000
AXPZ20 KNHC 190338
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED DEC 19 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0245 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 06N78W TO 09N84W TO 06N95W. ITCZ 
CONTINUES TO 08N120W TO BEYOND 07N140W. SCATTERED MODERATE 
WITHIN 90 NM N OF AXIS BETWEEN 123W AND 131W.

...DISCUSSION...
A COLD FRONT EXTENDS FROM NORTHERN BAJA CALIFORNIA TO 30N118W  
TO 25N127W WHERE IT BEGINS TO DISSIPATE TO 22N140W. THE MOST 
RECENT SCATTEROMETER DATA ALONG WITH SOME SHIP OBSERVATIONS 
SHOWED WINDS OF 20-30 KT BEHIND THE COLD FRONT WITH SEAS TO 
AROUND 14 FT IN NW SWELL. AN ALTIMETER PASS ALSO INDICATED SEA 
HEIGHTS IN THE 11 TO 14 FT RANGE OVER THE NW WATERS. A 1034 MB 
HIGH PRES FOLLOWS THE FRONT AND IT IS NOW CENTERED NEAR 34N145W. 
THE FRONT WILL CONTINUE TO DISSIPATE DURING THE NEXT 12-24 HOURS 
EXTENDING FROM 30N114W TO 23N120W TO 21N130W BY WED MORNING. 
THIS PATTERN WILL MAINTAIN THE PRESSURE GRADIENT N OF THE 
DISSIPATING FRONT WITH THE FRESH TO STRONG WINDS COVERING MUCH 
OF THE FORECAST AREA N OF 20N AND W OF THE FRONT. THE HIGH PRES 
IS EXPECTED TO MOVE E-SE REACHING A POSITION NEAR 32N125W IN 
ABOUT 24 HOURS. FRESH TO STRONG TRADE WINDS ARE NOTED BETWEEN 
THE HIGH PRES AND THE ITCZ...PARTICULARLY FROM 08N TO 20N W OF 
130W. AN OSCAT PASS CONFIRMED THE PRESENCE OF THESE WINDS. THE 
HIGH PRES IS FORECAST TO WEAKEN WED NIGHT INTO THU...WHICH WILL 
HELP TO DECREASE THE AREA OF TRADEWINDS AS WELL AS THE WINDS 
ACROSS THE N WATERS.   

THE SET OF NW SWELLS WILL CONTINUE TO SPREAD S AND E OVER THE 
NEXT 24-48 HOURS WITH SEAS SUBSIDING TO 9 FT N OF 20N W OF 114W 
BY THU EVENING. HOWEVER...A NEW COLD FRONT WILL REACH THE FAR NW 
PART OF THE FORECAST REGION BY THU EVENING FOLLOWED BY ANOTHER 
ROUND OF LONG PERIOD NW SWELL AND BUILDING SEAS TO ABOUT 14 FT 
NW OF LINE FROM 30N130W TO 27N140W.

EXPECT ALSO INCREASING SW TO W WINDS ACROSS THE GULF OF 
CALIFORNIA AHEAD OF THE COLD FRONT TONIGHT THEN WINDS WILL VEER 
TO THE NW WITH THE FRONTAL PASSAGE AND INCREASE TO 20-25 KT N OF 
25N. THESE WIND SPEEDS WILL PERSIST THROUGH 48 HOURS AS HIGH 
PRES BUILDS ACROSS THE GREAT BASIN. 

GAP WINDS...
LOOKING AHEAD...A COLD FRONT WILL SHIFT RAPIDLY ACROSS THE 
GULF OF MEXICO ON THU. WINDS BEHIND THIS FRONT WILL FUNNEL 
THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC WHICH WILL 
LEAD TO A STRONG GAP WIND EVENT. NORTHERLY WINDS WILL START TO 
FUNNEL INTO THE GULF OF TEHUANTEPEC BY THU EVENING...WITH STRONG 
GALE...AND POSSIBLY STORM CONDITIONS...BY FRI MORNING. AT THIS 
TIME...THE GFS GLOBAL MODEL SUGGESTS WINDS OF 40-50 KT. SEAS ARE 
EXPECTED TO BUILD IN EXCESS OF 15-19 FT. THE FNMOC ENSEMBLE 
FORECAST SYSTEM ALSO DISPLAYS A HIGH PROBABILITY OF GALE FORCE 
WINDS BETWEEN FRI MORNING AND SAT MORNING.

WINDS WILL ALSO INCREASE ACROSS THE GULF OF PAPAGAYO BY FRI. 
EXPECT NE TO E WINDS OF 20-25 KT AND SEAS OF 8-10 FT IN AND 
DOWNSTREAM OF THE GULF TO ABOUT 92W BY SAT MORNING.

OF NOTE...THE MONTHLY DISTRIBUTION OF TEHUANTEPEC EVENTS SHOWS 
THAT THE LARGEST NUMBER OF GALE-FORCE EVENTS OCCURS IN DECEMBER. 
STORM-FORCE EVENTS OCCUR MOST OFTEN IN JANUARY. THE 2006-2007 
COLD SEASON HAS THE MOST STORM-FORCE EVENTS WITH A TOTAL OF 13.  

$$
GR