000 WTPZ44 KNHC 182034 TCDEP4 TROPICAL STORM DORA DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042011 200 PM PDT MON JUL 18 2011 DORA HAS CONTINUED TO STRENGTHEN DESPITE MODEST NORTHERLY UPPER-LEVEL WINDS AND THE RAGGED APPEARANCE OF THE LARGE CURVED BAND THAT NOW WRAPS ALMOST THREE QUARTERS OF THE WAY AROUND THE CENTER. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE T2.5/35 KT AND T2.0/30 KT...RESPECTIVELY...AND UW-CIMSS ADT ESTIMATES ARE T2.5/35 KT. HOWEVER...AN ASCAT OVERPASS AT 1610Z INDICATED A COUPLE OF 40-KT WIND VECTORS WITHIN A LARGE FIELD OF 34-KT WINDS...SO THE INITIAL INTENSITY IS SET AT 40 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS 280/12. DORA HAS BEEN WOBBLING ABOUT THIS MEAN MOTION AS SMALLER CIRCULATIONS HAVE BEEN ROTATING AROUND THE MEAN CENTER. HOWEVER...THE GENERAL TREND SHOULD BE FOR THE CYCLONE TO CONTINUE MOVING IN A WEST-NORTHWESTWARD DIRECTION THROUGHOUT THE FORECAST PERIOD AS DORA IS STEERED BY THE LARGE AND STRONG HIGH PRESSURE SYSTEM TO THE NORTH. BY 72-96 HOURS...THE WESTERN PORTION OF THE EXTENSIVE SUBTROPICAL RIDGE IS FORECAST TO WEAKEN...WHICH SHOULD RESULT IN A DECREASE IN FORWARD SPEED. HOWEVER...THE RIDGE IS NOT EXPECTED TO COMPLETELY ERODE LIKE THE GFDL AND HWRF MODELS ARE FORECASTING. AS A RESULT...THE CENTER OF DORA IS FORECAST TO REMAIN WELL SOUTH OF MAINLAND MEXICO. THE OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS ADVISORY AND IS CLOSE TO THE DYNAMICAL MODEL CONSENSUS...TVCN. CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE THE INNER CORE WIND FIELD HAS BECOME BETTER DEFINED AS THE LAST OF MULTIPLE SMALLER CIRCULATIONS HAS MERGED INTO THE MAIN LOW-LEVEL CIRCULATION CENTER. GIVEN THAT THE VERTICAL SHEAR IS FORECAST TO DECREASE OVER THE NEXT 24-36 HOURS AS DORA PASSES OVER PROGRESSIVELY WARMER WATER...A PERIOD OF RAPID INTENSIFICATION IS EXPECTED FOR AT LEAST THE NEXT 24 HOURS. CONTINUED STRENGTHENING IS FORECAST THROUGH 72-84 HOURS...AFTER WHICH RAPID WEAKENING IS EXPECTED TO BEGIN AS THE CYCLONE MOVES OVER MUCH COOLER WATER WEST OF 110W LONGITUDE. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND REMAINS WELL ABOVE ALL OF THE AVAILABLE INTENSITY GUIDANCE. WIND RADII ARE BASED ON THE 1610Z ASCAT OVERPASS. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 10.7N 92.9W 40 KT 45 MPH 12H 19/0600Z 11.1N 94.8W 55 KT 65 MPH 24H 19/1800Z 11.9N 97.6W 70 KT 80 MPH 36H 20/0600Z 13.0N 100.3W 85 KT 100 MPH 48H 20/1800Z 14.3N 102.8W 95 KT 110 MPH 72H 21/1800Z 17.0N 107.4W 105 KT 120 MPH 96H 22/1800Z 18.7N 110.4W 90 KT 105 MPH 120H 23/1800Z 20.0N 113.0W 60 KT 70 MPH $$ FORECASTER STEWART 000 WTPZ44 KNHC 182034 TCDEP4 TROPICAL STORM DORA DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042011 200 PM PDT MON JUL 18 2011 DORA HAS CONTINUED TO STRENGTHEN DESPITE MODEST NORTHERLY UPPER-LEVEL WINDS AND THE RAGGED APPEARANCE OF THE LARGE CURVED BAND THAT NOW WRAPS ALMOST THREE QUARTERS OF THE WAY AROUND THE CENTER. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE T2.5/35 KT AND T2.0/30 KT...RESPECTIVELY...AND UW-CIMSS ADT ESTIMATES ARE T2.5/35 KT. HOWEVER...AN ASCAT OVERPASS AT 1610Z INDICATED A COUPLE OF 40-KT WIND VECTORS WITHIN A LARGE FIELD OF 34-KT WINDS...SO THE INITIAL INTENSITY IS SET AT 40 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS 280/12. DORA HAS BEEN WOBBLING ABOUT THIS MEAN MOTION AS SMALLER CIRCULATIONS HAVE BEEN ROTATING AROUND THE MEAN CENTER. HOWEVER...THE GENERAL TREND SHOULD BE FOR THE CYCLONE TO CONTINUE MOVING IN A WEST-NORTHWESTWARD DIRECTION THROUGHOUT THE FORECAST PERIOD AS DORA IS STEERED BY THE LARGE AND STRONG HIGH PRESSURE SYSTEM TO THE NORTH. BY 72-96 HOURS...THE WESTERN PORTION OF THE EXTENSIVE SUBTROPICAL RIDGE IS FORECAST TO WEAKEN...WHICH SHOULD RESULT IN A DECREASE IN FORWARD SPEED. HOWEVER...THE RIDGE IS NOT EXPECTED TO COMPLETELY ERODE LIKE THE GFDL AND HWRF MODELS ARE FORECASTING. AS A RESULT...THE CENTER OF DORA IS FORECAST TO REMAIN WELL SOUTH OF MAINLAND MEXICO. THE OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS ADVISORY AND IS CLOSE TO THE DYNAMICAL MODEL CONSENSUS...TVCN. CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE THE INNER CORE WIND FIELD HAS BECOME BETTER DEFINED AS THE LAST OF MULTIPLE SMALLER CIRCULATIONS HAS MERGED INTO THE MAIN LOW-LEVEL CIRCULATION CENTER. GIVEN THAT THE VERTICAL SHEAR IS FORECAST TO DECREASE OVER THE NEXT 24-36 HOURS AS DORA PASSES OVER PROGRESSIVELY WARMER WATER...A PERIOD OF RAPID INTENSIFICATION IS EXPECTED FOR AT LEAST THE NEXT 24 HOURS. CONTINUED STRENGTHENING IS FORECAST THROUGH 72-84 HOURS...AFTER WHICH RAPID WEAKENING IS EXPECTED TO BEGIN AS THE CYCLONE MOVES OVER MUCH COOLER WATER WEST OF 110W LONGITUDE. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND REMAINS WELL ABOVE ALL OF THE AVAILABLE INTENSITY GUIDANCE. WIND RADII ARE BASED ON THE 1610Z ASCAT OVERPASS. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 10.7N 92.9W 40 KT 45 MPH 12H 19/0600Z 11.1N 94.8W 55 KT 65 MPH 24H 19/1800Z 11.9N 97.6W 70 KT 80 MPH 36H 20/0600Z 13.0N 100.3W 85 KT 100 MPH 48H 20/1800Z 14.3N 102.8W 95 KT 110 MPH 72H 21/1800Z 17.0N 107.4W 105 KT 120 MPH 96H 22/1800Z 18.7N 110.4W 90 KT 105 MPH 120H 23/1800Z 20.0N 113.0W 60 KT 70 MPH $$ FORECASTER STEWART