East Pacific Tropical Weather Discussion

000
AXPZ20 KNHC 162201
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT FEB 16 2013

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 
2100 UTC.

...SPECIAL FEATURE...
CURRENT GULF OF TEHUANTEPEC BEGINNING GALE EVENT QUICKLY 
INCREASE INTO DEVELOPING STORM AND EXPAND IN COVERAGE TO 12N 
TONIGHT.  COLDEST AIR MASS OF THE YEAR FUNNEL ACROSS CHIVELAS 
PASS THIS AFTERNOON REACHING AS HIGH AS 50 KT OVER THE WATER OF 
THE GULF OF TEHUANTEPEC.  HIGH PRES OVER GULF OF MEXICO DRIVING 
AIR INTO ISTHMUS IS SOON DISPLACED EASTWARD VEERING WINDS AND 
EFFECTIVELY BRINGING STORM FORCE WINDS TO A HALT BUT REMAINING 
AT GALE FORCE LEVEL THROUGH SUN NIGHT.  

PLUME OF BUILDING SEAS TO 15 FT SPREADS ACROSS E PAC S OF GULF 
OF TEHUANTEPEC.  SEAS EVENTUALLY MERGE WITH LESSER SWELLS CAUSED 
BY GULF OF PAPAGAYO GAP EVENT INCREASING AREA COVERAGE WITH SEAS 
TO 16-17 FT.  ECMWF AND UKMET GUIDANCE SOLUTIONS INDICATES SEAS 
COULD RUN AS HIGH AS WILL REACH AS HIGH AS 20 FT WHILE NWW3 
STOPS SIGNIFICANTLY LOWER...16 FT.  FORECAST WILL TAKE A MIDDLE 
OF THE ROAD APPROACH AND HOLD NEAR 17-18 FT.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH AXIS NOT DISCERNIBLE.  ITCZ EXTENDS FROM 03N102W 
TO 08N122W THEN FROM 06N127W TO 04N140W.  NO SIGNIFICANT 
CONVECTION NOTED.

...DISCUSSION...
WELL ESTABLISHED MID TO UPPER LEVEL ANTICYCLONE AT 13N98W HOLD 
ITS POSITION AS LONGWAVE UPPER LEVEL TROUGH N OF AREA CRUISES 
EAST WELL N OF AREA.  TROUGH EFFECTIVELY FLATTENS RIDGE CREST 
PROMPTING WINDS ALOFT TO BECOME PERFECTLY ZONAL N OF 18N ALL THE 
WAY FROM 135W ACROSS MEXICO THROUGH 80W IN THE ATLC OCEAN AND 
CARIBBEAN SEA BY THE END OF FORECAST PERIOD. 

FARTHER SOUTH...A NEGATIVELY TILTED UPPER TROUGH EXTENDING FROM 
15N131W TO 04N116W IS PROVIDING SUPPORT TO A SURFACE TROUGH 
BREAKING THE ITCZ NEAR 124W FROM 06N TO 11N. THE UPPER TROUGH IS 
ALSO ENHANCING CONVECTION IN THE CONVERGENT AREA AHEAD OF THE 
TROUGH NEAR 08N125W. GLOBAL MODELS SUGGEST THE SURFACE TROUGH 
WILL START TO DAMPEN OUT SUN AND MON AS IT TRANSITS W OF THE 
UPPER TROUGH WHICH WILL BE WEAKENING AND SHIFTING E.

LONGWAVE TROUGH EXTEND FROM 32N138W TO WELL DEFINED CYCLONE AT 
22N151W LIFT N BUT PRESSES RIDGE CREST THROUGH ENTIRE FORECAST 
PERIOD.  RIDGE MAINTAINS LID OVER VERTICAL LIFT AND AIR MASS 
REMAINS VERY DRY PUTTING A DAMPER TO CONVECTION ALONG TROPICAL 
LATITUDES.  NOT EVEN ITCZ NOR MONSOON TROUGH...WHICH COULD 
HARDLY BE IDENTIFIED...IS ABLE TO BREAK LID.  

...ELSEWHERE AT THE LOWER LEVELS...
HEALTHY HIGH PRES CENTER 1038 MB 42N142W MOVES S TO NW CORNER OF 
BASIN ADDING TO MORE STABILITY TO REGION...BUT PRESSING GRADIENT 
TO THE POINT OF INCREASING TRADES TO A FRESH BREEZE AND BUILDING 
SEAS TO 13-14 FT IN NW SWELL. 

GULF OF CALIFORNIA...PRES GRADIENT EASES AS AFOREMENTIONED HIGH 
PRES MOVES S RESULTING IN DIMINISHING WINDS ALONG COAST OF 
CALIFORNIA AND BAJA CALIFORNIA...ONLY TO RETURN LATE IN FORECAST 
PERIOD AND BEYOND AS HIGH PRES MAKES ITS MOVE W.

GULF OF PAPAGAYO...STRONG HIGH PRES OVER GULF OF MEXICO SLIPS 
INTO SW N ATLC BASIN INDUCING A SURGE OF TRADE WINDS INTO GULF 
OF PAPAGAYO LATE SAT INTO EARLY SUN...PERSISTING THROUGH END OF 
FORECAST PERIOD.  NEAR GALE NE WINDS EXPECTED OVERNIGHT AND 
EARLY MORNING HOURS WHILE DIMINISHING TO A STRONG BREEZE LATE 
MORNING THROUGH EARLY EVENINGS.   

$$
WALLY BARNES