000
AXPZ20 KNHC 310930
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED DEC 31 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 ALONG 06N77W TO 05N82W TO 09N107W TO 06N119W TO 
09N130W TO 09N140W. NUMEROUS MODERATE ISOLATED STRONG CONVECTION 
WITHIN 150 NM S OF AXIS BETWEEN 109W AND 113W. SCATTERED 
MODERATE WITHIN 120 NM N OF AXIS BETWEEN 127W AND 130W. 
SCATTERED MODERATE CONVECTION BETWEEN 90 AND 120 NM N OF AXIS 
BETWEEN 134W AND 140W.

...DISCUSSION...
WEAK HIGH PRESSURE OVER CENTRAL AND NORTHERN MEXICO...THE LAST 
VESTIGE OF A COOL AIR MASS WHICH ENTERED THE REGION DURING THE 
LAST DAY OR TWO...EXTENDS INTO THE ISTHMUS OF TEHUANTEPEC EARLY 
THIS MORNING.  THE CONFIGURATION OF MODEST HIGH PRESSURE TO THE 
NORTH AND RELATIVE LOW PRESSURE TO THE SOUTH HAS LED TO ANOTHER 
GULF OF TEHUANTEPEC GALE WIND EVENT...WHICH HAS NOW LASTED JUST 
OVER 24 HOURS. ALTHOUGH MODEL GUIDANCE HAS BEEN QUICK TO END THE 
EVENT...A 0046 UTC QUIKSCAT PASS AND AN EVEN MORE RECENT ASCAT 
PASS STILL SUGGEST N TO NE WINDS OF 30 TO 40 KT IN A NARROW 
REGION DOWNWIND OF THE GULF OF TEHUANTEPEC. ALTHOUGH THE FETCH 
WIDTH IS LIMITED AND THE DURATION HAS BEEN JUST BEYOND 24 
HOURS...A JASON PASS YESTERDAY SUGGESTED 12 FT SEAS IN THE 
VICINITY OF 13.5N95.5W. GIVEN THIS INFORMATION AND CURRENT 
WAVEWATCH GUIDANCE...IT IS ESTIMATED THAT 8 TO 12 FT SEAS COVER 
A LARGE PART OF THE AFFECTED AREA...WITH NE TO E SWELL NOW 
PROPAGATING WELL TO THE SOUTHWEST.

MODEL GUIDANCE SUGGESTS THAT THE CURRENT GULF OF TEHUANTEPEC 
GALE EVENT SHOULD WEAKEN SLIGHTLY THROUGH THIS MORNING BUT TO 
SURGE BACK TO ITS PRESENT STRENGTH BY THIS TIME TOMORROW. THIS 
IS LIKELY THE RESULT OF ADDITIONAL HIGH PRESSURE BUILDING BEHIND 
A NEW COLD FRONT ENTERING THE GULF OF MEXICO AND FAR NE MEXICO. 
ONCE THE SAME FRONT BEGINS TO LIFT NORTH AS A WARM FRONT LATER 
THU AND FRI...THE PATTERN SUPPORTING THE GALE WINDS SHOULD BEGIN 
TO BREAK AND ALLOW WINDS AND SEAS TO GRADUALLY DIMINISH AND 
SUBSIDE. 

TO THE SOUTH...A RECENT ASCAT PASS INDICATES THAT THE VERY 
PERSISTENT GAP WIND EVENT DOWNWIND OF THE GULF OF PAPAGAYO 
CONTINUES...ALBEIT IN A GREATLY WEAKENED STATE. NE TO E WINDS OF 
20 KT LIKELY EXIST OVER A NARROW AREA ABOUT 30 NM EITHER SIDE OF 
10.5N FROM THE COAST OUT TO 88W...WITH SEAS ESTIMATED TO STILL 
BE UP TO 9 FT. HIGH PRESSURE BRIDGING SOUTHEAST FROM MEXICO INTO 
CENTRAL AMERICA SHOULD LEAD TO A RESURGENCE OF THE GULF OF 
PAPAGAYO GAP WIND EVENT BY TONIGHT...WITH NE TO E 20 TO 25 KT 
AGAIN LIKELY. HOWEVER...AROUND 48 HOURS FROM NOW...WINDS SHOULD 
AGAIN BE DIMINISHING AND SEAS SUBSIDING.

ELSEWHERE...AN ENHANCED LOW-LEVEL SUBTROPICAL RIDGE N OF THE 
AREA NEAR 34N136W SHOULD HOLD SWAY OVER THE NEXT FEW DAYS. SOUTH 
OF THE RIDGE NE TO E WINDS OF 20 TO 25 KT ARE STILL ACTIVE OVER 
THE WESTERN PART OF THE FORECAST AREA...WITH STRONGEST WINDS 
GENERALLY FROM 11N TO 22N W OF 130W. WAVE HEIGHTS ARE ESTIMATED 
TO RANGE FROM 8 TO 11 FT OVER THIS AREA IN A MIXTURE OF LONG 
PERIOD NW SWELL AND NE WIND WAVES. OVER AN EVEN LARGER AREA 
COVERING MOST OF THE WESTERN HALF OF THE FORECAST AREA WINDS ARE 
LESS THAN 20 KT BUT SEAS OF 8 TO 9 FT EXIST PRIMARILY IN NW 
SWELL...WITH SEAS OF UP TO 10 FT IN THE FAR NORTH THANKS TO 
NEWLY ARRIVING NW SWELL. LITTLE CHANGE TO THIS PATTERN IS 
EXPECTED THROUGH FRI...EXCEPT FOR THE ADDITION OF SW SWELL S OF 
10N W OF 100W.

$$
KIMBERLAIN