000
WTPZ45 KNHC 200251
TCDEP5
TROPICAL STORM RICK DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP202009
800 PM PDT MON OCT 19 2009
 
RICK HAS BEEN WEAKENING AT A RAPID PACE...ALMOST AS FAST AS IT
STRENGTHENED SEVERAL DAYS AGO.  CONVENTIONAL AND MICROWAVE SATELLITE
DATA SHOW THAT THE LOW-LEVEL CENTER IS NOW COMPLETELY EXPOSED TO
THE WEST AND SOUTHWEST OF A SHAPELESS CLUSTER OF DEEP CONVECTION. 
DVORAK FINAL-T AND CI NUMBERS ARE NOW 3.5/4.5 FROM TAFB AND
SAB...BUT BOTH AGENCIES WERE CONSTRAINED BY THE DVORAK RULES AND
ACTUALLY HAD DATA T-NUMBERS OF 3.0.  IN ADDITION...THE LATEST
UW-CIMMS ADT 3-HOUR ESTIMATE IS 3.1 WITH A CI OF 3.6.  THEREFORE...
RICK IS DOWNGRADED TO A 60-KT TROPICAL STORM.

STRONG UPPER-LEVEL WESTERLY WINDS AND DRY...STABLE AIR TO THE WEST
OF RICK ARE THE LIKELY CAUSES FOR THE RAPID WEAKENING OF RICK OVER
THE PAST DAY OR SO.  SINCE THE SHEAR IS NOT EXPECTED TO ABATE AND
THE AMBIENT ENVIRONMENT IS FORECAST TO REMAIN STABLE...RICK SHOULD
CONTINUE TO WEAKEN OVER THE NEXT COUPLE OF DAYS.  THE NEW INTENSITY
FORECAST IS SIGNIFICANTLY LOWER THAN THE PREVIOUS ONE DUE TO THE
RECENT WEAKENING TREND...BUT IT IS STILL HIGHER THAN THAT SHOWN BY
THE STATISTICAL SHIPS AND LGEM MODELS.  ALL IN ALL...IT IS CLOSE TO
THE INTENSITY CONSENSUS AND INDICATES A MORE GRADUAL WEAKENING THAN
HAS OCCURRED OVER THE PAST DAY OR TWO.  RICK IS STILL FORECAST TO
BE A TROPICAL STORM AS IT MOVES NEAR SOUTHERN BAJA CALIFORNIA AND
TOWARDS THE COAST OF MAINLAND MEXICO.

RICK IS NOW MOVING NORTHWARD WITH AN INITIAL MOTION OF 350 DEGREES
AT 7 KT.  THE TRACK GUIDANCE IS STILL IN GOOD AGREEMENT IN SHOWING
A NORTH-NORTHEASTWARD TO NORTHEASTWARD TURN OVER THE NEXT 24 TO 36
HOURS AS RICK GETS PICKED UP BY A SHORTWAVE TROUGH CURRENTLY ALONG
THE WEST COAST OF THE UNITED STATES.  THE GUIDANCE ENVELOPE AND THE
MODEL CONSENSUS TVCN HAVE SHIFTED JUST A LITTLE TO THE EAST AND
CONTINUE TO SHOW THE CENTER OF RICK PASSING JUST TO THE SOUTHEAST OF
THE SOUTHERN TIP OF BAJA CALIFORNIA.
 
THE GOVERNMENT OF MEXICO HAS CHANGED THE HURRICANE WATCH FOR
SOUTHERN BAJA CALIFORNIA TO A TROPICAL STORM WATCH DUE TO THE
UPDATED INTENSITY FORECAST.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0300Z 19.1N 111.8W    60 KT
 12HR VT     20/1200Z 19.9N 111.6W    50 KT
 24HR VT     21/0000Z 21.3N 110.5W    50 KT
 36HR VT     21/1200Z 23.0N 108.8W    45 KT
 48HR VT     22/0000Z 24.8N 106.8W    30 KT...INLAND
 72HR VT     23/0000Z...DISSIPATED
 
$$
FORECASTER BERG/BROWN