Tuesday, October 25, 2011

Hurricane Rina: October 25, Update A

Hurricane Rina is turning out to be a bit too awkward for a not-quite-end-of-the-season pip squeak little storm! She’s moving soo sloowlllyyy and while she dilly dallys in the Caribbean the pressure fields around her continue to change, which makes track forecasting a bit tricky.

Officially she is at 17.5N, 84.8W, moving W at 3mph. Winds are now 110mph, making her a very strong cat 2/almost cat 3 (cat 2 range: 96-110mph). Central pressure is 966mb.

Track: Her track was shifted a little to the right this morning, but is beginning to shift back to the left now. Although the forecast track (below) still has her curving to the northeast after the Yucatan, today I think it will continue to shift to the left and may actually be over the Yucatan more than expected.

The reason is because the high pressure that I mentioned yesterday (that is causing her to move slowly) has expanded and is now a high pressure ridge stretching from central Mexico, across the Gulf and southern Florida and into Cuba. This means that she can’t move northwards, so she’ll keep moving very slowly to the west until there is a break in this high pressure. The NHC forecast is for this high to move to the east, so she will continue more-or-less on their forecast track. They have been rather good at their tracks in the past few storms and I don’t have any reason to doubt this at the moment. The problem is what will happen once she reaches the Yucatan. Until that high pressure shifts and she starts to move at a respectable hurricane-pace, it’s a little difficult to predict the track.  So tomorrow we should watch her to see if she picks up forward speed because that would show that the high pressure is shifting to the east.

Intensity: Although she is officially a strong cat 2 storm, I think she might be a tad bit weaker at the moment. There is no eye, which I would expect with a storm that strong. Also, the convection is not as strong as it could be, and the upper level divergence (remember that?... if not, let me know and I’ll send out a reminder J) is fairly weak. The water is still warm, with the upper ~150m warmer than 26 deg C and there is also very little wind shear. I think she is not a cat 3 already because she is interacting with land (well, her outer bands are). I think I’d place her as a strong cat 1/weak cat 2 storm.

Hmm… I was expecting more clarity this evening (although after a glass or two of wine, what can you expect? ;-)). As I said yesterday, everyone should keep an eye on this one for now. I’ll be back tomorrow of course. We should know by then what she’s up to because the forecast has her speeding up and approaching the Yucatan tomorrow evening.

It be late here now. Night night and 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.

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