000
AXPZ20 KNHC 071555
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI DEC 07 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

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

THE MONSOON TROUGH EXTENDS W FROM THE COLOMBIAN COAST AT 07N78W 
TO 06N80W THEN TURNS NW RUNNING PARALLEL OVER THE PANAMA COAST 
TO 09N85W...THEN TURNS SW TO 07N93W...THEN NW TO 08N100W WHERE 
LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ. THE ITCZ THEN 
WIGGLES WESTWARD BETWEEN 06-08N TO BEYOND 07N140W. ISOLATED 
MODERATE TO STRONG CONVECTION IS NOTED WITHIN 180 NM EITHER SIDE 
OF A LINE FROM 16N116W TO 08N125W AND ALSO WITHIN 30 NM EITHER 
SIDE OF A LINE FROM 08N127W TO 08N131W. ISOLATED MODERATE 
CONVECTION IS NOTED ALONG THE MONSOON TROUGH TO THE E OF 83W.

...DISCUSSION...

ALOFT...A LONGWAVE UPPER RIDGE HAS ITS MEAN AXIS OVER THE 
PACIFIC ALONG ROUGHLY 150W. AN UPPER CYCLONE IS EMBEDDED WITHIN 
THE LONGWAVE RIDGE AT 33N144W WITH A TROUGH EXTENDING SE TO 
25N140W. A SHORTWAVE RIDGE IS IMMEDIATELY TO THE E ALONG 14N140W 
TO 26N125W. DENSE UPPER MOISTURE IS NOTED BETWEEN THE SHORTWAVE 
FEATURES...WITHIN 180 NM OF A LINE FROM 21N140W TO 30N133W WHERE 
IT SPREADS OUT BETWEEN 128W-143W WELL TO THE N OF 32N.    

A LONGWAVE UPPER TROUGH DOMINATES N AMERICA WITH AN UPPER 
SHORTWAVE TROUGH MOVING THROUGH THE LARGER TROUGH PATTERN ALONG 
32N110W TO 23N120W INTO AN UPPER CYCLONE AT 17N124W WITH THE 
TROUGH CONTINUING SW TO BASE OVER THE DEEP TROPICS AT 02N122W.
AN UPPER ANTICYCLONE IS CENTERED OVER THE DEEP TROPICS AT 07N91W 
WITH AN UPPER RIDGE EXTENDING NW TO A CREST AT 25N116W. THIS 
PATTERN SETS UP AN AREA OF UPPER DIFFLUENCE ENHANCING THE 
CONVECTION PREVIOUSLY DESCRIBED BETWEEN 116-125W. THE RESULTANT 
DEBRIS MOISTURE IS ADVECTED N ALONG THE W PERIPHERY OF THE UPPER 
RIDGE...ROUGHLY WITHIN 360 NM OF A LINE FROM 10N119W TO 20N112W 
WHERE IT CROSSES OVER THE UPPER RIDGE AXIS...THEN THINS SOMEWHAT 
AS IT CONTINUES NE INTO THE LONGWAVE TROUGH PATTERN ACROSS THE 
SOUTHEASTERN CONUS. THE UPPER LEVELS ARE VERY DRY S OF 13N E OF 
100W AND SUPPRESSING CONVECTION TO THE COUPLE OF TOWERING 
CUMULUS CLUSTERS ALONG THE MONSOON TROUGH AXIS TO THE S OF 
PANAMA.

AT THE LOW LEVELS...A COLD FRONT IS WASHING OUT ALONG 32N114W TO 
27N121W TO 30N130W WITH A SURFACE RIDGE BRIDGING THROUGH THE 
DECAYING FRONT WITH THE RIDGE AXIS FROM 32N132W TO 14N100W. 
NORTHERLY WINDS AT 15-20 KT ARE OBSERVED N OF THE DECAYING FRONT 
WITH SEAS 7-10 FT IN MIXED N AND NE SWELL. THE TRADES SW OF THE 
RIDGE ARE AT 20-25 KT IN THE AREA FROM 08-23N W OF 127W...WITH 
SEAS 7-10 FT IN PRIMARILY NE SWELL. THE AFFECTED AREA OF NE 
TRADES WILL GRADUALLY SHRINK OVER THE NEXT 48 HOURS TO 12-20N W 
OF 135W AS THE WINDS DIMINISH TO 15-20 KT AND THE SEAS SUBSIDE 
TO 7-8 FT IN THE NE SWELL. THE NORTHERLY FLOW BEHIND THE 
DECAYING FRONT WILL DIMINISH BELOW 20 KT AS SEAS SUBSIDE BELOW 8 
FT ON SAT...BUT A SECONDARY NORTHERLY SURGE AT 15-20 KT WILL 
ENTER THE WATERS N OF 28N BETWEEN 122-132W ON SUN WITH SEAS 
BUILDING 7-10 FT. 

EXPECT NW WINDS AT 10 KT WITH SEAS 3-6 FT ALONG THE W COAST OF 
THE BAJA CALIFORNIA THROUGH SAT...THEN GENERALLY W-NW WINDS AT 
5-10 KT WITH SEAS 3-5 FT ON SUN. A COLD FRONT WILL SWEEP S INTO 
THE NE WATERS TO INCLUDE THE GULF OF CALIFORNIA ON SUN NIGHT. 
THIS WILL RESULT IN WINDS BECOMING NE 15-20 KT ALONG THE W COAST 
OF THE BAJA PENINSULA ON MON...BUT WINDS WILL BECOME NW AT 20-30 
KT IN THE NORTHERN GULF OF CALIFORNIA BRIEFLY LATE SUN NIGHT... 
WITH NW WINDS 15-20 KT SPREADING S ACROSS THE ENTIRE GULF BY MON 
NIGHT. EXPECT SEAS MAY BUILD TO 7-10 FT BRIEFLY IN THE NORTHERN 
GULF WATERS SUN NIGHT IN AREA OF LONG NW FETCH...AND 4-7 FT 
SOUTHERN GULF WATERS BY MON NIGHT.
     
GAP WINDS...
GULF OF TEHUANTEPEC...THE NEXT NORTHERLY SURGE AT 15-20 KT 
THROUGH THE CHIVELA PASS WILL ACCOMPANY A COLD FRONT LATE TUE 
NIGHT...WITH WINDS GRADUALLY INCREASING TO A MINIMAL GALE BY 
LATE WED AND CONTINUING INTO MIDDAY THU. 

GULF OF PAPAGAYO...NE WINDS WILL CONTINUE TO PULSE AT 10-15 KT 
IN AND DOWNSTREAM OF THE GULF OF PAPAGAYO THROUGH THE MIDDLE OF 
NEXT WEEK...WITH GUIDANCE SUGGESTING AN INCREASE TO 20-25 KT 
BEGINNING ON WED NIGHT.

$$
NELSON