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Eastern Pacific Tropical Weather Discussion (Text)

000
AXPZ20 KNHC 271005
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 UTC TUE JAN 27 2015

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC. 

...SPECIAL FEATURES...                                           
GULF OF TEHUANTEPEC GALE WARNING...A PERSISTENT TIGHT PRES 
GRADIENT ACROSS SOUTHEASTERN MEXICO IS PRODUCING A LONG DURATION 
EVENT OF N TO NE 30-40 KT WINDS THROUGH THE ISTHMUS OF 
TEHUANTEPEC AND THE GULF WITHIN 45 NM EITHER SIDE OF A LINE FROM 
16N95W TO 15N95W TO 14N96W. SEAS THERE ARE IN THE 11-17 FT 
RANGE. EARLIER OBSERVATIONS AS REPORTED EARLY MON EVENING AND 
DURING THE OVERNIGHT HOURS FROM SHIPS "ZCDI4"..."SLKR"...AND 
"ZOAY4" VERIFIED THE GALE WIND CONDITIONS WITH SHIP "ZCDI4" NEAR 
16N95W REPORTING 42 KT AT 00 UTC...SHIP "SLKR" NEAR 14N95W 
REPORTING 40 KT AT 06 UTC AND SHIP "ZOAY4" NEAR 14N96W REPORTING 
36 KT ALSO AT 06 UTC.

A LARGE AREA OF N-NE 20-30 KT WINDS IS ELSEWHERE WITHIN 75 NM OF 
A LINE FROM 16N95W TO 15N95W TO 12N98W WITH SEAS OF 10-15 FT. NE 
SWELLS THAT HAVE PROPAGATED DOWNSTREAM FROM THIS EVENT OVER THE 
PAST FEW DAYS ARE COMBINING WITH LONG PERIOD NW SWELLS FROM 08N-
14N BETWEEN 94W-101W...AND ALSO S OF 11N BETWEEN 101W-112W. THE 
COMBINATION OF THESE SWELLS IS RESULTING IN SEAS TO 9 FT. THE 
HIGH PRES TIED TO CULPRIT TIGHT PRES GRADIENT WILL GRADUALLY 
WEAKEN THROUGH THU ALLOWING FOR THE GALE WINDS TO DIMINISH TO 
MINIMAL THRESHOLD WITH MAX SEAS IN THE GULF EXPECTED AT AROUND 
13 FT AT THAT TIME.

GULF OF PAPAGAYO GALE WARNING...A TIGHTENING PRES GRADIENT 
ACROSS THE WESTERN CARIBBEAN SEA IS EXPECTED TO INCREASE THE 
PRESENT NE 20-25 KT THROUGH THE GULF OF PAPAGAYO TO 30 KT BY 
LATE TONIGHT...AND TO GALE FORCE OF 30-35 KT BY LATE WED NIGHT 
WITH SEAS BUILDING FROM 9 TO 12 FT AT THAT TIME. MEAN ENSEMBLE 
GUIDANCE FROM THE GFS MODEL SUGGESTS THAT THIS GALE EVENT IS 
LIKELY TO OCCUR...BUT SHOULD BE RATHER SHORT-LIVED. FRESH TO 
STRONG WINDS WILL EXTEND DOWNWIND FROM THE GULF ELSEWHERE FROM 
09N-13N E OF 88W...INCLUDING THE GULF OF FONSECA AND ALSO WITHIN 
60 NM OF A LINE FROM 09N88W TO 08N90W WITH SEAS OF 8-10 FT. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...           
THE MONSOON TROUGH EXTENDS FROM 02N78W TO 03N84W TO 05N89W WHERE 
SCATTEROMETER DATA SUGGESTS A TRANSITION TO THE ITCZ CONTINUING 
TO 06N102W TO 07N112W TO 07N122W TO 08N130W TO 06N140W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM N 
OF THE TROUGH BETWEEN 78W-79.5W. SCATTERED MODERATE CONVECTION 
IS WITHIN 60 NM S OF THE ITCZ BETWEEN 93W-94.5W.

...DISCUSSION...                                                
ALOFT...A LONGWAVE TROUGH STRETCHES FROM 32N133W SSE TO 
23N130W...AND TO NEAR 11N123W. BROAD SCALE RIDGING IS NOTED ON 
EITHER SIDE OF THE TROUGH WITH A RIDGE AXIS STRETCHING FROM THE 
TEXAS PANHANDLE SEWD TO SE MEXICO...AND TO ACROSS CENTRAL 
AMERICA. 

AT THE SURFACE...THE PREVIOUS COLD FRONT THAT MOVED INTO THE FAR 
NW PORTION OF THE AREA HAS STALL ALONG A POSITION FROM 31N135W 
TO 23N140W. A TIGHT PRES GRADIENT W OF THE FRONT IS INDUCING N-
NE WINDS OF 20-25 KT THERE WITH SEAS IN THE RANGE OF 9-10 FT.
THE FRONT IS FORECAST TO WEAKEN THROUGH LATE TONIGHT WITH THE 
GRADIENT BEHIND IT SLACKENING. THIS WILL DECREASE THESE WINDS TO 
15 KT WITH SEAS JUST UNDER 8 FT. E OF THE FRONT WEAK HIGH PRES 
OF 1019 MB CENTERED NEAR 33N123W EXTENDS A RIDGE SSE TO NEAR 
11N113W. THE ASSOCIATED PRES GRADIENT IS WEAK AS INDICATED IN 
ASCAT PASSES FROM JUST AFTER 04 UTC AND NEAR 0530 UTC THAT 
DISPLAYED MOSTLY GENTLE WINDS N OF 11N AND TO THE E OF THE 
FRONT. NE-E FRESH WINDS ARE S OF 11N...EXCEPT IN REGIONS OF GAP 
WINDS AS DESCRIBED ABOVE.   

LONG PERIOD NW SWELLS DOMINATE MUCH OF THE FORECAST WATERS AND 
ARE CURRENTLY MIXING WITH THE SHORT PERIOD WIND WAVES GENERATED 
IN THE AFOREMENTIONED GAP WIND REGIONS OF TEHUANTEPEC AND 
PAPAGAYO. ADDITIONAL PULSES OF NW SWELLS RELATED TO THE 
AFOREMENTIONED COLD FRONT ARE PROPAGATING SEWD OVER AN AREA TO 
THE N OF 14N AND W OF ABOUT 122W WITH RESULTANT MAX SEAS IN THE 
9-10 FT. SWELL ENERGY IS FORECAST TO GRADUALLY DISSIPATE THROUGH 
WED ALLOWING FOR SEAS TO SUBSIDE TO LESS THAN 8 FT. 

GAP WINDS...                                                  
SEE SPECIAL FEATURES FOR DETAILS. OTHERWISE...FRESH TO STRONG N 
WINDS ARE FUNNELING THROUGH THE GULF OF PANAMA FROM THE WESTERN 
CARIBBEAN SEA REACHING TO NEAR 04N BETWEEN 79W-81W. THESE WINDS 
WILL CHANGE LITTLE THROUGH WED NIGHT WITH SEAS THERE MAXING OUT 
TO 8 OR 9 FT.

$$ 
AGUIRRE