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Tropical Depression ERIKA (Text)

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TROPICAL DEPRESSION ERIKA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062009
500 PM AST THU SEP 03 2009
 
THE CENTER OF ERIKA IS EXPOSED AS A LOW-LEVEL SWIRL MOVING OUT AHEAD
OF THE WANING DEEP CONVECTION OVER THE LEEWARD ISLANDS. THE AIR
FORCE RESERVE RECONNAISSANCE HURRICANE HUNTER AIRCRAFT FOUND A
MINIMUM PRESSURE OF 1007 MB...BUT WERE UNABLE TO FIND ANY WINDS TO
SUPPORT TROPICAL STORM STATUS. AS A RESULT...ERIKA IS DOWNGRADED TO
A TROPICAL DEPRESSION ON THIS ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 280/10...WELL TO THE SOUTH OF THE
PREVIOUS OFFICIAL FORECAST TRACK AND THE MAJORITY OF ALL THE MODEL
GUIDANCE. SINCE ERIKA SHOULD MOVE WITH THE LOW-LEVEL FLOW...THE
SHALLOW BAM MODEL WAS FOLLOWED CLOSELY FOR THE NEW FORECAST TRACK.
THIS FORECAST TURNS ERIKA TOWARD THE WEST-NORTHWEST...TAKING THE
CYCLONE OR ITS REMNANT LOW SOUTH OF PUERTO RICO AND OVER HISPANIOLA
...WHERE THE LOW-LEVEL CENTER WILL LIKELY DISSIPATE OVER THE RUGGED
TERRAIN IN 48 HOURS.
 
THE OFFICIAL FORECAST ASSUMES THAT ERIKA WILL HAVE A DIFFICULT TIME
SUSTAINING ANY DEEP CONVECTION AS IT MOVES INTO AN ENVIRONMENT OF
INCREASING SHEAR AND DRY AIR IN THE LOWER TO MID-TROPOSPHERE. ERIKA
IS MAINTAINED AS A TROPICAL DEPRESSION THROUGH 12 HOURS...AND IS
FORECAST TO BE A REMNANT LOW BY 24 HOURS....ALTHOUGH THIS COULD
OCCUR SOONER IF THE CONVECTION EAST OF THE LOW-LEVEL CENTER OVER
THE LEEWARD ISLANDS CONTINUES TO WEAKEN. IT IS ALSO POSSIBLE THAT
THE CENTER OF ERIKA COULD BECOME POORLY DEFINED AND THE CYCLONE
COULD DEVOLVE INTO A TROPICAL WAVE AT ANY TIME. EVEN IF ERIKA LOSES
TROPICAL CYCLONE STATUS...ITS REMNANTS COULD PRODUCE HEAVY RAINFALL
OVER THE GREATER ANTILLES.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/2100Z 16.7N  65.3W    30 KT
 12HR VT     04/0600Z 17.2N  66.8W    30 KT
 24HR VT     04/1800Z 18.1N  68.6W    25 KT...REMNANT LOW
 36HR VT     05/0600Z 18.9N  70.3W    20 KT...REMNANT LOW
 48HR VT     05/1800Z 19.5N  72.2W    20 KT...DISSIPATING INLAND
 72HR VT     06/1800Z...DISSIPATED
 
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FORECASTER BRENNAN
 
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