000
AXPZ20 KNHC 212122
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON DEC 21 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...08N78W TO 
03.5N102W TO 06N116W TO 08N140W. SCATTERED MODERATE ISOLATED 
STRONG WITHIN 150 NM N AND 220 NM S OF AXIS E OF 88W. SCATTERED 
MODERATE WITHIN 100 NM N OF AXIS AND 90 NM S OF AXIS FROM 130W 
TO 134W. 

...DISCUSSION...
HIGH AMPLITUDE UPPER LEVEL TROUGH WITH AXIS W OF THE FORECAST 
AREA FROM 28N143W TO 05N156W. SW FLOW E OF THE TROUGH AXIS IS 
ADVECTING MID AND UPPER LEVEL MOISTURE ACROSS THE FORECAST AREA 
FROM 08N140W TO THE NORTHERN BAJA PENINSULA. A SHORT WAVE TROUGH 
LIES N OF THE AREA. A RIDGE EXTENDS FROM 06N120W TO THE GREAT 
BASIN REGION. THIS RIDGE IS FORCING THE SHORTWAVE TROUGH TO 
SLOWLY LIFT OUT. AS A RESULT...THE SURFACE COLD FRONT THAT 
ENTERED THE FORECAST AREA LOST ITS MOMENTUM SOURCE...STALLED AND 
HAS DISSIPATED. AN UPPER LEVEL TROUGH IS ACROSS THE E PORTION OF 
THE FORECAST AREA. WITH ONLY LIMITED ITCZ CONVECTION W OF 
90W...THE UPPER RIDGE WILL WEAKEN AND ALLOW THE TROUGH W OF THE 
AREA TO DRIFT EAST OVER THE NEXT COUPLE OF DAYS.

WEAK SURFACE HIGH PRESSURE 1021 MB IS CENTERED NEAR 25N120W. 
WITH ONLY A WEAK RIDGE ACROSS THE AREA...FRESH TO STRONG TRADES 
ARE CONFINED FROM 10N TO 15N W OF 130W. THE UPPER SHORT WAVE 
TROUGH MENTIONED IN THE PREVIOUS PARAGRAPH WILL SHIFT INTO THE W 
US TONIGHT...AND STRONG SURFACE HIGH PRESSURE WILL BUILD N OF 
THE AREA TUESDAY. THIS WILL BRING AN INCREASE IN WINDS N OF 27N 
FROM 118W TO 130W. WITH LOW PRESSURE OVER THE GREAT BASIN 
REGION...A TIGHT PRESSURE GRADIENT WILL RESULT...AND WINDS WILL 
INCREASE TO 20 KT IN THE GULF OF CALIFORNIA N OF 29N BY TUESDAY 
NIGHT. WITH HIGH PRESSURE N OF THE FORECAST AREA...TRADES WILL 
ALSO INCREASE BY WED. NW SWELL GENERATED BEHIND THE COLD FRONT 
PREVIOUSLY MENTIONED CONTINUE TO AFFECT MUCH OF THE FORECAST 
AREA N OF 08N W OF 118W.   

GAP N TO NE WINDS OF 20 TO 30 KT ARE OCCURRING THROUGH THE GULF 
OF TEHUANTEPEC ARE EXPECTED TO DIMINISH TUESDAY.

GAP NE TO E WINDS OF 20 KT ARE OCCURRING IN THE GULF OF PAPAGAYO 
REGION AND ARE FORECAST TO DIMINISH TUESDAY.

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