000
AXPZ20 KNHC 121608
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON NOV 12 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 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH AXIS FROM 09N75W TO LOW PRES NEAR 07N79W 1010 MB 
TO 09N84W TO LOW PRES NEAR 09N110.5W 1009 MB TO 08N116W WHERE IT 
TRANSITIONS TO ITCZ...CONTINUING ON TO LOW PRES NEAR 09N123W 
1009 MB TO 12N130W WHERE IT FRACTURES IN VICINITY OF TROUGH THEN 
RESUMES FROM 10N136W TO BEYOND 09N140W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION NOTED FROM 04N TO 06.5N E OF 83W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 210 
NM OF LOW PRES AT 09N110.5W...AND WITHIN 150 NM N SEMICIRCLE OF 
LOW PRES AT 09N123W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION NOTED FROM 08.5N TO 18.5N W OF 126W ASSOCIATED WITH 
TROUGH.

...DISCUSSION...
BROAD UPPER LEVEL RIDGE E OF 136W ANCHORED ON ANTICYCLONE AT 
14N116W COVER A LARGE PORTION OF THE BASIN AND CONTINUES TO 
BLOCK ANY SOUTHERN INTRUSION OF WEAK SHORTWAVE TROUGHS MOVING 
OVER RIDGE. BROAD MID LATITUDE TROUGH DEVELOPING TO W OF RIDGE 
ALONG ABOUT 155W...WITH SEVERAL SHORTWAVES N OF 20N MOVING 
THROUGH TROUGH. EQUATORIAL JET MOVES THROUGH BASE OF TROUGH S OF 
13N AND THEN TURNS NE OVER RIDGE AND ACROSS BAJA CALIFORNIA AND 
N HALF OF MEXICO. LARGE EQUATORIAL UPPER CYCLONE ALMOST DUE S OF 
ANTICYCLONE AT 116W AIDING IN DIVERTING UPPER FLOW TO THE SE AND 
AROUND THE UPPER CYCLONE...AND MAINTAINING LARGE ZONE OF UPPER 
DIVERGENCE BETWEEN 135W AND 128W...WHERE MOST ACTIVE CONVECTION 
HAS PREVAILED PAST 12-18 HOURS. ABUNDANT MIDDLE TO UPPER 
MOISTURE AND CONVECTIVE CLOUD DEBRIS ARE RIDING JET FLOW OVER 
RIDGE...WITH CONVECTION LIKELY S OF 18N IN THIS REGION BASED ON 
RECENT MICROWAVE TPW IMAGERY. A HIGH AMPLITUDE WAVE ALONG THE 
ITCZ HAS MOVED W INTO THIS REGION DURING THE PAST 24-36 HOURS... 
AND COMBINED WITH STRONG PRES GRADIENT TO THE N TO PRODUCE A 
ZONE OF STRONG NE TRADEWINDS AND VERY ACTIVE CONVECTION. AN 
OVERNIGHT OSCAT PASS AT 0906 UTC SHOWED N TO NE WINDS 30-35 KT 
WITHIN 270 NM TO THE NW OF THIS SURFACE TROUGH ALONG THE 
ITCZ...AND A GALE WARNING HAS BEEN ISSUED FOR THIS AREA. SEAS IN 
THE AREA ARE ESTIMATED 12-17 FT. GLOBAL MODELS INDICATE THIS IS 
A LIKELY SCENARIO...AND FORECAST GALE CONDITIONS TO CONTINUE NW 
OF THE WWD MOVING TROUGH THROUGH THIS EVENING BEFORE WEAKENING 
OVERNIGHT TO 25-30 KT BY TUE MORNING. 

...ELSEWHERE AT THE LOWER LEVELS...
SURFACE HIGH PRES 1028 MB AT 34N127W IS MAINTAINING STRONG TRADE 
WINDS AND SEAS TO 12 FT ACROSS MIDDLE OF BASIN FROM 10N TO 22N W 
OF 120W. PRES GRADIENT TO THE SE AND INSIDE GULF OF CALIFORNIA 
ALSO PRODUCING STRONG N-NW WINDS DOWN THE LENGTH OF THE 
GULF...WITH OVERNIGHT OSCAT PASS...0729 UTC...VERIFYING WINDS 
TO 30 KT THROUGH CENTRAL PORTIONS OF THE GULF. SEAS ACROSS S 
CENTRAL PORTIONS HAVE BUILT TO 10 FT THIS MORNING. THE RIDGE 
FORECAST TO HOLD IN POSITION THROUGH 24 HOURS BEFORE SHIFTING 
N-NE AND RELAXING GRADIENT INSIDE GULF OF CALIFORNIA...WHERE 
WINDS DROP BELOW 20 KT BY 36-48 HOURS.  

...GAP WINDS...
PULSES OF TRADE WINDS THROUGH GULF OF PAPAGAYO WILL PRODUCE 
FRESH TO STRONG NE WINDS WITH SEAS 6-8 FT EXPECTED TO CONTINUE 
THROUGH WED.

GULF OF TEHUANTEPEC...STRONG NORTHERLY WINDS EXPECTED DEVELOP IN 
GULF OF TEHUANTEPEC THIS AFTERNOON AND QUICKLY REACH GALE FORCE 
THIS EVENING...AND INCREASE TO 40 KT LATE TONIGHT AND TUE 
MORNING...WITH SEAS BUILDING TO 10-15 FT. 
 
$$
STRIPLING