Monday, October 11, 2010

Tropical Storm Paula: October 11, Update A

I was waiting for the Caribbean Blobette to be upgraded to Tropical Storm Paula ... and here she is. Yay! 16th named storm of the season.
I think this has been a Tropical Depression for a day or two, so going to a named Tropical Storm is not a big surprise because she didn't stay over land. It looks like the center just clipped the Nicaragua/Honduras corner earlier today (convection decreased, as did vorticity) and is back over water with low wind shear, so the convection is improving again. The vorticity isn't very strong at the moment, mostly in the lowest part of the troposphere. It is not as elongated as it was yesterday and looks like a TS. As it gets just north of Honduras I expect convection to improve because it is over warm water (temps >29 deg C) and deep warm water (warmer than 26.5 deg C in the upper 100m).
The upper level divergence and lower level convergence have also improved. Oooh... what the heck is she talking about now, I hear you say. <(New) SCIENCE ALERT!!! (how thrilling!! :-) )> Here's a rare attempt in these updates at a simple explanation of convergence and divergence! 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 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 of (new) SCIENCE ALERT> Phew. Time for some wine-convergence now I think.
A plane was sent into the system earlier today and found evidence that this was close to being a Tropical Storm. And there were other data and stuff (obvious technical jargon) that showed this too. She's heading towards the Belize/Yucatan area... moving NW at 10mph. Current center I'm estimating is around 16N, 84W, so she's *just* north of Honduras. Convection is strong near the center and Honduras (and bits of Nicaragua) are getting a few bucket-fulls of rain and some thundery weather. Oh, NHC just posted the official info. They agree with my center (good good). Winds are 60mph, making her a mid-size TS (range: 39-73mph). Central pressure is 1000mb. Track looks a little interesting... it doesn't quite make it to the Yucatan coast, but hangs out in the Caribbean as a hurricane. Oh dear. If that really is the track then we might have a big hurricane in a few days... that's the warmest (deepest warm) part of the waters out there. We'll see. I'll have a look tomorrow. For now...
...I got things to do. Wine to drink. Forms to fill in. Oh... and don't forget, I am giving a live twitter interview on Weds. afternoon! My first ever. For my fellow Twits (hahaha... I'll always get a chuckle out of that one), details have been posted on the internet: "To see the full interview you will need to follow (@metoffice) and (@metofficestorms)". Or use the hashtag #metqt. I'll also tweet the hashtag etc info @JyovianStorm. It's a Brave New World!!
More tomorrow!
p.s.... in case you didn't know... I work at the MetOffice over here. But this blog are my own views entirely, as I started this little hobby before joining them. And also, in case you didn't know... I'm moving back to the US. In just about 2 weeks - in time for Halloween... how scary for you! ;-)   
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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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