The tropical threesome

September 2, 2008

For residents of the southeast, the situation continues to look better with regards to Hanna.  Unfavorable upper-level winds are making life miserable for the storm as it sits just north of Hispanola.  Maximum sustained winds are down to 65 mph and I strongly suspect they will be even lower come the 5 AM advisory as the satellite appearence is terrible.

The NHC forecast is for the hostile conditions to subside and Hanna to regain hurricane strength as it crosses the Gulf Stream and heads towards the Georgia/South Carolina border.  Given current circumstances the intensity forecast may be a bit overdone and require adjustment downward.  Also looking at the GFS model that just came out (enhanced with upper-air data collected by the Gulfstream IV), it looks like the forecast landfall point will be shifted the north somewhat more towards North Carolina.  As the NHC discussions point out, though, one should focus more on the general idea than an exact landfall point as a small variation in storm heading shifts the landfall point substantially.

I’m not expecting much out of Hanna at this point.  Once it starts moving and nears land, its forward speed will be sufficient to keep rainfall totals from being especially exorbitant and the wind speeds should be more of a nuisance than a destructive force.

1500 miles to the east of Hanna is Tropical Storm Ike, which continues to be the forecaster’s friend so far as having a predictable track goes.  The Bahamas may take less of a liking to it as it could be the worst storm to affect the islands since Andrew.  The $64 question of the moment is the favorability of upper-level winds when Ike starts to pass north of the Antilles.  Favorable conditions would allow it to strengthen to a major hurricane (as forecast by the GFDL and HWRF models).  Unfavorable conditions, akin to what is plaguing Hanna right now, would put Ike much weaker. SHIPS, guided by the GFS, expects an inhospitable atmosphere to push Ike back down to tropical storm strength (with Ike availing itself of favorable conditions to get to a category one hurricane before the going gets rough).  The official forecast splits the difference.

Way out to the east/southeast of Ike is Josephine.  The forecast track puts it in a position where it is climatologically unlikely to affect the United States.  As such it will receive minimal attention for the time-being.

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