20 July 2009

Disturbance heading into eastern Caribbean...

An African easterly wave, generated over the Ethiopian Highlands back on July 6 exited the African coast on July 13, and is now located just east of the Lesser Antilles.  It has very slowly gotten better organized, and has a mid-level circulation and persistent deep convection near the center.

The disturbance is expected to continue tracking W-WNW at 15kts through the northern Caribbean over the next several days.  If it does manage to organize, it would become TD2 then TS Ana.  However, it's moving into the northern periphery of a Colombian High where vertical shear is excessive.  In the near future, islands in the Lesser Antilles can expect some rather stormy conditions for a couple days.

Please visit my tropical Atlantic headquarters.

08 July 2009

Bertha now on a weakening trend...

After peaking out at 105kts earlier today, Bertha has since encountered stronger vertical shear and drier air, and is now deteriorating.  At 21Z today, the intensity was estimated at 75kts and 980mb, tracking NW at 10kts.  The CAT1 hurricane is located at 22.7N 54.8W.  The deep convection is shifted  almost entirely to the northeast of the low-level center, a true sign of the stronger vertical wind shear.

Bertha is the 6th strongest pre-August hurricane on record, and the 5th earliest pre-August hurricane.  The combination of these traits yields the 3rd strongest hurricane so early in the season (105kts on Jul 8).  Only Audrey (6/27/57) and Alma (6/8/66) were earlier AND stronger.  Bertha also shattered the record for furthest east formation for a pre-August tropical storm, hurricane, and major hurricane.  Thanks to Phil Klotzbach and Jeff Masters for pointing these climatological features out!

It is possible that in a few days, conditions will improve slightly and the storm will be allowed to once again intensify.  Bermuda should still be watching this, but it seems more and more likely that Bertha will recurve just east of Bermuda given the current 4-5-day forecasts of the weakness in the subtropical ridge.

Elsewhere, a large easterly wave is just exiting the African coast today, but has little circulation associated with it, and none of the forecast models indicate development.

Please visit my tropical Atlantic headquarters.