Sunday, September 05, 2021

Hurricane Larry: 4 September, Update A

Normally this time of year I would be on Planet DragonCon. Alas, not this year but hopefully next! In the meantime, I've got a yummy lychee martini in hand and wondering... 

Well Captain, he is at 18N, 48W, heading WNW at 14mph and is still on track to be passing by the general Bermuda area on Thursday(ish). Although the island is still in the Cone of Uncertainty, it looks like the storm will pass to the east. He should be moving in a more NW direction tomorrow (looks like he may already be moving in that NW direction actually).  

Now for his intensity... he is currently still a cat 3 storm with winds of 120mph, central pressure of 958mb. This makes him a strong cat 3 storm as the range for this category is 111-129mph. His eye has grown to around 40 miles diameter (quite a big eye), but it isn't very robust - it's a bit wobbly really (technical term ;-)). His vorticity continues to be strong at all levels of the troposphere though, so overall, I agree with his cat 3 status. 

He was actually stronger earlier today with winds of 125mph (close to being a cat 4 storm), but it looks like that wind shear is having a little impact, along with some dry air, because the southwestern side is a little cropped and there are a few clouds (very few at the moment) streaming to his northeast: 

Although he is about to move over warmer ocean waters (from 27 deg C to 28 deg C), we will see if he gets any stronger. There are a couple of things in play that may stop him from getting stronger and becoming a cat 4 storm. 

First, there is still some dry air to his west and north (darker purple in the imagery below):

Second, it looks like the wind shear is quite a bit stronger ahead of him... 

<Forecasting Alert!> Wind Shear - where can you find out about wind shear? I go to the University of Wisconsin CMISS page, which is the excellent website that I've mentioned a few times this year - it has the Saharan Air Layer map and the vorticity maps. Here is the 'slightly' complicated map/data I look at (it's crystal clear after a couple of lychee martinis  ;-))...   

To help you get your bearings, first find Larry. You should be able to easily find him if you can spot his eye.  Second, the land is outlined in white. Found Florida? And the Caribbean? Got your bearings? Now, see the pink lines all over the place - those are the winds. The closer they are to each other, the stronger the wind shear. If you look to the northwest of Larry (in his future track), you can already see a faint grey stream of clouds that are being carried away because of the wind shear. The pink lines are the most important bits in this map. Hopefully it will persist tomorrow. The other colourful lines are contours showing wind shear and how favourable those areas are for storms. Red is not a good colour for storms. 

Go to if you want to look for yourself (and I'm sure you all do!! :-)). Click on the colour block in the lower map (Regional Real-Time Products) for the part of the world you are interested in (North Atlantic in this case), and in the drop-down menu you will see 'Winds & Analysis'. Click on that, and then click on 'Wind Shear' in the block of buttons at the top, and you will see the map above. Now you can check out wind shear for yourselves any time you like. :-) <End Forecasting Alert!>

Time for a refill... ;-) 
Toodle pip,

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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 local 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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