01 October 2008

Laura dissipates...

Convection has dissipated in TS Laura, and the circulation is now over 13C SSTs.  The estimated intensity at the final advisory is 40kts and 995mb.  While 13C is cold, what matters more to a storm is the difference between the "input" air temperature near the surface and the "exhaust" air temperature aloft.  In higher latitudes, the SSTs drop off, but so do the tropopause temperatures (the tropopause is the top of the layer of the atmosphere in which all of our weather occurs).  If the tropopause temperature gets colder faster than the SSTs, the storm "thinks" it's in a good environment!  That's the primary reason we just had a fully tropical system over such cold water.

The circulation is now located just east of Newfoundland and heading north.  It will start recurving to the east with the next mid-latitude trough in a day or two and become a potent extratropical storm affecting the UK this weekend.

Elsewhere, there's a strong easterly wave trekking across Guinea in western Africa.  It is traceable back about 5 days over the Ethiopian Highlands.  A majority of forecast models develop this system once it exits the coast in about 3-4 days.  And finally, there's an easterly wave centered near 14N 40W which is currently poorly organized but could slowly develop.

Please visit my tropical Atlantic headquarters.

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