000
AXPZ20 KNHC 300920
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 05N77W TO 07N92W TO 05N113W 09N123W TO 
09N134W TO 08N140W. SCATTERED MODERATE CONVECTION WITHIN 90 NM N 
OF AXIS BETWEEN 122W AND 125W AND WITHIN 150 NM S OF AXIS 
BETWEEN 125W AND 131W.

...DISCUSSION...
A PROGRESSIVE SHORTWAVE TROUGH NOW EXITING THE EASTERN CONUS HAS 
LEFT BEHIND A STATIONARY FRONT ACROSS THE NORTHERN GULF OF 
MEXICO AND ALONG THE EASTERN SLOPE OF THE SIERRA MADRE ORIENTAL 
AND NORTHEAST MEXICO. HIGH PRES BUILDING BEHIND THE FRONT HAS 
DESCENDED ALONG THE FRONT RANGE OF THE SIERRA MADRE...WITH THE 
INCREASING GRADIENT RESULTING IN A GALE EVENT NEAR AND DIRECTLY 
DOWNSTREAM OF THE GULF OF TEHUANTEPEC. ALTHOUGH THERE HAS BEEN 
NO RECENT SCATTEROMETER DATA OVER THIS REGION DURING THE LAST 12 
HOURS...MODEL GUIDANCE SUGGESTS N TO NE 30 TO 35 KT WINDS NEAR 
THE COAST. THE EDGE OF A 0112 UTC QUIKSCAT PASS DID SUGGEST THAT 
A BROADER AREA OF 20 TO 25 KT NE WINDS WERE FANNING OUT FROM THE 
GULF REGION...EXTENDING UP TO 200 NM EITHER SIDE OF 11N98W. WITH 
THE WEATHER PATTERN OVER MEXICO AND ADJACENT AREAS ALREADY IN A 
STATE OF FLUX...THE CURRENT GALE EVENT IN THE GULF OF 
TEHUANTEPEC IS EXPECTED TO RATHER BRIEF...ENDING NO LATER TUE 
EVENING. THE LIMITED FETCH WIDTH AND SHORT DURATION OF THE EVENT 
FAVORS WAVE HEIGHTS NO MORE THAN 10 FT.

HIGH PRESSURE BUILDING BEHIND THE GULF FRONT HAS SPILLED 
SOUTHEASTWARD INTO CENTRAL AMERICA...AND THE PRESSURES RISES ARE 
HELPING TO SUSTAIN NEAR CONSTANT NE TO E 20 TO 25 KT WINDS NEAR 
AND DOWNWIND OF THE GULF OF PAPAGAYO. RECENT QUIKSCAT AND ASCAT 
PASSES BOTH CONFIRM THESE WINDS IN A NARROW AREA ABOUT 45 NM 
EITHER SIDE OF 11N E OF 89W. ALTHOUGH THE FETCH WIDTH IS RATHER 
SMALL AT PRESENT...THE DURATION OF THE CURRENT EVENT HAS BEEN 
RATHER LONG. AS A RESULT...IT IS ASSUMED THAT WAVE HEIGHTS COULD 
BE UP TO AT LEAST...A FOOT OR TWO HIGHER THAN WHAT WAVEWATCH 
GUIDANCE SUGGESTS. AS THE SURFACE RIDGE TO THE NORTH GRADUALLY 
WEAKENS OVER THE NEXT 48 HOURS...THE CURRENT GULF OF PAPAGAYO GAP
WIND EVENT SHOULD VERY GRADUALLY DIMINISH IN STRENGTH. HOWEVER 
...MODEL GUIDANCE STILL SUGGESTS THAT IT WILL BE AROUND IN SOME 
FORM THROUGH AT LEAST LATE WED.  NE TO E SWELL OF UP TO 8 OR 9 
FT SHOULD COMBINE WITH SWELL COMING OUT OF THE GULF OF 
TEHUANTEPEC AND TRANSLATE FAR DOWNSTREAM IN A NARROW REGION FROM 
07N TO 12N AND AS FAR W AS 105W OVER THE NEXT FEW DAYS.

ELSEWHERE...AN ENHANCED LOW-LEVEL SUBTROPICAL RIDGE RESTING NEAR 
33N132W SHOULD MAINTAIN ITSELF OVER THE NEXT FEW DAYS WHILE 
SLOWLY SHIFTING W. NEAR AND S OF THE RIDGE NE TO E WINDS OF 
ABOUT 20 KT CONTINUE TO BLOW OVER A FAIRLY LARGE EXPANSE OF THE 
TROPICAL PACIFIC. WAVE HEIGHTS ARE GENERALLY 8 TO 12 FT IN A 
MIXTURE OF LONG PERIOD NW SWELL AND NE WIND WAVES. MODELS 
INDICATE A NEW WAVE OF LONG PERIOD NW SWELL ALREADY ENTERING THE 
FAR NORTHERN WATERS. THIS SWELL SHOULD PROPAGATE WELL INTO THE 
NORTHWEST HALF OF THE AREA OVER THE NEXT FEW DAYS.


$$
KIMBERLAIN