000
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/BROWN