Sunday, September 19, 2010

Hurricane Igor, Tropical Storm Julia, and the Atlantic Blobette: September 19, Update A

Today is a good day. I didn't meet any wild creatures and things are looking relatively good for Bermuda. Well, much better than they were a couple of days ago anyway.
Hurricane Igor:
Igor's convection has decreased A LOT and he's now a mid-level cat 1 storm with winds of 85mph (cat 1 range: 74-95 mph) and a central pressure of 952mb. He's at 30.8 N, 65.7W and is moving N at 16mph. His center will pass just west of Bermuda, which means that you guys will get a batch of really strong winds and thunderstorms, but after that it'll die down rapidly because he's not really got much convective activity on his southern side - it's just cloudy and windy. Not even much rain. I'm guessing another 7-10 hours and the main part of him will have passed by. He's still got high vorticity (circulation) in the lowest half of the troposphere, but it is slowly decreasing in the upper levels. Sea surface temperatures are 26-27 deg C.The lack of convection to the south is from a combination of wind shear from the south and also dry air and the farther north he gets, the more wind shear he's going to experience and of course, the colder the water gets.  
From Steve B. (on Bermuda):   
at 2.10pm (local time): " just went for walk in rain. very wet and a little windy. warm, so good walking conditions."
at 6.10pm (local time): " i am tired of this storm. it's windy"
I think he might be a bit bored. He's reading about heat transfer. And we are discussing whether latent heat processes belong in the field of chemistry or physics. I think we've got as far as agreeing that 'the Sun is important'. It's all very profound and philosophical stuff. ;-)  
The NHC have Igor as a cat 1 hurricane until Wednesday morning, when it reaches the northern North Atlantic where water temperatures are less than 24 deg C - far too cold to sustain a storm. I think that might be keeping him at that level too long and it should deteriorate before then. They might keep him at that level because they do things like that but he won't be a tropical storm, he'll be an extra-tropical storm (or post-tropical or whatever the new lingo is this year). 
Tropical Storm Julia:
She's still a mid-to-weak Tropical Storm with winds of 50mph and an estimated central pressure of 998mb. She's zipping off in an East-Northeast direction at 15mph and is currently centered at 34.2N, 50.3W. There is still some convection - and although it's not as wide-spread as Igor's, it is actually stronger. The vorticity has decreased a lot in this system and is now only strong in the lowest half of the troposphere. She's still undergoing wind shear from Igor as well.  She's forecast to dissipate by Tuesday morning. It all seems quite reasonable to me.
Atlantic Blobette:
I mention it now because it's certainly improved in structure today and circulation looks good in the lowest half of the troposphere. It looks like a Tropical Depression to me, even though the NHC still have it marked at the 80% level of storm formation. Convection is also slowly improving. I think the center is somewhere around 15.5-16N, 31W, and it's moving generally northwestward at 5mph. They anticipate upgrading it to a Tropical Depression tonight or tomorrow. I'll look at pressure fields etc when it's a TD.
So for my Bermudian friends, the worst weather is almost there but after that it should get better quickly. (And hello to the new Bermudian readers - Helene M. told me there are more people on the island reading this than I previously suspected! I hope you were sufficiently warned about my <ahem> intellectual and <ahem> literary writing! ;-) )
Be safe!
More tomorrow.  

p.s. I did manage to post a picture on the blog site! It IS a new era. Let's see... I think I shall call it 'The dawning of the Age of Aquarius' (because I am one). Surely no-one has thought of that before, have they?

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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 the National Weather Service announcements. This is not an official forecast. If I was there and was going to "run away, run away" (Monty Python), I'll let you know.

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