000
AXPZ20 KNHC 202204
TWDEP 

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

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 08N78W TO 06N99W THEN ITCZ TO 
BEYOND 08N140W. SCATTERED MODERATE FROM 95W TO 99W WITHIN 60 NM 
OF TROUGH.

...DISCUSSION...
A COLD FRONT EXTENDING FROM THE OREGON/CALIFORNIA BORDER TO 
AROUND 30N141W WILL MOVE SLOWLY SE...WEAKEN...AND DISSIPATE BY 
FRIDAY NIGHT. LARGE NW SWELL ASSOCIATED WITH THIS FRONT WILL 
SWEEP ACROSS THE NW PORTION OF THE DISCUSSION AREA THROUGH 
SAT...WITH COMBINED SEAS BUILDING TO 18-21 FT ALONG THE NORTHERN 
BOUNDARY W OF 133W FRI AND SAT. TRADEWINDS ACROSS THE AREA OF 
LARGE SWELL WILL BE GENERALLY NE AT 10-20 KT. HIGH PRESSURE WILL 
BUILD EASTWARD BEHIND THE FRONT ALONG 26N THROUGH MON NIGHT. THE 
HIGH WILL BECOME THE DOMINANT SYNOPTIC FEATURE ACROSS THE REGION 
SATURDAY THROUGH TUESDAY... WITH LIGHT WINDS AND SEAS SUBSIDING 
FROM 15-17 FT TO 8-10 FT N OF 22N BY CHRISTMAS DAY. THE HIGH 
WILL ALSO ENHANCE E-NE TRADEWINDS S OF THE RIDGE AXIS AND N OF 
THE CONVERGENCE ZONE. EXPECT FRESH TO STRONG TRADEWINDS BETWEEN 
09N AND 20N W OF 120W SUNDAY THROUGH TUESDAY. GENTLE TO MODERATE 
WINDS WILL PREVAIL ELSEWHERE.

GAP WINDS...
STRONG HIGH PRESSURE BEHIND A FAST-MOVING COLD FRONT MOVING 
SOUTHWARD IN THE WESTERN GULF OF MEXICO WILL INDUCE A SUDDEN 
INCREASE IN GAP WINDS THROUGH CHIVELA PASS INTO THE GULF OF 
TEHUANTEPEC WITHIN THE NEXT 6-9 HOURS. WINDS WILL SUDDENLY AND 
DANGEROUSLY SURGE FROM NEAR CALM CONDITIONS AHEAD OF THE COLD 
FRONT TO GALE FORCE CONDITIONS WITHIN MINUTES...THEN CONTINUE TO 
BUILD TO STORM FORCE TONIGHT. SEAS WILL RAPIDLY BUILD TO AROUND 
20 FT IN BY FRIDAY. GLOBAL MODEL GUIDANCE INDICATES STORM FORCE 
WINDS WILL BEGIN LATE TONIGHT AND CONTINUE THROUGH FRIDAY 
AFTERNOON...WITH GALE CONDITIONS THROUGH LATE SATURDAY NIGHT. 
WIND-DRIVEN SEAS WILL FAN OUTWARD FROM THE SOURCE REGION AS N-NE 
SWELL EXTENDING DOWNWIND FROM THE GULF OF TEHUANTEPEC TO 
110W...MERGING WITH NW SWELL FROM THE COLD FRONT MENTIONED 
EARLIER.

WINDS ACROSS THE GULF OF PAPAGAYO CONTINUE TO PULSE TO 20 KT AT 
NIGHT INTO EARLY MORNING HOURS FROM NOCTURNAL DRAINAGE FLOW. AS 
THE TRADEWIND FLOW INCREASES ACROSS THE SW CARIBBEAN BY 
FRIDAY... EXPECT NE TO E WINDS OF 20-30 KT AND SEAS BUILDING TO 
NEAR 11 FT IN AND DOWNSTREAM OF THE GULF OF PAPAGAYO BY SATURDAY 
AFTERNOON.

NW TO N WINDS WITHIN THE GULF OF CALIFORNIA LIKELY PEAKED AROUND 
30 KT THIS MORNING AS SUGGESTED BY AN ASCAT SCATTEROMETER PASS.  
THESE HAVE DIMINISHED SLIGHTLY THIS AFTERNOON.  FORCING FOR 
THESE WINDS WILL RELAX BY FRIDAY AFTERNOON.

$$
MUNDELL/LANDSEA