Tropical Depression HELENE

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TROPICAL DEPRESSION HELENE DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072012
1000 AM CDT SAT AUG 18 2012
 
SATELLITE DATA...SURFACE OBSERVATIONS...AND MEXICAN RADAR DATA FROM
ALTAMIRA INDICATE THAT THE CENTER OF HELENE IS LOCATED JUST INLAND
FROM THE COAST VERY NEAR TAMPICO MEXICO.  A NEW BURST OF DEEP
CONVECTION APPEARS TO BE DEVELOPING NEAR THE CENTER...BUT THE
DEEPEST CONVECTION LIES IN BANDS TO THE EAST OVER THE WATER. 
DVORAK FINAL-T ESTIMATES FROM TAFB AND SAB...AND SCATTEROMETER
DATA...NO LONGER SUPPORT TROPICAL STORM STATUS...AND HELENE IS
DOWNGRADED TO A TROPICAL DEPRESSION AT THIS TIME.  WEAKENING SHOULD
CONTINUE AS THE DEPRESSION MOVES OVER LAND...AND HELENE COULD
BECOME A REMNANT LOW BY TONIGHT.  ALTHOUGH THE GFS MODEL SHOWS
HELENE RE-STRENGTHENING OVER WATER IN 2-3 DAYS...THE OFFICIAL
FORECAST FOLLOWS THE OTHER MODELS AND INDICATES DISSIPATION BY 48
HOURS.
 
AFTER MOVING VERY LITTLE LAST EVENING...HELENE APPEARS TO HAVE
ACCELERATED OVERNIGHT AND HAS AN ESTIMATED MOTION OF 305/8 KT.  THE
CYCLONE SHOULD TURN NORTHWARD AND SLOW DOWN DURING THE NEXT DAY OR
SO SINCE IT WILL BE STEERED AROUND THE WESTERN PERIPHERY OF A
LOW/MID-LEVEL RIDGE...AND TRAPPED AGAINST THE EASTERN SLOPES OF THE
SIERRA MADRE OCCIDENTALS.  THE UPDATED NHC TRACK FORECAST IS JUST A
LITTLE SLOWER THAN THE PREVIOUS ONE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/1500Z 22.0N  98.0W   30 KT  35 MPH...INLAND
 12H  19/0000Z 22.6N  98.7W   25 KT  30 MPH...INLAND
 24H  19/1200Z 23.0N  98.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  20/0000Z 23.5N  98.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  20/1200Z...DISSIPATED
 
$$
FORECASTER BERG
 
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