000
AXPZ20 KNHC 221525
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT DEC 22 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1530 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH IS ALONG 06N77W TO 07N89W. THE INTERTROPICAL 
CONVERGENCE ZONE AXIS EXTENDS FROM 07N89W TO 07N110W TO 10N125W 
TO 08N140W. SCATTERED MODERATE WITHIN 120 NM S OF TROUGH BETWEEN 
78W AND 81W. SCATTERED MODERATE ISOLATED STRONG WITHIN 120 NM 
EITHER SIDE OF ITCZ W OF 119W.

...DISCUSSION...

A SURFACE TROUGH EXTENDS FROM THE BAY AREA OF CALIFORNIA THROUGH 
32N124W TO 27N130W. A 0732 UTC OSCAT PASS INDICATED MODERATE SW 
TO W WINDS IN THE VICINITY OF THE TROUGH ACROSS THE DISCUSSION 
WATERS. AN 0830 UTC ALTIMETER PASS SAMPLED LARGE NW SWELL UP TO 
21 FT JUST TO THE N OF THE DISCUSSION AREA ALONG 132W...ABOUT 3 
FT HIGHER THAN THE WAVEWATCH AND ECWAVE SOLUTIONS...WHILE THE 
UKMET WAVE MODEL PROGGED A MAXIMUM OF 20 FT FOR THE SAME TIME 
PERIOD. THIS SET OF VERY HIGH ENERGY NW SWELL HAS PEAK WAVE 
PERIODS OF 17-19 FT. THE SWELL WILL GRADUALLY DECAY TO A 
COMBINED MAXIMUM OF 12-13 FT BY 24 HOURS...WITH SEAS OF 8 FT OR 
GREATER REACHING THE EQUATOR BY 36 TO 42 HOURS. 

HIGH PRESSURE WILL BUILD EAST BEHIND THE TROUGH ALONG 26N 
THROUGH MON NIGHT. THIS HIGH AND ACCOMPANYING RIDGE WILL BECOME 
THE DOMINANT SYNOPTIC FEATURE ACROSS THE REGION SAT THROUGH TUE 
WITH GENERALLY LIGHT TO MODERATE WINDS ACROSS THE NORTHERN 
WATERS. THE HIGH WILL ALSO ENHANCE NE-E TRADES S OF THE RIDGE 
AXIS AND N OF THE ITCZ. TRADES ARE ALREADY 20-25 KT IN THE W 
CENTRAL WATERS AS INDICATED BY RECENT ASCAT PASSES. THE SHIFTING 
RIDGE TO THE E WILL HELP TO EXPAND THE TRADES TO 117W BY 48 
HOURS WHILE COMBINED SEAS WILL REMAIN 10-14 FT IN MIXED NE WIND 
WAVES AND THE NW SWELL SET ACROSS THE AREA OF ENHANCED TRADES.

AS THE RIDGE CONTINUES TO BUILD EASTWARD IN THE WAKE OF THE 
TROUGHS A TIGHT PRESSURE GRADIENT WILL ALSO SET UP NEAR THE BAJA 
CALIFORNIA PENINSULA WITH INVERTED TROUGHING LOCATED NEAR THE W 
COAST OF MEXICO. THIS MAY INDUCE NW TO N WINDS OF 20-25 KT IN 
THE SOUTHERN GULF OF CALIFORNIA AND WITHIN 120-180 NM W OF THE 
BAJA CALIFORNIA PENINSULA BY MON MORNING.

GAP WINDS...
STRONG 1029 MB HIGH PRESSURE CENTERED OVER SE LOUISIANA BEHIND A 
STRONG COLD FRONT IS PRODUCING A VERY IMPRESSIVE GAP WIND EVENT 
THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. EARLIER 
0316 UTC ASCAT AND 0549 UTC OCEANSAT OVERPASSES SHOWED A COUPLE 
40-45 KT RANGE. GIVEN THE 5 KT OR SO LOW BIAS OF THE ASCAT 
SCATTEROMETER AND TIMING OF DIURNAL PEAK DRAINAGE FLOW...OPTED 
TO KEEP THE STORM WARNING UP THROUGH THE 1200 UTC HIGH SEAS 
FORECAST PACKAGE. HIGH SEAS OF 20-21 FT ARE EMANATING FROM THE 
SOURCE REGION OF THE GULF OF TEHUANTEPEC WITH N-NE SWELL 
EXTENDING TO NEAR 110W. THESE SWELLS ARE MERGING WITH NW SWELL 
FROM THE NORTHERN PORTION OF THE DISCUSSION AREA NOTED ABOVE. 
THE PRESSURE GRADIENT IS FORECAST TO RELAX SIGNIFICANTLY OVER 
THE REGION LATE IN THE WEEKEND INTO EARLY NEXT WEEK WITH WINDS 
DIMINISHING BELOW GALE FORCE BY MID-DAY SUN...THEN TO 20 KT OR 
LESS BY EARLY MON MORNING. LOOKING AHEAD...A WEAKER COLD FRONT 
MAY MOVE THROUGH THE SW GULF OF MEXICO WED ALLOWING FOR A 
SHORT-LIVED MINIMAL GALE FORCE WIND EVENT IN THE GULF OF 
TEHUANTEPEC BEHIND ITS PASSAGE TO THE N BEGINNING WED EVENING.

INCREASED TRADES IN THE SW CARIBBEAN IS AIDING NE-E 20-30 KT 
WINDS IN THE GULF OF PAPAGAYO THIS MORNING. THE WINDS IN THE 
CARIBBEAN WILL INCREASE FURTHER LATER TODAY AS A STRONG COLD 
FRONT CURRENTLY IN THE NW CARIBBEAN CONTINUES A TREK TO THE SE. 
THE AREA OF WINDS WILL SPREAD DOWNSTREAM TO ALONG 100W. 
RESULTANT SEAS WILL ALSO BUILD TO UP TO 13 FT. WINDS AND SEAS 
WILL THEN GRADUALLY DIMINISH AND SUBSIDE BY EARLY NEXT WEEK AS 
THE TRADES IN THE CARIBBEAN BACK OFF.

LATEST MODEL GUIDANCE HAS TRENDED SLIGHTLY UPWARD WITH RESPECT 
TO THE STRENGTH OF NORTHERLY WINDS IN THE GULF OF PANAMA. FRESH 
TO STRONG WINDS ARE NOW ALSO LIKELY THERE FOR AN APPROXIMATELY 
18 HOUR PERIOD COMMENCING THIS EVENING.

$$
COBB