ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM MIRIAM DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132012 800 PM PDT WED SEP 26 2012 CONVECTIVE CLOUD TOPS CONTINUE TO WARM...AND DEEP CONVECTION IS LIMITED TO A BAND LOCATED ABOUT 150 N MI TO THE NORTH OF THE CENTER. DVORAK NUMBERS HAVE DROPPED TO T3.0/4.0 FROM TAFB AND T2.0/3.0 FROM SAB. BASED ON A BLEND OF THE FINAL-T AND CI NUMBERS...THE ADVISORY INTENSITY IS SET AT 40 KT. THIS IS SUPPORTED BY A CI NUMBER OF 2.8 FROM THE LATEST UW-CIMSS ADT ESTIMATE. MIRIAM WILL CONTINUE TO BE AFFECTED BY 20-25 KT OF DEEP-LAYER WEST-SOUTHWESTERLY SHEAR IN THE COMING DAYS...AND THE CENTER IS BEGINNING TO MOVE OVER WATER THAT IS COLDER THAN 26C. THIS ENVIRONMENT IS NOT LIKELY TO SUPPORT SIGNIFICANT DEEP CONVECTION... AND MIRIAM COULD BECOME POST-TROPICAL AS EARLY AS THURSDAY IF CURRENT CONVECTIVE TRENDS HOLD. THE NHC INTENSITY FORECAST FOLLOWS THE SAME WEAKENING SHOWN BY THE STATISTICAL GUIDANCE...AND MOST OF THE GLOBAL MODELS DISSIPATE THE REMNANT LOW IN ABOUT 5 DAYS. MIRIAM IS MOVING NORTH-NORTHWESTWARD AT ABOUT 6 KT AS IT ROTATES AROUND A MID-TROPOSPHERIC LOW LOCATED NOT TOO FAR TO ITS WEST. THE CYCLONE WILL SOON BE RUNNING INTO A LARGE AREA OF HIGH PRESSURE CENTERED TO THE WEST OF CALIFORNIA...AND IT IS LIKELY TO BEGIN MOVING SLOWLY WESTWARD OR EVEN SOUTHWESTWARD AFTER 48 HOURS. ALMOST ALL THE TRACK MODELS SHOW THE HIGH PRESSURE PUSHING MIRIAM SOUTHWARD BEFORE IT DISSIPATES...AND THAT SCENARIO IS INDICATED IN THE OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 27/0300Z 21.5N 115.7W 40 KT 45 MPH 12H 27/1200Z 22.2N 116.1W 35 KT 40 MPH 24H 28/0000Z 22.7N 116.6W 30 KT 35 MPH 36H 28/1200Z 22.8N 117.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 29/0000Z 22.9N 117.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 30/0000Z 22.9N 117.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 01/0000Z 22.5N 118.0W 15 KT 15 MPH...POST-TROP/REMNT LOW 120H 02/0000Z...DISSIPATED $$ FORECASTER BERG NNNN
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Page last modified: Monday, 31-Dec-2012 12:10:38 UTC