000
AXPZ20 KNHC 291532
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE DEC 29 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...05N77W TO 
06N85W TO 02.5N95W TO 05N105W TO 07N140W. SCATTERED MODERATE 
WITHIN 90 NM N OF AXIS AND 40 NM S OF AXIS E OF 81W. SCATTERED 
MODERATE ISOLATED STRONG WITHIN 75 NM EITHER SIDE OF AXIS W OF 
133W.
 
...DISCUSSION...

THE UPPER LEVEL SHORTWAVE TROUGH THAT MOVED ACROSS THE N PORTION 
OF THE FORECAST AREA THE PAST COUPLE OF DAYS HAS SHIFTED E OF 
THE AREA...WITH TROUGH AXIS NOW OVER MAINLAND MEXICO. WITH THE 
SHORTWAVE TROUGH EAST OF THE AREA...ZONAL FLOW PREVAILS N OF 
15N. UPPER LEVEL RIDGING PREVAILS S OF 15N W OF 109W DUE TO 
ACTIVE CONVECTION IN THE ITCZ. MID AND UPPER LEVEL MOISTURE FROM 
THIS CONVECTION IS BEING ADVECTED NE ACROSS SOUTHERN MEXICO INTO 
TEXAS. TROUGHING PREVAILS BETWEEN 87W AND 109W. AN UPPER 
ANTICYCLONE CENTERED OVER THE CENTRAL CARIBBEAN SEA EXTENDS A 
RIDGE ACROSS CENTRAL AMERICA INTO THE EPAC MAINLY E OF 87W. 

AT THE SURFACE...HIGH PRESSURE 1024 MB IS CENTERED NEAR 29N133W. 
RELATIVELY LOWER PRESSURES IN THE ITCZ DUE TO CONVECTION AND 
ASSOCIATED LATENT HEATING AND DIFFLUENCE ALOFT. THE PRESSURE 
GRADIENT BETWEEN THE LOWER PRESSURES IN THE ITCZ AND THE HIGH 
PRESSURE CENTERED IN THE N PORTION OF THE AREA IS RESULTING IN A 
LARGE SWATH OF FRESH TO STRONG TRADEWIND FLOW N OF THE ITCZ TO 
20N AND W OF 123W. WITH HIGH PRESSURE EXPECTED TO REMAIN 
CENTERED ACROSS THE N PORTION OF THE AREA THROUGH THU...THE 
FRESH TO STRONG TRADES WILL PREVAIL ACROSS MUCH OF THE AREA S OF 
22N AND W OF 115W.

GAP WINDS...
GULF OF TEHUANTEPEC...GALE FORCE WINDS ARE FORECAST TO DIMINISH 
TO 20 TO 30 KT THIS AFTERNOON...AND DIMINISH FURTHER TO 20 KT 
WEDNESDAY.

GULF OF PAPAGAYO...E WINDS OF 20 TO 25 KT AND OCCASIONALLY TO 30 
KT ARE EXPECTED TO CONTINUE THROUGH THURSDAY MORNING.

SEA CONDITIONS ARE DOMINATED BY LONG PERIOD NW SWELL (WAVE 
PERIODS OF UP TO 17 SECONDS) WITH SIGNIFICANT WAVE HEIGHTS AS 
HIGH AS 13 FT. THIS SWELL EVENT WILL CONTINUE TO SPREAD SE 
REACHING NEAR 90W IN ABOUT 48 HOURS.

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE
  
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AL