000
AXPZ20 KNHC 162148
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN DEC 16 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 SW FROM THE COSTA RICA COAST AT 
10N85W TO 06N100W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO 
AN ITCZ WHICH CONTINUES W BETWEEN 05-07N TO BEYOND 140W. 
ISOLATED MODERATE CONVECTION IS NOTED WITHIN 60 NM OF LINE FROM 
05N81W TO 05N85W TO 08N100W TO 08N110W. ISOLATED MODERATE TO 
STRONG CONVECTION IS OBSERVED WITHIN 30 NM OF 07N126W.

...DISCUSSION...

ALOFT...A SHARP UPPER TROUGH EXTENDS SW INTO THE AREA WITH ITS 
MEAN AXIS ALONG 32N108W TO 24N126W TO 18N140W. AN UPPER 
ANTICYCLONE IS CENTERED AT 31N142W WITH A RIDGE SE TO A SHARP 
CREST AT 27N130W. DRY UPPER AIR IS NOTED TO THE N OF THE TROUGH 
AXIS EXCEPT FOR SOME UPPER MOISTURE SHIFTING SE ACROSS THE AREA 
N OF 30N BETWEEN 120-117W.

AN INVERTED UPPER TROUGH IS OBSERVED OVER THE DEEP TROPICS TO 
THE S OF 07N ALONG 131W AND CONTINUES TO SEPARATE THE UPPER 
LEVEL FLOW ACROSS THE TROPICAL PORTION OF THE DISCUSSION AREA. 
WEAK UPPER LEVEL ANTICYCLONIC FLOW IS NOTED OVER THE DEEP 
TROPICS TO THE W OF THIS TROUGH. AN UPPER ANTICYCLONE IS 
CENTERED AT 15N98W WITH AN UPPER RIDGE EXTENDING SW TO A SHARP 
CREST AT 09N129W. AN UPPER RIDGE ALSO EXTENDS E FROM THE 
ANTICYCLONE ACROSS THE CENTRAL AMERICA AD W CARIBBEAN ALONG 17N. 

STRONG UPPER WESTERLIES CONTINUE TO ADVECT A DENSE PLUME OF 
UPPER MOISTURE NE ACROSS THE DISCUSSION AREA...WITHIN 330 NM 
EITHER SIDE OF A LINE FROM 12N140W TO 23N106W TO BEYOND 32N91W. 
WEAK UPPER DIFFLUENCE ALONG THE SOUTHERN PERIPHERY OF THE LARGE 
ANTICYCLONE OVER THE SE PORTION HAS BEEN ENHANCING THE ISOLATED 
CONVECTION PREVIOUSLY MENTIONED BETWEEN 80-110W.

LOW LEVELS...A WEAKENING COLD FRONT HAS DIPPED INTO THE 
N-CENTRAL WATERS N OF 29N ALONG 120W. A SURFACE RIDGE EXTENDS 
FROM 29N140W TO 20N108W. SURFACE WINDS ARE AT 10-15 KT ACROSS 
THE ENTIRE SUBTROPICAL WATERS WITH SEAS 6-7 FT EXCEPT FOR SOME 
REMNANT N SWELL AND 8 FT SEAS TO THE N OF 29N BETWEEN 130-135W. 
SEAS SHOULD SUBSIDE TO 3-6 FT IN NW SWELL ALONG THE ENTIRE W 
COAST OF THE BAJA PENINSULA FROM LATE MON THROUGH LATE TUE. 

FURTHER S...NE TRADES CONTINUE AT 20-25 KT TO THE SW OF THE 
RIDGE ACROSS THE WATERS FROM 07-17N TO THE W OF 128W...WITH 
SEAS 9-12 FT IN MOSTLY NE SWELL. THE TRADES ARE AT 15-20 KT 
SURROUNDING THIS AREA FROM 06-24N TO THE W OF 111W WITH SEAS
7-9 FT IN MIXED N AND NE SWELL. EXPECT A WEAK LOW LEVEL TROUGH 
TO FORM FROM 13N-18N BETWEEN 135-140W ON MON MAINTAINING NE-E 
20-25 KT WITHIN THAT AREA...WITH ENHANCED TRADES CONTINUING 
ELSEWHERE FROM ABOUT 03N-21N W OF 115W. CROSS EQUATORIAL SE 
SWELL WILL MIX WITH NE TRADE WINDS SWELL ACROSS THE WATERS S OF 
07N W OF 115W ON MON. 

LOOKING FURTHER OUT...THE WEAK TROUGH OVER THE SW PORTION WILL 
DISSIPATE TUE AS A STRONG BUT DRY COLD FRONT SWEEPS RAPIDLY SE 
INTO THE SUBTROPICAL WATERS ACCOMPANIED BY N-NE 20-25 KT 
WINDS...WITH SEAS BUILDING 8-15 FT W OF THE FRONT. NW 20-25 KT 
WINDS AND SEAS 8-10 FT WILL ARRIVE AT THE W COAST OF THE BAJA 
PENINSULA TUE EVENING. THE GRADIENT IS EXPECTED TO RELAX FROM 
THE NW TO SE ON WED AS WINDS CLOCK TO THE NE AND DIMINISH TO 
15-20 KT ALONG THE BAJA PENINSULA TO THE N OF 25N.
    
GULF OF TEHUANTEPEC...WINDS ARE EXPECTED TO BECOME LIGHT AND 
VARIABLE LATE TONIGHT. BEST GUESS IS THE NEXT NORTHERLY EVENT 
WILL BEGIN LATE MON NIGHT...BUT PEAK AT ONLY 20 KT. ANOTHER 
STRONG EVENT NORTHERLY BEGINS THU AFTERNOON WITH STORM 
CONDITIONS BY LATE THU NIGHT. 

$$
NELSON