000
AXPZ20 KNHC 150336
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT DEC 15 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 W-SW FROM THE W COLOMBIAN COAST AT 
07N78W TO 06N100W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO 
AN ITCZ WHICH CONTINUES SW TO 05N119W THEN NW TO BEYOND 08N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 30 
NM OF 06N81W...AND WITHIN 90 NM EITHER SIDE OF A LINE FROM 
10N134W TO 10N141W.  

...DISCUSSION...

ALOFT...A SERIES OF UPPER TROUGH SHORTWAVES TROUGHS ARE ROTATING 
E ACROSS THE THE N-CENTRAL AND NE PORTIONS OF THE AREA...WITH AN 
UPPER RIDGE SHIFTING SE OVER THE FAR NW PORTION OF THE 
DISCUSSION AREA. UPPER MOISTURE IS SQUEEZED BETWEEN THESE UPPER 
TROUGHS...AND IS ROTATING E-NE ACROSS SOUTHERN CALIFORNIA... 
ARIZONA AND NORTHERN NEW MEXICO. A INVERTED UPPER TROUGH IS 
NOTICED TO THE S OF 08N BETWEEN 105-120W. AN UPPER RIDGE EXTENDS 
E INTO THE DEEP TROPICS FROM 06N140W TO 02N130W. AN UPPER 
ANTICYCLONE IS CENTERED NEAR 17N95W 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 BETWEEN 07-20N 
TO ALONG 125W WHERE THE PLUME THEN TURNS NE IN RESPONSE TO THE 
UPPER TROUGHS TO ITS N. THE PLUME NARROWS AS IT CONTINUES NE  
ACROSS THE SOUTHERN BAJA PENINSULA AND GULF OF CALIFORNIA... 
ACROSS MOST OF NORTHERN OLD MEXICO...ACROSS SE TEXAS AND FANNING 
OUT OVER THE SOUTHERN MISSISSIPPI VALLEY OF THE CONUS. 
THUNDERSTORMS ARE FLARING WITHIN 15 NM OF 15.5N121.5W. UPPER 
DIFFLUENCE JUST S OF THE EASTERN TROPICAL RIDGE HAS BEEN 
ENHANCING THE ISOLATED CONVECTION ALONG THE MONSOON TROUGH AS 
PREVIOUSLY DESCRIBED. THE RESULTANT DEBRIS MOISTURE IS ADVECTED 
NE ACROSS THE RIDGE AXIS AND SEEMS TO EVAPORATE OVER CENTRAL 
AMERICA TO THE E OF 92W.

LOW LEVELS...AN INITIAL COLD FRONT EXTENDS SW ACROSS THE GULF OF 
CALIFORNIA FROM 26N108W TO ACROSS THE BAJA PENINSULA BECOMING 
VERY DIFFICULT TO LOCATE OVER THE E PACIFIC NEAR 22N114W. A 
SECOND COLD FRONT EXTENDS FROM 32N121W TO 30N129W. A SURFACE 
RIDGE CONTINUES FROM 30N140W TO 20N110W. WINDS HAVE DIMINISHED 
TO 10-15 KT ACROSS THE SUBTROPICS...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. EXPECT THE AREA OF NE TRADES TO 
EXPAND EASTWARD ACROSS THE WATERS FROM 06-22N TO THE W OF 115W 
OVER THE NEXT COUPLE OF DAYS. THE SECONDARY COLD FRONT WILL 
SWEEP SE ACROSS THE BAJA PENINSULA AND GULF OF CALIFORNIA OVER 
THE WEEKEND ACCOMPANIED BY A SW-W-NW 20-25 KT WIND SHIFT ALONG 
THE FRONT TO THE N OF 28N. THE GRADIENT RELAXES W OF THE FRONT 
WITH WINDS QUICKLY DIMINISHING TO 10-15 KT ACROSS THE 
SUBTROPICAL WATERS BY EARLY SUN. THE EXCEPTION IS AN AREA OF 
NORTHERLY 15-20 KT WINDS WHICH WILL CONTINUE ALONG THE SURFACE 
RIDGE CREST... ROUGHLY FROM 17-23N BETWEEN 105-107W THROUGH 
EARLY NEXT WEEK.

GULF OF TEHUANTEPEC...N WINDS HAVE DIMINISHED TO 20-25 KT AND 
EXPECTED TO GRADUALLY WEAKEN LATE TONIGHT INTO SAT BECOMING 
LIGHT AND VARIABLE SAT EVENING. BEST GUESS IS THE NEXT NORTHERLY 
EVENT WILL BEGIN LATE MON NIGHT...PEAKING AT 20 KT. ANOTHER 
STRONG EVENT BEGINS NEXT THU EVENING WITH STORM CONDITIONS BY 
SUNRISE FRI. 

$$
NELSON