000 AXPZ20 KNHC 210316 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SUN OCT 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0230 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 12N87W TO 10N100W TO 11N107W TO 10N117W TO 08N123W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N123W TO 12N130W THEN RESUMES FROM 11N134W TO 10N140W. SCATTERED MODERATE CONVECTION IS WITHIN 150 NM N OF THE TROUGH AXIS BETWEEN 95W AND 100W...WITHIN 120 NM S OF THE TROUGH AXIS BETWEEN 100W AND 104W...AND ALSO FROM 08N TO 10N BETWEEN 109W AND 115W. ...DISCUSSION... AN UNSTABLE UPPER LEVEL RIDGE EXTENDS FROM 31N140W TO 31N130W TO NEAR POINT CONCEPTION CALIFORNIA. TWO LARGE QUASI-STATIONARY UPPER CYCLONES DOMINATE THE SUBTROPICS W OF 118W WITH CENTERS NEAR 29N122W AND 21N144W. SOME UPPER LEVEL MOISTURE IS OBSERVED OVER THE NW SEMICIRCLE OF THE EASTERN CYCLONE...AND CONTINUES TO SPREAD NE ACROSS THE EXTREME NW PORTION OF THE BAJA PENINSULA AND SOUTHERN CALIFORNIA 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 THE NORTHERN GULF OF CALIFORNIA. 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 IN THE SECTION 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 17N W OF 128W AS INDICATED BY RECENT SCATTEROMETER PASSES. MODEL GUIDANCE IN THE NW CORNER OF THE AREA INDICATES 7-8 FT SEAS ALTHOUGH A SHIP APPROACHING THE AREA FROM THE SW HAS BEEN REPORTING 9-10 FT SEAS AND GRIDDED DATA HAS BEEN NUDGED UPWARD IN THIS AREA TO REFLECT THE OBSERVATIONS. WINDS HAVE DIMINISHED IN THIS REGION TO 15-20 KT DURING THE PAST FEW HOURS AND EXPECT THE SEAS TO SUBSIDE TO LESS THAN 8 FT LATER TONIGHT. THE LOW LEVEL TROUGH WILL 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 THE PENINSULA ON TUE NIGHT... THEN TO 20-25 KT WED NIGHT WITH SEAS BUILDING TO 8-10 FT. SEAS OF 1-3 FT ARE EXPECTED ACROSS THE ENTIRE GULF OF CALIFORNIA THROUGH LATE MON. GUIDANCE INDICATES NW WINDS INCREASING 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 EVENING. 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