000 WTPZ45 KNHC 180839 TCDEP5 HURRICANE RICK DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP202009 200 AM PDT SUN OCT 18 2009 INFRARED SATELLITE IMAGES SHOW THAT RICK IS MAINTAINING AN EXTREMELY WELL-DEFINED 15 N MI DIAMETER EYE EMBEDDED WITHIN VERY COLD CLOUD TOPS. THE UPPER-TROPOSPHERIC OUTFLOW IS QUITE EXTENSIVE AS WELL. BOTH OBJECTIVE AND SUBJECTIVE DVORAK T-NUMBERS ARE CLOSE TO 7.5 WHICH CONTINUE TO SUPPORT AN INTENSITY OF ABOUT 155 KT...I.E. CATEGORY FIVE STRENGTH. MICROWAVE IMAGERY SUGGESTS THAT A CONCENTRIC EYEWALL MAY BE TRYING TO FORM WHICH COULD PRESAGE AN EYEWALL REPLACEMENT...AND POSSIBLY SOME WEAKENING. IN ANY EVENT... RICK HAS PROBABLY REACHED ITS MAXIMUM INTENSITY AS IT WILL BE MOVING INTO AN ENVIRONMENT THAT WILL GRADUALLY BECOME LESS CONDUCIVE FOR STRENGTHENING. ALTHOUGH SEA SURFACE TEMPERATURES SHOULD BECOME ONLY SLIGHTLY COOLER ALONG THE TRACK OF RICK...GLOBAL MODEL FORECASTS INDICATE A GRADUAL INCREASE IN VERTICAL SHEAR. THE SHIPS MODEL SHOWS SOUTHWESTERLY SHEAR OF 20-30 KT IN ITS 3-5 DAY PREDICTION. THE OFFICIAL INTENSITY FORECAST IS BETWEEN THE SHIPS AND LGEM GUIDANCE THROUGH 48 HOURS AND SOMEWHAT ABOVE THOSE MODELS AND THE INTENSITY MODEL CONSENSUS THEREAFTER...TO ALLOW FOR THE POSSIBILITY THAT THE HURRICANE WILL NOT BE AFFECTED SO MUCH BY THE SHEAR. THE INITIAL MOTION...285/12...CONTINUES ABOUT THE SAME AS BEFORE. THERE ARE NO IMPORTANT CHANGES TO THE TRACK FORECAST SCENARIO. RICK IS BEING STEERED BY THE FLOW TO THE SOUTH OF A WEAKENING SUBTROPICAL RIDGE. A BREAK IN THE RIDGE...ASSOCIATED WITH A MID-TROPOSPHERIC TROUGH MOVING OVER CALIFORNIA IN A DAY OR TWO...SHOULD CAUSE THE HURRICANE TO GRADUALLY TURN TOWARD THE NORTH OVER THE NEXT 48-72 HOURS. AFTERWARDS...THE TRACK MODELS ARE IN REASONABLY GOOD AGREEMENT THAT RICK WILL TURN NORTH-NORTHEASTWARD AND NORTHEASTWARD. THE U.K. MET OFFICE MODEL REMAINS THE OUTLIER OF THE DYNAMICAL GUIDANCE IN THAT IT SHOWS LITTLE MOTION BEYOND 48 HOURS AND IS WELL TO THE SOUTHWEST OF THE MODEL CONSENSUS. THE NHC FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS ONE...AND SHOWS A TRACK OVER SOUTHERN BAJA AND WESTERN MAINLAND MEXICO IN THE LATTER PART OF THE PERIOD. HOWEVER INTERESTS IN THESE AREAS SHOULD BEAR IN MIND THAT SIGNIFICANT ERRORS IN LANDFALL LOCATION AND TIMING ARE POSSIBLE IN THE 4- AND 5-DAY TIME FRAME. ALTHOUGH THE HURRICANE IS NOT LIKELY TO MAINTAIN CATEGORY FIVE STRENGTH WHEN IT APPROACHES BAJA CALIFORNIA...IT COULD STILL BE QUITE POWERFUL BY THAT TIME. INTERESTS IN THAT AREA AND ALONG THE SOUTHWEST COAST OF MAINLAND MEXICO SHOULD CLOSELY FOLLOW THE PROGRESS OF THIS EXTREMELY DANGEROUS HURRICANE OVER THE NEXT SEVERAL DAYS. FORECAST POSITIONS AND MAX WINDS INITIAL 18/0900Z 15.3N 107.2W 155 KT 12HR VT 18/1800Z 15.9N 109.0W 150 KT 24HR VT 19/0600Z 17.0N 110.7W 140 KT 36HR VT 19/1800Z 18.0N 111.7W 130 KT 48HR VT 20/0600Z 19.1N 112.0W 115 KT 72HR VT 21/0600Z 21.5N 111.0W 95 KT 96HR VT 22/0600Z 24.5N 109.0W 75 KT 120HR VT 23/0600Z 28.0N 104.0W 25 KT...DISSIPATING INLAND $$ FORECASTER PASCH