000 AXPZ20 KNHC 212137 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 12N87W TO 11N100W TO 08N125W TO 11N131W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N135W TO 10N140W. SCATTERED MODERATE CONVECTION IS S OF THE TROUGH AXIS TO 10N E OF 90W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 180 NM S OF THE TROUGH AXIS BETWEEN 93W AND 102W...AND WITHIN 240 NM N OF THE TROUGH AXIS BETWEEN 96W AND 102W. SCATTERED MODERATE CONVECTION IS FROM 08N TO 10N BETWEEN 103W AND 108W...WITHIN 90-120 NM S OF THE TROUGH AXIS BETWEEN 113W AND 125W...AND ALSO WITHIN 120 NM N OF THE TROUGH AXIS BETWEEN 118W AND 124W. ...DISCUSSION... THE AXIS OF THE SUBTROPICAL JET EXTENDS FROM 15N145W AND CUTS NE INTO THE AREA NEAR 20N140W...THEN SPILLS EASTWARD TO SOUTHERN BAJA CALIFORNIA. SATELLITE DERIVED WINDS IN ASSOCIATION WITH THIS JET WERE IN THE 90-110 KT RANGE. THIS JET IS ADVECTING SOME UPPER LEVEL MOISTURE OVER THE AREA FROM 10N TO 24N BETWEEN 130W AND 140W. OTHERWISE THE UPPER LEVELS APPEAR MAINLY DRY N OF 14N W OF 110W SUPPRESSING CONVECTION. AN ELONGATED UPPER ANTICYCLONE IS E OF THIS JET NEAR 16N121W. WEAK UPPER DIFFLUENCE ON THE S AND W SIDES OF THE ANTICYCLONE IS SUPPORTING CONVECTION ALONG THE MONSOON TROUGH AND ITCZ DESCRIBED IN THE SECTION ABOVE. THE EASTERN PORTION OF THE DISCUSSION WATERS IS DOMINATED BY A QUASI-STATIONARY ELONGATED UPPER ANTICYCLONE OVER SE MEXICO NEAR 18N96W WITH A RIDGE EXTENDING N TO A CREST OVER CENTRAL TEXAS. THE ENVELOPE OF ANTICYCLONIC FLOW EXTENDS S OVER THE DISCUSSION AREA N OF 07N TO THE E OF 110W. THIS UPPER LEVEL EASTERLY FLOW IS ADVECTING DEBRIS MOISTURE WESTWARD FROM THE MONSOON TROUGH CONVECTION NOTED E OF 110W. A WEAK SURFACE TROUGH EXTENDS FROM 15N127W TO 10N134W WITH SCATTERED SHOWERS POSSIBLE WITHIN 120 NM W OF THE TROUGH AXIS. RECENT SCATTEROMETER PASSES INDICATED ONLY 5 TO 15 KT IN THE VICINITY OF THE TROUGH. THIS FEATURE WILL MOVE W OF THE AREA BY 48 HOURS. OTHERWISE...A BROAD SURFACE RIDGE COVERS THE SUBTROPICS N OF THE MONSOON TROUGH. SCATTEROMETER DATA ALSO INDICATED TRADE WINDS OF 5 TO 15 KT N OF THE MONSOON TROUGH...WITH THE EXCEPTION OF A FEW POCKETS OF 15 TO 20 KT WINDS NEAR AREAS OF CONVECTION ASSOCIATED WITH THE MONSOON TROUGH. A WEAK COLD FRONT IS FORECAST TO SKIRT ACROSS 30N MON AND TUE WITH WINDS REMAINING 20 KT OR LESS AHEAD OF AND BEHIND IT IN THE FAR NORTHERN WATERS. THE WAVEWATCH MODEL GUIDANCE KEEPS SEAS LESS THAN 8 FT THROUGH 48 HOURS WHILE THE ECMWF WAVE AND UKMET WAVE MODELS HAVE AN AREA OF 8 TO 9 FT NW SWELL BREACHING 30N BY 42 TO 48 HOURS. GAP WINDS...A 1532 UTC HIGH RESOLUTION ASCAT PASS INDICATED N TO NE 20 TO 25 KT WINDS PULSING IN THE GULF OF TEHUANTEPEC. THESE WINDS ARE EXPECTED TO CONTINUE TO PULSE THROUGH THE NEXT 48 HOURS WITH THE STRONGEST DRAINAGE FLOW OCCURRING DURING THE LATE NIGHT HOURS UNTIL JUST AFTER SUNRISE EACH DAY. THE GFS NWP GUIDANCE CONTINUES TO SUGGEST THAT THIS NORTHERLY FLOW WILL HELP TRIGGER LOW PRESSURE DEVELOPMENT WITHIN THE MONSOON TROUGH NEAR 10N98W BY TUE. THE GFS REMAINS THE AGGRESSIVE OUTLIER IN ITS SOLUTION WHILE OTHER NWP MODELS FAVOR A WEAKER BROAD LOW CLOSER TO CENTRAL AMERICA WHICH DRIFTS TO THE E AS A POSSIBLE DEVELOPING TROPICAL CYCLONE IN THE CARIBBEAN EXERTS GREATER INFLUENCE ON THE OVERALL PATTERN. THIS MORE CONSERVATIVE SOLUTION...IN THE PACIFIC...IS FAVORED AT THIS TIME AND LOW PRES IS NOT REFLECTED IN FORECAST WIND WAVE CHARTS THROUGH 48 HOURS. A BLEND OF THE GFS...ECMWF AND THE PREVIOUS FORECAST WAS USED IN THE GRIDDED WIND FIELDS. ASSOCIATED WAVE HEIGHTS FOLLOW A BLEND OF THE WAVEWATCH AND ECMWF WAVE MODELS WITH HEIGHTS CAPPED AT 11 FT THROUGH THE FORECAST PERIOD. $$ LEWITSKY