[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 180232
TCDAT2

TROPICAL STORM HELENE DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072012
1000 PM CDT FRI AUG 17 2012

A HURRICANE HUNTER PLANE INVESTIGATED HELENE FOR SEVERAL HOURS THIS
EVENING AND FOUND THAT THE DEVELOPMENT TREND OBSERVED EARLIER TODAY
IS NO LONGER OCCURRING. HELENE IS EITHER WEAKER OR ON A STEADY
STATE WITH MAXIMUM WINDS OF 35 KNOTS. THE CYCLONE STILL HAS A WELL
DEFINED CIRCULATION AS INDICATED BY THE RECONNAISSANCE PLANE BEFORE
IT LEFT THE AREA...AND ALTHOUGH THE SATELLITE PRESENTATION HAS
DETERIORATED...ENVIRONMENTAL CONDITIONS ARE SOMEWHAT FAVORABLE FOR
HELENE TO REGAIN SOME STRENGTH BEFORE IT MOVES INLAND IN ABOUT 24
HOURS OR EARLIER. AFTER LANDFALL...A STEADY WEAKENING IS
ANTICIPATED.

FIXES FROM THE RECONNAISSANCE PLANE INDICATE THAT HELENE WAS
MEANDERING OR DRIFTING NORTHWARD DURING THE PAST COUPLE OF HOURS.
HOWEVER...THERE IS ENOUGH RIDGING TO THE NORTH OF THE CYCLONE TO
FORCE HELENE SLOWLY NORTHWESTWARD AT ABOUT 6 KNOTS TOWARD THE COAST
OF MEXICO. ALTHOUGH THIS IS THE MOST LIKELY SCENARIO AS INDICATED IN
THE OFFICIAL FORECAST...ONE SHOULD NOTE THAT VARIOUS MODELS
INCLUDING THE GFS AND THE ECMWF KEEP A LOW...OR PERHAPS THE MODEL
REPRESENTATION OF HELENE DRIFTING NORTHWARD VERY CLOSE TO THE COAST
OF MEXICO FOR SEVERAL DAYS...AND IN FACT...THE GFS RESTRENGTHENS
THIS FEATURE.

NEVERTHELESS...THE MAIN THREAT FROM HELENE WILL BE HEAVY
RAINFALL...WHICH WILL CONTINUE EVEN AS THE CYCLONE SLOWLY MOVES
INLAND AND WEAKENS.


FORECAST POSITIONS AND MAX WINDS

INIT  18/0300Z 21.0N  96.4W   35 KT  40 MPH
 12H  18/1200Z 21.7N  97.2W   40 KT  45 MPH
 24H  19/0000Z 22.2N  97.8W   45 KT  50 MPH...ON THE COAST
 36H  19/1200Z 23.0N  98.0W   30 KT  35 MPH...INLAND
 48H  20/0000Z 24.0N  98.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  21/0000Z...DISSIPATED

$$
FORECASTER AVILA


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