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Generally, larger tropical cyclones are less likely to be affected by more transient influences on steering, especially if they are deep systems and well developed. On the other hand, it is typically more common to see smaller tropical cyclones jog, dip, or simply be steered by similar blocking ridges or even weak troughs. Actually, I have not found any greater significance to a hurricane being very strong or not, with regards to how it is steered by weaker influences. Simply that smaller storms in general seems to more easily alter course. Perhaps also stands to reason, how in some cases if a hurricane is a very deep system, but quite large, that it is itself impacting the environment ( i.e. warming the upper layers by means of extensive outflow ). Though powerful, I do not believe that a small hurricane would tend to alter the larger overall environment. Well, looking at the overnight runs of GFS into this morning, I cannot help but believe that Ike will in fact gain a little more latitude than NHC has presently forecasted. This could of course be a good thing - if enough poleward motion is attained in the short term. What I mean by this is such: The building 594 high pressure ridge is actually forecast to form close to the point where Ike is to be today, into tommorrow. I have a hard time seeing how the heights are not rising first to the hurricanes north and northeast, however the GFS models seems to suddenly have such high mid level heights to the storms NW in the near term. At minimum, I believe that Ike will gain more latitude than NHC believes, and will cross north of 25N latitude. If in fact the height rises are distincly more to the NE of Ike, along with the existing weakness off the U.S. seaboard, than the possibility might really exist for Ike to perhaps slow down, but continue more NW'ward that forecast. If such occured for 36hr.'s or more, than I can see an issue of where Ike could be caught in a COL and have minimal steering for a while. I am less sure of the ultimate result then, if left with the prospect of Ike possibly affecting the Carolinas or mid Atlantic states, or eventually just swinging up ahead of some possible eventual weakness. On the other hand, and assume greater short term accuracy by NHC, and perhaps Ike remains south of 25N. Then, I do not see a real WSW motion, because of the close proximity of Ike to the center of this strong mid level high, but more of a general westward motion. Worse yet, timing would now be possibly changed because again, Ike might not be situated far enough to the south of the center of this ridge, but more "indented" into it. I would imagine a slower motion than we've seen - and perhaps an agonizingly slow westward crawl at about 8-10mph. Now, without such a southward bend to its course, it on one hand would be seemingly unlikely for a hurricane this far east at such a latitude to be able to simply continue to travel westward for too long, yet I do not see nearly enough of a reason for significant poleward motion throughout, because I do not see any obvious troughing to break down the W. Atlantic ridge. What appears to me to occur, is that the 594 W. Atlantic high maintains its integrity, but simply slides more eastward. One would then assume that Ike would follow the coutour of the more eastward strong high, thus creating a more NW motion. I however only see where a small temporary WNW motion would ensue, more or less just as Ike rounds the larger W. Atlantic high, until the next primary steering influence takes over. As far as I can see, that would be another, though weaker high centered over the Gulf Of Mexico and extending over eastward from there. If given any significant dip in the westerlies or short wave off the U.S. east coast, one could easily make the argument that this will degrade this weak ridge - and such would likely happen. Looking at the available 6Z GFS data ( and previous run as well ), I see what appears a a large dip of the westerlies, almost like a weak but broad trough, entirely over the central CONUS, with the 500mb 582mb line not coming much south of Kansas. This trough does not appear to be digging, nor dropping a short wave down the U.S. east coast. Therefore, by my interpretation, there would seem to be significant ridging from the W. Atlantic well west into the Gulf of Mexico ( at least around 25N latitude ). Steering could be weak and perhaps even maintain only a slow 5kt. forwad motion, but I cannot see how Ike would not be forced more or less West to WNW at most, at the very end of the forecast time frame. This all said, I would tend to think an area from w. Palm Beach, Florida, north to Fort Pierce, Florida - perhaps to be of greatest risk of a possible Cat. 3/4 ( ASSUMING the many possible changes in long range steering which certainly is realisitic to realize given projections based on data so far out in time ). As a disclaimer, please keep in mind, that the 12z GFS ( as well as a myriad of additional model data ) will update shortly, and this hypothesis could be just as easily be "thrown out the window" in a matter of hours. Simply my take on circumstances "of the moment". |