000
AXPZ20 KNHC 102124
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU DEC 10 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...06N77W TO 
07N110W TO 09N124W TO 07N140W. SCATTERED MODERATE CONVECTION IS 
NEAR 06N98W...AND NEAR 08N114W.

...DISCUSSION... 

SEAS W OF 110W ARE BEING DOMINATED BY LARGE AND LONG PERIOD NW 
SWELL...WITH WAVE PERIODS OF UP TO 20 SECONDS AND SIGNIFICANT 
WAVE HEIGHTS AS HIGH AS 18 FEET. THIS SWELL EVENT WILL CONTINUE 
TO PROPAGATE SE OVER THE NEXT TWO DAYS. A WEAKENING COLD FRONT 
EXTENDS FROM 30N126W TO 25N135W. THE FRONT IS ASSOCIATED WITH A 
BROAD UPPER TROUGH OVER THE EASTERN PACIFIC CENTERED OVER 
FORECAST WATERS ALONG 125W N OF 12N. THE FRONT WILL CONTINUE TO 
DISSIPATE TONIGHT. 

AN UPPER-LEVEL ANTICYCLONE...CURRENTLY CENTERED OVER THE NW 
CARIBBEAN...EXTENDS A RIDGE OVER SE MEXICO AND NORTHERN CENTRAL 
AMERICA INTO THE EPAC E OF 110W. STRONG UPPER LEVEL SUBSIDENCE 
AND IMPLIED DRY AIR MASS IS SEEN UNDER THE INFLUENCE OF THE 
RIDGE. SLY WINDS BETWEEN THIS RIDGE AND THE AFOREMENTIONED BROAD 
UPPER-LEVEL TROUGH ARE TRANSPORTING ABUNDANT MID TO UPPER LEVEL 
MOISTURE FROM THE ITCZ TO THE N AND NE INTO NORTHERN MEXICO 
AROUND THE NW PORTION OF THE ANTICYCLONE. 

CONVECTION ALONG THE ITCZ HAS DIMINISHED SINCE YESTERDAY AS WELL 
AS ALONG THE SURFACE TROUGH EXTENDING FROM FROM 20N120W TO 
08N126W. THE LOW THAT WAS EMBEDDED ALONG THIS TROUGH HAS 
DISSIPATED. W OF THE SFC TROUGH...AN AREA OF ELY TRADE WINDS OF 
20 KT IS NOTED. THE TRADES ARE EXPECTED TO INCREASE TO 20-25 KT
IN ABOUT 48 HOURS AS THE AFOREMENTIONED SFC TROUGH BECOMES 
DIFFUSE.  

THE NEXT COLD FRONT WILL ENTER THE FAR NW PORTION OF THE 
FORECAST REGION FRI...WITH SW WINDS OF 20 TO 25 KT AHEAD OF THE 
FRONT. NW WINDS OF 20 KT AND SEAS OF UP TO 11 FT ARE EXPECTED IN 
THE WAKE OF THE FRONT. 

GAP WINDS...
WINDS ARE EXPECTED TO INCREASE TO 20 KT ONCE AGAIN BY EARLY FRI 
MORNING ACROSS THE GULF OF PAPAGAYO AS THE DRAINAGE FLOW OFF THE 
CENTRAL AMERICA LANDMASS INCREASES AND THE PRES GRADIENT BUILDS 
ACROSS THE WESTERN CARIBBEAN...ALLOWING EASTERLY TRADE WINDS 
TO BLEED ACROSS COSTA RICA AND NICARAGUA INTO THE PACIFIC. 

$$
GR/LL