000
AXPZ20 KNHC 271554
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT DEC 27 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ALONG A LINE FROM 
06.5N78W TO 08N85W TO 06N91W TO 08N140W. SCATTERED MODERATE 
CONVECTION WILL CONTINUE NEXT 12 HOURS WITHIN 90 NM N OF AXIS 
BETWEEN 78W AND 84W. NUMEROUS MODERATE AND ISOLATED STRONG 
CONVECTION WILL CONTINUE NEXT 12 HOURS WITHIN 90 NM EITHER SIDE 
OF AXIS FROM 122W TO 140W.

...DISCUSSION...
A PROGRESSIVE SHORTWAVE TROUGH EXTENDING FROM THE NORTHERN 
PLAINS THROUGH THE DESERT SOUTHWEST AND NORTHWESTERN MEXICO HAS 
DRIVEN A COLD FRONT THROUGH EXTREME NORTHERN MEXICO AND ALL BUT 
THE SOUTHERN TIP OF BAJA CALIFORNIA...CONTINUING WESTWARD ACROSS 
THE OPEN PACIFIC JUST NORTH OF 20N THIS MORNING. THE GRADIENT 
BETWEEN LOW PRESSURE OVER THE PLAINS AND ENHANCED HIGH PRESSURE 
OVER THE EASTERN PACIFIC N OF 30N IS RESULTING IN NORTHERLY 
WINDS OF 20 TO 25 KT WINDS ADJACENT TO BAJA CALIFORNIA AND S OF 
26N...WHILE N WINDS 20 TO 25 KT...WITH LIKELY SMALL ISOLATED 
POCKETS TO 30 KT...HAVE SPREAD S THROUGH THE ENTIRE LENGTH OF 
THE GULF OF CALIFORNIA. THESE WINDS SHOULD CONTINUE THROUGH THE 
NEXT 18 TO 24 HOURS AND THEN GRADUALLY DIMINISH AS THE UPPER 
TROUGH HEADS FARTHER EAST AND THE PRESSURE GRADIENT RELAXES. 
THESE WINDS WILL GENERATE BUILDING SEAS OF 6 TO 8 FT OVER THE 
SOUTHERN HALF OF THE GULF OF CALIFORNIA BY THIS AFTERNOON AND 
THEN RAPIDLY SUBSIDE LATER SUN AND MON AS THE WINDS VEER N TO NE 
AND DIMINISH. 

SOUTH OF THE ENHANCED SURFACE RIDGE SITTING NORTH OF THE AREA 
NEAR 33N138W...MODERATE TO STRONG TRADES ARE BLOWING OVER A 
LARGE EXPANSE OF THE FORECAST AREA. OVERNIGHT SCATTEROMETER 
PASSES INDICATED MAINLY NE 20 TO 25 KT WINDS FROM 08N TO 27N W 
OF 123W...AND WILL SPREAD W AND NW TOWARDS THE SOUTHERN HALF OF 
THE BAJA TODAY AS HIGH PRESSURE BUILDS IN FURTHER BEHIND THE 
COLD FRONT.

AT THE SAME TIME...LONG PERIOD NW TO N SWELL GENERATED ACROSS 
THE CENTRAL AND NE PACIFIC WILL CONTINUE TO PROPAGATE THROUGH 
THE NW HALF OF THE FORECAST AREA THROUGH TONIGHT...WITH WAVE 
HEIGHTS RANGING FROM 9 TO 12 FT OVER THE AREA IMMEDIATELY NW OF 
A LINE RUNNING FROM THE SOUTHERN TIP OF BAJA CALIFORNIA TO TO 
12N120W TO 06N140W...WHILE HIGHER SEAS OF 12 TO 16 FT PREVAIL 
ACROSS THE FAR NW AND N PART OF THE AREA. OVER THE NEXT FEW DAYS 
THE SURFACE RIDGE WILL GRADUALLY WEAKEN AND SHIFT SLIGHTLY E... 
RESULTING IN SLOWLY WEAKENING TRADES. MEANWHILE...THE LONG 
PERIOD NW TO N SWELL WILL GRADUALLY FADE AS IT PROPAGATES 
THROUGH THE AREA AND ACROSS THE EQUATOR...AND THEN OUT OF THE 
AREA BY 72 HOURS. 

FINALLY...A STRONG HIGH PRES RIDGE OFF THE E COAST OF THE U.S. 
EXTENDING INTO THE SW GULF OF MEXICO AND NW CARIBBEAN IS 
RESULTING IN STRONG TRADES BLOWING ACROSS CENTRAL AMERICA...AND 
PRODUCING NORTHEASTERLY GAP FLOW S AND E OF THE YUCATAN.  THIS 
IS YIELDING GAP WINDS NEAR AND DOWNWIND OF THE GULFS OF PAPAGAYO 
AND PANAMA. NE TO E WINDS OF 20 TO 25 KT...WITH SMALL POCKETS 
NEAR 30 KT...ARE EXPECTED TO CONTINUE OVER A NARROW AREA WITHIN 
THE GULF OF PAPAGAYO AND DOWNWIND A FEW HUNDRED MILES FROM THE 
COAST...WITH SEAS BUILDING UP TO 9 FT BY 24 HOURS. ACROSS THE 
GULF OF PANAMA...A WELL DEFINED CYCLONIC CIRCULATION ALONG THE 
ITCZ AND THE COLUMBIAN COAST IS AIDING IN 20 TO 25 KT NORTHERLY 
FLOW N AND W OF THE ITCZ...AND THROUGH THE GULF OF PANAMA... 
WHILE 20 TO 25 KT SW TO S FLOW IS OCCURRING S AND E OF THE LOW. 
THIS CONVERGENCE AND AMPLE TROPICAL MOISTURE WILL CONTINUE TO 
YIELD ACTIVE CONVECTION E OF 80W THROUGH 48 HOURS. 

WHILE THE PAPAGAYO EVENT BEGINS TO WIND DOWN ON MONDAY...THE 
COLD FRONT NOW OVER NORTHWEST MEXICO WILL HAVE REACHED THE 
ISTHMUS OF TEHUANTEPEC. IN RESPONSE...MODELS INDICATE WINDS NEAR 
AND DOWNSTREAM OF THE GULF OF TEHUANTEPEC WILL BEGIN 
BLOWING...POSSIBLY TO GALE FORCE...BY MON NIGHT. 

$$
STRIPLING