000
AXPZ20 KNHC 132154
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU DEC 13 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS W FROM THE W COLOMBIAN COAST AT 
07N78W ACROSS THE SOUTHERN TIP OF PANAMA TO 08N86W...THEN SW TO 
06N97W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ 
THAT EXTENDS NW TO 10N110W...THEN TURNS SW TO 07N122W...THEN 
W-NW TO BEYOND 09N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS OBSERVED WITHIN 90 NM OF 05.5N80W. ISOLATED 
MODERATE TO STRONG CONVECTION IS OBSERVED FROM 05-10N BETWEEN 
83-93W...AND ALSO WITHIN 30 NM EITHER SIDE OF A LINE FROM 
08N132W TO 09N140W. 

THE SURFACE LOW PREVIOUSLY NEAR 10N110W HAS WEAKENED TO AN OPEN 
TROUGH EMBEDDED WITHIN THE ITCZ AND LACKS CONVECTION. 

...DISCUSSION...

ALOFT...A LONGWAVE TROUGH IS OVER THE WESTERN SEABOARD OF N 
AMERICA WITH ITS MEAN AXIS EXTENDING S INTO THE DISCUSSION AREA 
FROM 32N121W TO 20N130W...ACCOMPANIED BY DRY UPPER AIR TO THE N 
OF 22N W OF 120W. A BROAD UPPER TROUGH IS NOTICED TO THE S OF 
15N ALONG 120W EFFECTIVELY SEPARATING THE UPPER FLOW OVER THE 
TROPICS W OF 100W. AN UPPER RIDGE EXTENDS E INTO THE AREA FROM 
08N140W TO 03N123W. AN UPPER ANTICYCLONE IS AT 11N100W WITH A 
RIDGE EXTENDING SW TO 08N115W. STRONG UPPER WESTERLIES CONTINUE 
TO ADVECT A 700 NM WIDE PLUME OF UPPER MOISTURE E ACROSS THE 
TROPICS TO ALONG 125W WHERE SOME OF THE MOISTURE TURNS SE AROUND 
THE WESTERN TROPICAL RIDGE. THE REMAINING MOISTURE TURNS NE AS 
IT PASSES E OF THE UPPER TROUGH...AND CONTINUES ACROSS THE 
SOUTHERN BAJA PENINSULA AND ACROSS MOST OF NORTHERN MEXICO.

A BROAD INVERTED UPPER TROUGH IS OBSERVED OVER THE DEEP TROPICS 
TO THE S OF 09N ALONG 98W AND IS PROGRESSING WESTWARD. AN UPPER 
ANTICYCLONE IS CENTERED OVER THE SW CARIBBEAN AT 11N79W RIDGING 
W TO THE ANTICYCLONE PREVIOUSLY MENTIONED AT 11N100W. UPPER 
DIFFLUENCE JUST S OF THIS RIDGE IS ENHANCING CONVECTION ALONG 
THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED...WITH THE RESULTANT 
DEBRIS MOISTURE ADVECTED NE ACROSS THE RIDGE AXIS...AND OVER 
CENTRAL AMERICA TO THE E OF 90W. 

LOW LEVELS...A COLD FRONT EXTENDS THE EXTREME NW PORTION OF THE 
BAJA PENINSULA SW TO 22N131W. SOUTHWESTERLY WINDS HAVE INCREASED 
TO 20-25 KT TO THE N OF 25N WITHIN 180 NM E OF FRONT WITH SEAS OF
5-6 FT. ALTHOUGH NW WINDS ARE ONLY AT 15-20 KT TO THE N OF 24N W 
OF THE FRONT...NW SWELLS RESULT IN COMBINED SEAS OF 8-11 FT. NE 
TRADES CONTINUE AT 20-25 KT WITH SEAS 8-11 FT ACROSS THE WATERS 
FROM 11-24N W OF 130W. THE FRONT WILL WEAKEN TO A FRONTAL TROUGH 
AS IT PASSES ACROSS THE BAJA PENINSULA TONIGHT. THE NW SWELL 
WILL SUBSIDE ON SAT WITH SEAS AT 8-10 FT ACROSS THE WATERS N OF 
25N TO THE E OF 135W. THE AREA OF NE 20-25 KT TRADES WILL SHRINK 
FROM 12-24N TO THE W OF 135W WITH SEAS 6-9 FT. THE N SWELLS 
RESULTING IN SEAS TO 8 FT WILL PROPAGATE SE ACROSS THE WATERS 
ELSEWHERE NW OF LINE FROM THE BAJA PENINSULA AT 112W TO 10N140W.
 
GENERALLY EXPECT SEAS TO BUILD TO 5-8 FT IN THE NW SWELL TONIGHT 
ACROSS THE WESTERN BAJA COASTAL WATERS TO THE N OF 27N. 
SOUTHWESTERLY 20-25 KT WINDS CURRENTLY ACROSS THE GULF OF 
CALIFORNIA TO THE N OF 29N WILL SPREAD S TO ALONG 25N ON FRI 
THEN DIMINISH BEHIND THE DISSIPATING COLD FRONT.  
     
GAP WINDS...
GULF OF TEHUANTEPEC...GALE CONDITIONS HAVE ENDED. N WINDS 
EXPECTED AT 20-30 KT TONIGHT THROUGH SUNRISE FRI...THEN WINDS 
WILL QUICKLY DIMINISH. BEST GUESS IS THE NEXT NORTHERLY EVENT 
WILL BEGIN LATE TUE NIGHT.

GULF OF PAPAGAYO...NE WINDS WILL CONTINUE TO PULSE AT 15-20 KT 
WITH AN OCCASIONAL SURGES TO 20-25 KT TONIGHT THEN DIMINISH TO 
15-20 KT ON FRI.

$$
NELSON