Tropical Weather Discussion
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000
AXPZ20 KNHC 271539
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1500 UTC.

...SPECIAL FEATURES...

GULF OF TEHUANTEPEC GALE WARNING...A STRONG COLD FRONT IS MOVING
ACROSS THE GULF OF MEXICO FOLLOWED BY GALE FORCE WINDS. THE
FRONT IS FORECAST TO MOVE ACROSS THE BAY OF CAMPECHE TODAY. HIGH
PRES IS BUILDING SOUTHWARD ALONG THE MEXICO COASTAL PLAINS IN
THE WAKE OF THE FRONT. THIS 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. THEN...WINDS WILL INCREASE
TO GALE FORCE...30-40 KT...EARLY 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...

THE MONSOON TROUGH EXTENDS FROM 07N93W TO 05N110W TO A 1010 MB
LOW PRES NEAR 05N107W TO 06N117W TO 05N123W. THE ITCZ CONTINUES
FROM 05N123W TO BEYOND 06N140W. SCATTERED MODERATE CONVECTION IS
NOTED FROM 03N TO 09N BETWEEN 101W AND 110W. SCATTERED MODERATE
ISOLATED STRONG CONVECTION IS FROM 05N TO 09N BETWEEN 110W AND
118W. SCATTERED MODERATE CONVECTION CAN BE FOUND FROM 07N TO 09N
BETWEEN 127W AND 130W.

DURING MARCH AND APRIL OF EACH YEAR...A DOUBLE ITCZ IS PRESENT
IN THE SOUTHERN HEMISPHERE OF THE EASTERN PACIFIC BASIN. THIS
MORNING...AN ACTIVE ITCZ IS NOTED ON SATELLITE IMAGERY ALONG
10S82W TO 06S100W TO 3.4S110W. CLUSTERS OF MODERATE TO 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 30N135W TO 25N140W. AN UPPER-
LEVEL TROUGH STRETCHING FROM 30N137W TO BEYOND 21N140W SUPPORTS
THE FRONT THAT IS FORECAST TO 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 21N W
OF 132W. 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 WEAKENING 1025 MB HIGH NEAR 30N131W. 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. AN ALTIMETER PASS PROVIDED
OBSERVATIONS OF 8-11 FT SEAS ROUGHLY S OF 13N BETWEEN 120W AND
130W LIKELY IN ASSOCIATION WITH LONG PERIOD SOUTHERLY SWELL THAT
DOMINATES MOST OF THE WATERS W OF 110W. LONG PERIOD NW SWELL ARE
ALREADY SPREADING ACROSS THE NW CORNER OF THE DISCUSSION AREA.

A STRONG PULSE OF CROSS EQUATORIAL SOUTHERLY SWELL HAS REACHED
THE COASTS OF CENTRAL AMERICA AND MEXICO...AND COULD GENERATE
STRONG AND DANGEROUS SURF ALONG THE LOCAL COASTLINES AND REEFS.
THIS SWELL EVENT IS ALSO AFFECTING THE WATERS E OF THE GALAPAGOS
ISLANDS AND IS FORECAST TO SLOWLY SUBSIDE OVER THE WEEKEND.

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.

$$
GR


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