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117 WTPZ45 KNHC 210238 TCDEP5 TROPICAL STORM RICK DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP202009 800 PM PDT TUE OCT 20 2009 CONVECTION HAS INCREASED MARKEDLY THIS EVENING WITH RICK AS VERY DEEP THUNDERSTORMS ARE LOCATED NORTH AND NORTHWEST OF THE CENTER. ALTHOUGH THE SATELLITE PRESENTATION HAS IMPROVED ON THE INFRARED CHANNEL...MICROWAVE DATA SUGGEST THE SYSTEM IS EXPERIENCING SHEAR WITH THE APPARENT LOW-LEVEL CENTER WELL SOUTHWEST OF THE MID-LEVEL CENTER. SATELLITE INTENSITY ESTIMATES REMAIN AT 55 KT...AND SO WILL THE INTITIAL WIND SPEED. LITTLE CHANGE IN INTENSITY IS EXPECTED UNTIL LANDFALL DUE TO INCREASING VERTICAL WIND SHEAR LIKELY CANCELLING OUT THE EFFECTS OF WARMER WATERS. AFTER LANDFALL... WEAKENING IS LIKELY TO BE QUITE RAPID AS RICK RUNS INTO THE SIERRA MADRE MOUNTAIN CHAIN...AND THERE PROBABLY WILL NOT BE MUCH LEFT OF THE TROPICAL CYCLONE BY 36 HR. THE CENTER HAS BEEN DIFFICULT TO LOCATE SINCE RECONNAISSANCE LEFT... BUT AN ESTIMATE OF 050/10 IS USED AS A COMPROMISE OF CONVENTIONAL AND MICROWAVE IMAGERY. A LARGE TROUGH DIGGING INTO NORTHWESTERN MEXICO IS EXPECTED TO STEER RICK NORTHEASTWARD AND CAUSE AN INCREASE IN FORWARD SPEED. MOST OF THE MODELS ARE IN REASONABLE AGREEMENT ON THIS SCENARIO AND THE OFFICIAL FORECAST TRACK IS ADJUSTED ONLY SLIGHTLY TO THE RIGHT OF THE PREVIOUS ONE. THE ONLY FLY IN THE OINTMENT WOULD BE IF THE TROPICAL CYCLONE WERE TO DECOUPLE... LEAVING THE LOW-LEVEL CENTER BEHIND WHILE THE MID-LEVEL CENTER MOVES QUICKLY TO THE NORTHEAST. IF THAT SITUATION OCCURS...THE SYSTEM COULD MOVE SLOWER AND TO THE RIGHT OF THE OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 21/0300Z 20.9N 109.2W 55 KT 12HR VT 21/1200Z 22.0N 107.8W 55 KT 24HR VT 22/0000Z 23.7N 105.5W 35 KT...INLAND 36HR VT 22/1200Z 25.5N 103.0W 20 KT...DISSIPATING INLAND 48HR VT 23/0000Z...DISSIPATED $$ FORECASTER BLAKE/BROWNReturn to the Tropical Systems Page for RICK Back to main Tropical Weather page
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