[StBernard] Jeff Masters' blog on Weather Underground

[Westley Annis]

Dr. Jeff Masters' WunderBlog
<http://www.wunderground.com/blog/JeffMasters/show.html> 

A very complicated weather situation over the Gulf of Mexico and Atlantic
waters off the Southeast U.S. coast associated with a non-tropical low
pressure system (93L)
<http://www.wunderground.com/tropical/tracking/at200793_model.html> , has
brought heavy rains to Florida, Georgia, and South Carolina over the past 12
hours. A cold-cored upper level low pressure system a few hundred miles
southwest of Tampa, Florida is primarily responsible for the the action.
Late yesterday afternoon, a separate area of surface low pressure formed
near Daytona Beach, bringing high surf and heavy rains of up to five inches
along the Florida coast from Daytona to Jacksonville. This low moved inland
over Florida, but the associated surge of moisture rotated northwards all
the way to South Carolina. High surf warnings and coastal flood watches have
been posted for Charleston, South Carolina
<http://www.wunderground.com/cgi-bin/findweather/getForecast?query=charlesto
n%2C+sc>  today. This morning's QuikSCAT pass
<http://manati.orbit.nesdis.noaa.gov/dataimages21/cur/zooms/WMBas19.png>
showed winds up to 50 mph well offshore of South Carolina. These winds have
created a storm surge of up to two feet along the South Carolina coast. This
second low pressure system was identified as "93L" by NHC beginning at 2 pm
EDT yesterday. However, now that the low has weakened crossing the Florida
Peninsula, the "93L" designation has been taken away from it, and attached
to the upper level low pressure system in the Gulf of Mexico. 

Recent Satellite loops <http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html>
and the Tampa Bay long range radar
<http://www.wunderground.com/radar/radblast.asp?zoommode=pan&prevzoom=zoom&n
um=1&frame=0&delay=15&scale=1.000&noclutter=0&ID=TBW&type=N0Z&showstorms=0&l
at=0&lon=0&label=you&map.x=400&map.y=240&scale=1.000&centerx=400&centery=240
&showlabels=1&rainsnow=0&lightning=0&lerror=20&num_stns_min=2&num_stns_max=9
999&avg_off=9999>  show that this non-tropical low pressure system is
beginning to get more organized and is acquiring tropical characteristics.
Substantial pressure falls are occurring at the surface underneath the upper
level low, and this system is on its way to becoming a subtropical
depression. A surface low pressure system vertically aligned with a
cold-cored upper level low will usually take two or more days to make the
transition to a warm-cored tropical storm. Rapid intensification cannot
occur until the system is fully warm-core. Since landfall is expected
Saturday between the Florida Panhandle and Southeast Louisiana, 93L probably
does not have time to become fully tropical. If 93L makes landfall Saturday,
it should not have winds stronger than about 55 mph. The GFDL, HWRF, and
SHIPS intensity models all keep 93L's winds below 55 mph. If the storm
spends an extra day over water and makes it to Texas, as the ECMWF model
predicts, 93L could become fully tropical and make landfall as a strong
tropical storm with 60-70 mph winds. However, there is plenty of dry air in
the environment, and I don't think the storm will be able to intensify to a
strong tropical storm. The primary threat from 93L will be heavy rain, and
the northern Gulf Coast from the Florida Panhandle to Texas border can
expect a soaking from this system.

The Air Force Hurricane Hunters are scheduled to investigate 93L this
afternoon at 2pm EDT.

Jim