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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


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Erika, Where Are You? ... and Where Are You Going?...
      #86842 - Thu Sep 03 2009 01:28 PM

...or maybe 'If you are going'? At first it seemed like Erika was going to be a nightmare to forecast but if you throw out the models and their forecasts (ALL of them), then maybe its not a nightmare after all. Most of the models utilize the centerpoint initialization data provided by the Hurricane Center (any Center - U.S., Canadian, or U.K.), but if that starting point data is wrong then the model output hasn't got a chance at being anywhere near accurate.

This morning Erika has thrown out yet another low-level swirl - and some of these have been utilized as the honest-to-goodness real time you gotta believe it centerpoint - with horrible results in the model outputs. The initial forecast by NHC is going to have a forecast error of about 225 miles - at the 48 hour point - and probably close to 300 miles at the 72 hour point - ouch!

At 03/15Z, the latest low-level swirl was located at 16.8N 64.3W (moving west) and the NHC location was given as 16.9N 63.4W (moving west northwest). Its quite possible that the actual location was 16.3N 61.5W - over Guadeloupe - moving slowly westward. At 15Z, Guadeloupe had moderate rain with a south wind gusting to 31mph. What appears to be the primary southern rainband would coincide nicely with this location.

If the location suggested above is anywhere closer to reality, then the current model output is already toast (burned toast). Okay, so if thats where she is, then where does she go if she goes anywhere? Well if she stays on more of a generally west to slightly north of due west movement, the upper environment would be a little more favorable (as suggested by SSEC steering winds). What I mean is favorable to hold together, not necessarily favorable to strengthen much. As an aside, the best track match thus far in the hurricane archives is Holly, 1969, but to be fair, see also Storm #3 in 1880, Ella in 1958, and maybe even Cleo in 1964 (which was a lot stronger when it went through the Islands).

Possible scenarios include dissipation - the eventual toll of the windshear, but Erika has shown remarkable tenacity with regard to the windshear that has been disrupting her for the last couple of days. Another scenario would be total disruption if she hits Hispaniola as a weak system. A third possibility, and one that I tend to favor, would keep Erika plodding west and west nothwestward hitting the Isthmus of Haiti (which would probably not weaken her too much) and then eastern Cuba (which would weaken her significantly) and finally re-entering the Atlantic on a more north northwesterly course toward the far western Bahamas as a much-weakened system trying to reorganize.

Since all of these possibilities have some level of reality, the message is simply to maintain a close watch with this storm, even if she is downgraded to an open tropical wave for a portion of her journey to the west northwest.
ED


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