000
AXPZ20 KNHC 182136
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE DEC 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 06N78W TO 08N85W TO 06N95W. ITCZ 
CONTINUES TO 08N120W TO 07N140W. SCATTERED MODERATE CONVECTION 
CAN BE FOUND WITHIN 90 NM S OF AXIS BETWEEN 107W AND 111W AND 
WITHIN 120 NM N AXIS FROM 128W TO 135W.

...DISCUSSION...
HIGH PRESSURE 1037 MB IS CENTERED NW OF THE AREA NEAR 35N145W. 
LOW PRESSURE 1005 MB IS CENTERED INLAND ALONG THE CALIFORNIA/ 
NEVADA BORDER NEAR 36.5N116.5W WITH THE ASSOCIATED COLD FRONT 
EXTENDING SW ACROSS THE NORTH WATERS TO 30N120W TO 23N140W. 
THE PRESSURE GRADIENT BETWEEN THESE FEATURES IS PRODUCING A 
LARGE AREA OF 20-30 KT N-NE WINDS TO THE N OF THE COLD FRONT AS 
DEPICTED BY SEVERAL SHIP OBSERVATIONS. THESE STRONG WINDS ARE 
ALLOWING SEAS TO BUILD TO 14 FT BEHIND THE FRONT WHICH IS 
FORECAST TO DISSIPATE IN ABOUT 24 HOURS AS THE STRONG HIGH PRES 
MOVES E-SE TO NEAR 31N130W. THIS PATTERN WILL MAINTAIN THE 
PRESSURE GRADIENT N OF THE WEAKENING FRONT WITH THE FRESH TO 
STRONG WINDS COVERING MUCH OF THE FORECAST AREA N OF 20N AND W 
OF 115W BY WED MORNING. 

THE SET OF NW SWELLS WILL CONTINUE TO SPREAD S AND E OVER THE 
NEXT 24-48 HOURS WITH SEAS SUBSIDING TO 10 FT N OF 20N W OF 115W 
BY THU AFTERNOON.

THE AREA OF HIGH PRESSURE WILL WEAKEN LATE WED INTO THU...WHICH 
WILL HELP TO DECREASE THE TRADEWINDS AS WELL AS THE WINDS OVER 
THE NORTHERN PART OF THE FORECAST AREA. 

EXPECT INCREASING SW TO W WINDS ACROSS THE GULF OF CALIFORNIA 
TONIGHT AHEAD OF THE COLD FRONT THEN NW WINDS WILL INCREASE TO 
20-25 KT N OF 25N AS HIGH PRES BUILDS ACROSS THE GREAT BASIN. 

ANOTHER COLD FRONT WILL REACH THE FAR NW PART BY THU WITH A NEW 
SET OF NW SWELL...RAISING SEAS TO ABOUT 14 FT NW OF LINE FROM 
30N128W TO 27N140W.  

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. WINDS 
WILL ALSO INCREASE ACROSS THE GULF OF PAPAGAYO BY FRI.

$$
GR