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Tropical Storm ILEANA (Text)

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TROPICAL STORM ILEANA DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092012
200 PM PDT WED AUG 29 2012

ILEANA CURRENTLY SHOWS A WELL-ORGANIZED CURVED BAND CONVECTIVE
PATTERN WITH OCCASIONAL ATTEMPTS TO WRAP UP AN EYEWALL AND EYE. 
SATELLITE INTENSITY ESTIMATES ARE 65 KT FROM SAB AND 55 KT FROM
TAFB...AND A RECENT CIMSS AMSU INTENSITY ESTIMATE WAS 62 KT.  SINCE
THE CENTRAL CONVECTION DOES NOT QUITE WRAP ALL THE WAY AROUND THE
CENTER...THE INITIAL INTENSITY WILL BE HELD AT 60 KT.  THE STORM IS
IN A LIGHT VERTICAL WIND SHEAR ENVIRONMENT WITH GOOD CIRRUS OUTFLOW
IN ALL DIRECTIONS.
 
WHILE THE CENTER HAS BEEN WOBBLING TODAY...THE OVERALL MOTION
REMAINS TOWARD THE NORTHWEST...320/7.  FOR THE NEXT 72 HR...THE
CYCLONE SHOULD BE STEERED NORTHWESTWARD BY THE COMBINATION OF A
MID-/UPPER-LEVEL RIDGE TO THE NORTHEAST AND A DEVELOPING
MID-/UPPER-LEVEL TROUGH WEST OF CALIFORNIA.  WHILE THE GUIDANCE
GENERALLY AGREES WITH THIS SCENARIO...THE UKMET AND THE NOGAPS SHOW
A MORE NORTHWARD MOTION DURING THIS TIME.  AFTER 72 HR...THE
GUIDANCE DIVERGES FURTHER...WITH THE GFS SHOWING ILEANA TURNING TO
THE NORTH BEFORE IT WEAKENS...AND THE ECMWF FORECASTING A TURN
TOWARD THE WEST.  THE TRACK FORECAST LEANS MORE TOWARD THE LATTER
SCENARIO...SHOWING A GRADUAL TURN TOWARD THE WEST AFTER 72 HR.  THE
NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK AND LIES
SOMEWHAT TO THE LEFT OF THE CENTER OF THE TRACK GUIDANCE ENVELOPE.

THE FORECAST TRACK TAKES ILEANA OVER PROGRESSIVELY COOLER SEA
SURFACE TEMPERATURES...AND IT PROBABLY HAS 12-24 HR LEFT TO
STRENGTHEN UNDER THE FAVORABLE UPPER-LEVEL WIND PATTERN.  BASED ON
THIS...THE INTENSITY FORECAST CALLS FOR THE CYCLONE TO BECOME A
HURRICANE IN ABOUT 12 HR AND MAINTAIN THAT STATUS THROUGH 24 HR. 
AFTER THAT...THE DECREASING SSTS SHOULD CAUSE STEADY WEAKENING...
WITH THE SYSTEM FORECAST TO BECOME A TROPICAL DEPRESSION BY 96 HR
AND A REMNANT LOW BY 120 HR.  THE NEW INTENSITY FORECAST IS A BLEND
OF THE SHIPS...LGEM...AND INTENSITY CONSENSUS MODELS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/2100Z 18.5N 113.0W   60 KT  70 MPH
 12H  30/0600Z 19.3N 113.7W   65 KT  75 MPH
 24H  30/1800Z 20.2N 114.5W   65 KT  75 MPH
 36H  31/0600Z 21.1N 115.4W   60 KT  70 MPH
 48H  31/1800Z 21.8N 116.6W   55 KT  65 MPH
 72H  01/1800Z 23.0N 119.0W   40 KT  45 MPH
 96H  02/1800Z 24.0N 122.0W   25 KT  30 MPH
120H  03/1800Z 24.5N 125.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BEVEN
 
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