000 WTPZ45 KNHC 190244 TCDEP5 HURRICANE RICK DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP202009 800 PM PDT SUN OCT 18 2009 DRY AIR AND SOUTHWESTERLY SHEAR...LOCATED BENEATH THE CIRRUS OUTFLOW LAYER...HAVE CONTINUED TO ERODE THE DEEP CONVECTION ON THE WESTERN SIDE OF THE HURRICANE. THE EYE REMAINS DISTINCT IN INFRARED IMAGERY...AND A 2101 AMSR-E MICROWAVE PASS SUGGESTED THAT THE HURRICANE HAD A PARTIAL CONCENTRIC EYEWALL STRUCTURE. THE DEGRADATION OF THE CLOUD PATTERN HAS RESULTED IN DVORAK FINAL-T AND CI NUMBERS OF 6.5/7.0 FROM TAFB AND 6.0/7.0 FROM SAB. IN ADDITION...THE OBJECTIVE ESTIMATE FROM UW-CIMSS IS NOW 6.1/6.7... AND THE ADVISORY INTENSITY IS SET AT 125 KT. RICK IS TURNING NORTHWESTWARD WITH AN INITIAL MOTION OF 305 DEGREES AT 11 KT NOW THAT THE SUBTROPICAL RIDGE TO ITS NORTH HAS BEGUN TO WEAKEN. THE RIDGE IS EXPECTED TO CONTINUE TO BREAK DOWN AS A SHORTWAVE TROUGH LOCATED WEST OF NORTHERN CALIFORNIA MOVES EAST AND AMPLIFIES OVER THE WESTERN UNITED STATES OVER THE NEXT 48 HOURS. AS A RESULT...THE EVOLVING STEERING FLOW WILL TURN RICK TOWARD THE NORTH AND NORTH-NORTHEAST OVER THE NEXT COUPLE OF DAYS. ONLY THE UKMET CONTINUES TO SHOW A WESTWARD MOTION DURING THAT TIME...AND A CONSENSUS OF THE OTHER DYNAMICAL MODELS SUGGESTS THAT RICK WILL ACCELERATE TOWARD THE NORTHEAST BY DAY 3. THE NEW NHC FORECAST IS VERY CLOSE TO THAT CONSENSUS AND NOT VERY DIFFERENT FROM THE PREVIOUS FORECAST. ADDITIONAL WEAKENING IS EXPECTED OVER THE NEXT FEW DAYS DUE TO INCREASING VERTICAL SHEAR AND INGESTION OF DRY AND MORE STABLE AIR LOCATED TO THE WEST OF THE HURRICANE. THE NEW OFFICIAL FORECAST IS A LITTLE FASTER IN WEAKENING RICK THAN WAS SHOWN IN PREVIOUS FORECASTS...BUT THIS IS MAINLY DUE TO THE FACT THAT THE INITIAL INTENSITY IS ALREADY LOWER THAN EXPECTED. MOST IMPORTANTLY...RICK IS STILL EXPECTED TO BE A SIGNIFICANT HURRICANE AS IT MOVES NEAR THE SOUTHERN TIP OF BAJA CALIFORNIA AND INTO NORTHWESTERN MEXICO IN 2 TO 3 DAYS. A 96-HOUR POSITION IS SHOWN TO MAINTAIN CONTINUITY IN THE INTENSITY FORECAST...BUT IT IS DOUBTFUL THAT A WELL-DEFINED SURFACE CENTER WILL EXIST AT THAT TIME. A HURRICANE WATCH MAY BE REQUIRED FOR PORTIONS OF SOUTHERN BAJA EARLY MONDAY. INTERESTS THROUGHOUT SOUTHERN BAJA AND ALONG THE WEST-CENTRAL COAST OF MAINLAND MEXICO SHOULD CLOSELY MONITOR THE PROGRESS OF RICK. FORECAST POSITIONS AND MAX WINDS INITIAL 19/0300Z 17.0N 110.3W 125 KT 12HR VT 19/1200Z 17.9N 111.2W 115 KT 24HR VT 20/0000Z 19.0N 111.8W 105 KT 36HR VT 20/1200Z 20.2N 111.6W 95 KT 48HR VT 21/0000Z 21.7N 110.6W 85 KT 72HR VT 22/0000Z 25.0N 107.5W 70 KT...INLAND 96HR VT 23/0000Z 26.5N 106.0W 30 KT...INLAND 120HR VT 24/0000Z...DISSIPATED $$ FORECASTER BERG