000
AXPZ20 KNHC 270915
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT DEC 27 2008

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0930 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ALONG THE LINE 07N78W 
TO 06N90W TO 08N110W TO 09N129W TO 07N140W. ISOLATED MODERATE 
CONVECTION WITHIN 90 NM N OF AXIS BETWEEN 78W AND 80W. NUMEROUS 
MODERATE ISOLATED STRONG CONVECTION WITHIN 90 NM EITHER SIDE OF 
LINE FROM 128W TO 133W.

...DISCUSSION...
A PROGRESSIVE SHORTWAVE TROUGH EXTENDING FROM THE NORTHERN 
PLAINS THROUGH THE DESERT SOUTHWEST AND NORTHWESTERN MEXICO HAS 
DRIVEN A COLD FRONT THROUGH MUCH OF BAJA CALIFORNIA AND EXTREME 
NORTHERN MEXICO EARLY THIS MORNING. THE GRADIENT BETWEEN LOW 
PRESSURE ON THE PLAINS AND ENHANCED HIGH PRESSURE WEST OF THE 
UPPER TROUGH IS RESULTING IN NW TO N 20 KT WINDS ADJACENT TO 
BAJA CALIFORNIA AND 20 TO 25 KT THROUGH THE NORTHERN HALF OF THE 
GULF OF CALIFORNIA BEHIND THE FRONT. THESE WINDS SHOULD CONTINUE 
THROUGH THE FIRST HALF OF THE WEEKEND AND THEN GRADUALLY 
DIMINISH AS THE UPPER TROUGH HEADS FARTHER EAST AND THE PRESSURE 
GRADIENT RELAXES. ALTHOUGH OF LIMITED FETCH...THE MODERATE TO 
OCCASIONALLY STRONG WINDS SHOULD CAUSE SEAS TO BUILD TO 5 TO 8 
FT OVER THE SOUTHERN HALF OF THE GULF OF CALIFORNIA AT THEIR 
PEAK AND THEN RAPIDLY SUBSIDE LATER SUN AND MON AS THE WINDS 
DIMINISH. 

SOUTH OF THE ENHANCED SURFACE RIDGE SITTING NORTH OF THE AREA 
NEAR 33N138W...MODERATE TO STRONG TRADES ARE BLOWING OVER A 
LARGE EXPANSE.  A QUIKSCAT PASS SEVERAL HOURS EARLIER INDICATED 
NE TO E 20 TO 25 KT WINDS FROM 11N TO 27N W OF 130W...WITH 
SPOTTIER WINDS OF UP TO 20 KT E OF THERE TO NEAR BAJA 
CALIFORNIA. AT THE SAME TIME...LONG PERIOD NW TO N SWELL 
PROPAGATING OUT OF THE CENTRAL AND NE PACIFIC CONTINUES TO 
ARRIVE OVER THE NW HALF OF THE FORECAST AREA...WITH WAVE HEIGHTS 
RANGING FROM 9 TO 12 FT OVER THE IMMEDIATELY NW OF A LINE 
RUNNING FROM 24N111W TO 12N127W TO 9N140W TO 14 TO 18 FT OVER 
THE FAR NW AND N PART OF THE AREA. OVER THE NEXT FEW DAYS...THE 
SURFACE RIDGE WILL GRADUALLY WEAKEN AND SHIFT E...RESULTING IN A 
GRADUALLY WEAKENING TRADES. MEANWHILE...THE HEART OF THE LONG 
PERIOD NW TO N SWELL ONLY SLOWLY SUBSIDE WHILE CONTINUING ON A 
PATH WELL TO THE S...WITH THE SWELL EVEN MAKING IT INTO THE 
SOUTHERN HEMISPHERE W OF 110W. 

FINALLY...STRONG HIGH PRES EXTENDING FROM THE WESTERN ATLANTIC 
INTO THE CARIBBEAN IS RESULTING IN STRONG TRADES BLOWING INTO 
CENTRAL AMERICA. THIS HAS...IN TURN...LED TO A GAP WIND EVENT 
NEAR AND DOWNWIND OF THE GULF OF PAPAGAYO. NE TO E WINDS OF 20 
TO 25 KT ARE EXPECTED TO CONTINUE OVER A NARROW AREA WITHIN A 
FEW HUNDRED MILES OF THE COAST...WITH SEAS BUILDING UP TO 9 FT. 
WHILE THE EVENT BEGINS TO SHOW SIGNS OF WINDING DOWN LATER THIS 
WEEKEND...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. 

$$
KIMBERLAIN