000
AXPZ20 KNHC 290924
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON DEC 29 2008

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 05N77W TO 08N85W TO 06N9100W TO 
06N110W TO 10N128W TO 10N140W. ISOLATED MODERATE CONVECTION 
WITHIN 60 NM S OF AXIS BETWEEN 78W AND 79W. SCATTERED MODERATE 
CONVECTION WITHIN 90 NM S OF AXIS BETWEEN 122W AND 125W. 
ISOLATED MODERATE CONVECTION WITHIN 90 NM N OF AXIS BETWEEN 138W 
AND 140W.

...DISCUSSION...
A WEAKENING MID- TO UPPER-LEVEL TROUGH EXTENDING FROM THE 
CENTRAL MISSISSIPPI VALLEY THROUGH NORTHERN MEXICO SHOULD 
CONTINUE LIFTING NORTHEAST TODAY...REPLACED BY STRONG 
SUBTROPICAL RIDGING BUBBLING WESTWARD FROM THE GULF OF MEXICO. 
AS A RESULT...A COLD FRONT WHICH HAS BEEN PUSHING SOUTHWARD 
THROUGH NORTHERN MEXICO DURING THE LAST 24 TO 48 HOURS SHOULD 
COME TO A HALT TO THE LEE OF THE SIERRA MADRE ORIENTAL OVER THE 
ISTHMUS OF TEHUANTEPEC. HIGH PRESSURE BUILDING BEHIND THE FRONT 
SHOULD SET THE STAGE FOR A GAP WIND EVENT NEAR AND DOWNWIND OF 
THE GULF OF TEHUANTEPEC...WITH WINDS LIKELY INCREASING TO GALE 
FORCE WITHIN ABOUT 12 HOURS.  SINCE THE SHORTWAVE DEPOSITING THE 
COLD FRONT WILL BE RATHER PROGRESSIVE...THE GALE EVENT SHOULD BE 
RATHER SHORT-LIVED AND NOT LAST MUCH LONGER THAN 24 HOURS. 
EXPECT SEAS TO BUILD UP TO 10 FT DOWNWIND OF THE GULF OF 
TEHUANTEPEC PRIMARILY IN NE WIND WAVES BUT ALSO IN LONG PERIOD 
NW SWELL.

THE SAME SURFACE RIDGING BUILDING BEHIND THE COLD FRONT OVER 
NORTHERN MEXICO WILL BRIDGE SOUTHEASTWARD INTO CENTRAL AMERICA 
OVER THE NEXT DAY OR SO AND LED TO A REVIVAL OF GAP WINDS NEAR 
AND DOWNSTREAM OF THE GULF OF PAPAGAYO. A 0300 UTC ASCAT PASS 
SUGGESTED THAT NE TO E WINDS OF 20 TO 25 KT CONTINUE WITHIN 
ABOUT 180 NM DOWNWIND OF THE GULF OF PAPAGAYO AND NOAA WAVEWATCH 
GUIDANCE TAKEN IN COMBINATION WITH A SIMPLE WAVE NOMOGRAM 
CALCULATION YIELDS WAVE HEIGHTS OF AT LEAST SPOTTY 9 FT SEAS 
OVER THIS AREA.  AFTER BRIEFLY INCREASING AND EXPANDING OVER THE 
NEXT 24 HOURS...GAP WINDS NEAR THE GULF OF PAPAGAYO WILL BEGIN 
TO DIMINISH...BUT THE NE TO E SWELL GENERATED SHOULD PROPAGATE 
AS FAR W AS 105W OVER A NARROW REGION BETWEEN 8N AND 12N OVER 
THE NEXT DAY OR TWO.

FARTHER NORTHWEST...NW WINDS BLOWING THROUGH THE GULF OF 
CALIFORNIA AND ADJACENT WATERS SEEM TO HAVE PEAKED BUT ARE ONLY 
GRADUALLY DECREASING. AN EARLIER QUIKSCAT PASS STILL REVEALED 20 
TO 25 KT WINDS N OF 23N IN THE GULF OF CALIFORNIA...WITH AN AREA 
OF 20 KT WINDS NEAR THE SW TIP OF MEXICO NEAR PUERTO VALLARTA 
AND MANZANILLO. ALTHOUGH THERE ARE NO OBSERVATIONS...IT IS 
ASSUMED THAT SEAS OF UP TO 8 FT ARE OCCURRING OVER THE SOUTHERN 
PART OF THE GULF OF CALIFORNIA AS A RESULT OF THE ENHANCED WINDS 
BLOWING FOR THE LAST 36 TO 48 HOURS. MODEL GUIDANCE SUGGESTS 
THAT WINDS AND SEAS SHOULD DIMINISH AND SUBSIDE FAIRLY QUICKLY 
DURING THE NEXT 24 HOURS.

ELSEWHERE...ENHANCED LOW-LEVEL RIDGING OVER THE NORTHEAST 
PACIFIC LED TO MODERATE TO OCCASIONALLY STRONG TRADES OVER A 
LARGE EXPANSE OF THE TROPICAL AND SUBTROPICAL EAST PACIFIC 
ROUGHLY FROM 11N TO 26N W OF 115W.  SINCE YESTERDAY...THE AREAL 
COVERAGE OF STRONG WINDS HAS BEEN SHRINKING BUT SEAS OF 10 TO 14 
FT STILL EXIST OVER MOST OF THIS AREA IN A MIXTURE OF NE WIND 
WAVES AND LONG PERIOD NW TO N SWELL. OVER THE NEXT FEW DAYS 
...ENHANCED TRADES SHOULD CONTINUE TO VERY GRADUALLY DIMINISH 
AND SHIFT WESTWARD WHILE A NEW BATCH OF LONG PERIOD NW SWELL 
COMES OUT OF THE FAR NE PACIFIC AND ENTERS THE NW HALF OF THE 
AREA. AS A RESULT...WAVE HEIGHTS OF 8 TO 11 FT WILL STILL BE 
COMMON GENERALLY W OF 115W.


$$
KIMBERLAIN