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.

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