Sometime today Hurricane Dean may well be officially pronounced a Category 5 storm.
Stop and think about that for a second. As had long been predicted, once Dean got into the warm Caribbean, the storm--which is, in essence, a heat engine--had an overabundance of fuel available to it in the form of warm water. And so last night Dean exploded in intensity. It is currently a very strong Category 4 storm with winds of 150 miles per hour and a minimum pressure, just sampled by aircraft, of 930 millibars (27.46 inches of mecury).
With Dean racking up numbers like these, it's truly sobering to contemplate that the storm has not yet even reached the parts of the Caribbean where the deepest warm water lies. In order to get there, it looks like Dean will first have to plow directly over the island of Jamaica. As you can see below, this island is literally surrounded by deep warm water. An absolutely devastating head-on Category 5 landfall is a serious possibility here; in fact, it's what's officially forecast.
In contemplating paths that Hurricane Dean might follow, impacts it might have, and intensities that it might achieve, it's instructive to consider some possible historical parallels. A few days back Hurricane guru Jeff Masters of Weather Underground threw out two of them: Hurricane Ivan of 2004 and Hurricane Gilbert of 1988. Both of these past storms were terrifying, albeit in different ways. Ivan spent more time at Category 4 intensity or higher than any other Atlantic hurricane, and looked for a while as if it might strike New Orleans. Gilbert, meanwhile, was the most intense hurricane ever measured in the Atlantic basin until 2005, when its record minimum pressure of 888 millibars was shattered by Hurricane Wilma's 882. (In my book Storm World I relate how hurricane scientist Chris Landsea of the National Hurricane Center took his very first storm flight into Gilbert at its peak--pretty much the most intense experience you can hope for as a student of hurricanes.)
Lately, the forecast track for Dean has been looking a lot more like that of Gilbert than that of Ivan--which is a good thing for the United States and a bad thing for Mexico. Here's the Dean forecast: Gilbert directly hit Jamaica, killing 45 people; then almost directly hit the Cayman Islands; and then struck the northeastern Yucatan at Category 5 strength. The storm achieved its most extreme intensity in the Western Caribbean, which is an area Dean is also forecast to travel over (and where the hurricane heat potential is highest). After smacking the Yucatan--destroying 60,000 homes--Gilbert then went on to a final landfall south of the Texas-Mexico border.
While Dean's future is currently forecast to be very similar, much could still change. The further out you go with these types of forecasts, the more uncertainty there is, and if Dean takes a northward turn in the Gulf of Mexico or earlier, a U.S. landfall becomes a serious possibility. It would be cruel indeed if, as the August 29 anniversary of Hurricane Katrina approaches, we have another massive hurricane threat to the United States Gulf Coast. And even if we don't, Hurricane Dean is going to cause a lot of pain in the Caribbean and elsewhere.
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