000
AXPZ20 KNHC 170338
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC MON DEC 17 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0330 UTC.

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

THE MONSOON TROUGH EXTENDS SW FROM THE COLOMBIAN COAST AT 07N77W 
TO 05N81W THEN TURNS NW TO THE COAST OF COSTA RICA AT 
10N85W...THEN SW TO 07N94W TO 06N110W WHERE LOW LEVEL WINDS 
INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES W ALONG 05N TO 
BEYOND 140W. BROKEN-OVERCAST LOW-MID LEVEL CLOUDS WITH ISOLATED 
MODERATE CONVECTION IS NOTED WITHIN 75 NM OF EITHER SIDE OF A 
LINE FROM 05N80W TO 05N95W TO 08N109W...AND A LINE FROM 06N124W 
TO 08N140W.

...DISCUSSION...

ALOFT...A NARROW UPPER TROUGH EXTENDS SW INTO THE AREA WITH ITS 
MEAN AXIS ALONG 32N103W TO 25N130W TO 18N140W. AN UPPER 
ANTICYCLONE IS CENTERED AT 30N138W WITH A RIDGE SE TO A SHARP 
CREST AT 26N128W. DRY UPPER AIR IS NOTED TO THE N OF THE TROUGH 
AXIS.

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 AND ADVECTING MOISTURE SE TO 
ALONG 03N TO THE W OF 131W. AN UPPER ANTICYCLONE IS CENTERED AT 
15N98W WITH AN UPPER RIDGE EXTENDING SW TO A SHARP CREST AT 
07N122W. AN UPPER RIDGE ALSO EXTENDS E FROM THE ANTICYCLONE 
ACROSS THE CENTRAL AMERICA AD W CARIBBEAN ALONG 15N. 

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 32N81W. 
WEAK UPPER DIFFLUENCE ALONG THE SOUTHERN PERIPHERY OF THE LARGE 
ANTICYCLONE OVER THE SE PORTION HAS BEEN ENHANCING THE ISOLATED 
CONVECTION PREVIOUSLY MENTIONED BETWEEN 80-109W.

LOW LEVELS...A SURFACE RIDGE EXTENDS FROM 30N140W TO 20N108W. 
SURFACE WINDS ARE AT 10-15 KT ACROSS THE ENTIRE SUBTROPICAL 
WATERS WITH SEAS 5-7 FT. 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 12-18N TO THE W OF 127W...WITH 
SEAS 9-11 FT IN MOSTLY NE SWELL. THE TRADES ARE AT 15-20 KT 
SURROUNDING THIS AREA FROM 06-24N TO THE W OF 115W WITH SEAS
7-10 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 THE EQUATOR TO 20N 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 8-14 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