Isabel Forecast 9

[ncweatherwizard]

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Hurricane Isabel Forecast 9<BR>
12:45PM EDT WED SEPT 10 2003<P>

...Isabel moving westward...<P>

<I>...Based on 1615 UTC images...</I><P>

Although these forecasts are verified as reliable, refer to the <A HREF="http://www.nhc.noaa.gov">National Hurricane Center</A> for official forecasts, watches, and warnings.<P>

Undisputably, Isabel is now moving west; finally, the forecast becomes easier. The hurricane looks really misshaped right now, with little shear at all on the south side of the storm, and the ridge building in along the north side of the storm. Isabel actually has a relatively large eye from yesterday based on visible images; infrared indicates some cooling of the cloudtops in the eye; there Isabel has likely peaked in intensity, or has come close to it. Initial intensity is set at 115KTS, with T numbers of 5.5/6.0.<P>

Intensity forecast is fairly straightforward, since fluctuations in intensity are possible on occasion. Isabel will continue under favorable conditions through at least 72 hours as it is harbored under the south side of a westward building ridge over the Atlantic. Dry air is absent, and high shear values are also not present in the hurricane's path now. Therefore, the intensity forecast holds Isabel at 115kts for the next 72 hours. After 72 hours, Isabel may be exposed to a little more shear, as it rides west-northwestward up the southwest side of this ridge, in response to a slow-moving trough that will be moving to the East Coast in about 96 hours. Thus, intensity is slightly adjusted through 120 hours, but keeping Isabel a major hurricane. Based on the fact, that I steadily weakened Fabian too quickly in the same situation, I will keep Isabel as a major hurricane throughout the forecast period.<P>

Now to the track forecast. Obviously, since yesterday's forecast had gotten carried away with the northwestward motion a little bit, carrying it to 22 degrees north before the turn, the forecast will be shifted to the left, which I figured would probably happen eventually. Through 72 hours, the track forecast is exceptionally easy, assuming that Isabel should maintain its current forward speed around 12 to 13 knots. This is reflected in the track forecast given. After 72 hours, the forecast becomes a bit more difficult. A trough over the northwestern United States will continue to move southeastward and eastward across the nation, as a trough currently over the eastern US will move out of the area in 36 hours or so. Already, indications support that although this trough will not be terribly strong, it will be stronger than what models currently indicate. (This is also included in the daily local forecasts for the region which now include rain for Friday into Saturday.) If the trough were so weak, then one would reason that it would dissipate before it even made it to the East Coast; however, associated dry air has become increasingly well-defined---albeit slowly---over the past 24 hours, and it will likely deepen before reaching the East Coast. After 72 hours, I turn Isabel west-northwest, and show a northwestward turn and a slowing motion at 120 hours.<P>

Basically past 120 hours, we have three possbilities: the trough weakens as it moves eastward, allowing Isabel to slide north then move west to the Bahamas and Florida, which contradicts my reasoning prior to 120 hours. 2) The trough picks it up, but doesn't carry it away, carrying the storm northwestward, taking the storm on a Hugo-like path. 3) Personally, the idea that I currently favor the most: this trough will be a bit stronger than models have been indicating. I have trouble in seeing a ridge build almost all the way across the Atlantic, with the exception of a trough in the Eastern Atlantic. First of all, a trough still must move off the US coast <I>before</I> the trough that would affect Isabel comes through. In addtion, the second trough would also have some effect on the subtropical ridge. So currently, I say with relatively decent confidence that the United States is safe from Isabel---but at least eight to nine days remain before landfall. We shall see.<P>

NOW 21.1N 51.1W 115KTS<BR>
12HR 21.1N 53.5W 115KTS<BR>
24HR 21.1N 55.8W 115KTS<BR>
36HR 21.2N 58.2W 115KTS<BR>
48HR 21.3N 60.6W 115KTS<BR>
72HR 21.4N 65.0W 115KTS<BR>
96HR 22.7N 68.6W 110KTS<BR>
120HR 25.1N 71.3W 110KTS<P>

Powell<P>

[Stormcenter]

Too many things need to happen for your scenario to pan out. I don't see it happening. I think she's made up (westward) her mind until at least she reaches the Fl. coastline. After that, who knows where she goes?
But as I've stated MANY times before we have a long way to go and a lot of things can happen to change both our predictions.