000 AXPZ20 KNHC 221545 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS EXTENDS FROM 09N78W TO 06N85W TO 08N107W. ITCZ AXIS EXTENDS FROM 08N107W TO 10N117W TO 07N130W TO 06N140W. SCATTERED MODERATE WITHIN 120 NM N OF AXIS BETWEEN 126W AND 136W AND WITHIN 90 NM EITHER SIDE OF TROUGH FROM 10N TO 13N. ...DISCUSSION... THE UPPER PATTERN FEATURES A MEAN TROUGH OVER NRN MEXICO AND ACROSS THE SW CONUS WITH A RIDGE EXTENDING FROM AN ANTICYCLONE CURRENTLY LOCATED NEAR 14N108W THROUGH 20N125W TO 27N130W. THIS ANTICYCLONE WILL DRIFT NE INTO SOUTHERN MEXICO OVER THE NEXT FEW DAYS. MEANWHILE...THE TROUGHING OVER NW MEXICO IS IN THE PROCESS OF BEING REINFORCED 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 LATE THIS AFTERNOON AND SEEP THROUGH THE BAJA CALIFORNIA PASSES INTO THE ADJACENT PACIFIC OVERNIGHT AND FRI. SEE THE GAP WINDS SECTION BELOW FOR DETAIL ON THE GULF OF CALIFORNIA GALE WIND EVENT. HIGH PRES N OF THE AREA HAS WEAKENED SINCE THIS TIME YESTERDAY DUE TO A COLD FRONT IMPINGING UPON IT FROM THE NW. A RIDGE EXTENDS INTO THE AREA 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 13N117W 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 YESTERDAY HAS ABATED. TO THE N OF THE TROUGH...PATCHES OF POSSIBLE 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 FRESHEN LATE 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 ARE FORECAST TO REACH GALE FORCE OVERNIGHT FRI INTO SAT 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 THIS AFTERNOON. BUILDING HIGH PRESSURE OVER CENTRAL AMERICA WILL ALLOW FOR 20 KT GAP WINDS TO RESUME BY SAT MORNING. $$ COBB