000 WTPZ44 KNHC 130846 TCDEP4 TROPICAL STORM PATRICIA DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP192009 200 AM PDT TUE OCT 13 2009 SSMIS...TRMM...AND QUIKSCAT DATA THAT ARRIVED JUST AFTER THE ISSUANCE OF THE PREVIOUS ADVISORY INDICATE THAT PATRICIA MOVED UNEXPECTEDLY NORTH-NORTHEASTWARD EARLY THIS EVENING. THE SCATTEROMETER AND TRMM DATA AS WELL AS A RECENT SHIP OBSERVATION SUGGEST THAT THE PREVAILING NORTHWESTERLY LOW-LEVEL FLOW ALONG THE SOUTHERN BAJA PENINSULA HAS DISRUPTED THE NORTHERN PORTION OF THE CIRCULATION...RESULTING IN A SOUTH-SOUTHEAST TO NORTH-NORTHWEST ELONGATION OF THE SYSTEM. PATRICIA CONTINUES TO LACK BANDING FEATURES. CLOUD TOPS ASSOCIATED WITH THE LARGE MASS OF DEEP CONVECTION WARMED DURING THE PAST SEVERAL HOURS...BUT MORE RECENTLY A NEW BURST OF CONVECTION HAS DEVELOPED NEAR THE ESTIMATED CENTER. THE QUIKSCAT DATA SHOWED SOME BELIEVABLE 45-50 KT WIND VECTORS AND THIS IS THE BASIS FOR MAINTAINING AN INITIAL INTENSITY OF 50 KT. A 12-HOUR MOTION ESTIMATE YIELDS AN INITIAL HEADING OF 360/5. PATRICIA HAS BEEN MOVING AROUND THE WESTERN PERIPHERY OF A MID-LEVEL RIDGE TO ITS EAST. THIS RIDGE IS FORECAST TO BUILD WESTWARD AS A MID-LEVEL TROUGH CURRENTLY TO THE NORTHWEST OF THE CYCLONE LIFTS OUT TODAY. THIS SHOULD RESULT IN THE CYCLONE TURNING NORTHWESTWARD...THEN WESTWARD TO THE SOUTH OF THE BUILDING RIDGE. THE TRACK GUIDANCE GENERALLY AGREES WITH THIS SCENARIO...HOWEVER THERE ARE LARGE DIFFERENCES IN THE GUIDANCE AS TO HOW SOON THE RIDGE BUILDS...AND WHEN PATRICIA TURNS WESTWARD. THE ECMWF AND GFS MODELS ARE ON THE NORTHERN EDGE OF THE MODEL ENVELOPE AND TAKE PATRICIA OVER OR VERY CLOSE TO THE COAST OF THE SOUTHERN BAJA PENINSULA IN ABOUT 24 HOURS. THE UKMET AND NOGAPS ARE ON THE SOUTHERN EDGE AND PREDICT AN ALMOST IMMEDIATE WESTWARD TURN. THE OFFICIAL TRACK FORECAST HAS BEEN ADJUSTED A LITTLE NORTH OF THE PREVIOUS TRACK...DUE TO THE RECENT MOTION AND MORE EASTWARD INITIAL POSITION. THIS TRACK IS BETWEEN THE MODEL CONSENSUS AND THE ECMWF AND GFS SOLUTIONS. PATRICIA IS FORECAST TO REMAIN OVER WARM WATERS AND IN A LOW SHEAR ENVIRONMENT DURING THE NEXT DAY OR TWO. WHILE THESE FACTORS FAVOR STRENGTHENING...DRY AND STABLE AIR TO THE WEST OF THE CYCLONE WILL LIKELY INHIBIT SIGNIFICANT STRENGTHENING. THE OFFICIAL FORECAST SHOWS SLIGHT INTENSIFICATION TODAY...BUT IS LOWER THAN THE PREVIOUS FORECAST. THE NEW FORECAST IS IN GOOD AGREEMENT WITH A BLEND OF THE SHIPS...LGEM...AND GFDL MODELS. THE HWRF IS CONSIDERABLY STRONGER AND IS CONSIDERED AN OUTLIER AT THIS TIME. FORECAST POSITIONS AND MAX WINDS INITIAL 13/0900Z 20.7N 109.3W 50 KT 12HR VT 13/1800Z 21.5N 109.5W 55 KT 24HR VT 14/0600Z 22.1N 110.1W 55 KT 36HR VT 14/1800Z 22.4N 111.1W 50 KT 48HR VT 15/0600Z 22.5N 112.5W 45 KT 72HR VT 16/0600Z 22.5N 115.5W 35 KT 96HR VT 17/0600Z 22.5N 118.5W 25 KT...REMNANT LOW 120HR VT 18/0600Z...DISSIPATED $$ FORECASTER BROWN/ROBERTS