000
AXPZ20 KNHC 100330
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU DEC 10 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 07N78W TO 08N105W TO 11N121W 
THEN RESUMES FROM 09N126W TO 07N140W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION IS FROM 06N TO 08N W OF 130W.  

...DISCUSSION...
REGIONAL SEAS ARE BEING DOMINATED BY LARGE AND LONG PERIOD NW 
SWELL (WAVE PERIODS OF UP TO 20 SECONDS) WITH SIGNIFICANT WAVE 
HEIGHTS AS HIGH AS 20 FEET. THIS SWELL EVENT WILL CONTINUE TO 
PROPAGATE SE ACROSS MUCH OF THE FORECAST AREA AND IS ALREADY 
REACHING THE EQUATOR W OF 130W. THIS SWELL IS MOVING OUT AHEAD 
OF A COLD FRONT EXTENDING FROM 30N131W TO 23N138W. THE FRONT IS 
ASSOCIATED WITH AN UPPER LEVEL TROUGH WITH AXIS ALONG 130W N OF 
16N. S TO SW WINDS OF 20 KT ARE BLOWING N OF 29N E OF FRONT TO 
126W. THE LEADING EDGE OF THE LARGE SWELL IS ALSO REACHING THE 
WEST COAST OF BAJA CALIFORNIA PENINSULA RAISING SEAS TO 9 FT. 

EAST OF THE ABOVE MENTIONED TROUGH...THERE IS A BROAD UPPER- 
LEVEL RIDGE ANCHORED ON A HIGH LOCATED JUST W OF THE GULF OF 
TEHUANTEPEC. STRONG UPPER-LEVEL SUBSIDENCE AND IMPLIED DRY AIR 
MASS IS SEEN WITHIN THE RIDGE AXIS PARTICULARLY S OF 22N AND E 
OF 110W...INCLUDING SE MEXICO AND MOST OF CENTRAL AMERICA. SLY 
WINDS BETWEEN THE RIDGE AND THE 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. 

ELSEWHERE...A 1011 MB LOW PRESSURE SYSTEM REMAINS EMBEDDED 
WITHIN THE ITCZ...LOCATED NEAR 08N123W...ALONG A SURFACE TROUGH 
THAT EXTENDS FROM 17N120W TO 13N121W TO THE LOW CENTER. 
CONVECTION HAS DIMINISHED EITHER SIDE OF THE TROUGH AXIS SINCE 
EARLY THIS EVENING AND NOW IS CONCENTRATED NEAR THE LOW 
CENTER...MAINLY TO THE NE QUADRANT. THE LOW AND TROUGH WILL 
CONTINUE TO MOVE TO THE W AROUND 10 KT TONIGHT...BUT WILL 
DISSIPATE WITHIN THE NEXT 24 TO 48 HOURS. PRES GRADIENT BETWEEN 
THE TROUGH AND A 1019 MB SFC HIGH LOCATED NEAR 29N121W...IS 
PRODUCING AN AREA OF NE WINDS 20 TO 25 KT FROM 15N TO 19N 
BETWEEN 117W AND 122W PER AN EARLIER ASCAT PASS.  

THE NEXT COLD FRONT IS EXPECTED TO ENTER THE FAR NW PORTION OF 
THE FORECAST REGION IN ABOUT 42 HOURS...FRI AFTERNOON...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 OR GREATER ONCE AGAIN BY 
LATE THU NIGHT ACROSS THE GULF OF PAPAGAYO...AS THE PRES 
GRADIENT BUILDS IN ACROSS THE WESTERN CARIBBEAN AND AS THE 
DRAINAGE FLOW OFF THE CENTRAL AMERICA LANDMASS ALSO INCREASES. 

$$
GR