000 AXPZ20 KNHC 202132 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC SAT OCT 20 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 2100 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 12N87W TO 10N100W TO 11N114W TO 09N120W TO 10N124W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N124W TO 13N129W THEN RESUMES FROM 11N132W TO 09N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 120 NM N OF THE TROUGH AXIS BETWEEN 94W AND 98W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF THE TROUGH AXIS BETWEEN 91W AND 102W...AND WITHIN 90 NM S OF THE TROUGH AXIS BETWEEN 112W AND 115W. SIMILAR CONVECTION IS WITHIN 90 NM N OF THE ITCZ W OF 138W. ...DISCUSSION... AN UNSTABLE UPPER LEVEL RIDGE EXTENDS FROM 31N140W TO 31N130W TO NEAR POINT CONCEPTION CALIFORNIA. TWO LARGE UPPER CYCLONES DOMINATE THE SUBTROPICS W OF 118W WITH CENTERS NEAR 29N122W AND 21N144W. SOME UPPER LEVEL MOISTURE IS OBSERVED OVER THE N SEMICIRCLE OF THE EASTERN CYCLONE...AND CONTINUES TO SPREAD NE ACROSS THE EXTREME NW PORTION OF THE BAJA PENINSULA THIS AFTERNOON. OTHERWISE THE UPPER LEVELS APPEAR VERY DRY N OF 20N W OF 115W WITH CONVECTION SUPPRESSED. AN UPPER CYCLONE IS OVER THE DEEP TROPICS NEAR 03N128W SETTING UP AN AREA OF WEAK UPPER DIFFLUENCE OVER THE WESTERN SEGMENT OF THE MONSOON TROUGH AND ITCZ...AND SUPPORTING SPORADIC CONVECTION ALONG THE MONSOON TROUGH AND ITCZ W OF 125W. SOME OF THE DEBRIS MOISTURE IS BEING ADVECTED NE TO 20N WHICH MAY ORGANIZE INTO A TROPICAL PLUME WITH INCREASING SOUTHERLY FLOW SE OF THE NORTHERN UPPER CYCLONES. THE EASTERN PORTION OF THE DISCUSSION AREA IS DOMINATED BY A QUASI-STATIONARY UPPER ANTICYCLONE OVER W-CENTRAL MEXICO AT 19N103W WITH A RIDGE EXTENDING NW-N TO A CREST OVER WESTERN ARIZONA. UPPER MOISTURE CONTINUES TO STREAM E ACROSS THE SOUTHERN BAJA PENINSULA...AND ACROSS THE RIDGE OVER NORTHERN MEXICO TO OVER W TEXAS. THE ENVELOPE OF ANTICYCLONIC FLOW EXTENDS S OVER THE DISCUSSION AREA N OF 10N TO THE E OF 111W. UPPER EASTERLY FLOW IS ADVECTING DEBRIS MOISTURE FROM THE MONSOON TROUGH CONVECTION MENTIONED ABOVE. A BROAD SURFACE RIDGE COVERS THE SUBTROPICS W OF A LOW LEVEL SNAKY TROUGH EXTENDING FROM 27N123W TO 24N124W TO 21N126W. MODERATE TO FRESH NE WINDS ARE NOTED N OF 22N W OF 130W AS INDICATED BY RECENT SCATTEROMETER PASSES. SEAS TO 9 FT IN MIXED NE AND NW SWELL IS IN THE FAR NW CORNER W OF A LINE FROM 30N133W TO 24N140W WHERE THE STRONGEST WINDS ARE PRESENT. THIS AREA OF ENHANCED WINDS WILL GRADUALLY DIMINISH TO 15 KT TONIGHT WITH SEAS SUBSIDING TO 6-7 FT LATER THIS EVENING. EXPECT THE LOW LEVEL TROUGH TO FILL TONIGHT AS THE SURFACE RIDGE BUILDS E ACROSS THE ENTIRE WATERS N OF 17N W OF 108W BY LATE TOMORROW. SEAS OF 3-5 FT IN NW SWELL ARE EXPECTED ALONG THE ENTIRE PACIFIC COAST OFF THE BAJA CALIFORNIA PENINSULA THROUGH LATE TUE...THEN GUIDANCE SUGGESTS NW WINDS WILL INCREASE TO 15-20 KT WITH SEAS BUILDING 5-7 FT ALONG THE W SHORE OF PENINSULA ON TUE NIGHT. SEAS OF 1-3 FT ARE EXPECTED ACROSS THE ENTIRE GULF OF CALIFORNIA THROUGH LATE MON. GUIDANCE INDICATING NW WINDS WILL INCREASE TO 15-20 KT...WITH SEAS BUILDING TO 3-4 FT...OVER THE GULF WATERS TO THE S OF 24.5N BEGINNING MON NIGHT. LOOKING AHEAD...INTENSE AND COLD HIGH PRES BUILDING OVER THE U.S. GREAT BASIN LATE IN THE WEEK INTO NEXT WEEKEND MAY HELP TO INDUCE A NEAR GALE FORCE EVENT ACROSS MUCH OF THE GULF FRI INTO NEXT SAT. GAP WINDS...A NORTHERLY SURGE OF 20-25 KT WINDS CONTINUES IN THE GULF OF TEHUANTEPEC AND IS EXPECTED TO PULSE THROUGH MON AFTERNOON. THE STRONGEST DRAINAGE FLOW WILL OCCUR LATE EACH NIGHT UNTIL JUST AFTER SUNRISE EACH MORNING. THE GFS GUIDANCE CONTINUES TO SUGGEST THIS NORTHERLY FLOW WILL HELP TRIGGER LOW PRES DEVELOPMENT WITHIN THE MONSOON TROUGH NEAR 12N103W BY EARLY WED. ALTHOUGH THERE IS A HINT OF LOW PRES DEVELOPMENT ALONG THE MONSOON TROUGH AXIS IN OTHER NWP GUIDANCE...THE GFS REMAINS THE MOST AGGRESSIVE SOLUTION AND THUS THIS FEATURE HAS BEEN TONED DOWN CONSIDERABLY IN THE EXPERIMENTAL GRIDDED FIELDS INITIALIZED WITH THE GFS. $$ LEWITSKY