000 WTPZ44 KNHC 280843 TCDEP4 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