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October 2011

Rina weakens significantly, but still a hurricane hit coming for Cancun

   Posted by Levi at 8:46am on October 26, 2011

I woke up to a very different Rina than I went to bed with last night. Recon data from a new plane shows that the pressure has risen to 984mb, and Rina’s winds have backed off to Cat 1 strength, indicating that she has weakened considerably, and her eyewall has collapsed almost entirely. There are only really two possible explanations for this. One is dry air entrainment, and the other is cold water upwelling underneath the slow-moving storm. I am dismissing the former in favor of the latter. TPW products and microwave imagery don’t indicate that dry air penetrated Rina’s core, and she was embedded in a pretty moist environment last night with beautiful outflow aloft. Her problems seem to have been caused from the inside, and she has likely depleted the water beneath her of energy.

The big question on everyone’s minds is likely why we didn’t see this coming. The answer is that we knew it was a possibility with a slow-moving storm, but my idea was that it would not be a significant problem for Rina, based on a comparison with Wilma. Wilma was moving just about as slow as Rina at her peak, and through the same area of the Caribbean over similar ocean heat content. However, despite being the strongest hurricane on record, Wilma did not suffer from this upwelling problem. Logic seemed to dictate that Rina, being weaker and moving at a similar speed, would not suffer from it either. My guess is that I was wrong about that.

The northeastern Yucatan is getting off extremely fortunate now, as Rina will not be a major hurricane brushing through the Cancun area. However, she is not falling apart completely, and is beginning to move faster over warmer waters again. She will likely still be a hurricane delivering a hit to the region, perhaps even restrengthening slightly, but not nearly as strong as she would have been. Folks should still be prepared for a bad storm in the Cancun area.

This also changes the end-game track for Cuba and Florida. In some ways it seems like some of the global models saw this coming, though it’s hard to tell since Rina was not being resolved properly on some of the models. As a weaker Rina approaches the Gulf of Mexico, she will be more susceptible to dry air and wind shear, and should weaken quickly to a tropical storm. The resulting intensity and track should be fairly similar to Hurricane Paula from last year. The forecast from yesterday was based on Rina being a cross between Paula and Wilma, but with the recent weakenig, it will be much closer to a Paula-type situation. Rina may not make it to south Florida if she is very weak coming away from the Yucatan, and may actually follow yesterday’s NHC track closely. Had she been as strong as she was forecasted to be coming into Cancun, she likely would have tracked farther north. A weaker system, however, will be more likely to be pushed on by the front over the north gulf coast in 3-4 days, and get somewhat trapped near Cuba and the Florida Straights. While some weather may still affect Florida, it likely won’t be more than a blustery weekend, not quite as blustery as it would have been.

We shall see what happens!

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