000 AXPZ20 KNHC 220913 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC THU DEC 22 2011 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0715 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM 10N84W TO 07N90W TO 09N99W TO 08N102W. THE ITCZ AXIS EXTENDS FROM 08N102W TO 11N117W TO 08N122W TO 08N140W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE AXIS BETWEEN 114W AND 116W AND WITHIN 45 NM EITHER SIDE OF THE AXIS BETWEEN 101W AND 104W. ...DISCUSSION... THE UPPER PATTERN FEATURES A MEAN TROUGH OVER NW MEXICO AND A RIDGE EXTENDING FROM AN ANTICYCLONE CURRENTLY LOCATED NEAR 14N112W THROUGH 20N125W TO 30N130W. THIS ANTICYCLONE WILL DRIFT NE INTO SOUTHERN MEXICO OVER THE NEXT FEW DAYS. MEANWHILE...THE TROUGHING OVER NW MEXICO WILL RELOAD LATER TODAY WITH NORTHERN STREAM ENERGY CURRENTLY PASSING S THROUGH THE U.S. GREAT BASIN. THE TROUGH WILL BRIEFLY ATTEMPT TO PHASE WITH THE NORTHERN STREAM OVER THE U.S. FRI. THE RESULT AT THE SURFACE WILL BE A SURGE OF COOLER AIR AND NORTHERLY WINDS BEGINNING TO MOVE THROUGH THE GULF OF CALIFORNIA LATER TODAY AND BLEED THROUGH BAJA CALIFORNIA INTO THE ADJACENT PACIFIC OVERNIGHT. SEE THE GAP WINDS SECTION BELOW FOR DETAIL ON THE GULF OF CALIFORNIA GALE WIND EVENT. HIGH PRES N OF THE AREA HAS WEAKENED SOMEWHAT SINCE THIS TIME YESTERDAY DUE TO A COLD FRONT IMPINGING UPON IT FROM THE NW. A RIDGE EXTENDS FROM 1026 MB HIGH PRES NEAR 32N146W THROUGH 31N125W TO 22N110W. THE PRES GRADIENT BETWEEN THIS ZONAL RIDGING AND TROUGHING ALONG THE ITCZ IS GENERATING A LARGE SWATH OF FRESH TO STRONG TRADE WINDS THAT EXTENDS AS FAR E AS 112W. THESE TRADE WINDS WILL REMAIN RELATIVELY UNCHANGED THROUGH FRI MORNING...BUT THEY ARE EXPECTED TO EXPAND OVER MUCH OF THE AREA N OF 10N W OF 110W BY FRI NIGHT INTO SAT MORNING AS THE HIGH PRES OVER THE PACIFIC MERGES WITH THE BUILDING HIGH OVER THE U.S. GREAT BASIN. MID-LEVEL ENERGY JUST SW OF THE ANTICYCLONE ALOFT IS REFLECTING A SURFACE TROUGH FROM 12N117W TO 08N119W. THE STRENGTHENED PRES GRADIENT BETWEEN THE SUBTROPICAL HIGH AND THIS TROUGH IS ALLOWING FOR THE STRONGEST TRADE WINDS TO LIE PRIMARILY W OF THE TROUGH. THE MODERATE TO STRONG CONVECTION THAT HAD ACCOMPANIED THIS TROUGH WED HAS ABATED...WITH PRECIPITABLE WATER IMAGERY SHOWING MOISTURE POOLED NEAR THE TROUGH HAS ALSO DIMINISHED. TO THE N OF THE TROUGH...ISOLATED MODERATE CONVECTION IS NOTED OVER THE VAST AREA FROM 11N TO 20N W OF 109W UNDER THE DIFFLUENT REAR RIGHT QUADRANT OF THE JET ALOFT. GAP WINDS... GULF OF CALIFORNIA...NW WINDS WILL BECOME FRESH THIS AFTERNOON IN THE NORTHERN GULF OF CALIFORNIA AND WILL INCREASE OVERNIGHT TONIGHT AS THEY SPREAD SOUTHWARD IN RESPONSE TO HIGH PRES BUILDING IN EXCESS OF 1040 MB IN THE GREAT BASIN. GALE CONDITIONS ARE EXPECTED BY SUNRISE FRI. THE GALE SHOULD BE RELATIVELY SHORT LIVED AS HIGH PRES IS EXPECTED TO SHIFT EASTWARD INTO THE PLAINS OVER THE WEEKEND...WEAKENING THE PRES GRADIENT OVER THE GULF OF CALIFORNIA. GULF OF TEHUANTEPEC...THE COLD FRONT CURRENTLY PASSING INTO THE FAR NW GULF OF MEXICO WILL BE SLOW TO MOVE UNTIL THE AIR MASS EXPECTED TO PLOWED THROUGH NW MEXICO TODAY ARRIVES ON FRI AND REINFORCES THIS COLD FRONT. THE COLD FRONTAL PASSAGE THROUGH CHIVELA PASS EARLY FRI WILL BRING FRESH TO STRONG N WINDS INTO THE GULF OF TEHUANTEPEC. WINDS WILL APPROACH NEAR GALE FORCE BY THE END OF THE PERIOD EARLY SAT MORNING AS HIGH PRES BEGINS TO EMERGE IN THE SOUTHERN PLAINS...TIGHTENING THE PRES GRADIENT OVER TEHUANTEPEC. GULF OF PAPAGAYO...THE PRES GRADIENT ACROSS CENTRAL AMERICA BETWEEN HIGH PRES OFF THE SE U.S. COAST AND THE MONSOON TROUGH N THE PACIFIC IS BEGINNING TO WEAKEN. THIS HIGH IS EXPECTED TO WEAKEN AS A FRONT SLOWLY APPROACHES ITS NE SIDE. THIS WILL DECREASE THE PRES GRADIENT AND FINALLY BRING WINDS BELOW 20 KT BY THIS AFTERNOON. $$ SCHAUER