ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM RICK DISCUSSION NUMBER 24 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP202009 200 AM PDT WED OCT 21 2009 INFRARED SATELLITE IMAGERY INDICATES THAT THE CLOUD PATTERN ASSOCIATED WITH RICK HAS CHANGED LITTLE DURING THE LAST FEW HOURS. THE CYCLONE CONTINUES TO CONSIST OF A SHIELD OF PULSATING DEEP CONVECTION ORGANIZED IN A BANDING FEATURE OVER THE NORTHWEST SEMICIRCLE...WITH A DISTINCT MID-LEVEL CIRCULATION CENTER EVIDENT TO ITS SOUTHEAST. DVORAK T-NUMBERS AT 0600 UTC WERE 3.0 AND 3.5 FROM SAB AND TAFB...RESPECTIVELY...AND AGREE FAIRLY WELL WITH A 0148 UTC QUIKSCAT PASS THAT SUGGESTED A MAX INTENSITY OF AT LEAST 55 KT. ON THIS BASIS...THE INITIAL INTENSITY IS HELD AT 55 KT. UW-CIMSS ANALYSES CURRENTLY INDICATE NEARLY 25 KT OF SOUTHWESTERLY SHEAR OVER RICK...AND THE SHIPS MODEL OUTPUT SUGGESTS A FURTHER INCREASE IN THE SHEAR DURING THE NEXT 12-24 HOURS. THE PROHIBITIVELY HIGH VALUES OF SHEAR SHOULD RESULT IN WEAKENING PRIOR TO LANDFALL IN SPITE OF SSTS WARMING ALONG THE FORECAST TRACK. DISSIPATION IS LIKELY IN 24-36 HOURS ONCE THE CENTER QUICKLY MOVES WELL INLAND OVER THE RUGGED TERRAIN OF THE SIERRA MADRE MOUNTAINS. THE CENTER REMAINS EXCEEDINGLY DIFFICULT TO FIND...EVEN WITH MICROWAVE AND SCATTEROMETER PASSES...BUT THE FORWARD MOTION APPEARS TO HAVE INCREASED AND IS ESTIMATED AT 050/12. AN AMPLIFIED MID- TO UPPER-LEVEL TROUGH PROGRESSING THROUGH THE SOUTHERN ROCKIES AND NORTHERN MEXICO DURING THE NEXT 24 HOURS SHOULD STEER RICK ON A CONTINUED NORTHEASTWARD COURSE WITH INCREASING FORWARD SPEED...AT LEAST UNTIL LANDFALL...WHEN SOME OF THE GUIDANCE INDICATES THAT RICK WILL SHEAR APART. FORECAST POSITIONS AND MAX WINDS INITIAL 21/0900Z 21.8N 108.2W 55 KT 12HR VT 21/1800Z 23.1N 106.7W 50 KT 24HR VT 22/0600Z 24.3N 104.7W 20 KT...REMNANT LOW INLAND 36HR VT 22/1800Z...DISSIPATED $$ FORECASTER KIMBERLAIN/FRANKLIN NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:31 UTC