000
AXPZ20 KNHC 170343
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN FEB 17 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...SPECIAL FEATURE...
GULF OF TEHUANTEPEC GALE FORCE WINDS INCREASE TO STORM FORCE AND 
EXPAND IN COVERAGE TO 12N EARLY TONIGHT WITH SEAS BUILDING TO 
17-20 FT.  COLDEST AIR MASS OF THE YEAR FUNNEL ACROSS CHIVELAS 
PASS REACHING AS HIGH AS 50 KT OVER THE WATERS IN THE GULF OF 
TEHUANTEPEC.  HIGH PRES OVER GULF OF MEXICO FUNNELING COLD AIR 
INTO ISTHMUS IS SOON DISPLACED EASTWARD VEERING WINDS AND 
EFFECTIVELY BRINGING STORM FORCE WINDS TO A HALT BY EARLY SUN 
BUT REMAINING AT GALE FORCE LEVEL THROUGH SUN NIGHT.  

PLUME OF SEAS BUILDING TO 15 FT SPREAD 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.  18Z NWW3 RUN SOLUTION INDICATE SEAS COULD RUN AS HIGH 
AS 20 FT WHICH IS MORE IN CONSONANCE WITH ECMWF AND UKMET 
PREVIOUS RUNS AND GIVE MORE CONFIDENCE IN FORECAST.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH AXIS NOT DISCERNIBLE.  ITCZ EXTENDS FROM 02N98W 
TO 07N112W TO 08N127W TO 04N140W.  ISOLATED MODERATE CONVECTION 
WITHIN 90 NM S OF AXIS FROM 128W TO 133W.

...DISCUSSION...
WELL ESTABLISHED MID TO UPPER LEVEL ANTICYCLONE AT 13N94W 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 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. 

LONGWAVE TROUGH EXTEND FROM 32N137W TO WELL DEFINED CYCLONE AT 
22N150W 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.  MONSOON TROUGH BECOME ILL-DEFINED AND ITCZ AXIS 
BARELY HAS ISOLATED MODERATE CONVECTION WITHIN 90 NM OF AXIS 
FROM 128W-133W.  

...ELSEWHERE AT THE LOWER LEVELS...
HEALTHY HIGH PRES CENTER 1037 MB 41N141W MOVES S TO NW CORNER OF 
BASIN ADDING MORE STABILITY TO REGION...BUT PRESSING GRADIENT TO 
THE POINT OF INCREASING TRADES TO A FRESH BREEZE AND BUILDING 
SEAS TO 11-12 FT IN NW SWELL. 

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 TONIGHT...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.

HIGH PRES EASTWARD MOVE INTO SW N ATLC INCREASES SW CARIBBEAN 
SEA TRADES TO A STRONG BREEZE ENHANCING N WINDS OVER GULF OF 
PANAMA LATE IN FORECAST PERIOD.  

$$
WALLY BARNES