS Harvey, TS Irene, and the Atlantic Blob: August 20, Update A

My, my, we are on a role today, aren’t we? Two Tropical Storms in one sitting! So much activity… it must be a weekend. ;-)

TS Harvey:
He made landfall in Belize at around 1pm EST this afternoon, as a mid-to-strong Tropical Storm with winds of 60mph (TS range: 39-73mph) and central pressure of 998mb. Over the last 7 hours or so he has lost some of that intensity and is now a mid-level Tropical Storm with winds of 50mph (central pressure still estimated to be around 998mb). Although he is over land, his circulation is still very good in the lower half of the troposphere and he is dumping bucket-loads of rain over Belize, Guatemala, and the Yucatan Peninsula.  He is not very well organized so I can’t really see where his center is at the moment. The NHC have it at around 17.2N, 88.8W with him moving WNW at 13mph. It almost looks like he’s a bit south of that, but I’ll go with the NHC center.

TS Irene:
This one is going to be interesting to watch. She’s currently still on the Atlantic side of the Leeward Islands. According to the NHC, her winds are around 50mph, central pressure is estimated to be 1006mb. There is a bit of wind shear, but she is also still in that Saharan Air Layer, which is keeping her a little off-kilter. Water temperatures are 28-29 deg C, with the upper ~100m warmer than 26 deg C.

At the moment both her circulation and her convection is a bit messy (she really should clean her house and she can even listen to Rick Springsteen as she’s doing it if she likes. It’s ok, we won’t judge ;-)).  Because she’s so messy, I can’t quite make out the center of circulation in her either (the theme for this evening!). It kinda looks like it is a bit south of where the NHC center of cone is, but it is night now so the satellite imagery is not very clear. I am not convinced of her forecast track yet, which takes her to the Dominican Republic by Monday evening:



If her center is south of her current official location, then I think she might continue moving a little farther west than the track shows – that’s hopefully something we’ll find out tomorrow.

The track takes this to the Dominican Republic, potentially as a hurricane. Until she crosses the leeward islands and gets out of that Saharan Air Layer, I am not certain of this intensity forecast either.

I’ve heard from Tom in St. Thomas (US Virgin Islands) who is as ready as they can be for whatever Irene brings them.  The outer bands have just about reached the US VI according to the satellite images, but it seems that the folks there did not get much warning. From Tom about 40 minutes ago: “we expect rain soon...we did not see anyone getting prepared for this storm and there was a brief mention of some wind and rain for late tonight and sunday on a news website”.

I think everyone should keep an eye on this one – of course those in the Caribbean, but also in Florida (both sides of the state) and along the US eastern seaboard. The long-range computer models have her going from a panhandle/west Florida landfall, all the way to heading east of Miami and along the east coast. If she heads along the current forecast track, she is unlikely to be a major hurricane because of the northern Caribbean Islands. At the moment there is a lot of uncertainty about Irene. I’ll run out tomorrow when the shops open and get some window cleaner so hopefully things will be a bit clearer tomorrow and we can see the center.

Atlantic Blob:
The blob that came off Africa still has stronger circulation than Irene, but the convection is a bit of a mess now. They have downgraded this to a 20% chance of forming. With Irene (and Harvey) out there, I’ll refrain from writing about this one unless something happens. My brain is already full! ;-)

That’s it for now. I’ll keep you updated with any in the field reports tomorrow.
Toodles!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Tropical Storm Harvey and other assorted Atlantic Blobs: August 19, Update A

Tropical Storm Harvey
Haha... Harvey was named this afternoon (about time). This amuses me no end, as you may have guessed from one or two things I’ve said before. A storm that got upgraded and named as it was already impacting land (and presumably people). Quelle surprise.

His center is just off the coast of Honduras and he is interacting with land. His current center is estimated to be at 16.2N, 85.2W, and he is moving W at 9mph, towards Belize. He has strengthened during the day and apparently has winds of 60mph, central pressure of 994mb. I say apparently, only because the winds I’m seeing from satellites are around 35-40knots or 40.25 – 46 mph (1 knot = 1.15mph). However, I think it is very possible that the snapshot I have access to is a few hours old and the winds (and convection) have picked up since then.  Looking at the physics of the situation (ooh… physics!! How exciting! ;-) ), I can see why the winds and convection might increase, despite his proximity to land: the center is still over warm water (just about), with surface temperatures of 29-30 deg C and the upper 100m of the water column warmer than 26 deg C, so there is plenty to keep Harvey well-fed puppy for a few more hours.

Atlantic Blobette
There are a couple more blobby things out there:


There’s a blobette at around 15N, 52.5W. They give it a 60% chance of forming into a Tropical Storm. It certainly has some circulation in the lower troposphere, but it is still not very well defined. And there is not much in the way of convection at the moment, as you can see in the IR satellite image:


The Saharan Air Layer extends out to the Leeward Islands, which I hear have been put on alert. I am not sure it will pick up much convection until after it has crossed those. I’ll have a better look at this one tomorrow but the official word is that it is moving generally westward at 20mph.

Atlantic Blob
This is the one that came off the coast of Africa yesterday(ish).  The circulation is not very well defined at the moment, although there is more convection in this system than in the Atlantic Blobette. I’ll look at this one more carefully tomorrow as well.

Now it’s time for a bit-o-beauty-sleep (sometimes available in a jar from your local grocery store ;-)).
Night!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Tropical Depression 8, the Atlantic Blobette and Blob: August 18, Update A

Ben in California finally figured it out… apparently I missed the memo saying that any storm that is about to make landfall would be waaay too obvious to name, so this year they would only name tropical storms if they were in the Arctic. Sigh. ;-)

The NHC finally decided to upgrade my Caribbean Blob to an official Tropical Depression (number 8). It is, of course, already interacting with the central America land mass and is practically on top of Nicaragua/Honduras at this point so I don’t know if it will even have a chance to be named (I think they might have missed the boat on this one). It is heading West at 12mph, central pressure 1006mb, winds 35mph. Fortunately there isn’t much convection to this blob, certainly not as much as there was a couple of days ago anyway, and the winds are fairly light so it should all be groovy. A plane went in today to see if it could find a closed surface circulation because until this morning (or maybe it was last night) they said it didn’t have any. I am afraid my “Computer Says No” (hee hee, Little Britain ref) … I have been saving snapshots of the vorticity (circulation) over the past few days, showing quite clearly that it had good circulation in the lower half of the troposphere. Maybe it will be named for a couple of minutes, we’ll see.  

There is another Blob and also a Blobette out in the Atlantic:


The cloud that the NHC have marked with a 20% chance (yellow) of something developing currently has just a smidgen more convection than a desert on a dry day and the circulation is pretty weak and not well defined. The area where the NHC have a 30% chance (orange) of something developing just came off Africa and does actually have more circulation and convection, so I’ll agree with their assessment of that one for now. 

The next three names are: Harvey, Irene and Jose. Hmm. I know a Harvey, Irene and Jose.

(non-sequiter) <cheese break><yumyum> (end non-sequiter)

We are on Tropical Depression number 8, and have had 7 named storms so far. I believe this is the first year since satellite observations began in the 1970s that we have not had a hurricane in the first 7 named storms! I think there are a few reasons for this:
1. They are naming storms that, in the days of yore, wouldn’t be named Tropical Storms.
2. Satellites are picking up storms out in the Atlantic that we would not have detected otherwise because they would be short-lived or small.
3. There are factors that are inhibiting storms. We’ve seen these in other seasons – things like wind shear, cooler water temperatures, atmospheric dynamics etc. This year (so far) I think the most likely culprit is the dust in the Saharan Air Layer (SAL) that I mentioned a few days ago – lots and lots of that zero-calorie ;-) dry dusty air around. You can see an up-to-date map at   http://tropic.ssec.wisc.edu/real-time/salmain.php?&prod=splitEW&time and even watch a movie of the SAL over the past 5 days (ooh… who has the popcorn? ;-)).

These little tropical storms are useful things. For example, tropical storms account for at least 25% of Florida’s annual rainfall. We need them to bring some lovely rain and keep us out of drought conditions. It’s just when they get a bit too big for their boots that we get into trouble.

Time for another cheese break I think. J
Ciao (chow!) for now.  
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Tropical Storm Gert and the Caribbean Blob: August 16, Update A

A note with my morning cuppa tea. J

TS Gert officially has winds of 45mph, central pressure of 1005mb and is at around 36.4N, 59.6W heading NE at 22mph. I don’t think there’s really much left of this storm. The convection is practically non-existent and the vorticity (circulation) is decreasing. It looks like the NHC are forecasting to downgrade her tomorrow, but I don’t think there’s anything that indicates she’s that strong so this is my last entry on Gert.

The Caribbean Blob is still one I’m watching. The NHC currently have this at a 20% chance of developing into a TS in the next 48 hours. This is possible, but at the moment I wouldn’t be totally surprised if we have a TS within 48 hours. The vorticity is actually a little stronger in this one than in Gert, all it needs is a new outfit and a few clouds with rain and it’s good to go. We’ll see how quickly it picks those up – it has already changed in appearance over the last few hours with those thundery clouds developing just north of its center of circulation. It is moving westward at somewhere around 15-20 mph. What is really remarkable is that despite the low convection, you can already see a clear outer band in the satellite IR image. It stretches from South America all the way north past the Dominican Republic. Very pretty.



More when something happens!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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Tropical Storm Gert and a Caribbean Blob: August 15, Update A

Tropical Storm Gert:
Although Tropical Storm Gert has winds of 60mph, making her a mid-intensity tropical storm (TS range: 39-73mph), she’s been pretty well behaved. She stayed well east of Bermuda. From the satellite images it looked like they had some cloudy weather and maybe a spot of rain here or there. As she was zooming by, Steve from Bermuda wrote “slight breeze here. More wind generated by the passing traffic than gust-less Gert in Bermuda.” This surprised me because from the satellite images it doesn’t look like Bermuda is big enough to have more than one car so I can only assume he was talking about golf cart and Segway traffic. ;-)

She is currently at around 33.5N, 62W, heading NNE at 14mph. She has some convection, but not the really deep stuff. Water temperatures are 27-29 deg C, and there is some wind shear. I don’t see her developing into anything more and she’s just heading out into the Atlantic. She’s a cute little storm really. Just like her name.

Oh, speaking of her name… to David from Florida: no, she’s GERT, not GORT. <sci-fi diversion!> In case any of you were wondering, Gort is the name of the alien robot from The Day The Earth Stood Still:


The 2008 remake starred Keanu Reeves. It will come as no big surprise to my friends that a perfectly innocent conversation about an Atlantic Tropical Storm has turned into a conversation about Keanu Reeves. I don’t know how these things happen. ;-) I think if the NHC run out of names, we should begin naming tropical storms after characters from sci-fi (we could expand to other genres if we run out of names). J I mean really, how scary could Tropical Storm Jar Jar Binks possibly get? On the other hand I suppose Tropical Storm Davros might turn into something scary. <end of sci-fi diversion!>

Caribbean Blob:
Just like Keanu Reeves, this Caribbean Blob is one to watch. Yesterday it was over the Atlantic and had a lot of convection, but until this morning the circulation was pretty pathetic. However, today the circulation picked right up. Fortunately for us it was crossing the Windward Islands so it’s convection took a hit (and is now pretty pathetic). It is now in the Caribbean, with good circulation but poor convection. The reason we need to watch this is because the wind shear is low, it is on the western edge of the Saharan Air Layer (dust) (SAL), the sea surface water temperature is 29-30 deg C, with water warmer than 26 deg C in the upper 75-100m. I’m estimating the center is somewhere around 14N, 62W and it appears to be moving westward(ish). We’ll see if this picks up steam again. The next name is Harvey.

Until tomorrow,
Toodle pip!
J.

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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