000
AXPZ20 KNHC 212204
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI DEC 21 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 ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 08N78W TO 06N91W...THEN ITCZ 
FROM 06N91W TO 09N124W TO 07N140W. SCATTERED MODERATE 
CONVECTION EXISTS WITHIN 60 NM OF TROUGH BETWEEN 122W AND 132W 
AND AGAIN W OF 138W.

...DISCUSSION...
A DYING FRONTAL BOUNDARY EXTENDS FROM CENTRAL CALIFORNIA TO 
25N140W. LARGE 15-18 SECOND NW SWELL ASSOCIATED WITH THE FRONT 
IS SWEEPING S OF 30N INTO THE TROPICS...AND WILL CONTINUE TO 
PROPAGATE SOUTHWARD INTO THE SOUTHERN HEMISPHERE THROUGH 
CHRISTMAS DAY AND SLOWLY DECAY. COMBINED SEAS AROUND 12-15 FT 
ALONG LEADING EDGE OF THE SWELL TRAIN WILL PEAK AT 15-18 FT 
TONIGHT AND ON SATURDAY OVER NORTHERN PORTION OF THE DISCUSSION 
AREA W OF 125W. THE EUROPEAN ASCAT SCATTEROMETER SHOWS ONLY 
MODERATE TO FRESH WINDS ALONG EITHER SIDE OF THE DISSIPATING 
FRONTAL BOUNDARY.

HIGH PRESSURE WILL BUILD EAST BEHIND THE FRONT ALONG 26N THROUGH 
MONDAY NIGHT.  THIS HIGH PRESSURE RIDGE WILL BECOME THE DOMINANT 
SYNOPTIC FEATURE ACROSS THE REGION SATURDAY THROUGH TUESDAY WITH 
LIGHT WINDS AND SEAS SUBSIDING FROM 15-18 FT TO ONLY 5-8 FT N OF 
22N BY CHRISTMAS DAY. THIS HIGH WILL ALSO SOMEWHAT ENHANCE NE-E 
TRADEWINDS S OF THE RIDGE AXIS AND N OF THE ITCZ. EXPECT FRESH 
TRADEWINDS FROM 10N TO 15N BETWEEN 120W-130W TONIGHT...THEN 
SPREADING ACROSS THE WATERS FROM 10N TO 20N W OF 125W BY LATE 
SATURDAY NIGHT THROUGH TUESDAY.

GAP WINDS...
STRONG 1033 MB HIGH PRESSURE CENTERED OVER SOUTH TEXAS BEHIND A 
COLD FRONT IS PRODUCING VERY STRONG GAP WIND EVENT THROUGH THE 
CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. TWO SHIPS REPORTED 
GALE FORCE WINDS AND A THIRD SHIP...THE ELXU2...REPORTED A 50 KT 
VISUAL ESTIMATE WIND WITH 32 FT SEAS.  MODEL GUIDANCE INDICATES 
WINDS WILL REMAIN AT OR NEAR STORM FORCE THROUGH LATE TONIGHT OR 
EARLY SATURDAY...WITH GALE CONDITIONS PERSISTING THROUGH EARLY 
SUNDAY. WIND-DRIVEN SEAS WILL QUICKLY FAN OUTWARD FROM THE 
SOURCE REGION AS N-NE SWELL EXTENDING DOWNWIND FROM THE GULF OF 
TEHUANTEPEC TO NEAR 110W...MERGING WITH NW SWELL FROM THE DYING 
FRONT MENTIONED ABOVE. LOOKING AHEAD...THE PRESSURE GRADIENT IS 
EXPECTED TO RELAX SIGNIFICANTLY OVER THE REGION BY EARLY NEXT 
WEEK WITH SOUTHERLY FLOW BECOMING ESTABLISHED IN THE SW GULF OF 
MEXICO BY EARLY MONDAY...ALLOWING FOR WINDS TO DIMINISH TO 5-10 
KT IN THE GULF OF TEHUANTEPEC ALONG WITH 3-5 FT SEAS BY EARLY 
MONDAY.

INCREASED TRADEWIND FLOW IN THE SW CARIBBEAN WILL ALLOW WINDS IN 
THE GULF OF PAPAGAYO TO REACH 25-30 KT BY SATURDAY MORNING 
...WITH SEAS BUILDING TO 11-12 FT DOWNSTREAM FROM PAPAGAYO 
REGION SATURDAY.  FRESH NORTHERLY WINDS ARE ALSO POSSIBLE 
FARTHER S IN THE GULF OF PANAMA SATURDAY AND SUNDAY.

$$
MUNDELL/LANDSEA