000 AXPZ20 KNHC 120341 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC WED DEC 12 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 0330 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W FROM THE PANAMA AND COLOMBIA BORDER TO ACROSS CENTRAL PANAMA TO 08N94W...THEN TURNS NW TERMINATING AT AN EMBEDDED LOW PRESSURE CENTER AT 10.5N103.5W. LOW LEVEL WINDS INDICATE THAT THE ITCZ FORMS W OF THE LOW PRESSURE CENTER NEAR 09N108W THEN WIGGLES WESTWARD TO BEYOND 09N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED FROM 04-09N E OF 86W AND WITHIN 60 NM EITHER SIDE OF A LINE FROM 11N111W TO 13N119W TO 11N122W TO 08N123W TO 10N130W. THE EMBEDDED SURFACE LOW IS ACCOMPANIED BY SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 45 NM EITHER SIDE OF A LINE FROM 09.5N98.5W TO 10N103W. SIMILAR CONVECTION IS ALSO OBSERVED N OF THE EXPOSED LOW LEVEL CENTER...WITHIN 30 NM EITHER SIDE OF A LINE FROM 14N101W TO 12N103W. THIS LOW IS EXPECTED TO CONTINUE TO MOVE W-NW TONIGHT INTO AN AREA OF INCREASING W SHEAR AND SHOULD WEAKEN TO AN OPEN TROUGH ON WED. SINCE THIS LOW PRES IS LIKELY TO GENERATE ONLY NE-E-SE WINDS AT 15-20 KT OVER ITS NORTHERN PERIPHERY WITH SEAS OF 5-7 FT...IT IS NOT MENTIONED IN THE TEXT HIGH SEAS...BUT WAS DEPICTED ON THE 24 HOUR PROGNOSTIC MARINE FACSIMILE CHARTS. ...DISCUSSION... ALOFT...AN UPPER LEVEL LONGWAVE TROUGH DISSECTS N AMERICA WITH ITS MEAN AXIS CONTINUING SW INTO THE DISCUSSION AREA ALONG 32N100W TO 22N111W. A REINFORCING SHORTWAVE TROUGH IS APPROACHING THE W PORTION AND IS CURRENTLY ALONG 35N128W TO 33N142W. AN UPPER CYCLONE HAS CUT OFF AT 25N135W. A SHORTWAVE RIDGE EXTENDS FROM 32N145W TO A CREST AT 30N12W BUT IS RAPIDLY WEAKENING AS IT IS SQUEEZED BETWEEN THE TWO UPPER TROUGHS. SOME UPPER MOISTURE IS NOTED OVER SOUTHERN ARIZONA AND WESTERN NEW MEXICO AND IS SHIFTING SE OVER EXTREME NORTHERN OLD MEXICO. THE REINFORCING SECONDARY TROUGH IS PRECEDED BY A DENSE...BUT VERY NARROW MOISTURE BAND. OTHERWISE THE UPPER LEVELS APPEAR VERY DRY FROM 23-32N W OF 104W. THE UPPER FLOW IS ZONAL ACROSS THE TROPICS FROM 10-22N TO THE W OF 100W. THESE STRONG WESTERLIES ARE ADVECTING DENSE UPPER MOISTURE EASTWARD TO ALONG 105W WHERE THE MOISTURE PLUME THEN TURNS NE IN RESPONSE TO THE LONGWAVE TROUGH OVER THE CONUS. THIS MOISTURE FEEDS INTO THE CONVECTION ALONG A COLD FRONT EXTENDING SW FROM N FLORIDA TO THE BAY OF CAMPECHE IN THE SOUTHERN GULF OF MEXICO. AN UPPER ANTICYCLONE IS QUASI-STATIONARY OVER S AMERICA AT 07N70W WITH A RIDGE EXTENDING NW TO 12N88W. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING CONVECTION ALONG THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED...WITH THE RESULTANT DEBRIS MOISTURE ADVECTED NE ACROSS PANAMA...COSTA RICA AND THE SW CARIBBEAN. ELSEWHERE AT THE LOW LEVELS...A SURFACE RIDGE EXTENDS FROM 32N140W TO 20N115W. NE WINDS AT 15-20 KT ARE CROSSING THE RIDGE OVER THE AREA N OF 10N TO THE W OF 127W WITH SEAS TO 9 FT IN THE ACCOMPANYING NE SWELL THAT IS STILL MIXING WITH DECAYING NW SWELL. THE GRADIENT IS EXPECTED TO TIGHTEN ON WED WITH THE NE WINDS INCREASING TO 20-25 KT TO THE W OF A LINE FROM 30N125W TO 20N136W. BY THEN A COLD FRONT WILL HAVE MOVED INTO THE DISCUSSION AREA FROM 32N117W TO 24N124W AND WILL REACH FROM 32N117W TO 24N120W ON THU...AND PASS ACROSS THE BAJA PENINSULA AND THE GULF OF CALIFORNIA ON FRI. NE WINDS WILL CONTINUE AT 20-25 KT WITH SEAS 7-10 FT FROM 12-20N W OF 132W. THESE NW 15-20 KT WINDS WILL ARRIVE AT THE W COAST OF THE BAJA PENINSULA LATE THU NIGHT BUT DIMINISH TO 15 KT BEFORE REACHING SOUTHERN BAJA LATE FRI. GENERALLY EXPECT SEAS OF 3-5 FT ALONG WESTERN BAJA THROUGH LATE THU...THEN BUILD TO 5-8 FT IN THE NW SWELL THU NIGHT INTO FRI. LIGHT AND VARIABLE WINDS ARE EXPECTED ACROSS THE GULF OF CALIFORNIA ON WED...BECOMING SOUTHERLY WED NIGHT AND INCREASING 15-25 KT ON THU AHEAD OF THE COLD FRONT. THE POST FRONTAL NORTHERLY FLOW IS NOT EXPECTED TO BE VERY STRONG ACROSS THE GULF OF CALIFORNIA AND GENERALLY IN THE 10-15 KT RANGE. GAP WINDS... GULF OF TEHUANTEPEC...A COLD FRONT IS CURRENTLY ADVANCING SLOWLY SE ACROSS THE WESTERN BAY OF CAMPECHE WITH THE ASSOCIATED NORTHERLY WINDS EXPECTED TO SURGE AT 15-20 KT THROUGH THE CHIVELA PASS IN A COUPLE OF HOURS...GRADUALLY INCREASING 20-25 KT BY SUNRISE WED...THEN REACHING GALE FORCE AROUND SUNSET WED...FURTHER INCREASING TO MAXIMUM OF 40 KT LATE WED NIGHT. THE GALE SHOULD PERSIST THROUGH SUNRISE THU THEN RAPIDLY DIMINISH THU NIGHT AND FRI. GULF OF PAPAGAYO...NE WINDS WILL CONTINUE TO PULSE AT 10-15 KT WITH AN OCCASIONAL SURGES TO 15-20 KT TONIGHT. THESE NE WINDS ARE EXPECTED TO INCREASE TO 20-25 KT BEGINNING WED MORNING AND CONTINUE THROUGH EARLY FRI. THE SOUTHERN EXTENT OF THESE NE WINDS WILL BE NEAR 09N92W LATE THU. $$ NELSON