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Eastern Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 280248
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
0405 UTC SAT MAR 14 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0130 UTC. 

...SPECIAL FEATURES...  

GULF OF TEHUANTEPEC GALE WARNING...A STRONG COLD FRONT HAS MOVED 
ACROSS THE W HALF OF THE GULF OF MEXICO FOLLOWED BY GALE FORCE 
WINDS IN THE WESTERN BAY OF CAMPECHE. THE FRONT IS FORECAST TO 
MOVE ACROSS THE E BAY OF CAMPECHE AND INTO THE YUCATAN PENINSULA 
TONIGHT. HIGH PRES BUILDING SOUTHWARD ALONG THE MEXICO COASTAL 
PLAINS IN THE WAKE OF THE FRONT WILL TIGHTEN THE PRESSURE 
GRADIENT ACROSS SOUTHERN MEXICO RESULTING IN STRONG NORTHERLY 
WINDS QUICKLY BLASTING ACROSS THE CHIVELAS PASS AND THROUGH THE 
GULF OF TEHUANTEPEC EARLY THIS AFTERNOON AND EVENING...AND 
INCREASE TO GALE FORCE BEFORE SUNSET. WINDS THERE ARE EXPECTED 
TO INCREASE TO 35-40 KT THIS EVENING WITH BUILDING SEAS TO 16-17 
FT BY TONIGHT. WINDS WILL LIKELY REMAIN NEAR GALE FORCE SAT 
NIGHT BEFORE SLOWLY DIMINISHING BELOW GALE FORCE SUNDAY 
MORNING...WITH WIND AND SEAS THEN SUBSIDING QUICKLY SUN 
AFTERNOON AND EVENING. 

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

A WEAK TROUGH EXTENDS FROM 07N94W TO 05N112W TO 04N120W. THE 
ITCZ EXTENDS FROM 05N122W TO 10N137W TO BEYOND 06.5N140W. 
SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM S 
AND 270 NM N OF TROUGH BETWEEN 101W AND 115W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION NOTED WITHIN 180 NM N OF ITCZ W OF 
125W. 

DURING LATE WINTER TO EARLY SPRING SEASONS...FROM LATE FEBRUARY 
TO EARLY APRIL OF EACH YEAR...A DOUBLE ITCZ CAN BE PRESENT 
ACROSS THE EASTERN PACIFIC...ONE ON EACH SIDE OF THE EQUATOR. 
TODAY THROUGH THIS EVENING...AN ACTIVE SOUTHERN ITCZ WAS NOTED 
ON SATELLITE IMAGERY ALONG 08.5S82W TO 07S90W TO 03S110W. 
CLUSTERS OF MODERATE ISOLATED STRONG CONVECTION ARE ALONG THE 
AXIS.

...DISCUSSION...                                                

A COLD FRONT IS WEAKENING ACROSS THE NW CORNER OF THE FORECAST 
AREA AND CURRENTLY EXTENDS FROM 30N131W TO 27N134.5W TO 25N140W. 
AN UPPER-LEVEL TROUGH STRETCHING FROM 30N134W TO 08N149W 
SUPPORTS THE FRONT...BUT THE FRONT WILL GRADUALLY STALL SAT AND 
DISSIPATE IN ABOUT 12-24 HOURS. NW SWELL IN THE WAKE OF THE 
FRONT HAS RAISED SEAS TO AROUND 9 FT. AS THE FRONT 
DISSIPATES...SEAS WILL SUBSIDE TO LESS THAN 8 FT BY SAT MORNING 
ACROSS THE NW PART OF THE REGION. HIGH PRES BEHIND THE FRONT 
WILL MOVE NE TO A POSITION NEAR 35N135W SAT AFTERNOON WHILE 
STRENGTHENING. THIS WILL BRING AN INCREASE IN THE TRADE WIND 
FLOW ON SAT MORNING...PARTICULARLY FROM 15N TO 20N W OF 134W. 
THESE FRESH TO STRONG WINDS WILL ALLOW SEAS TO BUILD 8 TO 
10 FT. 

A SURFACE RIDGE COVERS THE AREA N OF 16N W OF 115W...CENTERED ON 
A COLLAPSING 1025 MB HIGH NEAR 30N132W...JUST AHEAD OF THE COLD 
FRONT. SOUTH OF THE RIDGE...THE PRES GRADIENT BETWEEN THE HIGH 
AND LOWER PRES ALONG THE ITCZ IS PROMOTING MODERATE TO LOCALLY 
FRESH NE TRADEWINDS S OF 22N W OF 120W...WHERE SEAS ARE 7-9 FT. 
ALTIMETER OBSERVATIONS FROM ACROSS THE REGION DURING THE PAST 24 
HOURS SHOW THAT COMPUTER MODEL WAVE FORECASTS HAVE BEEN A FEW 
FEET LOW...AND THAT SEAS OF 9-11 FT DOMINATE THE WATERS S OF A 
LINE FROM 13N91W TO 19N120W...ASSOCIATION WITH VERY LONG PERIOD 
SOUTHERN HEMI SWELL. THE PEAK OF THIS SWELL WILL REACH THE 
CENTRAL AMERICAN AND MEXICAN COASTLINES THROUGH BAJA CALIFORNIA 
TONIGHT THROUGH SATURDAY AND GENERATE VERY LARGE AND POWERFUL 
WAVES...AND DANGEROUS CONDITIONS WITHIN THE SURF ZONE.  

GAP WINDS...

GULF OF PAPAGAYO...EXPECT INCREASING WINDS ACROSS THIS GAP WIND 
REGION BY EARLY SUN MORNING AS HIGH PRES BUILDS ACROSS THE NW 
CARIBBEAN AND NORTHERN CENTRAL AMERICA.  

$$ 
STRIPLING


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Page last modified: Saturday, 28-Mar-2015 02:48:11 UTC