|
Show Selection: |
| #376406 (Received by flhurricane at: 5:05 AM 16.Sep.2010) TCDAT2 HURRICANE JULIA DISCUSSION NUMBER 17 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010 500 AM AST THU SEP 16 2010 THE SATELLITE PRESENTATION OF JULIA HAS CONTINUED TO DETERIORATE OVER THE PAST FEW HOURS. MOST OF THE DEEP CONVECTION IS DISPLACED NORTH OF THE ESTIMATED CENTER POSITION...AND CLOUD TOPS HAVE CONTINUED TO WARM. JULIA IS CURRENTLY SITUATED OVER WATERS OF 26-27C...AND THE MID- TO UPPER-LEVEL TROUGH/LOW BETWEEN JULIA AND HURRICANE IGOR IS IMPARTING 20 TO 30 KT OF SOUTHWESTERLY SHEAR OVER JULIA ACCORDING TO THE UW-CIMSS SHEAR ANALYSIS. BASED ON A BLEND OF SUBJECTIVE AND OBJECTIVE DVORAK INTENSITY ESTIMATES THE INITIAL INTENSITY IS LOWERED TO 90 KT FOR THIS ADVISORY. WHILE THE SHIPS MODEL OUTPUT SHOWS THE SHEAR DECREASING TO LESS THAN 20 KT FROM 12 TO 24 HOURS...JULIA WILL REMAIN OVER MARGINAL SSTS THROUGH THAT TIME. THEN BY 36 HOURS OR SO...WHEN JULIA TEMPORARILY MOVES BACK OVER WARMER WATERS...THE SHEAR INCREASES TO AROUND 30 KT AND REMAINS HIGH FOR THE REST OF THE PERIOD. THIS SCENARIO SHOULD RESULT IN A GRADUAL WEAKENING FOR THE FIRST 48 HOURS...WITH MORE RAPID WEAKENING TOWARD THE END OF THE PERIOD. THE OFFICIAL FORECAST REFLECT THIS AND FOLLOWS A BLEND OF THE LGEM AND SHIPS MODELS THROUGH 48 HOURS...AND IS CLOSEST TO THE LGEM THEREAFTER. WITH A LACK OF MICROWAVE IMAGERY OVER THE PAST FEW HOURS...THE INITIAL MOTION ESTIMATE OF 310/16 IS BASED LARGELY ON CONTINUITY AND THE ASSUMPTION THAT THE LOW-LEVEL CENTER REMAINS DISPLACED SOUTH AND EAST OF THE DEEP CONVECTION. THE TRACK FORECAST REASONING REMAINS UNCHANGED FROM THE PREVIOUS PACKAGE. JULIA IS CURRENTLY BEING STEERED NORTHWESTWARD BY THE UPPER-LEVEL LOW TO ITS SOUTHWEST AND A LARGE MID-LEVEL RIDGE TO ITS EAST...AND THIS WILL CONTINUE FOR THE NEXT DAY OR SO. THEN...AS JULIA MOVES AWAY FROM THE UPPER-LOW...THE CYCLONE WILL MOVE AROUND THE WESTERN PERIPHERY OF THE RIDGE AND TURN EAST-NORTHEASTWARD BY THE END OF THE PERIOD AS IT COMES UNDER THE INFLUENCE OF THE MID-LATITUDE WESTERLIES. SOME DIFFERENCES REMAIN IN HOW SHARPLY JULIA MOVES AROUND THE RIDGE... WITH THE UKMET SHOWING A SHARPER TURN...WHILE THE ECMWF AND HWRF SHOW A WIDER TURN. THE OFFICIAL FORECAST HAS BEEN ADJUSTED TOWARD THE TVCN MULTI-MODEL CONSENSUS...AND IS CLOSE TO THE GFS FOR THE FIRST 72 HOURS...WHICH REPRESENTS A COMPROMISE BETWEEN THE ECMWF AND UKMET. THE NEW NHC FORECAST IS ALSO FASTER THAN THE PREVIOUS PACKAGE DURING THE FIRST 24 HOURS...ACCOUNTING FOR THE OBSERVED ACCELERATION OF JULIA. FORECAST POSITIONS AND MAX WINDS INITIAL 16/0900Z 21.2N 36.2W 90 KT 12HR VT 16/1800Z 22.8N 38.8W 85 KT 24HR VT 17/0600Z 24.6N 42.4W 80 KT 36HR VT 17/1800Z 26.4N 45.5W 75 KT 48HR VT 18/0600Z 28.3N 47.7W 70 KT 72HR VT 19/0600Z 32.5N 49.5W 65 KT 96HR VT 20/0600Z 35.0N 46.5W 50 KT 120HR VT 21/0600Z 36.0N 42.5W 40 KT $$ FORECASTER BRENNAN |
