Friday, August 18, 2017

Ex-Hurricane Gert, Tropical Storm Harvey, the Atlantic Blobette, and the Atlantic Stormling: August 17, Update A

I’m going to start by saying that Jaffa Cakes are yummy. Although there is a serious philosophical discussion on whether they are cakes or biscuits, it doesn’t really matter… they are pretty scrumptious. Just thought I’d make sure my friends on the Gin and Cake podcast (@ginandcakepod) knew my position on Jaffa Cakes! ;-)

And to continue with things I mentioned yesterday… as we saw Gert was winding down and she has now pretty much gone bye-bye. She was last seen somewhere north of 45N, 45W drifting off to the northeast, so this is my last update on well-behaved Gert.

Tropical Storm Harvey
As expected, the Atlantic Blob that we saw yesterday that was heading out of the dry area of the SAL and over an area of warmer ocean waters did slowly develop into a Tropical Storm. Harvey is currently at 13N, 58.1W, heading W at 17mph and is approaching the Leeward Islands:

His central pressure is 1005mb, and the winds are an estimated 40mph so he is barely a Tropical Storm (range: 39-73mph). I would agree with this because the circulation has improved today, as we can see from the vorticity maps. Here are the maps at 850mb (lowest level of the troposphere):

and 500mb (middle of the troposphere):

There is no signal at the highest level of the troposphere (200mb), so we know he is definitely not a hurricane. Interestingly, you can see the offset between the lowest level and mid-level maps in the center of that circulation, which is an indication of wind shear. Because of this, and because he is about to interact with the Leeward Islands (which are a little hilly!), he won’t really develop much very quickly in the next day or so. But he is over warm water, so once he clears the islands, I expect some slow development.

From the NHC track, it looks like he will stay to the south and move across the Caribbean.

Atlantic Blobette
This one is at around 15.5N, 48W, heading WNW at 20mph. She hasn’t really managed to gain too much traction, although from the vorticity maps we see that she has some circulation over the entire lower half of the troposphere. She is struggling a little because of the convection, which is quite weak at the moment because she is in a region of dry and dusty air.

She is about to move over an area of slightly warmer water which will help her to develop some of that convection, but the wind shear will also increase in a couple of days, so it really is a battle between the ocean and atmosphere in this case! Given that she has some circulation, I think the ocean may win out in the short term (a day), and then the atmosphere will take over with the wind shear and dry and dusty air and inhibit her from developing too much more beyond that.

Atlantic Stormling
And then there’s that poor little Stormling, currently at around 13N, 30W moving generally north-westward at around 20mph. The circulation is very weak and it is quite entangled in the Saharan Air Layer:

I don’t expect anything much to happen in the next few days – not until it clears some of that SAL at the very least. I think I’ll hold off on any more on this one until something happens.

And finally, I have to say that the world is definitely on the wobbly side of wonky these days! My condolences to Spain!  

That’s it from me for now. Over and out 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.   


Thursday, August 17, 2017

Hurricane Gert, the Atlantic Blob, the Atlantic Blobette, and the Stormling: August 16, Update A

I’ve had a glass of wine, a cup of tea, a slice of cake…hmm... is it time for a spot of ice cream to round off the evening? ;-) Speaking of cups of tea, we have a lot brewing out there today. It’s a veritable smorgasbord of stormy delights: a Hurricane, a Blob, a BlobetteTM, and a StormlingTM!! Mother Nature is having a jolly good time! 



Hurricane Gert
She is currently at 40.1N, 58.4W heading ENE at a whopping 37mph. She is officially a cat 2 storm with winds of 105mph (cat 2 range: 96-110mph), minimum pressure of 967mb.

I would say she was definitely a hurricane of around 90-100mph earlier today because she had a well-formed eye, as we can see in this Infra-red satellite image:


But it looks like it dissipated about 2 hours ago (at least), so I would actually classify her as a cat 1 storm with winds of around 85-90mph now.

She has been moving over an area of relatively warm water, even though she is out of the tropics. This is because she is over the Gulf Stream, which is a very strong warm ocean current that moves along the eastern seaboard to Cape Hatteras before it leaves the US coastline and heads across the Atlantic, carrying warm water from the tropics to the northern latitudes (and the UK – land of cups of tea and jaffa cakes). The upper ~70m of the Gulf Stream in this area is warmer than 26 deg C, so she has definitely had something to eat along the way!

The physical structure of Gert has remained robust, as we can see from the vorticity (circulation) maps. Here are the maps at 850mb (lowest level of the troposphere):

500mb (middle troposphere):

And 200mb (upper troposphere):

Again, this indicates that she is a hurricane. But I think she is on a downward spiral (pun proudly intended as every pun is its own reword ;-)) now as she is going to move away from that warm water and is moving into an area of stronger wind shear (which we can see from her satellite image, which shows some of her clouds being whisked away to the northeast).

Atlantic Blob and Blobette
These two are so close to each other that I might as well group them together! One (91L, if you follow those numbers and things) is at around 13.5N, 53W, heading westward at around 15-20 mph, and the other (92L) is at around 14.5N, 40.5W, moving WNW at 15-20mph.

From the vorticity (circulation) maps, we see that although there are two very nice red splodges (highly technical term for ‘red splodge’) in the lowest level of the troposphere in those regions, a little higher up, in the mid-troposphere, the one at around 53W (to the left) isn’t looking as good at the moment as the one around 40W (to the right), which suggests the storm structure is better for the second Blob.

From the satellite images, we see that there really isn’t much convection associated with either of them at the moment:

Although the left one (weaker structure) has more convection than the right one. But there are good reasons for the convection looking like this.

First, this Blob and Blobette are skirting the edge of the Saharan Air Layer (remember that from earlier this season?) which means there is not much room for the atmosphere to be moist enough to help a storm:

Second, the reason why the one on the left, although with a weaker structure, has more convection is because it is approaching an area of warmer water. As it moves further west, two things will happen: it will move away from the SAL and it will continue to move over warmer water. Also, there isn’t much wind shear around here, so I anticipate this storm to develop, although slowly.

The NHC track looks like this Blob will cross the Lesser Antilles and head into the Caribbean on Friday.

Meanwhile, the Blobette is a little more to the north and is heading WNW. That means she will remain closer to the SAL, so even though she has a better structure and the water is around 27 deg C (warm enough for it to be fed), it will be inhibited from developing too quickly – if at all really, because it looks like the wind shear will increase if she carries on in that direction.

The NHC thinks this Blobette will head north of the Leeward Islands – I think it’s a little too soon to say for sure on this one though.

Stormling
This little Stormling currently has a 0% chance of becoming a storm (in the next 2 days anyway) according to the NHC. I think they just threw it on there because they were bored. ;-)

This one just came off Africa and is somewhere in the vicinity of 12N, 25W, heading generally westward at around 15mph. From the vorticity maps you can see some activity in that area in the lower and middle troposphere, but it is definitely not well developed yet. There isn’t much convection with it yet either, but because of the vorticity, it is definitely one to keep an eye on.

That’s it for now! Gosh… so much for short posts for the rest of this year! Why do I even say these things? J

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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Wednesday, August 16, 2017

Hurricane Gert and the Atlantic Stormlings: August 15, Update A

Sorry my peeps! I was busy – work, travel, work, following current events and drinking wine, work, drinking wine, work, eating ice cream. You know, the usual things. J I think the rest of this year may be a season of relatively short updates, but we’ll see how things go.

In the meantime, Hurricane Gert is out there in the Atlantic and has been for a few days. She currently has winds of 85mph, central pressure of 979mb. She’s at 34.8N, 70.3W, heading NE at a good 15mph. She is a pretty good looking little storm:

It looks like she is weakening a little at the moment as the really strong convection (the red area in the satellite image above) is getting smaller. This may be a temporary cycle – slightly too soon to say at the moment. She is definitely a hurricane because there is a vorticity (circulation) signal throughout the troposphere – even at the 200mb level as you can see here:

And until that goes away, she will remain a hurricane.

She has been a reasonably well-behaved storm so far, doing her very best to avoid as many landmasses as possible. I guess she figured that there wasn’t any point hitting anything over the last few days as there isn’t much space in the news these days for natural storms when man-made storms are brewing fast and furious – here in the US at any rate.

I will try and be back tomorrow. I see there are three little StormlingsTM (ooh, I just created a new category ;-)... it's the technical term for the yellow ‘x’s’ that the NHC have on their map, which means a chance of a storm developing is less than 30%) out there:

I think two of these may actually be close to being Tropical Storms because the lower half of the troposphere has a good vorticity (circulation) signal, which you can see in this 500mb (middle troposphere) circulation map:

The only reason they aren’t quite there yet is because the convection in both cases is a little on the weak side of wobbly:

The next three named storms are: Harvey, Irma, and Jose.

Until tomorrow,
Ciao!
J.

p.s. It's the 70th Anniversary of the Partition... there are some amazing stories of what people went through then (including my Dad's, which I have read and hope to one day be able to share), so if you have a chance and find some, check them out! 

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, August 08, 2017

Tropical Storm Franklin: August 8, Update A

Today is Franklin’s Day. The Atlantic Blobette isn’t doing much, but Franklin has been to the buffet table quite a lot since yesterday, so he’s definitely the one to look at today.

Tropical Storm Franklin is currently at 19.1N, 87.3W, heading WNW at 14mph. His minimum pressure is 995mb with winds at 60mph, which makes him a mid-to-strong Tropical Storm (TS range: 39-73mph).

First, the track. The NHC were er… on track <grin> with their track forecast – again showing that they have that part sorted out to at least one day in advance. Hurray!! And there was much rejoicing. :-) That’s one big step for forecasting and one small step towards my retirement from this blog! Don’t worry, we have a couple more big steps to go before I can step back and hand things over to our benevolent robot overlords. ;-) 

The track from the NHC takes him over the Yucatan peninsula (he’s about to make landfall) and that seems right:

Second, the intensity. They currently have him as a mid-to-strong TS, but in my opinion he was a very weak hurricane - although as he interacts with land, he may be weakening already). You can see the signal of a well-formed storm in the vorticity maps (circulation). Here are the maps from the 850mb level (the lowest level of the troposphere), the 500mb level (mid-troposphere) – these you have seen in the past. But I have also added the 200mb level – the upper troposphere:



In addition to the fully formed Tropical Storm signal in the lower and mid troposphere (that deep red , even a little white, indicates a strong circulation), you can also see a signal in the 200mb level, which means his circulation extends from the bottom to the top of the troposphere – this means that his circulation extends from ground level to around 10-12 km above the surface of our planet! That is a lot of circulation in a storm, and something we see with hurricanes. The upper level is slightly off-set from the mid and lower level circulation, which indicates some light wind shear, but that is actually diminished from yesterday. 

If we look at the infrared satellite images, you can see that he is a pretty large storm in extent – with some of the outer bands extending over 1000 miles (you can estimate this because each degree in longitude is approximately 60-70 miles).  It does look like his convection is beginning to weaken as he moves away from the very hot sea surface waters and from interaction with land:

The NHC think he will remain a storm as he crosses the Yucatan and moves into the Bay of Campeche, even getting up to hurricane strength once he is there. A storm that takes a day to cross the Florida peninsula generally goes down by at least one and possibly to two categories, so I am not sure that he would still be a storm as he goes over the Yucatan, and if he is, he will be very very weak, which means the possibility of him regenerating into a hurricane is smaller. The thing to watch though is not his convection... it's his circulation (of course! you could have guessed that :-)). If he keeps his circulation pattern at 200mb, that means he has the physical structure to be a hurricane and all he needs is some yummy warm water to eat. That’s the key and the thing to look for as he crosses land.

I will try and post tomorrow, but the next two days look a little tricky (yes, I will be too busy eating ice cream, and cheese and wine … ;-))!

If you are in the Yucatan - stay safe!! 

I’ll be back when I can.
Ciao,
J.

(p.s. any chocolate martini fans out there? If there is no ice-cream on the dessert menu, I have found an alternate. :-))

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.