ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM RICK DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP202009 800 AM PDT TUE OCT 20 2009 THE SATELLITE APPEARANCE OF RICK HAS GENERALLY CHANGED LITTLE OVER THE PAST SEVERAL HOURS. AN AREA OF DEEP CONVECTION WITH CLOUD TOPS TO -80 C IS MAINLY CONFINED TO THE NORTH OF THE ESTIMATED LOW-LEVEL CENTER...DUE TO ABOUT 20 KT OF VERTICAL WIND SHEAR. DVORAK CURRENT INTENSITY NUMBERS ARE A UNANIMOUS 3.5 FROM BOTH TAFB AND SAB...AND BASED ON THIS DATA...THE INITIAL INTENSITY IS HELD AT 55 KT. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS CURRENTLY EN ROUTE TO INVESTIGATE RICK AND WILL PROVIDE VALUABLE DATA TO HELP DETERMINE THE INTENSITY AND STRUCTURE OF RICK LATER TODAY. STATISTICAL AND DYNAMICAL REGIONAL HURRICANE MODELS DIFFER ON THE FUTURE INTENSITY OF RICK PRIOR TO LANDFALL. THE SHIPS AND LGEM SHOW STEADY WEAKENING TO A WEAK TROPICAL STORM. HOWEVER...THE GFDL AND HWRF MODELS SHOW STRENGTHENING BACK TO A HURRICANE IN THE SHORT-TERM. SINCE SHEAR MAY RELAX SLIGHTLY AND SEA SURFACE TEMPERATURES WARM A COUPLE OF DEGREES ALONG THE EXPECTED TRACK... THIS FORECAST WILL HOLD RICK STEADY-STATE THROUGH LANDFALL RATHER THAN SHOWING WEAKENING AS PREVIOUSLY FORECAST. AFTER LANDFALL... STEADY WEAKENING SHOULD COMMENCE AS THE CIRCULATION WILL LIKELY BECOME DECOUPLED BY THE RUGGED TERRAIN OF MAINLAND MEXICO. THE LOW-LEVEL CENTER OF RICK IS DIFFICULT TO LOCATE...EVEN WITH THE FIRST VISIBLE IMAGES OF THE DAY. HOWEVER...IT DOES APPEAR THAT THE CYCLONE CONTINUES TO GRADUALLY TURN TOWARD THE RIGHT...WITH AN INITIAL MOTION ESTIMATE OF 040/06. WATER VAPOR IMAGES SHOW A MID- TO UPPER-LEVEL TROUGH AMPLIFYING OVER THE SOUTHWESTERN UNITED STATES. GLOBAL MODELS ARE IN GOOD AGREEMENT IN SHOWING FURTHER AMPLIFICATION OF THE TROUGH DURING THE NEXT 12 TO 24 HOURS. THIS WILL CAUSE RICK TO ACCELERATE NORTHEASTWARD THROUGH LANDFALL. THE OFFICIAL TRACK FORECAST IS NUDGED SLIGHTLY TO THE RIGHT AND IS A LITTLE FASTER TO TREND TOWARD THE MODEL CONSENSUS. ON THIS TRACK...THE CENTER OF RICK IS EXPECTED TO PASS SOUTH OF THE SOUTHERN TIP OF BAJA CALIFORNIA TONIGHT AND MAKE LANDFALL OVER MAINLAND MEXICO WITHIN 36 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 20/1500Z 20.1N 110.8W 55 KT 12HR VT 21/0000Z 21.1N 109.8W 55 KT 24HR VT 21/1200Z 22.7N 107.7W 55 KT 36HR VT 22/0000Z 24.5N 105.3W 35 KT...INLAND 48HR VT 22/1200Z 26.4N 102.7W 20 KT...DISSIPATING INLAND 72HR VT 23/1200Z...DISSIPATED $$ FORECASTER CANGIALOSI/PASCH NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:31 UTC