Saturday, August 29, 2015

The Remains of Tropical Storm Erika and note about Hurricane Katrina: August 29, Update A

This morning the NHC officially declared Tropical Storm Erika a remnant 'low' and have stopped issuing advisories on her. This means that she does not a have a closed circulation anymore (i.e. the winds aren't all going in a circle around in a central point). She still has winds of ~30-35mph (last known central pressure was 1011mb) and was moving WNW along the northern coast of Cuba at ~22mph. She is still generating rain, and quite a lot of it, as you can see in the latest IR satellite image:

There is still a small chance that she will re-develop, primarily because she still has some circulation in the lower half of the troposphere, and because that circulation is centered just off the coast, over water temperatures of 30-31 deg C (exceedingly warm!!), and she is heading to a region between Florida and Cuba where the upper ~150m of the water column is warmer than 26 deg C (exceedingly deep warm water). If her circulation was a bit weaker or if she was more directly over Cuba, then I would not be thinking this. So, still worth keeping an eye on her for another day at least. 

Interacting with the island of Hispaniola was a mixed bag really. Yes, it did reduce her intensity... but unfortunately over 20 people lost their lives in the flooding that occurred on Hispaniola. With a storm it is not the wind, but rather the flooding on land (storm surge, overflowing rivers, breaking levees, mudslides etc) that is usually the largest reason for loss of life. 

As you know, today is the 10 year Anniversary of Hurricane Katrina, where lives were also lost from the flooding that followed. There are numerous stories in the media this week about what happened and the recovery process, but perhaps the best interactive site I've seen with then and now photos is, appropriately, from New Orleans The Times-Picayune website: 
http://www.nola.com/katrina/index.ssf/2015/08/katrina_then_and_now_watch_200.html. Do check it out if you haven't seen this site already.

And I think that will be all for today folks. I will be back tomorrow to wrap up Erika or give another update (hopefully the former!).

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.

Tropical Storm Erika: August 28, Update A

Even in California I am prepared for a Tropical Storm... having a sip of wine and thinking about the Cappuccino gelato in the freezer. ;-)

Tropical Storm Erika is looking a bit worse for wear this evening. They did shift her center, and she did stay on a more westward path today, so the entire forecast track shifted to the west and mostly outside the cone from yesterday. She is currently at 18.5N, 72.9W and is now heading WNW at 20mph. Here's the latest forecast track: 
This seems far more reasonable to me today as tracks go. Although difficult to see, I also think the location of her center seems to be more on target: 

They did also increase her winds to 50mph, but have brought her back to 45mph (central pressure 1008mb). I agree with the increased winds (possibly an underestimate), and also with the subsequent decrease in winds ... although I think her winds may be less than 45mph now. She is barely a Tropical Storm - mostly a bunch of rain clouds and strong thunderstorms (Keith L., I agree with you!): 

The reason she still looks like she's packing a punch is because she is interacting with the warm waters of the Caribbean - sea surface temperatures are 29-30 deg C, with the upper 150-175 m(!!!) warmer than 26 deg C just south of Hispaniola! There's the real source of convection and all that rain she is dumping over the Dominican Republic and Haiti. Haiti is, unfortunately, a tough place for this much rain by the way, because they are prone to mudslides. At the very least, I would expect the convection and thunderstorms to remain strong until she gets to Cuba.

I received a note from our intrepid on-the-ground reporter, Tom, on St. Thomas yesterday about the 'buckets' of rain she dumped there... "Here in north side of St. Thomas Not enough rain to fill a child's beach bucket." So, not quite as rainy as it looked like it might be and definitely not too windy.

There is a bit of wind shear and she is interacting with land, which will help to reduce her intensity. What will really help though is crossing Cuba along the length of the island (more or less) - like the path shown in the forecast track above. I am not sure if she will survive in any real form after that crossing, so she may not be too much of a problem for Florida. The thing to watch out for is how she fares as she crosses from Hispaniola to Cuba. As I said, there is some very warm water lurking in this part of the world. 

(ok, that's enough 'thinking' about the gelato in the freezer, it's time for some action... ;-)).

Looking at her circulation and the vorticity maps (see yesterday's post for a description) you can see that she is much weaker in the lower half of the troposphere now compared to the images I showed you yesterday. Here are her maps from 850mb and 700mb today: 



And here is her map from 500mb (the middle of the troposphere):

The bright red, well developed round 'splodge' from yesterday's map is not there now. Instead, at 500mb she is a longer 'swash' of yellow. A sure sign that she is structurally weaker - primarily due to interaction with land. 

I'll be back tomorrow, the anniversary of landfall for Hurricane Katrina, who was, 10 years ago today, an amazingly strong category 5 storm that dominated the Gulf of Mexico. 

Adieu until then,
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.

Friday, August 28, 2015

Tropical Storm Erika: August 27, Update A

Deary me, I turn my back for one moment and Tropical Storm Erika tries to make a run for it. I flew through the night so I'm a bit weary, but I thought I'd better have a look at what was going on with our storm-du-jour before things got too blurry. :-)  

Hmm. It looks like the effects of warm surface water, deeper warm ocean water, plus the lack of dry air slightly outweighed the impacts of wind shear and crossing the islands. She is now firmly in the Caribbean, officially at 16.6N, 65.3W and heading W at 17mph. Current winds are 45mph, central pressure is 1008mb. 

'Luckily' her bark is bigger than her bite at the moment. She does look quite large and fierce with all that convection (as you can see in her infrared satellite imagery):

and there are areas of red (and gray), which means heavy thunderstorms with some of the islands, including the VIs are getting bunches'o'rain! But I am not surprised by this convective activity because she continues to move through an area of humid air (the brown dry air is quite far from her center - you can see it to her north and east, in the Atlantic, in this water vapor satellite imagery):

and she is also moving over sea surface waters with really warm temperatures of 29-30 deg C with the upper 100-125m warmer than 26 deg C. I expect her convection to continue while she is in the Caribbean.

She is growing in size which you can also see in the above satellite images... but that is her 'bark', not her bite. How about her circulation? The NHC currently have her winds at 45mph, which makes her a very weak Tropical Storm (TS range: 39-73mph). I think this is a slight underestimate. Her circulation (vorticity) is very well developed in the lower half of the troposphere and I think her winds are actually at least 60mph, possibly higher (oh, if only we had good measurements all over the ocean how much easier it would be to know!). She is not a hurricane (not yet anyway) as there is no real circulation signal in the upper troposphere. 

<Science Alert!> Although satellite images are one piece of the information puzzle, the biggest clue about what sort of storm we have is in the circulation (or vorticity as this is supposed to be all 'sciency' and stuff :-)) and what that looks like at different levels of the troposphere - this gives us a glimpse into the structure of the storm. A tropical storm will have a well-defined circular "splodge" (in an effort to sound intelligent, you can see that I continue to use only the most technical terms here ;-)) on a map of vorticity. The stronger the storm, the more cohesive the "splodge" at all levels of the troposphere. 

What does Erika look like at different levels of the troposphere? 

Here are the vorticity maps in the lower levels of the troposphere at 850mb:
and 700mb:

Here is the vorticity map for the middle of the troposphere at 500mb:

You can see her strong vorticity quite clearly as that deep round red "splodge" at these three levels  of the troposphere. The 500mb is the middle of the troposphere. Looking higher into the troposphere, we don't see the same round splodge (which we would otherwise see if she was a hurricane): 

Although there is some vorticity up there, as you can see with the green/yellow patches, it is not very well defined so it's not really the structure of a hurricane. It is more like a 'front' up there. You can look at these maps for yourself at the University of Wisconsin site I mentioned a few days ago: http://tropic.ssec.wisc.edu/tropic.php. Click on the winds and analysis for the area you are interested in, and look at the 850mb, 700mb, 500mb, and 200mb maps. <End Science Alert!>

Despite the increase in convection, she is still undergoing some wind shear which is why she isn't very strong at the moment (certainly not as strong as you would think just looking at her convection). You can see this in the vorticity maps above as well because the splodges don't all line up in the same geographical area from one level of the troposphere to the next. 

Regarding her track... I don't think the location they officially have is actually her center of circulation. In looking at her visible satellite imagery (the best place to 'see' her center), although it is murky because it is night-time, I just don't see a center of circulation as far west as 65.3W... do you? 

It looks to me like she is centered somewhere closer to 64.5W than 65.3W. We'll have a better idea by daylight. But, this may mean her forecast track is also a wee bit off. 

I know I said that the NHC forecast has been really good at ~2 days out. In this case, it may be a bit wonky though if they don't have the correct center location. They do say that there is more uncertainty in their 3-5 day forecast than usual for this storm. However, if I were in that white cone of uncertainty, I would definitely be ready or getting ready! (...have you got your wine, ice cream, and water supplies?).

The NHC are forecasting a WNW-NW turn in the next few hours. If she doesn't get too much stronger, I think there is still a chance she will continue on a more westward track for tomorrow. If she does get stronger, I can see that WNW turn happening sooner. 

I'll be back tomorrow. Good luck out there... and stay safe my friends!
Toodles 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.

Wednesday, August 26, 2015

Tropical Storms Danny and Erika: August 25, Update A

Due to severe technical difficulties (my computer has been having a rather bad hair day since yesterday), I missed the end of Tropical Storm Danny. I'm here on a 'borrowed' machine (thank you hubby dearest! :-)).

Not surprisingly, I see Danny didn't quite survive the journey across the the islands. So, that's the end of that one and we move right along to little Miss Tropical Storm Erika. She is at 16.0N, 55.2W, heading west at 18mph. Winds are 40mph, central pressure is 1006mb. This makes her a very weak Tropical Storm (TS range: 39-73mph). She has circulation in the lower half of the troposphere and some convection.

There are a couple of factors working against her intensifying too much... first, she is heading into an area of higher wind shear, and second, given the track she is supposed to be on means that she will also interact with the islands. But there are also a couple of factors that may allow her to intensify! First, she is not running into as much dry/dusty air as Danny did (he took care of that for her!), and she is currently moving over water that is 27-29 deg C, and the upper 75-150m is warmer than 26 deg C (also warmer than Danny).

I think this means that we will see an increase in convection before she crosses the islands, but she won't get too strong and doesn't look like she'll get to hurricane strength before the islands. As I said with Danny, the track forecast from the NHC for 1-2 days out is pretty good now, so I'll go with that.

That's it for now. Must return ze machine (before someone realizes it's in use ;-)). I have another travel day tomorrow so I may not manage to get on but we'll see.

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.

Sunday, August 23, 2015

Tropical Storm Danny, Tropical Storm Kilo, and the blobette: August 23, Update A

Tropical Storm Danny. Hurray! That's much better than a major hurricane! :-)

He is currently at 15.8N, 58.1W, heading due W at 15mph:


The models did correctly forecast the high pressure would turn his track to the west, which is great! This is further proof that the track forecast has improved for a ~2 day lead time! The intensity is still fairly rubbish, but once the NHC improve on that, I can 'retire' and become rich and famous by posting funny videos of cats instead. ;-) 

You can see the center of circulation in the satellite image above, as the clouds are mostly to the north and east. The convection is still quite strong, and as it is to the north and east, the VIs and other islands will get some rain and possibly a bit of thundery weather, but not so much of the sustained strong winds. 


The forecast track takes him on a WNW path once he enters the Caribbean. This may shift slightly to the south, but I'll go with it in general. He is leaving the area of stronger wind shear, however his interactions with the island will keep his intensity low. I don't think he will completely vanish before crossing the Leeward Islands though, but it is unlikely he will intensify further. 

Now, there is a blobette in the Atlantic. She's at around 13N, 36W (the bunch of clouds to the south and east of Danny) and is not yet officially a Tropical Depression (although she does have enough circulation in the lower troposphere to be a non-named TD!): 

I'll have a look at her properly once she's done her hair and make-up! ;-)

Meanwhile... over here in the central Pacific, we have Tropical Storm Kilo. I didn't think you would be interested in this one, but apparently Dan P. is on Maui too! (by the way, we were the ones hanging off the cliff on Hana Highway yesterday... "guard rails", huh... ;-)...
)

So, for anyone in Hawaii: unless you are staying inside with the curtains closed, you may have noticed it is a little cloudier today. This is courtesy of TS Kilo, who is currently centered somewhere around 15N, 164W I think:

You can see that the clouds are streaming off the storm because of wind shear (we are the little pink islands to the top right of the IR loop above). TS Kilo is to our southwest, but is expected to curve to the north and then east:

If anything, it may clip the northern end of the island chain next week, so anyone on the Big Island (Hawaii), Maui, Ohau etc. should be fine. It may be a bit cloudier, more rain, and thundery weather (like we had last night) for the next few days, so not quite as spectacularly scenic as it would be on a sunny day, but the surf should be fun! And what more could you ask for in a 'rainforest' than buckets of rain? :-)

That's it for now. The red flag just went up on 'my' beach here. Guess that means no snorkeling today... time to put the wellies on. ;-)

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.





Saturday, August 22, 2015

Hurricane Danny: August 22, Update A

Hey look, Danny has weakened and is now officially a cat 1 storm with winds of 90mph (central pressure estimated 985mb)! (Cat 1 range: 74-95mph). Hurray! :-) 

Actually, looking at his visible and infrared satellite imagery, I would say he's weaker than that because he's not had an eye for a long time (as seen in the visible image)...

and the convection is looking quite ragged and not as concentrated in the infrared...

As I explained yesterday, this is in response to both the wind shear and the SAL. He is still moving through the region of high wind shear and dry, dusty air. You can see the impact of the wind shear in the satellite images with the clouds streaming off to the northeast. 

Also, although his circulation is strong in the lower half of the troposphere, there is a definite weakening in the upper troposphere, which means he is losing that strong structure that makes him a hurricane. I would say he is a fairly weak cat 1 storm at this time, with winds around 75-80mph. 

Another satellite image to look at is the water vapour:


You can see the dry air he is moving through... but this also shows us the approximate area of high pressure that he's been bumping into - that paler brown region to his north and west, stretching across the northern Caribbean. The NHC think that the high pressure will rebuild to his north, which is why they are maintaining a track to the west and over the northeastern Caribbean islands (including the VIs) on Monday/Tuesday.

This is quite possible, but they have been consistently tracking him a smidgen (technical term ;-)) to the south of the actual storm position at two days out, so although he could pass directly over, he may also just skim to the north. The cone of uncertainty is the thing. In either case, he will be much weaker by the time he gets there. 

More tomorrow... with hopefully a 'Tropical Storm' Danny on the books!
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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Friday, August 21, 2015

Hurricane Danny: August 21, Update A

For once I'm not at an airport waiting for a plane! This is my view today, from the beautiful island of Maui in the Pacific... :-)


Meanwhile, back in the Atlantic, Hurricane Danny was just upgraded to a cat 3 storm with winds of 115mph, central pressure of 974mb (cat 3 range: 111-129mph). Categories 3-5 are considered 'Major' storms - so Danny is the first major storm of the season.  I may have agreed with the NHC if they had upgraded him a few hours ago,  but it looks like he has already weakened, and with no visible eye, it suggests that winds are actually in the ~90 mph range (cat 1):


He still has strong circulation in the lower half of the troposphere, with a weaker circulation signal in the upper levels of the troposphere, which is what we would see with a Hurricane as opposed to the weaker Tropical Storm. He is still over sea surface water temperatures of ~27 deg C, with the upper ~50-70m warmer than 26 deg C. So why is he weakening? First, he is moving deeper into that dry, dusty Saharan Air Layer:


And second, more critically, he is moving into a region of strong wind shear which will really knock his socks off:

In the image above, the red areas are areas of high wind shear, and the blue are areas with low wind shear.

<Forecasting Tool Alert!>This wind shear map and the SAL map, are from the fantastic University of Wisconsin website: http://tropic.ssec.wisc.edu/tropic.php, should you want to have a look for yourselves (and I'm sure you do! :-)). Click on colour block in the lower map for the part of the world you are interested in (North Atlantic in this case), and in the drop down menu (amongst a number of things) you will see 'Saharan Air Layer Analysis' or 'Winds & Analysis'. The Saharan Air Layer takes you to the map immediately. Under the Wind Analysis, there are a number of useful products. The wind shear, the upper and lower level winds, upper and lower convergence/divergence (I covered this a couple of years ago, but will talk about it again at some point I'm sure), and, most useful is the vorticity at different levels of the troposphere, which is where I get my circulation and storm structure information from. To understand the circulation/vorticity maps, check out the <Science Alert!&lgt; from last year: http://jyotikastorms.blogspot.com/2014/08/hurricane-bertha-august-4-update-a.html. (I'm allowed to be lazy... I'm at the beach! ;-)) Easy peasy! <End Forecasting Tool Alert!>

As for his track, although the official word is WNW at 10mph (currently at around 14.3N, 48.6W), I still think he is moving to the north of that. The forecast is to take him over the northeastern Caribbean islands, but I think there is a good possibility (should he survive) that he may just skim those and stay in the Atlantic:


That's about it for now. I may pop back later! Still best to keep an eye on Danny though, and I say that because he has a vorticity signal in the upper troposphere. He has a good structure until that goes away.

Oh, and before I leave, here's a really neat image of a cross-section of Typhoon Atsani (in the Pacific) from NASA to give you a different perspective on what a tropical storm looks like:


Toodle pip!
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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Thursday, August 20, 2015

Hurricane Danny: August 20, Update A

Here I am, waiting for yet another flight - 3rd in 3 days... I'm on a roll, which is also what Danny-boy is on!

I agree with the upgrade to Hurricane Danny today. He did have an eye, which he has since lost, but because another clue is that his circulation (vorticity) signal is all the way to the upper troposphere and it has improved since I first saw a glimpse a couple of days ago. It doesn't look like he will strengthen too much more in the next few hours.


He is currently at 13N, 47.5W. Central pressure is 990mb, and winds are 80mph, which makes him a good size cat 1 storm (cat 1: 74-95mph). Officially he is moving WNW at 10mph. It looks to me like he is moving more NW, which means the track may move to the north. Central pressure is 990mb, and winds are 80mph, which makes him a good size cat 1 storm (cat 1: 74-95h). For the track, as I said yesterday, the NHC has been good at forecasting 1-2 days out, but after that it could change... so whether he passes over the northeast Caribbean, or even farther north, we will know tomorrow. Best to keep an eye on him if you are in the Caribbean/US east coast/Bermuda!

Eek... boarding now! Must run. Back 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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