000 AXPZ20 KNHC 121530 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC WED DEC 12 2012 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1500 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 08N78W TO 07N95W TO LOW PRES NEAR 10N105W 1011 MB. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM THE LOW TO 08N120W TO 07N140W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF THE TROUGH BETWEEN 79W AND 89W. SIMILAR CONVECTION IS WITHIN 45 NM EITHER SIDE OF A LINE FROM 16N110W TO 12N120W. ...DISCUSSION... E OF 110W... THE MAIN FORECAST ISSUE REMAINS THE DEVELOPMENT OF GALE FORCE WINDS THROUGH THE GULF OF TEHUANTEPEC BY THIS EVENING. A STALLED COLD FRONT OVER THE GULF OF MEXICO WILL RECEIVE A REINFORCING SHOVE FROM AN UPPER TROUGH CURRENTLY DIGGING TOWARD THE U.S. MISSISSIPPI VALLEY. A TIGHT PRES GRADIENT IS ALREADY IN PLACE AHEAD OF THE FRONT WITH FRESH TO STRONG NORTHERLY WINDS HAVING COMMENCED THIS MORNING. ONCE THE FRONT RESTARTS AN EASTWARD MOVEMENT LATER TODAY THE PROGRESSION OF COOLER AND DRIER AIR INTO THE WESTERN GULF OF MEXICO WILL ALLOW FOR THE WINDS IN THE GULF OF TEHUANTEPEC TO INCREASE TO GALE FORCE. THE PROGRESSIVE NATURE OF THE PATTERN WILL ALLOW THE AIRMASS N OF THE AREA TO SHIFT E...TEMPERING GALE FORCE CONDITIONS THROUGH THU. ANOTHER SHOT OF NEAR GALE FORCE WINDS CAN BE EXPECTED THU NIGHT INTO FRI MORNING WITH THE AID OF LOCALIZED OVERNIGHT DRAINAGE EFFECTS. FOR SAT AND BEYOND...THE PRES GRADIENT WILL WEAKEN WITH MODERATE TO FRESH BREEZES PREVAILING IN THE EARLY MORNING HOURS. SURFACE RIDGING OVER THE SPINE OF CENTRAL AMERICA COMBINED WITH LOWER PRES TO THE S ALONG THE MONSOON TROUGH WILL HELP TO FORCE FRESH TO STRONG WINDS IN THE GULF OF PAPAGAYO THROUGH THE REMAINDER OF THE WEEK. THE WINDS WILL RELAX DURING THE AFTERNOON HOURS WITH THE STRONGEST WINDS OCCURRING DURING THE LATE NIGHT AND EARLY MORNING. AN OVERNIGHT WINDSAT PASS INDICATED A WEAK CIRCULATION ALONG THE MONSOON TROUGH NEAR 11N103W...WITH AN ESTIMATED PRES AROUND 1011 MB. THIS LOW HAS LOST ITS UPPER SUPPORT AND CONVECTION HAS PRETTY MUCH DISSIPATED. GLOBAL MODELS INDICATE THIS WILL OPEN UP INTO A TROUGH TODAY...THEN WILL GRADUALLY FLATTEN OUT THROUGH FRI. W OF 110W... AN UPPER LEVEL TROUGH IS WELL DEFINED ON SATELLITE IMAGERY PUSHING SE ALONG THE WEST COAST OF THE U.S. AN ASSOCIATED COLD FRONT EXTENDS FROM NEAR POINT CONCEPTION CALIFORNIA TO 31N130W TO 31N140W...WITH A PRE-FRONTAL TROUGH REACHING FROM THE CHANNEL ISLANDS THROUGH 30N126W TO 27N138W. THIS FRONT WILL CONTINUE TO MOVE TO THE SE CROSSING 30N LATER TODAY. THE FIRST UPPER TROUGH WILL CUT OFF THROUGH LATE THU AS IT SWINGS ACROSS SOUTHERN CALIFORNIA AND THE NORTHERN BAJA CALIFORNIA PENINSULA...WITH THE COLD FRONT EXTENDING FROM 30N120W TO 26N123W TO 24N132W BY THU MORNING...THEN FROM 29.5N115W TO 26N118W THEN DISSIPATING TO 23N130W BY FRI MORNING. DEEP LAYERED RIDGING REMAINS SW-W OF THE TROUGHING WITH 1036 MB SURFACE HIGH PRES CENTERED NEAR 39N148W. THIS IS MAINTAINING FRESH TO STRONG TRADES W OF A LINE FROM 30N130W TO 24N140W ALONG WITH RESULTANT 8 TO 10 FT SEAS...AND ALSO FROM 14N TO 18N W OF 135W WITH SEAS TO 9 FT. REINFORCING N TO NE WINDS WILL PREVAIL OVER MUCH OF THE NW CORNER OF THE AREA FOR THE NEXT FEW DAYS AS THE HIGH PRES SAGS SE BEHIND THE COLD FRONT...WITH SEAS 8 TO 10 FT MAINLY N OF 23N BEHIND THE FRONT. LOOKING AHEAD TO SAT AND SUN...DYNAMIC AND ENSEMBLE MODELS ARE IN DECENT AGREEMENT SHOWING A SECOND UPPER TROUGH CURRENTLY OVER THE ALEUTIANS FOLLOWING BEHIND THE FIRST TROUGH AND DIGGING SE INTO SOUTHERN CALIFORNIA AND NORTHERN BAJA. THE ECMWF AND UKMET MODEL SOLUTIONS REMAIN IN GOOD AGREEMENT TRENDING A LITTLE MORE QUICKLY THAN EARLIER RUNS. ALTHOUGH THERE REMAINS SOME DISAGREEMENT WITH REGARD TO EXACT TIMING AND PLACEMENT...GENERAL CONSENSUS INDICATES A SURFACE LOW PRES AREA WILL FORM OFF OF SOUTHERN CALIFORNIA AND NORTHERN BAJA BY EARLY SAT...N OF ELONGATED SURFACE RIDGING ALONG 27N. WITH THIS SETUP THERE WILL BE SOME POTENTIAL FOR FRESH TO STRONG W TO NW WINDS N OF 28N E OF 125W BY LATE SAT. GULF OF CALIFORNIA...SW WINDS WILL INCREASE BY THU MORNING OVER THE FAR NORTHERN GULF AHEAD OF A COLD FRONT PUSHING INTO THE AREA. THE WINDS WILL PERSIST INTO FRI BEFORE VEERING NW AND GRADUALLY DIMINISHING THROUGH SAT. $$ LEWITSKY