000
AXPZ20 KNHC 142152
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI DEC 14 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 W COLOMBIAN COAST AT 
08N78W TO 06N81W...THEN TURNS NW TO 09N88W...THEN SW AGAIN TO  
TO 06N101W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN 
ITCZ. THE ITCZ THEN CONTINUES W-NW TO 10N140W. ISOLATED MODERATE 
TO STRONG CONVECTION IS NOTED WITHIN 120 NM EITHER SIDE OF A  
LINE FROM 05N78W TO 07N96W...AND ANOTHER LINE EXTENDING FROM 
08N121W TO 09N132W TO 11N140W.  

...DISCUSSION...

ALOFT...A SERIES OF UPPER TROUGH SHORTWAVES TROUGHS ARE ROTATING 
E ACROSS THE THE N-CENTRAL AND NE PORTION OF THE AREA WITH AN 
UPPER RIDGE SHIFTING SE OVER THE FAR NW PORTION. UPPER MOISTURE 
IS SQUEEZED BETWEEN THE TROUGHS...AND IS NOW SPREADING NE ACROSS 
SOUTHERN CALIFORNIA AND THE EXTREME N GULF OF CALIFORNIA. A 
BROAD UPPER TROUGH IS NOTICED TO THE S OF 08N ALONG 117W. AN 
UPPER RIDGE EXTENDS E INTO THE DEEP TROPICS FROM 08N140W TO 
04N123W. AN UPPER ANTICYCLONE IS CENTERED NEAR 16N93W WITH A 
RIDGE EXTENDING SW TO 12N109W. STRONG UPPER WESTERLIES CONTINUE 
TO ADVECT A 700 NM WIDE PLUME OF UPPER MOISTURE E ACROSS THE 
TROPICS TO ALONG 125W WHERE THE PLUME TURNS NE IN RESPONSE TO 
THE UPPER TROUGHS TO THE N...THEN CONTINUES E ACROSS THE 
SOUTHERN BAJA PENINSULA...ACROSS MOST OF NORTHERN OLD MEXICO AND 
NOW ACROSS THE NW GULF OF MEXICO...AND EVENTUALLY FANS OUT OVER 
THE S-CENTRAL CONUS. UPPER DIFFLUENCE JUST S OF THE EASTERN 
TROPICAL RIDGE IS ENHANCING THE ISOLATED MODERATE TO STRONG 
CONVECTION ALONG THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED. THE 
RESULTANT DEBRIS MOISTURE IS ADVECTED NE ACROSS THE RIDGE AXIS 
BUT SEEMS TO EVAPORATE OVER CENTRAL AMERICA TO THE E OF 90W.

LOW LEVELS...AN INITIAL COLD FRONT EXTENDS ACROSS THE GULF OF 
CALIFORNIA AND THE BAJA PENINSULA TO THE E PACIFIC...ROUGHLY  
FROM 26N109W TO 22N116W. A SURFACE RIDGE CONTINUES FROM 30N140W 
TO 21N108W. SW WINDS AHEAD OF THE WEAKENING COLD FRONT HAVE 
DIMINISHED TO 15-20 KT...BUT NW SWELLS MAINTAIN SEAS AT 7-10 FT. 
NE TRADES CONTINUE AT 20-25 KT TO THE SW OF THE RIDGE ACROSS THE 
WATERS FROM 12-25N TO THE W OF 133W...WITH SEAS 8-10 FT IN 
MOSTLY NE SWELL. ALTHOUGH SURFACE WINDS ARE ONLY AT 10-15 KT... 
SEAS REMAIN AT 7-9 FT IN NW SWELL ACROSS THE REMAINDER OF THE 
PACIFIC WATERS N OF LINE FROM THE BAJA PENINSULA AT 115W TO 
10N135W. THIS INITIAL FRONT WILL SOON BEGIN TO DISSIPATE AS A 
SECOND COLD FRONT SWINGS SE INTO THE N-CENTRAL WATERS TONIGHT 
FROM 30N119W TO 25N120W. WINDS WILL SHIFT AGAIN FROM SW-W-NW AT 
20-25 KT TO THE N OF 28N ALONG THE FRONT...WITH SEAS CONTINUING 
AT 8-10 FT IN THE NW SWELL. THIS SECOND FRONT WILL MOVE ACROSS 
THE BAJA PENINSULA AND THE THE NORTHERN GULF OF CALIFORNIA ON 
SAT THEN DISSIPATE OVER MEXICO ON SUN. EXPECT A SW-W WIND SHIFT 
ALONG THE FRONT OVER THE GULF OF CALIFORNIA TO THE N OF 30N ON 
SAT...BUT THE WINDS WILL QUICKLY DIMINISH BEHIND THE FRONT.

GULF OF TEHUANTEPEC...N WINDS HAVE DIMINISHED TO 20-25 KT AND 
EXPECTED TO GRADUALLY WEAKEN TONIGHT AND SAT BECOMING LIGHT AND 
VARIABLE SAT EVENING. BEST GUESS IS THE NEXT NORTHERLY EVENT 
WILL BEGIN LATE MON NIGHT...PEAKING AT 20 KT.

$$
NELSON