000 AXPZ20 KNHC 281538 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC THU NOV 28 2013 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1400 UTC. ...SPECIAL FEATURES... A STORM WARNING REMAINS IN EFFECT FOR THE GULF OF TEHUANTEPEC. BOTH THE 0316 UTC ASCAT-B AND 0402 UTC ASCAT-A PASSES SHOWED WINDS TO AT LEAST 45 KT IN THE GULF. THE STORM WARNING SEEMS WARRANTED WHEN TAKING INTO ACCOUNT THE ASCAT LOW BIAS AT SUCH STRONG WIND SPEEDS AND THE FACT THAT THE OBSERVATIONS OCCURRED WELL PRIOR TO THE TIME OF PEAK NOCTURNAL DRAINAGE FLOW OFF THE LAND. SHIP PHSG REPORTED 35 KT N WINDS AND 12 FT SEAS NEAR 14.2N93.5W...WELL SE OF THE GULF OF TEHUANTEPEC COAST. THESE OBSERVATIONS SUGGEST THAT THE NUMERICAL GUIDANCE IS RUNNING LOW WITH BOTH THE WINDS AND SEAS HERE. SIGNIFICANT WAVE HEIGHTS IN THE GULF HAVE LIKELY PEAKED NEAR 25 FT THIS MORNING. STORM CONDITIONS ARE EXPECTED TO PERSIST UNTIL AROUND SUNSET TONIGHT WHEN THEY WILL DIMINISH BACK TO GALE FORCE. WINDS ARE THEN EXPECTED TO REMAIN AT GALE FORCE THROUGH THE END OF THE FORECAST PERIOD ON SAT MORNING. THE PROLONGED PERIOD OF STRONG GAP WINDS WILL RESULT IN AN IMPRESSIVE PLUME OF NE SWELL WHICH WILL PROPAGATE S TO THE EQUATOR BY SUNRISE FRI. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM 08N78W TO 09N90W TO 07N100W TO 08N110W. THE ITCZ AXIS EXTENDS FROM 08N110W TO 10N120W TO 08N140W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION LIES WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 96W AND 105W. SCATTERED MODERATE CONVECTION LIES WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 112W AND 120W AS WELL AS WITHIN 90 NM EITHER SIDE OF THE AXIS W OF 133W. ...DISCUSSION... A WEAKENING COLD FRONT STEMS FROM 1000 MB LOW PRES NEAR 34N128W AND ENTERS THE FORECAST AREA AT 30N121W THEN PASSES THROUGH 25N124W TO 21N140W. FRESH TO STRONG NW WINDS ARE CONFINED TO THE AREA N OF 29N BETWEEN 130W AND 136W...WHILE NW SWELL CONTINUES TO CARRY SEAS TO 18 FEET THIS MORNING. SWELL OVER 8 FT IS BEGINNING TO OOZE SE OF THE FRONTAL POSITION AND WILL COVER THE REGION W OF A LINE FROM 30N AT THE BAJA CALIFORNIA PENINSULA THROUGH 17N120W TO 08N140W BY EARLY FRI. SEAS WILL BEGIN TO SUBSIDE AND THE FRONT WILL WEAKEN STARTING LATER TODAY. THE LOW PRES SYSTEM IS FORECAST TO SINK S AND WEAKEN OVER THE NEXT DAY OR SO...OPENING UP TO A TROUGH BY SAT MORNING. THE PRES GRADIENT WILL TIGHTEN OVER THE NW WATERS BETWEEN THE TROUGH AND BUILDING HIGH PRES NW OF THE AREA RESULTING IN FRESH TO STRONG NE WINDS N OF 26N W OF 130W BY EARLY SAT. A PAIR OF SURFACE TROUGHS ARE EMBEDDED IN THE MONSOON TROUGH AND ITCZ. THE EASTERN TROUGH EXTENDS FROM 17N120W TO 08N122W. SCATTERED MODERATE CONVECTION LIES WITHIN 180 NM E OF THIS TROUGH FROM 15N TO 17N. THE 0542 UTC ASCAT-A PASS INDICATES ONLY MODERATE WINDS NEAR THIS TROUGH WHILE SEAS ARE LESS THAN 8 FT. THE WESTERN TROUGH EXTENDS FROM 14N128W TO 08N132W. THE PRESSURE GRADIENT W OF THIS TROUGH IS TIGHT ENOUGH TO SUPPORT MODERATE TO FRESH TRADES AND A CORRESPONDING AREA OF 8-9 FT IN MIXED NE AND NW SWELL. THIS AREA OF SEAS OVER 8 FT IS ALREADY BEGINNING TO MERGE WITH NW SWELL FROM THE COLD FRONT DESCRIBED ABOVE. THE TROUGHS WILL WEAKEN WHILE CONTINUING WESTWARD AROUND 10 KT. GAP WINDS...FRESH TO STRONG NE WINDS ARE SURGING THROUGH THE GULF OF PAPAGAYO THIS MORNING. PEAK WINDS ARE BELIEVED TO BE AROUND 30 KT THIS MORNING WITH SEAS BUILDING TO 10 FT TODAY. SIMILAR CONDITIONS WILL PERSIST INTO THE WEEKEND WITH THE STRONGEST WINDS OCCURRING DURING MAXIMUM NOCTURNAL DRAINAGE EARLY EACH MORNING. $$ SCHAUER