000 AXPZ20 KNHC 182154 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC SUN NOV 18 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... MONSOON TROUGH EXTENDS FROM 09N84W TO 05N95W THEN THE ITCZ CONTINUES FROM 05N95W TO 08N115W TO 07N130W TO BEYOND 07N140W. A CLUSTER OF MODERATE TO STRONG CONVECTION IS ALONG THE ITCZ AXIS FROM 06N TO 09N BETWEEN 133W AND 139W. ...DISCUSSION... ALOFT...STRONG W TO SW WINDS 70-110 KT DOMINATE MOST OF THE FORECAST AREA N OF 19N AND W OF 110W...DEPICTING A SUBTROPICAL JETSTREAM FLOWING THROUGH THE BASE OF A BROAD UPPER LEVEL TROUGH NOW EXTENDING FROM 31N122W TO 22N135W. THIS JET CONTINUES TO TRANSPORT ABUNDANT MID/UPPER LEVEL MOISTURE ACROSS THE FORECAST REGION FROM THE HAWAIIAN ISLANDS TO BAJA CALIFORNIA AND NW MEXICO. SATELLITE IMAGERY SHOWS A WIDE BAND OF TRANSVERSE HIGH CLOUDS IN ASSOCIATION WITH THESE STRONG WINDS. A DOWNSTREAM RIDGE COVERS MUCH OF THE REGION S OF 19N W OF 110W...AND IS CENTERED ON A WEAKENING UPPER ANTICYCLONE NEAR 15N108W THAT EXTENDS NE ACROSS MEXICO AND TEXAS AND INTO THE CENTRAL UNITED STATES. A BROAD UPPER TROUGH EXTENDING FROM A CUT-OFF LOW LOCATED ALONG THE SOUTH CAROLINA COAST EXTENDS S-SW ACROSS THE EASTERN GULF OF MEXICO AND THE NW CARIBBEAN TO CENTRAL AMERICA NEAR 17N90W. A LINGERING TUTT EXTENDS FROM A WEAK MIDDLE LEVEL VORTEX NEAR 10N86W TO AN ELONGATED CYCLONIC VORTEX NEAR 06N112W. STRONG SUBSIDENCE ALONG THE N SIDE OF THIS TUTT IS LIMITING CONVECTION ALONG THE MONSOON TROUGH AND THE ITCZ AXIS E OF 110W. AT THE SURFACE...A DISSIPATING COLD FRONT IS CLIPPING THE FAR N WATERS AND EXTENDS FROM 30N125W TO 29N134W. A RIDGE CONTINUES TO BUILD ACROSS THE REGIONAL WATERS BRINGING AN INCREASE IN THE TRADE WIND FLOW...PARTICULARLY FROM 10N TO 20N W OF 125W. EXPECT THE RIDGE TO STRENGTHEN SLIGHTLY DURING THE NEXT 24 HOURS...AND A NEW HIGH CENTER TO REFORM NEAR 29N124W BY MONDAY AFTERNOON...WHICH WILL PRODUCE A BROADER ZONE OF NE TO E WINDS 20-25 KT FROM 10N TO 20N W OF 120W AND BUILDING SEAS OF 8 TO 10 FT ACROSS THIS AREA....WITH MINOR CHANGE THROUGH TUESDAY. LONG PERIOD NW SWELL GENERATED ACROSS THE NE PACIFIC BEHIND THE COLD FRONTS CONTINUES TO PUSH ACROSS THE NW PART OF THE REGION WITH COMBINED SEAS TO 10 FT. A SECOND PULSE OF NW SWELL THAT ENTERED NW PORTIONS THIS MORNING WILL CONTINUE TO PROPAGATE S AND E ACROSS THE REGIONAL WATERS OVER THE NEXT FEW DAY...AND COMBINE WITH NE WIND WAVES DEVELOPING WITHIN THE TRADE WIND ZONE TO PRODUCE COMBINED SEAS 8 TO 10 FT. THE NEXT PULSE OF INCREASING NW SWELL IS EXPECTED TO INVADE THE N WATERS EARLY TUESDAY. AS PREVIOUSLY MENTIONED...A CLUSTER OF MODERATE TO STRONG CONVECTION IS NOTED ALONG THE ITCZ IN ASSOCIATION WITH A SURFACE TROUGH CURRENTLY ALONG 136W. A DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE THE CONVECTIVE ACTIVITY ASSOCIATED WITH THIS FEATURE THAT WILL CONTINUE TO MOVE WWD. GAP WINDS... PERSISTENT NORTHERLY WINDS 20-30 KT ARE BLOWING ACROSS THE GULF OF TEHUANTEPEC...AS A RIDGE CONTINUE TO DOMINATE THE WESTERN PART OF THE GULF OF MEXICO AND THE EASTERN SLOPES OF THE SIERRA MADRE MOUNTAINS. WINDS EXITING THE CHIVELAS PASS CONTINUE TO BE ENHANCED BY NOCTURNAL DRAINAGE FLOW ACROSS THE GULF OF TEHUANTEPEC...AND HAVE BEEN REACHING MINIMAL GALE FORCE ROUGHLY BETWEEN 0600 AND 1200 UTC EACH OF THE PAST FEW DAYS. HOWEVER... THIS AFTERNOON...SHIP CALL SIGN V72G9 LOCATED NEAR 14N95W REPORTED 34 KT SUSTAINED WINDS AND 12 FT SEAS. IN ADDITION...A WINDSAT PASS SHOWED SEVERAL WIND BARBS OF 30 KT. SO DECIDE...TO ISSUE A GALE WARNING ACROSS THE GULF OF TEHUANTEPEC BEGINNING AT 18/1800 UTC AND WILL CONTINUE DURING THE FORECAST PERIOD. LATEST GLOBAL MODEL GUIDANCE SUGGESTS THAT THE NOCTURNAL PEAK IN WINDS WILL INCREASE TO 35-40 KT EARLY MONDAY MORNING...WITH SEAS BUILDING TO AROUND 13-14 FT DOWNSTREAM OF TEHUANTEPEC. SEE LATEST NHC HIGH SEAS FORECAST UNDER AWIPS/WMO HEADERS HSFEP2/FZPN03 KNHC FOR DETAILS ON THIS FLUCTUATING GAP WIND EVENT. PULSING OF NOCTURNAL WINDS ARE ALSO EXPECTED TO CONTINUE ACROSS THE GULF OF PAPAGAYO...WITH NOCTURNAL WINDS FORECAST TO REACH AROUND 20 KT FROM 0600 TO 1200 UTC...WITH SEAS OF 6-7 FT THROUGH AND DOWNWIND OF THE GULF. $$ GR