000
AXPZ20 KNHC 092156
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED DEC 09 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 ITCZ AXIS IS ANALYZED ALONG 07N77W TO 08N95W TO 09N120W TO 
08N130W TO 06N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION IS FROM 05N TO 08N W OF 128W. 

...DISCUSSION...
LONG PERIOD NW SWELL (WAVE PERIODS UP TO 20 SECONDS) WITH 
SIGNIFICANT WAVE HEIGHTS AS HIGH AS 20 FEET HAVE MOVED INTO THE 
NW WATERS. THIS SWELL IS MOVING OUT AHEAD OF A COLD FRONT 
EXTENDING FROM 30N132W TO 23N140W. THIS FRONT IS ASSOCIATED WITH 
AN UPPER LEVEL TROUGH WITH AXIS ALONG 132W N OF 16N. S TO SW 
WINDS OF 20 TO 25 KT ARE NOTED N OF 28N WITHIN 120 NM AHEAD OF 
THE FRONT PER AN ASCAT PASS FROM AROUND 1800 UTC. THE SWELL IS 
REACHING THE WEST COAST OF BAJA CALIFORNIA PENINSULA RAISING 
SEAS TO 10 FT. THIS NEW BATCH OF NW SWELL WILL CONTINUE TO 
PROPAGATE TO THE SE ACROSS THE DISCUSSION AREA REACHING TO THE 
EQUATOR AND BEYOND WITHIN THE NEXT 24 TO 48 HOURS. E 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 20N AND E OF 112W... 
INCLUDING SE MEXICO AND MOST OF CENTRAL AMERICA. SLY WINDS 
BETWEEN THESE TWO UPPER-LEVEL FEATURES ARE ADVECTING ABUNDANT 
MID TO UPPER LEVEL MOISTURE FROM THE ITCZ TO THE N AND NE INTO 
NORTHERN MEXICO AROUND THE NW PORTION OF THE ANTICYCLONE. AT THE 
SAME TIME...THE RIDGE IS ENHANCING CONVECTION ALONG A SURFACE 
TROUGH THAT EXTENDS FROM 18N118W TO 14N120W TO 09N122W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN 60 NM 
EITHER SIDE OF TROUGH FROM 11N TO 17N. 

ELSEWHERE...A 1012 MB LOW PRESSURE SYSTEM IS EMBEDDED WITHIN THE 
ITCZ...POSITIONED NEAR 09N122W...ALONG THE AFOREMENTIONED 
SURFACE TROUGH. THE LOW AND TROUGH WILL CONTINUE TO MOVE TO THE 
W AROUND 10 KT TONIGHT...BUT WILL DISSIPATE WITHIN THE NEXT 48 
HOURS AS THESE FEATURES ENCOUNTER INCREASING SW SHEAR ALOFT. NE 
WINDS OF 20 TO 25 KT ARE OBSERVED WITHIN 150 NM W OF TROUGH FROM 
14N TO 19N. AN ASCAT PASS FROM AROUND 1800 UTC CONFIRMED THESE 
WIND SPEEDS.

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/JL