Saturday, October 18, 2014

Hurricane Gonzalo: October 17, Update A

I can see clearly now the rain has gone, it's gonna be a bright bright sunshiny day (J. Nash)... Hurray! Bermuda, that little pink dot in the middle of the Atlantic, is just about emerging after a day of Gonzalo's rain and windy weather.

I heard from Steve on Bermuda about 7 hours ago, who said it was a storm, and windy outside. He doesn't recommend going out in a hurricane by the way.

Circulation remained strong throughout the troposphere, so Gonzalo was/is definitely a hurricane. The question is what was the intensity.

I checked in on the winds at the island airport throughout the day and the highest sustained winds I saw were 93mph, which would make Gonzalo a strong cat 1 storm (Cat 1 range: 74-95mph). The strongest observed winds when the edge of the eye made landfall (at around 8.30pm local time) were around 76mph, again indicating a cat 1 storm. The NHC had estimated winds of 110mph, which would put him as a strong cat 2 storm (cat 2 range: 96-110mph).

Although he had an eye in the IR satellite and radar images, it wasn't clear in the visible satellite images (this was pulled earlier in the day) as there were clouds covering the eye, which further supports that reasoning that this was a cat 1 storm:

We'll find out tomorrow how Bermuda faired. I thought I'd keep this update brief... for now, it's definitely wine-o-clock!

More 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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Friday, October 17, 2014

Hurricane Gonzalo: October 16, Update A

Dear Bermuda, I hope you are ready for whatever tomorrow brings! I hope it brings some clouds, a bit of rain, maybe a strong breeze and short thunderstorm or two, some super high surf, and not much more.

I (and I'm sure you) have been watching Gonzalo the live long day and following, with avid interest, the advisories and forecasts from the NHC so you would have seen that for most of today they had Gonzalo as a cat 4 storm with winds of 145mph. They have now brought him down to 140mph, 943mb - he's still officially a cat 4 storm (cat 4 range: 130-155mph) and the NHC forecast that he'll remain a cat 4 for the next 24 hours (until Saturday night).

I agree that he was looking like a stronger storm today, and he may have been a strong cat 3/weak cat 4 (probably not quite with 145mph winds). He had good outflow in the satellite images, there was a pretty nice and strong eye for most of the day, and wind shear had clearly decreased because clouds weren't streaming off willy nilly. Even the lower level convergence(LLC)/upper level divergence (ULD) that I mentioned a couple of days ago looked better. To show you what the difference is in LLC/ULD between a weak hurricane (my opinion 2 days ago) and a stronger one, I have some figures to show you (from the U. Wisconsin):

Lower level convergence two days ago (when the NHC had him as a cat 3 and I thought he was weaker):
 
Low lever convergence today (NHC say cat 4, I more-or-less agree):

There are more/tighter concentric rings today, which is what you would expect with a stronger storm.
 
Upper level divergence two days ago: 
 
Upper level divergence today: 

As I said, I'm not sure he was as strong as 145mph winds would suggest, but I suspect the reason they kept him at that level was to spur you guys on Bermuda to get ready!

At the last advisory he was at 28.6N, 67.3W, heading NNE at 15mph. The eye looks like it will pass pretty much over/slightly west of Bermuda tomorrow evening:

Having said all that, there are some interesting things in the latest IR satellite loop:
I said yesterday that he would weaken as he got to 30 deg N because the warmer waters underneath the surface of the ocean become shallower around that location. The eye he had all day started to fracture when the 'real' outer bands reached around that latitude, and it looks like the convection is taking a bit of a hit from the lack of deep warm water. The sea surface temperatures are around 28-30deg C, so definitely warm enough to sustain him. The wind shear is still low, but it looks like he'll head into an area of slightly stronger shear tomorrow afternoon.

Here is the image on a larger north Atlantic map:

I wish I could stay awake long enough to see what happens to the center when it reaches around 30 deg N... maybe I'll wake up at 3am to have a quick peek! If that trend continues, Bermuda (located at ~32N) may not get hit by a major hurricane at least. Fingers crossed! (because that's how science works... ;-)).

Regardless, be prepared for something worse and pay attention to your Emergency Managers. And remember: run from the water, hide from the wind!

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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Thursday, October 16, 2014

Hurricane Gonzalo: October 15, Update A

No time for a cup of tea and a nice chat when one has a few words to say. Starting with... would you like to see a Hurricane that is intensifying from a cat 3 to a cat 4 storm? Here's one:
 
See how that eye became clearer? Oh and how about that increase in convective activity(more reds and grays)? Nope? Ok, how about that beautiful outflow pattern one sees with major hurricanes? Still nada? Hmm. How odd, I don't see any of those things either. I would normally rant a bit here, but too much to cover, so I'll just say I can't believe the NHC thought this storm went from 125mph winds (cat 3) to 130mph winds (cat 4)! This barely had a murky eye! They have been a bit off on the intensity of this storm all along, but this really took the biscuit!

Gonzalo is currently at 25N, 68.7W, heading N at 9mph. He slowed down as expected and I do agree with the NHC in their track forecast for the next couple of days:

Bermuda is going to get some dark and stormy weather alright, alas. He is heading north but is due to be swept to the NNE and then northeast by a front (the same one that caused some topsy turvey weather in the US a few days ago). You can see Gonzalo relative to the front in this IR satellite image of the Atlantic:

If you squint (or have a few drinkies), the front looks like a cricket bat about to hit the ball (storm).

His winds are now 125mph, central pressure of 953mb, which makes him a strong cat 3 storm (cat 3 range: 111-130mph). Finally, I think the NHC updates are coming more into alignment with what he actually is. They did (obviously) back down from yesterday's forecast which called for 140mph winds today! The forecast says he will remain as a cat 3 for a few days and then decrease in intensity.

I think that he now looks like a proper cat 3 storm for the first time in his little history:
There is a strong, clear eye, and the convection is also stronger (more red with a hint of grey), although not really strong enough to be a cat 4! He also doesn't quite have the classic outflow, but we do see a fairly good and clear vorticity signal in the upper troposphere at last:

The reason why I think he has intensified (from what was obviously not a cat 3 to a cat 3) is that the wind shear has decreased, and looks like it will continue to decrease, and he is going over a patch of very toasty sea surface temperatures (29-31 deg C). He should start moving away from such very warm temperatures tomorrow, but the water will still be warm enough to sustain him. The upper 50-75m of the water column are currently warmer than 26 deg C, but by the time he reaches 30N (still south of Bermuda) that should be limited to the upper 25-50m and we should start to see some weakening (still a storm though).

In short... I hope you are ready Bermuda. Even if he does decrease in intensity, I know it is really tough having a second hit in a week! I'll be watching tomorrow and may tweet updates.

Good luck and 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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Wednesday, October 15, 2014

Hurricane Gonzalo: October 14, Update A

Very little time for sloth and idleness these days!

Mr. Gonzalo is looking healthy these days, isn't he? He is officially a strong cat 3 storm with winds of 125mph, central pressure 954mb. He is heading NW at 13mph and is centered at 22.2N, 66.6W (hmm, interesting... 666... generally not considered the most happy-go-lucky number but I guess he's ready for Halloween).
He is definitely stronger than a cat 1 storm as the eye is pretty consistently there! But he's not the best looking storm I've seen, and he is a little ragged for a cat 3 storm. At the most, I'd give him a cat 2 status.

Why? Well I'm so glad you asked...

1. The convection is rather weak for a cat 3 storm. The infrared satellite image shows none of those gray areas that show us that the clouds are really high and there is a lot of very deep convection,

2. There is very good vorticity (circulation) in the lower half of the troposphere, but the vorticity (circulation) structure is just not there at the highest level of the troposphere:
In the <Science Alert!> reminder link I had yesterday, you can see what the upper (200mb) of the troposphere vorticity should look like for a strong hurricane - it should be a stand-alone round(ish) 'splodge' (technical term ;-)), not an area of higher vorticity that stretches across a large area - those are troughs!

3. There is wind shear, which is clearly impacting this storm as the cloud pattern is not circular. You can see in the satellite image that they stretch off to the northeast.

4.There is remarkably little upper level divergence and relatively little lower level convergence. Oooh... what the heck is she talking about now, I hear you say. Time for a New <Science Alert!> (how exciting!) A tropical storm has low pressure in the center, near the surface. That's why we all keep mentioning the central pressure - the lower it is, the stronger the winds (usually). A low pressure is an area that the air is 'pulled' towards. By extending that image to a circular storm, you can imagine the winds are pulled in from all around - i.e., they converge. So we have Low Level Convergence. Now the problem is that if you keep pulling winds in at the low levels, they have to go somewhere. It might come as a surprise to you, but they don't just gather around the center and have a game of poker. ;-) The ground (or sea) is underneath, so the only way the air can go is up. And when the air reaches the top of the storm the only way the winds can flow is out and away from the center. So at the top we have Upper Level Divergence. The stronger the convergence/divergence of a storm, the better the formed it is. Ta-da. <End Science Alert!> Phew. Time for a little lip-wine-convergence now I think.

I could go on with my list,
but you get the gist.
 (Poetry at last! A rival for William McGonagall? ;-))

The official forecast says that Gonzalo will become a cat 4 storm with winds of 140mph within 12 hours. Officially it might, but I expect there to be actual evidence of this in 3 out of 4 of the above in that case! In reality, it seems unlikely to get quite that strong at the moment. Although sea surface temperatures are 28-29 deg C, Gonzalo is moving to an area where waters warmer than 26 deg C can be found in the upper 50-75m compared to the current 75-100m. Wind shear looks like it will continue for a bit too (at least into tomorrow).

Popping back to St. Thomas for a moment. Tom (on the ground there) said that although the NHC said the storm would be strong,"there was not a puff of wind all of last night" and so they "Slept well with no wind or rain pounding on roof".

Looking ahead, it does look like Gonzalo has shifted a bit to the west and may not be a direct hit on Bermuda now. It also looks like he may shift a bit more to the west than the current trajectory shows and he will slow down a bit (which is already shown to some extent in the track for tomorrow).
Unfortunately for you Bermudians, this means you will be hanging out on the wrong side of the tracks (insert 'as usual' jokes here)! As you can see, most of the convective activity is on the east side so get ready! I'm probably right (as I generally like to use The Force), but I'm going to give the NHC the benefit of advanced technology and say that this may be a stronger disturbance than nature is indicating. Best listen to the local folks as you make your preparations.

Speaking of local people to listen to, Steve B., from Bermuda, certainly hasn't been asleep at the wheel (fortunately for everyone on that island) and is obviously already preparing as he says in a note I got earlier today: "We could be in for a sticky weekend. I doubt if much cricket will be played! I had better fortify myself!". Words of wisdom. Spot on! :-)

That's it for this evening. More from me and Mr. Gonzalo (and anyone from Bermuda who wants to pipe up) tomorrow,
Night 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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Tuesday, October 14, 2014

Hurricane Gonzalo: October 13, Update A

So I woke up this morning and was a little miffed to see that this system was still considered to officially be a weak Tropical Storm with winds of 45mph:
Luckily for us (and the people that were already under/in the path of this storm!), hurricane hunter planes have been in the system all day and returned data to say that the storm was stronger than the official word/forecast. What would we do without them?! The NHC have been steadily increasing the intensity to hurricane strength over the past day and it now has winds of 85mph, central pressure of 984mb.

I'm not surprised with this increase in intensity. He already looked a little stronger than 45mph when I wrote last, and as I said then, the only thing that would keep Gonzalo from getting out of order would be his interactions with the islands - everything else was in favour (with a 'u' ;-)) of a little more intensification. Throughout the day I had a look at the vorticity maps (ok, I know it's been months since you read about these - not my fault it's been a gloriously quiet season :-) - see here for the <Science Alert!> on Vorticity Maps: http://jyotikastorms.blogspot.com/2014/08/hurricane-bertha-august-4-update-a.html). He has really good circulation in the lower half of the troposphere, and some circulation in the upper troposphere - enough to be a cat 1 hurricane, but no more. It looks like he is heading into an area of stronger wind shear, so even though the water temperatures are warm, I would not expect him to get much stronger than a cat 1 storm.

He is currently centered at 18.7N, 63.4W, heading NW at a regal 12mph. He passed just north of St. Maarten and his eye went directly over the island of Anguilla. He has quite a lot of convection - rain and thundery weather:

I heard from my great on-the-ground reporter, Tom on St. Thomas throughout the day (thank you for the updates Tom!!), who said they needed the rain and started the day expecting the storm to pass directly over them. It passed to their east, however they did lose power for a few hours. It's back (last I heard... and he needed a well earned drink! ;-)).

Once Gonzalo clears the islands, it looks like it's heading for Bermuda, which obviously needs another storm a week after a direct hit from the last one!
I have a pretty strong sneaky suspicion (ooh, alliteration!) that this track will shift to the west. But of course, Bermuda better get ready and stock up on the barrels of rum just in case.
 
Now a quick word about Fay... she fizzled out over the Atlantic. Done. Counting fishes would tire anyone!
 
That's all for today folks.
Night night!
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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Sunday, October 12, 2014

Hurricane Fay and Tropical Storm Gonzalo: October 12, Update A

A travel day today (sitting in San Francisco Airport as I write this) so I'll jump right into the thick of things... and I have to say, there are a few thick things about! We have a veritable smorgasbord of storms today as in the last ~24 hours three, yes three, storms made landfall (and one overachieving storm decided to make landfall twice)!

In the western Pacific, Typhoon Vongfong made landfall in Okinawa as a cat 3 and then moved on to make landfall on the island of Kyushu in southern Japan as a weak cat 3. Last week this storm was out there in the Pacific as a cat 5 storm with winds of 160mph. It has caused quite a bit of havoc as it's moved along.

In the Indian Ocean, Cyclone Hudhud made landfall in eastern India as a strong cat 3 storm. About 400,000 people were evacuated ahead of this storm in an effort to save loss of life.

Meanwhile, in the Atlantic, Tropical Storm Fay passed directly over Bermuda. She was still a strong Tropical Storm at the time, not a Hurricane, but they got quite a lot of strong thundery weather. She has since moved away and it looks like Bermuda may have re-opened for business.
 
I agree with the NHC on their analysis of this one in that she will not be a hurricane for long (currently she is a weak hurricane with winds of 75mph, central pressure 986mb). She is heading into the Atlantic to hang out with the cute fishies for a while:

That leaves one of the Atlantic Blobs from yesterday, which is now the very weak Tropical Storm Gonzalo with official winds of 45mph, central pressure 1002mb. He is centered at 16.4N, 59.7W and is heading west at 10mph. He does have some circulation, which you can see in the visible satellite image:

But the convective action is not yet fully developed as we see in the infrared satellite images:
However, this one will definitely develop. I think he may be a little stronger than 45mph at the moment, but not by much. Wind shear is pretty weak and looks like it will remain weak. The sea surface temperatures are currently between 28-30 deg C, and it looks like they will increase to 29-31 deg C closer to the Leeward Islands. Water warmer than 26 deg C can be found in the upper 100-125m of water, which means he has lots of stuff (technical term ;-)) to fuel him.

His current forecast trajectory takes him through the northeast corner of the Caribbean as a Tropical Storm on Monday and Tuesday.
The only reason he won't intensify too quickly is because he is going to be interacting with the islands soon. He should bring some rain - you guys want rain, right?

I've gotta run and catch my flight (it's a long walk from SF to LA!), but more tomorrow!
Tally ho!
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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Saturday, October 11, 2014

Tropical Storm Fay and the Atlantic Blobs: October 11, Update A

Oh tropical storms, how I have missed you! ;-) I know, I know, I've been incommunicado for a month and missed the last two storms but I was rather super busy (I'll tell you what shenanigans I was up to later) and luckily they weren't too much of a bother. Actually, you may have missed Dolly yourself as she was a named storm for about 3 seconds on Sept 2, reaching max. wind speeds of 50mph (a nice breeze). I'm not sure she should have been named. TS Edouard was named on Sept. 11, and although he was a proper storm (reaching hurricane strength with official max winds of  115mph on Sept. 16th, making him the first major hurricane of the season), he remained a gentleman and stayed in the Atlantic.

And now we have Fay and the Atlantic Blobs (please note: this is not a band from the 50s! ;-)).

Currently Tropical Storm Fay has winds of 70mph, central pressure of 990mb, and is therefore a very strong Tropical Storm (TS range: 39-73mph). She is definitely a storm and this intensity seems reasonable given how much circulation and convection she has:



The bulk of the convection (which includes some severe thunderstorms because the infrared satellite image is red) is on the western side of the center which indicates that she is experiencing a lot of wind shear. The sea surface water temperatures are 27 deg C, so warm enough to keep her going.
That little pink 'dash' close to 32N, 65W is the lovely Bermuda. Although Fay is officially centered at 25.9N, 65.4W, heading N at 18mph, from the visible satellite image it looks like the center may be a bit west of that location, at 25.9N, 65.9W. The forecast track has her curving to the NE and passing just south of Bermuda, which is why the location of the center is important...

If the center is west of the current location, there is a small chance that the center will pass to the west of Bermuda, which would be better for Bermuda because most of those thunderstorms will also pass to the west. If the center does stay in that current cone of uncertainty or if the center actually goes over Bermuda (quite possible), then the weather will be a bit crummy for Bermuda tonight and over the next day or so. Hopefully everyone has dusted the cobwebs out of their wellies and canceled the golf games!

There are a couple of Atlantic blobs out there as well:
Both are still in the 'Whoa, where are we?' stage of development. I'll talk about them tomorrow methinks. For today, it's all about Bermuda and, obviously, that means it is time for a Dark & Stormy! :-)

Before I pop off and partake of above mentioned beverage, the reason why I wasn't around in September was because I was at the Monterey Bay Aquarium Research Institute, testing competition Entries for the $2 million Wendy Schmidt Ocean Health XPRIZE! (oceanhealth.xprize.org). We have 18 Entries from 6 countries competing for this prize and the goal is to develop accurate, robust and affordable pH sensors to help detect and understand ocean acidification. I have to say I've learned that there's never a dull moment being part of a competition! :-)

Until tomorrow,
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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