Just when you thought Hurricane Ernesto was about to do that rapid intensification thing that we all grew so accustomed to last year with Katrina, Rita, Wilma et al., the exact opposite happened. Rapid stengthening? Ha! Try rapid weakening! As noted earlier, Ernesto was downgraded to a tropical storm at 5:00 PM EDT. What happened? Blame Hispaniola:

APPARENTLY…THE HIGHLY MOUNTAINOUS TERRAIN OF THE SOUTHWESTERN PENINSULA OF HAITI HAS DISRUPTED THE CIRCULATION OF ERNESTO. THE LOW-LEVEL CENTER HAS BECOME BROAD AND ILL-DEFINED…THE MINIMUM PRESSURE HAS RISEN TO ABOUT 1004 MB…AND THE HIGHEST OBSERVED FLIGHT-LEVEL WINDS WERE 42 KT. IT IS PRESUMED THAT STRONGER WINDS ARE OCCURRING IN THE NORTHEAST QUADRANT OF THE CYCLONE VERY NEAR THE COASTLINE OF HAITI. THE CURRENT INTENSITY IS SET…PERHAPS GENEROUSLY…AT 50 KT [60 MPH].

Dr. Jeff Masters explains further:

Ernesto is has been clobbering Hispanolia all morning with tropical storm force winds and torrential rains. But now, the island has bitten back. Ernesto is struggling to hold his eye together, thanks to the mountainous terrain on the southwestern peninsula of Haiti. The 1:10pm and 3pm EDT Hurricane Hunter eye reports found a surface pressure estimated at 1007 mb, a big increase from this morning’s 995 mb. Moreover, the eye was substantially tilted, with the calm at the surface about 25 miles south of the calm at the 10,000 foot flight level. The plane could find maximum winds of only 35 mph during that 2-hour period.

Ernesto should restrengthen somewhat as he moves away from land:

The upper level outflow still looks strong, wind shear is weak, and an upper-level anticyclone (clockwise-rotating region of winds) is still in place, so Ernesto will no doubt reorganize tonight once he moves away from Haiti. However, given Ernesto’s small size and the difficultly he is having with Hispaniola, there is hope that the expected 1-2 day traverse of Cuba will significantly weaken him.

Intensification will resume after the trek across Cuba, but how much of Ernesto will be left to restrengthen? SciGuy predicts: “[D]epending on how long Ernesto remains over Cuba, it may well emerge north of Cuba as a tropical storm, perhaps even a depression.” That would leave the storm with a significant uphill struggle to become a major threat again. Dr. Masters says: “It may take Ernesto a day or two to regain hurricane strength once he emerges into the Florida Straits. This bodes well for the Florida Keys, which may dodge another hurricane. I think that only if Ernesto makes landfall north of Tampa will he have time to organize into a major hurricane.”

Even so, I’m glad to hear that the evacuations have begun in the Florida Keys. You can’t be too careful with these unpredictable beasts. Remember: if the local authorities tell you to get the hell out, get the hell out! Simple as that.

P.S. Incidentally, the title of this post says Ernesto’s interaction with Haiti and Cuba is “good news for Florida,” and it is — but it certainly isn’t good news for Haiti and Cuba. At this point, Ernesto is more a rain event than a wind event, but particularly in Haiti, a major rain event is plenty bad enough. Only time (and damage reports) will tell, but Ernesto’s legacy could be widespread devastating mudslides in the deforested mountain areas of Haiti. Let’s hope not.