There is lot’s of interest in our area on the future track of Hurricane Dean. Dean is the first hurricane of the 2007 hurricane season, and it also a special class of storm called a Cape Verde storm. These storms form south of the Cape Verde Islands and track a long distance across the Atlantic, some re-curving and others marching into the Caribbean and perhaps the Gulf of Mexico.
There is always a great deal of speculation on where these storms are going, and there is almost no skill in making those assessments very far into the future. But because the GFS, Global Forecast System model, is generated out to 384 hours, it’s interesting to watch the changes with time.
I wished that I had started earlier, but around August 14th I began to write down the projected landfall positions from each model run of the GFS. Initially, just as suspected, the GFS had some wild swings in landfall positions. But starting with the 06Z run on August 15, the GFS has been very consistent with a landfall in Mexico. The position has gradually moved northward in Mexico, and the last run prior to this writing, the 17th 06Z model run, almost has it in South Texas, but the center is still crossing the coast in Mexico, albeit extreme northern Mexico.
Here is my tabulation of GFS landfall positions:
14/00Z SC/NC on 8/22/07 at 00Z
14/06Z S FL on 8/22/07 at 06Z
14/12Z TX on 8/24/07 at 12Z
14/18Z LA/SETX on 8/24/07 at 06Z
15/00Z TX/LA on 8/24/07 at 12Z
15/06Z Mexico on 8/23/07 at 06Z
15/12Z Mexico on 8/23/07 at 18Z
15/18Z Mexico on 8/23/07 at 18Z
16/00Z Mexico on 8/23/07 at 12Z
16/06Z Mexico on 8/23/07 at 06Z
16/12Z Mexico on 8/23/07 at 00Z
16/18Z Mexico on 8/23/07 at 00Z
17/00Z Mexico on 8/23/07 at 18Z
17/06Z Mexico on 8/23/07 at 12Z
So beginning almost 8 days out, the GFS began to focus in on one location. We’re still watching to see how well the GFS will do – or other models for that matter.
When looking at the forecast today, there are many factors that lead to great uncertainty. One of those is Erin and what the remnants of that storm do to affect the synoptic pattern that could play a role in the future course of Dean. Or that huge high over the Southeast US – what will its exact position be when Dean enters the Gulf of Mexico? Or that little upper low that began showing up on the GFS in the Central Gulf yesterday – what impact will that have in determining the final future course of Dean? Will a small weakness in the upper ridge be exploited by Dean and perhaps bring about a more northward turn?
Those are all BIG questions that meteorologists are struggling to evaluate. And I can’t help but think back to 1985 and Hurricane Elena. At one point as Elena was coming into the Gulf, the major computer guidance painted a near perfect five pointed star with future points near New Orleans, Tampa, Brownsville, South Florida, and the Bay of Campeche. Talk about divergence!! And it ended up that two of them were right – Elena was influenced by a trough over the US that turned it toward Central Florida, but the two features de-coupled, Elena stalled, and then moved back northwest to a point just east-northeast of New Orleans. That was certainly one for the books!
One item that I did not put on my list was the strength of Dean at landfall. I think there is little doubt that Dean could be a major hurricane when it does come ashore wherever that might be.
-Brian-
