000
AXPZ20 KNHC 280916
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN DEC 28 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 
0900 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ALONG A LINE FROM 
06N77W TO 08N84W TO 05N97W TO 09112W TO 08N130W TO 09N140W. 
SCATTERED MODERATE CONVECTION BETWEEN 180 AND 300 NM N OF AXIS 
BETWEEN 124W AND 128W.

...DISCUSSION...
THE TAIL OF A PROGRESSIVE SHORTWAVE TROUGH OVER THE MIDWEST 
EXTENDS WELL SOUTHWEST THROUGH NORTH CENTRAL MEXICO TO AROUND 
18N129W. AS THE SHORTWAVE COMES UP AGAINST A LARGE AND DOMINANT 
RIDGE OF HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC AND 
SOUTHEASTERN GULF OF MEXICO...LITTLE ADDITIONAL SOUTHEAST 
PROGRESS IS ANTICIPATED AND THE SHORTWAVE SHOULD BEGIN TO LIFT 
OUT.  A COLD FRONT ASSOCIATED WITH THE SHORTWAVE HAS PUSHED INTO 
THE NORTHERN HALF OF MEXICO AND HAS PASSED THROUGH THE BAJA 
CALIFORNIA PENINSULA AND SHOULD SAG SOUTHWARD ALONG THE FRONT 
RANGE OF THE SIERRA MADRE ORIENTAL SUN AND MON...BARELY PUSHING 
THROUGH THE ISTHMUS OF TEHUANTEPEC.  BRISK NW TO N WINDS OF 20 
TO 25 KT BEHIND THE FRONT ARE STILL BEING REPORTED THROUGHOUT 
MUCH OF THE GULF OF CALIFORNIA...WITH SEAS POSSIBLY UP TO 8 FT 
OVER THE SOUTHERN HALF OF THE AREA. AS WINDS BEGIN TO DIMINISH 
LATER SUN AND MON IN THE GULF OF CALIFORNIA...A FRESH SURGE OF 
HIGH PRESSURE BEHIND THE FRONT SHOULD CAUSE WINDS TO RAPIDLY 
INCREASE NEAR AND DOWNWIND OF THE GULF OF TEHUANTEPEC BY MON 
NIGHT. MODELS SUGGEST A BRIEF GALE EVENT AROUND THAT TIME INTO 
TUE...BUT A CHANGEABLE WEATHER PATTERN TO THE NORTH LATER TUE 
SHOULD SPELL A QUICK DEMISE TO THE EVENT.  STILL THOUGH...SEAS 
COULD BRIEFLY BUILD UP TO 9 OR 10 FT DOWNWIND OF THE GULF OF 
TEHUANTEPEC TUE BEFORE SUBSIDING WED.

WELL BEHIND THE COLD FRONT...THE SHORTWAVE HAS DEPOSITED A 1031 
MB SURFACE RIDGE NEAR 32N129W WHICH HAS BEEN SLIDING SLOWLY EAST 
OVER THE LAST 24 HOURS.  A STRONG PRESSURE GRADIENT SOUTH OF THE 
RIDGE OF THE TROPICAL EAST PACIFIC WATERS HAS LED TO MODERATE TO 
STRONG TRADES OVER A LARGE EXPANSE FROM 11N TO 26N W OF 115W. 
LONG PERIOD NW TO N SWELL PROPAGATING STRAIGHT OUT OF THE NORTH 
CENTRAL AND NE PACIFIC HAS BEEN FLOODING THE NW HALF OF THE 
FORECAST AREA AND HAS NOW COMBINED WITH NE WIND WAVES AND/OR 
SWELL AS A RESULT OF THE PERSISTENT...ENHANCED TRADES. THE 
COMBINED WAVE COMPONENTS HAVE RESULTED IN 10 TO 15 FT SEAS OVER 
THE ABOVE MENTIONED AREA...AND THE LEADING EDGE OF THE NORTHERLY 
WAVETRAIN MARCHING SOUTHWARD SHOULD PUSH INTO THE SOUTHERN 
HEMISPHERE TODAY. OVER THE NEXT FEW DAYS...THE NW TO N SWELL 
SHOULD RATHER QUICKLY SUBSIDE WHILE THE AREA OF ENHANCED TRADES 
GREATLY DIMINISHES.

FINALLY...AN ENHANCED LOW-LEVEL RIDGE OVER THE WESTERN ATLANTIC 
AND CARIBBEAN SEA HAS BEEN POWERING MODERATE TO OCCASIONALLY 
STRONG TRADES INTO CENTRAL AMERICA THE LAST FEW DAYS.  
CONSEQUENTLY...DOWNWIND OF THE GULF OF PAPAGAYO...NE TO E WINDS 
OF 20 TO 25 KT HAVE BEEN PREVAILING. AN EARLIER QUIKSCAT PASS 
SUGGESTED THAT THE AREAL COVERAGE OF STRONG WINDS HAS BEEN 
DECREASING...BUT LITTLE ADDITIONAL CHANGE IS EXPECTED DURING THE 
NEXT 24 TO 36 HOURS. THEREAFTER...AS SURFACE RIDGING EXPANDS 
SOUTHWARD BEHIND THE FRONT OVER MEXICO...A RESURGENCE OF GAP 
WIND CONDITIONS DOWNWIND OF THE GULF OF PAPAGAYO IS LIKELY.

$$
KIMBERLAIN