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| #531382 (Received by flhurricane at: 10:59 PM 02.Aug.2012) TCDAT5 TROPICAL STORM ERNESTO DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052012 1100 PM AST THU AUG 02 2012 SATELLITE IMAGERY AND RADAR DATA FROM BARBADOS INDICATE ERNESTO HAS BECOME A LITTLE BETTER ORGANIZED OVER THE PAST 6 HOURS. THESE DATA ALSO INDICATE THAT THE CENTER OF ERNESTO HAS MOVED OR DEVELOPED FARTHER NORTH OF THE PREVIOUS POSITION. THE INITIAL INTENSITY IS SUPPORTED BY THE UW-CIMSS ADT INTENSITY ESTIMATE OF T3.0/45 KT. THE INITIAL MOTION ESTIMATE IS 275/19 KT BASED PRIMARILY ON RADAR DATA AND MICROWAVE SATELLITE POSITIONS OVER THE PAST 9 HOURS. A DEEP-LAYER RIDGE SITUATED TO THE NORTH OF THE GREATER AND LESSER ANTILLES IS EXPECTED TO REMAIN INTACT THROUGHOUT THE FORECAST PERIOD AND STEER ERNESTO ON A WEST TO WEST-NORTHWESTWARD TRACK. BY DAYS 4 AND 5...A WEAKNESS IN THE RIDGE IS FORECAST TO DEVELOP ACROSS THE GULF OF MEXICO...WHICH SHOULD RESULT IN A SIGNIFICANT DECREASE IN THE FORWARD SPEED OF THE CYCLONE. THERE IS A LARGE SPREAD IN THE NHC MODEL GUIDANCE WITH THE ECMWF AND GFS MODELS TAKING ERNESTO INTO CENTRAL AMERICA...WHILE THE UKMET AND GFDL MODELS TAKE THE CYCLONE TO WESTERN CUBA BY 120 HOURS. THE REST OF THE GUIDANCE LIES BETWEEN THESE TWO EXTREMES. THE OFFICIAL FORECAST HAS BEEN SHIFTED NORTH OF THE PREVIOUS ADVISORY TRACK... MAINLY DUE TO THE MORE POLEWARD INITIAL POSITION...AND IS CLOSE TO THE NHC CONSENSUS MODEL...TVCN...WHICH HAS SHOWN VERY LITTLE CROSS-TRACK VARIATION OVER THE PAST 36 HOURS. THE RATHER FAST FORWARD SPEED COMBINED WITH SOME MODERATE VERTICAL WIND SHEAR FOR THE NEXT 12-24 HOURS SHOULD ONLY ALLOW FOR SOME SLIGHT STRENGTHENING TO OCCUR. AFTER THAT...HOWEVER...THE GFS-BASED SHIPS MODEL INDICATES THE SHEAR SHOULD WEAKEN TO LESS THAN 10 KT AND REMAIN THAT WAY FOR THE REMAINDER OF THE FORECAST PERIOD. THE COMBINATION OF WARMER SSTS...INCREASING MID-LEVEL MOISTURE...AND DECREASING SHEAR SHOULD ALLOW FOR MORE MODEST INTENSIFICATION TO OCCUR. IN FACT...IF ERNESTO REMAINS CLOSE TO THE FORECAST TRACK... MORE SIGNIFICANT STRENGTHENING COULD OCCUR BY DAYS 4 AND 5 AS INDICATED BY THE LGEM AND STATISTICAL HFIP EXPERIMENTAL INTENSITY MODELS... WHICH MAKE ERNESTO A MAJOR HURRICANE BY 120 HOURS WHEN THE CYCLONE WILL BE IN IDEAL ENVIRONMENTAL AND OCEANIC CONDITIONS. HOWEVER... THE LARGE SPREAD IN THE TRACK MODELS AND UNCERTAINTY IN WHETHER ERNESTO WILL BE AFFECTED BY LAND REQUIRES THAT THE INTENSITY FORECAST REMAIN CONSERVATIVE AT THIS TIME. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 13.4N 58.3W 45 KT 50 MPH 12H 03/1200Z 13.7N 61.1W 50 KT 60 MPH 24H 04/0000Z 14.0N 64.4W 50 KT 60 MPH 36H 04/1200Z 14.4N 67.5W 55 KT 65 MPH 48H 05/0000Z 15.0N 70.6W 60 KT 70 MPH 72H 06/0000Z 16.3N 76.6W 65 KT 75 MPH 96H 07/0000Z 17.9N 81.1W 70 KT 80 MPH 120H 08/0000Z 19.7N 84.6W 75 KT 85 MPH $$ FORECASTER STEWART |
