000 WTPZ45 KNHC 160235 TCDEP5 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