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AXPZ20 KNHC 272214
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI MAR 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2130 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 05N97W TO 04.5N120W. THE ITCZ EXTENDS FROM 04.5N122W TO BEYOND 06N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS NOTED FROM 03N TO 07N BETWEEN 98W AND 116W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS NOTED FROM 07N TO 13N W OF 125W.

DURING LATE WINTER TO EARLY SPRING SEASONS...FROM MARCH TO APRIL OF EACH YEAR...A DOUBLE ITCZ CAN BE PRESENT ACROSS THE EASTERN PACIFIC...ONE ON EACH SIDE OF THE EQUATOR. THIS MORNING AND AFTERNOON...AN ACTIVE ITCZ WAS NOTED ON SATELLITE IMAGERY ALONG 08.5S82W TO 07S89W TO 2.5S108W. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE ALONG THE AXIS.


...DISCUSSION...

A COLD FRONT IS WEAKENING ACROSS THE NW CORNER OF THE FORECAST AREA AND CURRENTLY EXTENDS FROM 30N133W TO 25N140W. AN UPPER- LEVEL TROUGH STRETCHING FROM 32N134W TO BEYOND 12N145W 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 IN ABOUT 24 HOURS WHILE STRENGTHENING. THIS WILL BRING AN INCREASE IN THE TRADE WIND FLOW ON SAT MORNING...PARTICULARLY FROM 14N TO 20N W OF 134W. THESE FRESH TO STRONG WINDS WILL ALLOW SEAS TO BUILD TO AROUND 9 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 20N W OF 115W...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 11N91W TO 17N122W...ASSOCIATION WITH VERY LONG PERIOD SOUTHERN HEMI SWELL. THE PEAK IN THIS SWELL WILL REACH THE CENTRAL AMERICAN AND MEXICAN COASTLINES THROUGH BAJA CALIFORNIA ON SATURDAY TO 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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