Tropical Storm RICK

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TROPICAL STORM RICK DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP202009
800 PM PDT THU OCT 15 2009
 
SATELLITE IMAGES SHOW THAT TROPICAL DEPRESSION TWENTY-E HAS
DEVELOPED INTO TROPICAL STORM RICK.  BANDS OF DEEP CONVECTION ARE
WRAPPING AROUND THE CENTER...WITH EVIDENCE OF A PRECURSORY INNER
CORE FORMING FROM A SSMI IMAGE AT 0030 UTC.  SUBJECTIVE DVORAK
ESTIMATES RANGE FROM 35 TO 45 KT...WITH THE LATEST AMSU ESTIMATES
EVEN HIGHER.  THE INITIAL INTENSITY IS RAISED TO 45 KT AS A BLEND
OF THESE DATA.

THE MAIN INTENSITY FORECAST PROBLEM TONIGHT IS NOT IF RICK WILL
INTENSIFY...BUT HOW QUICKLY.  ENVIRONMENTAL CONDITIONS ARE
EXCEPTIONALLY CONDUCIVE FOR STRENGTHENING DURING THE NEXT FEW DAYS
WITH SSTS OF ABOUT 30C...ABOUT 2C WARMER THAN AVERAGE...LIGHT
SHEAR...AND HIGH MID-LEVEL RELATIVE HUMIDITIES.  THE SHIPS RAPID
INTENSIFICATION INDEX RESPONDS TO THESE CONDITIONS BY SHOWING AN 82
PERCENT CHANCE OF A 30 KT INCREASE IN STRENGTH DURING THE NEXT 24
HOURS...ABOUT 11 TIMES HIGHER THAN THE SAMPLE MEAN.  WITH OTHER
GUIDANCE SHOW SIGNIFICANT STRENGTHENING...THE OFFICIAL FORECAST
WILL SHOW RAPID INTENSIFICATION DURING THE FIRST 24 HOURS OF THE
PERIOD...STARTING FROM A SYNOPTIC INTENSITY OF 40 KT.   LATER ON...
ALL RELIABLE GUIDANCE BRINGS RICK TO MAJOR HURRICANE INTENSITY
WITHIN THREE DAYS...AND SO DOES THE OFFICIAL FORECAST.  THE FLORIDA
STATE SUPERENSEMBLE AND THE HWRF SHOWS AN EVEN STRONGER SYSTEM THAN
THE NHC FORECAST...WHICH IS CERTAINLY POSSIBLE GIVEN THE FAVORABLE
CONDITIONS.  BY THE END OF THE FORECAST PERIOD...THE SYSTEM WILL
LIKELY BE MOVING OVER SOMEWHAT COOLER WATERS AND COULD EXPERIENCE
AN INCREASE IN SHEAR.   THUS...THE INTENSITY FORECAST IS DECREASED
AT THAT TIME...IN LINE WITH MUCH OF THE GUIDANCE.  

THE INITIAL MOTION ESTIMATE IS 295/8. RICK SHOULD BE STEERED BY A
LARGE MIDDLE TROPOSPHERIC RIDGE THAT IS CENTERED OVER NORTHWESTERN
MEXICO...KEEPING THE STORM ON A WEST OR WEST-NORTHWEST TRACK FOR
THE NEXT THREE DAYS OR SO.  AFTER THAT TIME...THE RIDGE SHOULD
WEAKEN AS A TROUGH MOVES OVER THE WESTERN UNITED STATES...WHICH
COULD ALLOW A MORE NORTHWESTWARD TO NORTHWARD MOTION OF THE
TROPICAL CYCLONE.  THERE IS A GOOD DEAL OF MODEL DISAGREEMENT IN
THE LONGER-TERM AS THE REGIONAL HURRICANE MODELS...GFDL/HWRF/
GFDN...SHOW RICK GAINING ENOUGH LATITUDE OVER THE NEXT FEW DAYS TO
ALLOW IT TO TURN EARLIER AND APPROACH OF BAJA CALIFORNIA.  THE REST
OF THE GLOBAL MODELS SUGGEST THE RIDGE WILL REMAIN STRONGER FOR A
LONGER TERM PERIOD OF TIME...RESULTING IN RICK REMAINING WELL
SOUTH-SOUTHWEST OF BAJA CALIFORNIA BY DAY FIVE.  IT IS A LITTLE
UNUSUAL TO SEE THE HURRICANE MODELS HAVE SUCH DIFFERENT SOLUTIONS
FROM THE GLOBAL MODELS...AND THAT DOES NOT LEND CONFIDENCE TO THE
FORECAST AT THIS TIME.  THE NHC FORECAST WILL STAY A LITTLE SOUTH
OF THE MODEL CONSENSUS SINCE THE GLOBAL MODELS HAVE BEEN A LITTLE
MORE SKILLFUL THAN THE REGIONAL MODELS SO FAR THIS SEASON...AND THIS
TRACK IS FAIRLY CLOSE TO THE PREVIOUS FORECAST.  

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0300Z 12.4N  97.7W    45 KT
 12HR VT     16/1200Z 12.8N  98.8W    55 KT
 24HR VT     17/0000Z 13.3N 100.3W    70 KT
 36HR VT     17/1200Z 13.8N 102.1W    80 KT
 48HR VT     18/0000Z 14.3N 104.5W    95 KT
 72HR VT     19/0000Z 15.7N 109.0W   115 KT
 96HR VT     20/0000Z 18.0N 112.0W   115 KT
120HR VT     21/0000Z 20.0N 112.5W   105 KT
 
$$
FORECASTER BLAKE
 
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