000
AXPZ20 KNHC 112155
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI DEC 11 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...08N82W TO 
07N102W TO 08N120W TO 07N140W. SCATTERED MODERATE CONVECTION IS 
WITHIN 100 NM S OF AXIS W OF 130W. 

...DISCUSSION... 

BROAD UPPER-LEVEL TROUGH WITH AXIS FROM SOUTHERN CALIFORNIA/ 
NORTHERN BAJA CALIFORNIA SOUTHWEST TO NEAR 20N122W DOMINATES THE 
NORTH WATERS WITH A NEARLY ZONAL FLOW COVERING THE AREA N OF 
20N.  

OTHERWISE A BROAD RIDGE IS OVER THE REGION IN THE MIDDLE AND 
UPPER LEVELS PRODUCING MODERATE TO STRONG SUBSIDENCE MAINLY E OF 
110W. THE EXCEPTION IS SOME LOCAL CONVECTION FROM 100W TO 102W 
ASSOCIATED WITH A WEAK SURFACE TROUGH EMBEDDED WITHIN THE ITCZ 
THAT EXTENDS ALONG 102 FROM 05N TO 11N. AN EARLIER ASCAT PASS 
SHOWED SOME WIND SHIFT ASSOCIATED WITH THIS TROUGH. 

AT THE SURFACE A WEAK RIDGE IS NORTH OF 15N WEST OF 112W WITH A 
1021 MB HIGH LOCATED NEAR 25N120W. ELSEWHERE A BROAD TROUGH 
CENTERED ALONG THE ITCZ IS ANALYZED AT THE SURFACE...AND RUNS 
FROM 20N124W TO 07N132W. W OF TROUGH...NE WINDS OF 20 TO 25 KT 
ARE OBSERVED. THE TROUGH IS FORECAST TO BECOME DIFFUSE IN ABOUT 
24 HOURS AND A BELT OF ELY TRADE WINDS WILL PERSIST PARTICULARLY 
FROM 07N TO 20N W OF 112W. 

MARINE CONDITIONS W OF 110W ARE BEING DOMINATED BY LARGE AND 
LONG PERIOD NW SWELL...WITH WAVE PERIODS OF 12 TO 18 SECONDS AND 
SIGNIFICANT WAVE HEIGHTS AS HIGH AS 15 FT. THIS SWELL EVENT WILL 
CONTINUE TO PROPAGATE SE BEYOND THE EQUATOR OVER THE NEXT TWO 
DAYS. THESE SEA HEIGHTS ARE EXPECTED TO GRADUALLY SUBSIDE.

A COLD FRONT IS CURRENTLY REACHING THE FAR NW PORTION OF THE 
FORECAST REGION WITH SW WINDS OF 20 TO 25 KT IN A SMALL AREA 
AHEAD OF THE FRONT. NLY WINDS LESS THAN 20 KT AND SEAS OF UP TO 
9 FT ARE EXPECTED IN THE WAKE OF THE FRONT. 

GAP WINDS...
WINDS HAVE INCREASED TO 20 KT ACROSS THE GULF OF PAPAGAYO AS  
THE PRES GRADIENT BUILDS ACROSS THE WESTERN CARIBBEAN...ALLOWING 
EASTERLY TRADE WINDS TO FUNNEL ACROSS COSTA RICA AND NICARAGUA 
INTO THE EPAC.

A WINDSAT PASS ALSO SHOWS NLY WINDS 20 TO 25 KT ACROSS THE GULF 
OF TEHUANTEPEC. THE NAM REGIONAL MODEL SUGGESTS THAT THIS WIND 
PATTERN WILL PERSIST ACROSS THIS AREA OVER THE NEXT COUPLE OF 
DAYS. 
  
$$
GR