150 
 WTPZ45 KNHC 201453
 TCDEP5
 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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