000 AXPZ20 KNHC 152155 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC SAT DEC 15 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS SW FROM THE W COLOMBIAN COAST AT 07N78W TO 06N79W THEN TURNS NW TO 08N86W...THEN SW AGAIN TO 08N93W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ. THE ITCZ THEN CONTINUES WSW TO 05N115W...THEN WIGGLES WNW TO BEYOND 08N140W. SCATTERED MODERATE CONVECTION IS NOTED WITHIN 90 NM EITHER SIDE OF A LINE FROM 05.5N78W TO 05N87W...AND WITHIN 120 NM OF 07.5N109W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FLARING INTERMITTENTLY WITHIN 75 NM EITHER SIDE OF A LINE FROM 15N118W TO 09N131W TO 08N140W. ...DISCUSSION... ALOFT...A SHARP UPPER TROUGH EXTENDS SW INTO THE AREA WITH ITS MEAN AXIS ALONG 32N117W TO 17N140W. IMMEDIATELY TO THE NW...AN UPPER RIDGE IS COLLAPSING SE ACCOMPANIED BY 100 KT PLUS NORTHERLY WINDS FEEDING INTO UPPER TROUGH ALONG 32N. AN AREA OF UPPER MOISTURE IS ALSO OBSERVED N OF 28N BETWEEN 123-140W. ANOTHER AREA OF UPPER MOISTURE IS NOTED E OF THE TROUGH AXIS AND RACING NE ACROSS ARIZONA AND WESTERN NEW MEXICO. A NARROW BAND OF DRY UPPER AIR IS OBSERVED WITHIN 180 NM EITHER SIDE OF A LINE FROM 21N140W TO 24N125W TO 32N118W...AND CONTINUING ACROSS SOUTHERN CALIFORNIA. AN INVERTED UPPER TROUGH IS OBSERVED OVER THE DEEP TROPICS FROM 10N120W TO THE EQUATOR AT 127W AND EFFECTIVELY SEPARATES THE UPPER LEVEL FLOW ACROSS THE TROPICAL PORTION. UPPER LEVEL ANTICYCLONIC FLOW IS NOTED OVER THE DEEP TROPICS TO THE W OF THIS TROUGH. AN UPPER ANTICYCLONE HAS SHIFTED S OVER THE PACIFIC AT 13N94W WITH AN UPPER RIDGE NOW EXTENDING SW TO A SHARP CREST AT 10N118W. AN UPPER RIDGE ALSO EXTENDS FROM THE ANTICYCLONE TO 10N85W. STRONG UPPER WESTERLIES CONTINUE TO ADVECT A DENSE PLUME OF UPPER MOISTURE NE ACROSS THE DISCUSSION AREA...WITHIN 360 NM EITHER SIDE OF A LINE FROM 12N140W TO 20N117W...TO OVER TEXAS AT 32N98W. SOME OF THE MOISTURE IS ADVECTED ANTICYCLONICALLY SE TOWARDS THE EQUATOR BETWEEN 128-138W. UPPER DIFFLUENCE ALONG THE SOUTHERN PERIPHERY OF THE LARGE ANTICYCLONE OVER THE SE PORTION IS ENHANCING THE SMALL AREAS OF CONVECTION PREVIOUSLY MENTIONED BETWEEN 78-87W AD NEAR 07.5N109W. LOW LEVELS...AN INITIAL COLD FRONT HAS ENTERED THE EXTREME NORTHERN GULF OF CALIFORNIA AND CONTINUES SW ACROSS THE BAJA PENINSULA TO OVER THE PACIFIC NEAR 26N128W WHERE IT IS BEGINNING TO DISSIPATE. A SECOND COLD IS APPROACHING THE N-CENTRAL PORTION NEAR 34N130W. A SURFACE RIDGE EXTENDS FROM 28N140W TO 20N110W. NORTHERLY WINDS NE OF THE RIDGE FROM 25-32N BETWEEN 130W AND THE BAJA PENINSULA...HAVE DIMINISHED TO 10-15 KT...BUT SEAS CONTINUE AT 8-11 FT IN THE NW SWELL. EXPECTING ONLY A SW-W-NE 15-20 KT WIND SHIFT ALONG THE SECOND COLD FRONT TONIGHT WITH THE WINDS DIMINISHING TO 5-10 KT ON SUN NEAR THE FRONT AS IT DISSIPATES BY EARLY MON. SEAS SHOULD SUBSIDE TO 3-6 FT IN NW SWELL ALONG THE ENTIRE W COAST OF THE BAJA PENINSULA FROM LATE MON THROUGH LATE TUE. FURTHER S...NE TRADES CONTINUE AT 20-25 KT TO THE SW OF THE RIDGE ACROSS THE WATERS FROM 13-18N TO THE W OF 126W...WITH SEAS 9-12 FT IN MOSTLY NE SWELL. THE TRADES ARE AT 15-20 KT SURROUNDING THIS AREA FROM 10-22N TO THE W OF 118W WITH SEAS 7-8 FT IN MIXED N AND NE SWELL. EXPECTING THE AREA OF AFFECTED NE TRADES TO COVER THE AREA FROM 08-22N W OF 115W ON SUN. THE FORECAST IS FOR A LOW LEVEL TROUGH TO FORM FROM 12N140W TO 16N137W ON MON MAINTAINING NE-E 20-25 KT WITHIN 180 NM OF THE TROUGH...WITH ENHANCED TRADES CONTINUING ELSEWHERE FROM ABOUT 08N-22N W OF 115W. LOOKING FURTHER OUT...THE TROUGH OVER THE SW PORTION WILL DEEPEN ON MON NIGHT AS A STRONG COLD FRONT SWEEPS SE INTO THE SUBTROPICAL WATERS ACCOMPANIED BY N-NE 20-25 KT WINDS...WITH SEAS BUILDING 8-15 FT W OF THE FRONT. NW 20-25 KT WINDS AND SEAS 8-10 FT WILL ARRIVE AT THE W COAST OF THE BAJA PENINSULA ON TUE NIGHT. THE GRADIENT IS EXPECTED TO RELAX ON WED AS WINDS CLOCK TO THE NE AND DIMINISH TO 15-20 KT ALONG THE BAJA PENINSULA TO THE N OF 25N. GULF OF TEHUANTEPEC...WINDS ARE EXPECTED TO BECOME LIGHT AND VARIABLE TONIGHT SAT EVENING. BEST GUESS IS THE NEXT NORTHERLY EVENT WILL BEGIN LATE MON NIGHT...BUT PEAK AT 20 KT. ANOTHER STRONG EVENT BEGINS NEXT THU EVENING WITH STORM CONDITIONS BY SUNRISE FRI. $$ NELSON