Tropical Storm Karen Dissipates

Tropical Storm Karen degenerated into a post-tropical low pressure system this morning, done in by dry air and high wind shear. Karen's demise brings the seasonal Accumulated Cyclone Energy (ACE) in the Atlantic up to 27, which is about 31% of average for this time of the year. Climatologically, the season should be about 85% over, and I expect we will see just one or two more named storms before the quiet Atlantic hurricane season of 2013 peters out. The next candidate to be a named storm is a low pressure area that emerged off the coast of Africa on Friday, and was located a few hundred miles south-southwest of the Cape Verdes Islands at 11 am Sunday morning. The disturbance is headed west-northwest into the Central Atlantic, and is unlikely to threaten any land areas. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave the disturbance 5-day development odds of 30%. The UKMET model develops the disturbance into a tropical depression late in the week, but the GFS and European models do not.

One item of interest regarding Karen, noted in the NHC discussion Saturday afternoon at 5 pm EDT:

THE 12Z HWRF RUN SHOWED CONSIDERABLY LESS INTENSIFICATION WITH KAREN COMPARED TO PREVIOUS RUNS AFTER ASSIMILATING DATA FROM THE FROM THE
NOAA P-3 TAIL DOPPLER RADAR. THIS MARKS THE FIRST TIME DOPPLER RADAR DATA HAVE BEEN ASSIMILATED INTO AN OPERATIONAL HURRICANE MODEL IN REAL TIME.

The integration of real-time radar data from the NOAA Hurricane Hunters into the HWRF model may make this model worthy of extra consideration in the future.


Figure 1. The remnants of Tropical Storm Karen were still generating some heavy rains over the Northern Gulf of Mexico at 11 am EDT Sunday morning.

Jeff Masters