Wednesday, September 23, 2015

Tropical Storm Ida: September 22, Update A

Time for a quick update. 

Tropical Storm Ida is at 20.9N, 46.8W, and is drifting ESE at a whopping 2mph! (i.e. she's stationary). She's been hovering over the same place for a few hours and is actually showing signs of weakening now, and you can see that the circulation (vorticity) in the middle troposphere is no longer a well formed as it was yesterday:
No circular red blob anymore at the 500mb level. 

There are a couple of reasons for this but the primary one is that there is actually quite strong wind shear today, with the shear being around 20-40 knots from the northwest. Her official wind speed is currently 40mph (central pressure 1005mb). So, with such strong wind shear we would expect the convection to be 'pushed off' to one side of the center, and sure enough, it is trailing spectacularly off to the east: 

If you are paying attention (like Mitch R.), you may have noticed a swirly-gig to the west of Ida, between Puerto Rico and Bermuda. This was ordered especially for Steve B. who is sailing this week from PR to Bermuda. ;-) (sorry Steve!). It is even more spectacular in the water vapor satellite imagery:

Although this blob has some circulation, it is not very well organized as you can see from the 500mb vorticity map above and more importantly, there is absolutely no circulation in the lower troposphere:
So I wouldn't worry too much about this one. 

Alas, that's all I have time for today. I'll try and get back tomorrow, but if not, then the following day!

Toodle pip,

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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.


John Sexton said...

Any comments on the convoluted mess leaving Africa now? It looked at first like it had good form but the last two frames of the Meteosat set shows it losing control of itself...

Jyo said...

Hello John, the blob leaving Africa doesn't have any real low-level circulation and very little convection. It doesn't look promising for development at the moment.

John Sexton said...

Thanks! And now,could you please ask Ida to NOT turn my way?