000 AXPZ20 KNHC 151545 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SUN DEC 15 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... GULF OF TEHUANTEPEC...THE 0546 UTC OSCAT PASS SHOWED THE ONSET OF NORTHERLY FLOW IN THE GULF OF TEHUANTEPEC THIS MORNING. WHILE WINDS AT THAT TIME WERE ONLY A FRESH BREEZE...THE PROGRESSION OF STRONG WINDS INTO THE PACIFIC THIS MORNING IS EVIDENT BY THE MOVEMENT OF THE LOW CLOUDS AWAY FROM THE GULF OF TEHUANTEPEC ON VISIBLE SATELLITE IMAGERY. SEA SURFACE TEMPERATURE MEASURED BY THE GOES SATELLITE WERE WELL OVER 25 CELSIUS IN THE AREA. THE COLD AIR MASS MOVING OVER THE WARM SEA SURFACE SHOULD PROMOTE VERTICAL MIXING THAT SHOULD ALLOW THE STRONGER WINDS ALOFT TO MIX DOWN TO THE SURFACE. WINDS ARE CURRENTLY BELIEVED TO BE GALE FORCE AND ARE EXPECTED TO BECOME STORM FORCE BY SUNSET. SEAS WILL QUICKLY BUILD TO OVER 20 FT TONIGHT. STORM CONDITIONS ARE EXPECTED TO PERSIST UNTIL JUST AFTER SUNRISE MON BEFORE DIMINISHING BACK TO GALE FORCE. THE GALE EVENT IS EXPECTED TO CONTINUE THROUGH AT LEAST THE END OF THE FORECAST PERIOD ON TUE MORNING. NE SWELL FROM THE EVENT WILL PROPAGATE WELL SW OF TEHUANTEPEC...WITH THE AREA FROM 05N TO 13N BETWEEN 92W AND 109W EXPECTED TO SEE SEAS OVER 8 FT BY TUE MORNING. GULF OF CALIFORNIA...THE 0720 UTC OSCAT PASS SHOWS GALE FORCE WINDS CONTINUING IN THE WESTERN GULF OF CALIFORNIA WITH A STRONG BREEZE FOUND ELSEWHERE IN THE GULF AS WELL AS SPILLING THROUGH THE MOUNTAIN PASSES OF CENTRAL AND SOUTHERN BAJA CALIFORNIA INTO THE OPEN PACIFIC WATERS WITHIN 45 NM OF THE COAST. ASCAT PASSES FROM 0406 UTC AND 0452 UTC ALSO SHOW STRONG N WINDS ALONG THE CABO CORRIENTES COAST TO THE S OF THE GULF OF CALIFORNIA. THIS EVENT IS PRIMARILY DRIVEN BY A TIGHT PRESSURE GRADIENT BETWEEN PRONOUNCED TROUGHING ACROSS NW MAINLAND MEXICO AND SHARP RIDGING ACROSS THE GULF OF CALIFORNIA EXTENDING FROM STRONG HIGH PRESSURE OVER THE U.S. GREAT BASIN REGION. GALE FORCE WINDS ARE FORECAST TO SHIFT NORTHWARD THROUGH THIS EVENING...WITH A STRONG BREEZE EXPECTED TO BLOW THROUGH GAPS IN THE NORTHERN BAJA CALIFORNIA PENINSULA INTO PORTIONS OF THE E PACIFIC. WINDS IN THE GULF WILL GRADUALLY DIMINISH TO 20 KT OR LESS BY MON EVENING AS THE PRESSURE PATTERN WEAKENS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM 10N84W TO 06N100W TO 08N115W TO 08N125W. THE ITCZ AXIS EXTENDS FROM 08N125W TO 07N140W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION LIES S OF THE AXIS TO 05N BETWEEN 80W AND 85W AS WELL AS WITHIN 180 NM EITHER SIDE OF THE AXIS BETWEEN 112W AND 120W. ...DISCUSSION... AN UPPER LOW NEAR 29N133W HAS DIRECTED THE UPPER JET FROM S TO N ON ITS SE SIDE. THE REAR RIGHT QUADRANT OF THE JET IS GENERATING DIFFLUENT FLOW ALOFT WHICH IS LIFTING THE MOIST AIRMASS POOLED NEAR THE MONSOON TROUGH BETWEEN 110W-120W AND ENHANCING CONVECTION. THIS CONVECTION IS DESCRIBED IN THE SECTION ABOVE. THE CONVECTION LIES NEAR A BEND IN THE MONSOON TROUGH NEAR 116W. RECENT SCATTEROMETER PASSES SHOW THE WINDS N OF THE MONSOON TROUGH HERE ARE A FRESH TO STRONG BREEZE DUE TO THE ENHANCED PRESSURE GRADIENT BETWEEN THE TROUGH AND THE SUBTROPICAL RIDGE. THE UPPER JET IS FORECAST TO WEAKEN AS THE UPPER LOW SLOWLY JOGS NORTHWARD...DIMINISHING THE CHANCE FOR ORGANIZED DEEP CONVECTION AND FLATTENING THE MONSOON TROUGH OVER THE NEXT TWO DAYS AS A RESULT. A 1033 MB SUBTROPICAL HIGH DOMINATES THE OPEN PACIFIC WATERS OVER THE DISCUSSION AREA N OF 15N. THE MOST RECENT ASCAT AND OSCAT PASSES SHOWED A LARGE AREA OF FRESH TRADE WINDS FROM 15N TO 28N W OF 125W...WITH WINDS TO 25 KT WITHIN THE REGION FROM 17N TO 25N BETWEEN 130W AND 135W. THIS AREA OF TRADES IS FORECAST TO WEAKEN AND SHRINK AS THE DRIVING HIGH PRESSURE CENTER SHIFTS NORTHWARD...WEAKENING THE PRESSURE GRADIENT BETWEEN IT AND THE ITCZ/MONSOON TROUGH AXIS. LONG PERIOD NW SWELL IS MIXING WITH THE ASSOCIATED NE TRADE WIND SWELL AND WITH LONG PERIOD CROSS-EQUATORIAL SOUTHERLY SWELL. THE RESULT IS COMBINED SEAS OF 7-11 FT WITHIN THIS AREA THAT ARE EXPECTED TO SHIFT SOUTHEASTWARD AND GRADUALLY SUBSIDE TO 9 FT THROUGH TUE MORNING. GULF OF PAPAGAYO...SHIP C6FR3 REPORTED 25 KT WINDS NEAR THE GULF OF PAPAGAYO AT 1300 UTC THIS MORNING. NE-E WINDS HERE ARE EXPECTED TO PULSE AT 20-25 KT DURING THE MAXIMUM NOCTURNAL DRAINAGE THROUGH THE END OF THE FORECAST PERIOD TUE MORNING. NE SWELL FROM PAPAGAYO WILL COMBINE WITH NW SWELL FROM THE GULF OF TEHUANTEPEC TO BRING SEAS TO 9 FT BY EARLY TUE MORNING. $$ SCHAUER