Dennis has amazingly continued to deepen at a steady rate through the day, now a category 4 hurricane as of 11pm. The system underwent an eyewall replacement cycle earlier today as evidenced by the high-density recon data and vortex reports this evening, highlighting an eye size of 9 mi. in diameter (circular in nature) replaced later by an elliptical eyewall of 16-30 mi. in diameter. Usually this would portend a halt to intensification or some weakening of the storm; however, with Dennis, the storm continued to get stronger (perhaps only slowing for about an hour during the cycle). Were it not for landfall along the Cuban coast at this time, the storm would likely continue to strengthen. Nevertheless, we are seeing something rather rare for this basin. The waters near and just south of Cuba are some of the warmest in the basin and are particularly deep, meaning they have a high hurricane heat content. With low shear and gradual organization, it's not a big surprise to have seen Dennis rapidly intensify today -- just perhaps not to this degree!
18z model guidance shifted back slightly to the west, probably as a response to some slight enhancement of the ridge over the Florida peninsula this afternoon. This likely is a direct result of the hurricane's outflow contributing to warming aloft in the vicinity of the ridge, resulting in it becoming stronger. However, this is likely only temporary, as 00z radiosonde observations over the central Plains suggest that the models are underforecasting the intensity of the shortwave trough passing towards the Gulf coast at this time. Assuming they capture this accurately in the 00z runs -- and assuming no big surprises in the upper-air data from the recon flights -- I imagine the model guidance might vascillate a bit back to the right at 00z (if not remain nearly the same). It's still an issue of timing, but with the storm less than 24hr from the Gulf, I feel confident that the shortwave will be at the right time and intensity to capture Dennis and result in a Florida landfall. That does not mean that those outside of Florida should let their guard down; the threat is still very real for an impact as far west as New Orleans.
Thanks must go to two friends here in Tallahassee for their help on the analysis.
Stay tuned for more updates as conditions warrant. Remember, the best way to be prepared for the storm is to stay informed and not to panic. Shopping for supplies myself this evening, I noticed a lot of others doing the exact same thing. Being prepared ahead of time -- whether at the start of the season or now -- is the single best thing you can do to help weather any possible threat of a storm. Blanket statements by the media, emergency managers, laypeople, and/or other entities should be taken with a grain of salt until the NHC says otherwise. Pay attention to the long-term track of the storm and do not focus on every little wobble; the time for focusing on wobbles is not yet here for us and has already passed for Cuba and Jamaica.
Next analysis on my end will come in the early afternoon tomorrow as I prepare for a forecast discussion mid-afternoon here at FSU. Updates as warranted, of course.
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