typhoon_tip
(Meteorologist)
Mon Dec 05 2005 11:48 PM
Useful information...

Hi Folks...
I thought you might want to delve into this ...if you have not already that is..

http://hurricane.atmos.colostate.edu/Forecasts/2005/dec2005/

So...I Agree with HankFrank's earlier post regarding the "purist" nature of Epsilon.

It is important to note that Epsilon developed in the belly of a negative anomaly, a teleconnected (statistically favored result) weakness in the subtropical height field, for having a fairly powerful -NAO signal across the N Atlantic. Typical positive height fields existing near or above 50N latitude in the Atlantic have a dipolar negative near the latitude of the Azores and extending W across a good bit of the Atlantic Basin. In addition, this took place earlier than normal (...for those who have good fundemental awareness of climate, they know that the -NOA exerts a bigger influence during cold season months...), which aided in causing enhanced instability over a regional scale in that region.

A negative 30-40N anomaly associated with the -NAO: What this means in lay terms is that the sfc to upper altitude delta-T and dew point differentials "mock" the typical tropical sounding that you find over an 80F, truer tropical SST and associated tropospheric sounding. Clark has hammered this point in the past, and how lower SSTs can be sufficient in these rare circumstances.. That means/meant that the thermodynmic gradients were in sufficient measure/instability for the physics to play out like it were a truer tropical sounding - it is rare for this to happen; amazing to have it happen twice in a season like this!

John



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