Tropical Storm RICK
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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
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