000 WTPZ44 KNHC 130232 TCDEP4 TROPICAL STORM PATRICIA DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP192009 800 PM PDT MON OCT 12 2009 THE CLOUD PATTERN OF THE TROPICAL CYCLONE CONTINUES TO LACK BANDING FEATURES AND IS CHARACTERIZED PRIMARILY BY A CENTRAL DENSE OVERCAST WITH VERY COLD-TOPPED CONVECTION. DVORAK CURRENT INTENSITY ESTIMATES HAVE NOT CHANGED SINCE EARLIER TODAY SO THE INITIAL WIND SPEED IS KEPT AT 50 KT FOR THIS ADVISORY. PATRICIA IS EXHIBITING WELL-DEFINED UPPER-LEVEL OUTFLOW AND SHOULD REMAIN OVER WARM WATERS FOR THE NEXT COUPLE OF DAYS. THE SHIPS MODEL SHOWS WEAK SHEAR OVER THE SYSTEM FOR THE NEXT 36 HOURS...BUT ALSO INDICATES THAT STABLE AND RELATIVE DRY AIR AT MID-TROPOSPHERIC LEVELS WILL BE INHIBITING FACTORS FOR STRENGTHENING. THE OFFICIAL INTENSITY FORECAST...LIKE THE PREVIOUS ONE...SHOWS ONLY A MODEST INCREASE IN STRENGTH AND IS CLOSE TO THE STATISTICAL-DYNAMICAL LGEM GUIDANCE. GIVEN THE LIMITATIONS IN FORECASTING INTENSITY CHANGE...IT IS CERTAINLY POSSIBLE FOR PATRICIA TO BECOME STRONGER THAN INDICATED HERE. IN FACT...BASED ON HISTORICAL NHC INTENSITY FORECAST ERRORS...THERE IS ABOUT A 20 PERCENT CHANCE OF PATRICIA BECOMING A HURRICANE IN THE NEXT 24 HOURS OR SO. THE CENTER REMAINS HARD TO PINPOINT BUT BASED ON RECENT GEOSTATIONARY SATELLITE FIXES THE TRACK HAS BEEN SHIFTED SLIGHTLY EASTWARD. THE BEST ESTIMATE OF INITIAL MOTION IS SLOWLY NORTHWARD OR 350/5. PATRICIA HAS BEEN MOVING ON THE SOUTHWEST PERIPHERY OF A MID-LEVEL ANTICYCLONE CENTERED OVER THE GULF OF MEXICO. GLOBAL MODEL GUIDANCE SHOWS THE ASSOCIATED RIDGE BUILDING WESTWARD...AND TO THE NORTH OF THE TROPICAL CYCLONE...OVER THE NEXT DAY OR SO. THIS EVOLUTION SHOULD CAUSE THE MOTION TO BEND TOWARD THE NORTHWEST WITHIN 36 HOURS OR SO. A LITTLE LATER IN THE FORECAST PERIOD...THE MODELS SHOW THE ANTICYCLONE SHIFTING WESTWARD WHICH WOULD LIKELY RESULT IN PATRICIA TURNING TOWARD THE WEST. THE MAIN CONCERN IS HOW FAR NORTH THE TROPICAL CYCLONE WILL MOVE DURING THE NEXT 24 HOURS...AS THIS WILL LARGELY DETERMINE HOW MUCH IMPACT PATRICIA WILL HAVE ON SOUTHERN BAJA CALIFORNIA. EVEN THOUGH THE OFFICIAL FORECAST DOES NOT BRING THE TROPICAL CYCLONE ANY CLOSER TO THE BAJA PENINSULA THAN THE PREVIOUS ONE...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT PREDICTED TRACK DUE TO UNCERTAINTIES. AT THIS TIME...NO CHANGES TO THE TROPICAL STORM WATCH ARE NECESSARY. FORECAST POSITIONS AND MAX WINDS INITIAL 13/0300Z 20.0N 109.9W 50 KT 12HR VT 13/1200Z 20.7N 110.0W 55 KT 24HR VT 14/0000Z 21.6N 110.4W 60 KT 36HR VT 14/1200Z 22.1N 111.2W 60 KT 48HR VT 15/0000Z 22.3N 112.3W 60 KT 72HR VT 16/0000Z 22.5N 115.0W 50 KT 96HR VT 17/0000Z 22.5N 118.0W 35 KT 120HR VT 18/0000Z 22.5N 121.0W 25 KT...REMNANT LOW $$ FORECASTER PASCH/LANDSEA