000
AXPZ20 KNHC 230952
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE DEC 23 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...
ITCZ IS CENTERED ALONG 07N77W TO 07N90W TO 06N98W TO 08N110W TO 
07N114W TO 10N135W TO 07N140W. SCATTERED MODERATE AND ISOLATED 
STRONG CONVECTION IS EXPECTED TO CONTINUE NEXT 12 HOURS WITHIN 
150 NM N OF AXIS FROM 108W TO 138W. THIS CONVECTION WILL BE 
CONCENTRATED NEAR 3 PERTURBATIONS...OR EASTERLY WAVES...MOVING W 
ALONG THE ITCZ AND S OF 18N...LOCATED AT 0900 UTC ALONG 109W... 
128W...AND 134W.

...DISCUSSION...
A BLOCKING LOW LATITUDE UPPER PATTERN ACROSS THE DISCUSSION AREA 
FOR THE PAST FEW DAYS IS FORECAST BY GLOBAL MODELS TO BEGIN TO 
BREAK DOWN OVER THE NEXT 3 TO 4 DAYS. CURRENTLY A LARGE HIGH 
AMPLITUDE UPPER RIDGE CAN BE FOUND ACROSS AND THE NORTH OF THE 
HAWAIIAN ISLANDS...WITH A DEEP LAYERED CUT OFF LOW CENTERED NEAR 
20N142W...CONTINUING TO RETROGRADE W. THE DOWNSTREAM ASSOCIATED 
RIDGE COVERING THE EXTREME EASTERN PACIFIC THE PAST FEW DAYS HAS 
BROADENED AND BECOME FLAT...WITH ZONAL FLOW ALOFT ACROSS BAJA 
CALIFORNIA...MEXICO AND THE NORTHERN GULF OF MEXICO. AN UPPER 
TROUGH MOVING E ACROSS THE WESTERN U.S. WILL EXIT THE REGION TO 
THE EAST DURING THE NEXT 48 HOURS...WHILE ANOTHER SHORT WAVE 
CURRENTLY MOVING OVER THE HAWAIIAN UPPER RIDGE DROPS INTO THE 
BACKSIDE OF W COAST TROUGHING...AND WILL RE-ESTABLISH A MEAN 
UPPER TROUGH ALONG THE W COAST OF N AMERICA AFTER 48 HOURS. 

AT LOWER LEVELS...THE DEEP LAYERED CUT OFF LOW HAS A REFLECTION 
TO THE SURFACE ALONG ABOUT 142W...WHILE MID TO UPPER LEVEL 
ANTICYCLONIC SHEAR TO THE E AND SE OF THIS DEEP LOW CONTINUE TO 
INTERACT FAVORABLY WITH ABUNDANT MOISTURE TRAPPED ACROSS THE E 
CENTRAL PACIFIC BETWEEN 135W AND 120W...TO PRODUCE LARGE 
CLUSTERS OF SCATTERED MODERATE CONVECTION WITH ISOLATED STRONG 
CLUSTERS. THIS ZONE IS EXPECTED TO REMAIN ACTIVE CONVECTIVELY 
FOR THE NEXT 24 HOURS AS THE UPPER LOW CONTINUES TO SHIFT 
GRADUALLY W AND FILL...WHILE MAINTAINING DIFFLUENCE ALOFT. 

THE UPPER LEVEL TROUGH OVER N PORTIONS OF THE DISCUSSION AREA 
AND CURRENTLY ALONG THE W COAST IS SUPPORTING ANOTHER COLD FRONT 
THAN WILL ENTER N AND NE PORTIONS OF THE AREA DURING THE NEXT 24 
HOURS. A LARGE NW FETCH OCCURRING BEHIND THIS FRONTAL ZONE IS 
GENERATING HIGH SEAS OFF OF THE W COAST OF THE U.S. THAT WILL 
PROPAGATE INTO THE EASTERN PACIFIC WATERS DURING THE NEXT 24 TO 
48 HOURS...WITH MINIMAL GALE FORCE WINDS AND SEAS IN EXCESS OF 
12 FEET IN NW SWELL EXPECTED N OF 30N. 

HIGH PRES BUILDING N OF A FRONT IN THE GULF OF MEXICO HAS 
TIGHTENED THE GRADIENT OVER SOUTHERN MEXICO...WITH TWO 
CONSECUTIVE QUIKSCAT PASSES REVEALING GALE FORCE WINDS BLOWING 
THROUGH THE GULF OF TEHUANTEPEC. THESE GAP WINDS ARE EXPECTED TO 
DECREASE BELOW GALE FORCE LATER THIS MORNING...BUT REMAIN AT 20 
TO 25 KT FOR THE NEXT 24 HOURS.

THE PRESSURE GRADIENT ACROSS THE WEST AND SOUTHWEST CARIBBEAN IS 
ALSO SUPPORTING 20 TO 25 KT WINDS ACROSS CENTRAL AMERICA AND 
THROUGH THE GULFS OF PAPAGAYO AND PANAMA. SEAS DOWNWIND OF 
PAPAGAYO WILL REMAIN AT OR JUST BELOW 8 FEET FOR THE NEXT 24 
HOURS AS WIND CONDITIONS CHANGE LITTLE. 

AS THE NEXT COLD FRONT MOVES INTO SOUTHERN CALIFORNIA AND THE 
BAJA DURING THE NEXT 24 TO 48 HOURS...S TO SW WINDS 20 TO 25 
KNOTS AHEAD OF THE FRONT WILL AFFECT THE N HALF OF THE GULF OF 
CALIFORNIA...STIRRING SEAS TO NEAR 6 FEET BY 48 HOURS.

$$
STRIPLING