Category 4 Hurricane Dean Moving Westward Toward Jamaica

Having chased hurricanes for a good number of years, it would merely sound cliche' to state that each Hurricane track and landfall is unique. While each event involves differing steering mechanisms, along with distinct upper air conditions, these nuances sometimes introduce merely a wrinkle of sudden deepening or weekening or perhaps a tendancy to wobble due to a storms vorticity max rotating around the eye or perhaps a given land mass and the interaction with the approaching storm. I cannot help but remember comparing forecast models, only to be outwitted by one in particular - CLIPPER. While I remain a devout supporter of statistical data which would might support Dean to move on a predominant 275 to 285 degree heading, I cannot help but to defer some reference to Climatology and Persistance.

In the case of Hurricane Dean, a late July or August, a westward retrograding 594mb high ( or higher ) to move along with a hurricane is often a signal of primary steering for future storms that season. Somewhat puzzling to me is the practically trapped cut-off low, given the significance of the CONUS Plains ridging also in place. My first thought would be that with the upcomming digging trough along the E. U.S. Seaboard, that the cut-off would tend to be pulled N.E.ward. In many years, that loud "sucking sound" you hear, would be the sound of whatever Tropical Cylcone in the general vacinity getting sucked ahead and northward into the trough and up and out to the Atlantic storm graveyard. Given the fairly merged ridging however, this seems unlikely. Even the 0Z GFS seems to slow the forward progression slightly, as compared to same forecast periods 24 hours ago.

While not a dramatic alteration to the forecast track, I do beleive that as the cut-off low is slowly pushed southwestward or westward, at some point Dean's forward motion should slow down. Depending on the time which Dean "catches" up with the influences of this mid to upper low, some wobbles or short term variations in course could occur. This could potentially raise impacting conditions to Haiti and Cuba, and potentially work to lessen a direct hit on Jaimaca if a jog north ensues. If this cut-off low is held practically stationary in the Gulf, it may not fully reflect down to the 500mb level, certainly would seem to impact Dean's outflow. Best case would be for some shear to inhibit further strengthening, along with Dean's inflow being interupted if brushing close to mountainous regions of Haiti or E. Cuba. Of course if this cut-off low is ejected southwestward ahead of Dean, then i've got $10.00 on Dean maxing out as a Cat. 5 in the W. Carib. ( but I do not see that happening ).

Those of you who read the Cyclone Discussion at 11:00pm this evening will notice that the data from the research flight was basically not recieved ( late, lost, or what? ). This is a shame, as the raw data which each forecast model is based upon, will likely be mostly unchanged - thus the mostly unchanged cluster of forecasts for days 3-5. I was eagerly awaiting the 0Z GFS, but do not much reason to anticipate much variation from earlier runs today. As the NOAA plane continues to investigate upper air either tonight or tomm., I am actually expecting newer model runs ( either 12Z or later tomm. ) to start to introduce some more northward wrinkles to the long range ( and maybe even 24 hr - 48 hr. ) forecast tracks.

Regarding an earlier post regarding Dean possibly "imploding" due to forward speed, I'd equate those odds with the liklihood of a low latitude tropical cyclone producing lots of lightning and golf ball sized hail. Picture an Olimpic runner who is very fast. He does not eventually fall over because he is running so fast. Now picture that same Olimpic runner not looking ( just like in the movies ) and suddenly running "head high" into a tree limb. Now, thats my definition of "shear misfortune". For Dean, if an upper high remains over it, and without those pesky westerlies, than Dean can run as fast as it wants to.

( sorry about the long post )

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