Sun Sep 04 2011 03:08 PM
Re: TS Lee Pressure drop


Eye has become clearly visible on Katia in the last hour of IR passes. ADT raw T number is up to 5.4 with the eye now visible, which would be consistent with 95-100kt winds. Given original speeds of 85kt at 11am NHC update, in 2.5 hours that increase is plausible. AdjustedT numbers are still 4.8 by ADT, only because they require consistent higher raw T numbers to increase, which would be 85-90kt, or consistent with the 11am guidance.

I want to note that the 0Z NOGAPS has joined the UKMET is showing a non-recurving westward track. Still waiting on the 12Z NOGAPS and ECMWF. 12Z GFS is continuing to show recurvature, while 0Z ECMWF is showing a slower recurvature. Everyone needs to continue watching this storm.

Couple of quick comments on this:

The NOGAPS and UKMET are the less reliable guidance (statistically) of those mentioned.

The lesser intensity of the UKMET's cyclone may atone for that westerly placement, as a shallower system would be less integrated with the steering around the western periphery of the Atlantic subtropical ridge.

That said, the 12z NOGAPS and UKMET have joined in with the other numerical guidance in depicting a parabolic recurve into the N Atlantic with limited impact felt along the East Coast of north America beyond elevated surf. The important thing to remember is that average error balloons to at or greater than 250 nautical miles (although the current the 5-year running mean is a bit better) from the NHC.

It isn't entirely clear just how far west the weakness in the atmosphere left by Lee will induce a leftward position with Katia; that will become more clear with shorter term guidance in about 2 days. Until then, it appears the west trend in the runs has stopped for the time being and some consensus is emerging - that of course is never 100% at D4-6.

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