000
AXPZ20 KNHC 200328
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU DEC 20 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 
0300 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 07N78W TO 08N85W TO 07W90W THEN THE 
ITCZ CONTINUES TO 08N108W TO 07N120W TO 08N130W TO 07N140W. 
SCATTERED MODERATE CONVECTION IS NOTED FROM 06N TO 09N BETWEEN 
119W AND 123W. SIMILAR CONVECTION IS ALSO SEEN WITHIN 90 NM N OF 
AXIS W OF 138W.

...DISCUSSION...
A 1026 MB HIGH PRESSURE CENTERED NEAR 32N126W EXTENDS A RIDGE SE 
OVER THE FORECAST WATERS TO NEAR 20N110W. A COLD FRONT IS 
DISSIPATING ALONG 25N112W 20N125W. THE PRESSURE GRADIENT BETWEEN 
THESE FEATURES IS SUPPORTING FRESH TO STRONG N TO NE WINDS N OF 
THE FRONT AS WELL AS FROM 20N TO 25N W OF 125W. SCATTEROMETER 
DATA PROVIDED OBSERVATIONS OF THESE WIND SPEEDS. THE PRESSURE 
GRADIENT BETWEEN THE RIDGE AND LOWER PRESSURE IN THE VICINITY OF 
THE ITCZ IS MAINTAINING AN AREA OF FRESH TO STRONG TRADEWINDS 
FROM 08N TO 20N W OF 130W. THE HIGH PRESSURE CENTER WILL SHIFT 
SE TO A POSITION NEAR 29N125W AS A NEW COLD FRONT APPROACHES TO 
THE FORECAST REGION FROM THE NW. AS A RESULT...THE PRESSURE 
GRADIENT WILL RELAX AND WINDS WILL DIMINISH BELOW 25 KT ACROSS 
THE N WATERS BY THU MORNING. THE AREA OF TRADE WINDS WILL ALSO 
SHRINK BY THU MORNING WITH THE STRONGEST WINDS W OF 140W. 

A 1031 MB HIGH PRES CENTERED OVER THE GREAT BASIN IS PRODUCING 
FRESH TO STRONG WINDS ACROSS THE GULF OF CALIFORNIA OR SEA OF 
CORTEZ...MAINLY N OF 24N. THESE WINDS ARE FORECAST TO DIMINISH 
TO 20 KT OR LESS IN ABOUT 36 HOURS AS HIGH PRES MOVES EASTWARD. 

THE REGIONAL WATERS ARE DOMINATING BY LONG PERIOD NW SWELL AND 
NE WIND WAVES. THE NW SWELL WILL CONTINUE TO SPREAD S AND E 
WHILE CONTINUING TO SUBSIDE...WITH SEAS OF 8 TO 10 FT COVERING 
THE AREA FROM 08N TO 20N W OF 115W BY FRI EVENING. 

AS PREVIOUSLY MENTIONED...A NEW COLD FRONT WILL REACH 30N140W 
THU AFTERNOON AND EXTEND FROM 30N135W TO 28N140W THU EVENING... 
AND FROM 30N128W TO 25N136W FRI EVENING. WINDS BEHIND THE FRONT 
WILL REMAIN BELOW 25 KT. THIS FRONT WILL USHER IN A FRESH SET OF 
NW SWELLS INTO THE AREA. SEAS WILL REACH NEAR 14 FT OVER THE FAR 
NW PART OF THE FORECAST REGION BY THU EVENING...AND WILL PEAK 
NEAR 19 FT BY FRI MORNING BEFORE STARTING TO SLOWLY SUBSIDE LATE 
FRI INTO SAT.  
 
GAP WINDS...
ATTENTION REMAINS FOCUSED ON THE NEXT GULF OF TEHUANTEPEC WIND 
EVENT...FORECAST TO BE THE FIRST STORM FORCE WIND EVENT OF THE 
2012-2013 COLD SEASON. THIS GAP WIND EVENT WILL BE ASSOCIATED 
WITH A STRONG COLD FRONT FORECAST TO MOVE 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. STRONG NORTHERLY WINDS WILL 
START TO FUNNEL INTO THE GULF OF TEHUANTEPEC BY THU EVENING AND 
WILL RAPIDLY INCREASE TO STORM FORCE BY EARLY FRI. SEAS ARE 
EXPECTED TO BUILD IN EXCESS OF 15-20 FT IN ASSOCIATION WITH 
THESE STORM FORCE WINDS BY FRI MORNING. A STORM WARNING HAS BEEN 
ISSUED FOR THIS AREA. 

WINDS ACROSS THE GULF OF PAPAGAYO ARE PULSING TO 20 KT DURING 
THE OVERNIGHT AND EARLY MORNING HOURS WITH THE ASSISTANCE OF THE 
NOCTURNAL DRAINAGE FLOW. AS THE TRADE WIND FLOW INCREASES ACROSS 
THE SW CARIBBEAN BY FRI...EXPECT NE TO E WINDS OF 20-30 KT AND 
SEAS OF 8-10 FT IN AND DOWNSTREAM OF THE GULF OF PAPAGAYO TO 
ABOUT 92W BY SAT MORNING.

$$
GR