Tropical Storm ILEANA

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TROPICAL STORM ILEANA DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092012
200 AM PDT TUE AUG 28 2012
 
CONVENTIONAL SATELLITE IMAGERY AND A 0458 UTC METOP-A AMSU MICROWAVE
OVERPASS INDICATE LITTLE CHANGE IN THE CLOUD PATTERN DURING THE
PAST SEVERAL HOURS.  THE SATELLITE PRESENTATION ALSO SHOWS THAT THE
CENTER OF CIRCULATION RESIDES NEAR THE NORTHEASTERN EDGE OF THE
CLOUD CANOPY.  THE DVORAK SATELLITE CLASSIFICATIONS FROM TAFB AND
SAB REMAIN UNCHANGED FROM THE PREVIOUS ESTIMATES...AND THE INITIAL
INTENSITY IS HELD AT 40 KT FOR THIS ADVISORY.  LOW VERTICAL WIND
SHEAR AND WARM SEA SURFACE TEMPERATURES SHOULD PROVIDE AN
ENVIRONMENT CONDUCIVE FOR STRENGTHENING THROUGH THE 72 HOUR PERIOD. 
AFTERWARD...A WEAKENING TREND IS FORECAST AS THE CYCLONE TRAVERSES
COOLER WATER.  THE OFFICIAL INTENSITY FORECAST IS BASED ON THE IVCN
MULTI-MODEL INTENSITY CONSENSUS.
 
THE INITIAL MOTION ESTIMATE IS 290/10 KT. A MID-LEVEL TROPOSPHERIC
RIDGE OVER NORTHWESTERN MEXICO AND BAJA CALIFORNIA IS FORECAST TO
STEER ILEANA IN A GENERAL WEST-NORTHWESTWARD DIRECTION DURING THE
NEXT 48 HOURS. THROUGH DAY 4...THE LARGE-SCALE MODELS SHOW ILEANA
DECREASING IN FORWARD SPEED AND TURNING TOWARD THE NORTHWEST IN
RESPONSE TO A MID- TO UPPER-LEVEL TROUGH APPROACHING THE WEST COAST
OF THE U.S. BY THE END OF THE FORECAST PERIOD...THE GFS...
UKMET...AND THE ECMWF SHOW THE SUBTROPICAL RIDGE BUILDING BACK IN
NORTH OF THE CYCLONE. THIS CHANGE IN THE SYNOPTIC STEERING PATTERN
SHOULD INITIATE A TURN BACK TOWARD THE WEST-NORTHWEST. THE NHC
TRACK FORECAST IS CLOSE TO THE PREVIOUS ONE AND THE TVCE CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/0900Z 15.5N 108.6W   40 KT  45 MPH
 12H  28/1800Z 16.2N 110.0W   50 KT  60 MPH
 24H  29/0600Z 17.0N 111.5W   60 KT  70 MPH
 36H  29/1800Z 17.8N 112.6W   65 KT  75 MPH
 48H  30/0600Z 18.6N 113.3W   65 KT  75 MPH
 72H  31/0600Z 19.9N 114.6W   70 KT  80 MPH
 96H  01/0600Z 21.2N 116.8W   60 KT  70 MPH
120H  02/0600Z 22.3N 120.4W   50 KT  60 MPH
 
$$
FORECASTER ROBERTS
 
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