Goodbye, Dennis, Hello Emily!

The tropical wave that spun off the coast of Africa last week has acquired enough deep convection to be classified as Tropical Depression Five. I've been trying hard to ignore this one the past few days, because tropical waves in July NEVER develop into tropical storms so far out over the Atlantic, DUH! Well, DUH! This is the hurricane season of 2005, and Hurricane Dennis has already shown we need to re-write the rules. A check of the Historical Track Chart for this area shows only four July tropical depressions have formed so far out, and none of these ever made it to hurricane status. So ordinarily, I would say that this storm is probably nothing to worry about; conditions are marginal because sea surface temperatures are fairly cool over the mid-Atlantic. I've seen tropical depressions like this one fizzle and die many times. But I've learned my lesson. This is the hurricane season of 2005--and I fully expect this storm (soon to be named Emily) will become another major hurricane that will threaten the Caribbean and U.S. That's a pretty bold statement for a mere tropical depression in July way out over the open Atlantic, and statistically, the odds of me being correct are probably less than 20%. I hope the statistics are right, and I am wrong. But this is the hurricane season of 2005. The normal rules do not apply.

Where will TD 5 go? Well, a check of the Forecast Verification Chart for Hurricane Dennis reveals that the Navy's NOGAPS model was the best performer. The official NHC forecast was also quite good. The NOGAPS model (and not coincidentally, the official NHC forecast) both bring TD 5 into the central Caribbean. Its way too easy to speculate where the storm will hit land, but I've already been telling my friends who have travel plans to the Caribbean this week to rethink them.

Dennis turned out to be an average major hurricane for Florida, thanks to the sudden weakening that occurred in the few hours prior to landfall. Sudden weakening has afflicted the past three Category 4 hurricanes to threaten the Gulf Coast--Hurricane Opal (1995), Hurricane Ivan, and now Dennis. The reasons for this are probably due to the colder water that typically lies near shore, and the entrainment of dry air from the steering trough to the west. Luck is also an important factor--hurricanes go through natural cycles of intensification called eyewall replacement cycles, and we were lucky Dennis finished its intensification cycle 12 hours before hitting land. This luck does not always hold, as we saw when Hurricane Camille hit the same area of coast at the peak of it intensification cycle.

By coming ashore in a relatively unpopulated beach area, Dennis' damage total will have a tough time catching up to Ivan's $13 billion dollar price tag or Charley's $14 billion. Preliminary estimates peg the damage at $2 - $10 billion, still worthy of a place on the list of the most damaging hurricanes of all-time. Once again, Mobile and New Orleans got very lucky--just a small shift in course could have brought the core of this powerful hurricane over either city, causing incredible damage. One wonders how much longer the Big Easy can escape the Big One; the stretch of coast just to its west has seen two major hurricanes and two strong tropical storms (Arlene and Cindy) in the past year alone.

One also has to wonder about the location of the past four major hurricanes--Ivan and Dennis followed almost identical paths, as did Frances and Jeanne on Florida's east coast in 2004. If I lived in Punta Gorda, where Charley hit last year, I'd be a little nervous watching Tropical Depression Five east of Barbados, wondering if a repeat Charley hurricane might be in the works! This is VERY unlikely, though; direct strikes from major hurricanes are extemely rare for the Gulf Coast of Florida south of the Panhandle. Hurricane Donna (1960) and Hurricane Easy (1950) were the last major hurricanes before Charley.

Dr. Jeff Masters