Tropical Weather Discussion
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000
AXPZ20 KNHC 262218
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU MAR 12 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...

A STRONG COLD FRONT HAS MOVED INTO THE NW GULF OF MEXICO THIS
AFTERNOON AND WILL MOVE SE AND REACH THE BAY OF CAMPECHE
TONIGHT. GALE FORCE WINDS ARE EXPECTED BEHIND THE FRONT ALONG
THE MEXICAN COAST STARTING FRI MORNING. 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 BY EARLY FRI AFTERNOON..THEN
INCREASE TO GALE FORCE BY FRI AFTERNOON. WINDS ARE EXPECTED TO
INCREASE FURTHER TO AROUND 40 KT FRI NIGHT WITH SEAS BUILDING TO
17 FT BY EARLY SAT. WINDS WILL LIKELY REMAIN NEAR GALE FORCE SAT
NIGHT BEFORE SLOWLY DIMINISHING BELOW GALE FORCE MONDAY
MORNING...WITH WIND AND SEAS THEN SUBSIDING QUICKLY SUN
AFTERNOON.

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

A WEAK TROUGH EXTENDS FROM 06N90W TO 05N102W TO 05N113W...WHERE
SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS NOTED WITHIN
120 NM EITHER SIDE OF TROUGH FROM 06N90W TO 05N102W. THE ITCZ
EXTENDS FROM 05N113W TO 08N135W TO 07N140W. SCATTERED MODERATE
TO STRONG CONVECTION WAS NOTED FROM 05N TO 12N BETWEEN 116W AND
129W.

...DISCUSSION...

AN UPPER TROUGH IS JUST W OF THE FAR NW PORTION OF THE
DISCUSSION AREA...ALONG ABOUT 144W...AND IS SUPPORTING A COLD
FRONT THAT HAS JUST ENTERED THE AREA NEAR 29N139W THIS
AFTERNOON. NW SWELL BEHIND THE FRONT HAS RAISED SEAS 8 TO 9
FT...AND WILL GENERALLY STAY IN SYNCH WITH THE FRONT AS IT MOVES
SE AND WEAKENS OVER THE NEXT 24 HOURS.

A BROAD UPPER RIDGE IS GENERALLY S OF 24N AND BETWEEN 100W AND
130W...AND IS PART OF A LOW LATITUDE BLOCKING PATTERN OF RIDGE-
TROUGH-RIDGE S OF 20N SPANNING BETWEEN THE CENTRAL CARIBBEAN AND
100W. THIS UPPER TROUGH IS SUPPORTING CONVECTION ASSOCIATED WITH
THE WEAK TROUGH ACROSS E PORTIONS DESCRIBED ABOVE. N OF THE
BROAD UPPER RIDGE...A DEEP LAYERED UPPER TROUGH EXTENDS FROM THE
CENTRAL U.S. SW ACROSS W TEXAS AND NW MEXICO TO 26N120W.

AT THE SURFACE...A RIDGE COVERS THE AREA N OF 14N W OF
105W...CENTERED ON A WEAKENING 1024 MB HIGH NEAR 33N128W. THE
PRES GRADIENT BETWEEN THE HIGH AND LOWER PRES ACROSS BAJA
CALIFORNIA HAS WEAKENED IN THE PAST 24 HOURS...WITH NWLY WINDS
DIMINISHING THERE. THIS IS ALLOWING FOR A SLOW SUBSIDING TREND
IN THE NW SWELL MOVING FROM OFFSHORE OF CALIFORNIA SOUTHWARD
ACROSS THE WATERS OFFSHORE OF BAJA CALIFORNIA...WHERE SEAS WERE
7-8 FT THIS AFTERNOON. THIS NW SWELL WILL CONTINUE TO SUBSIDE
TONIGHT...WITH SEAS EXPECTED 6-7 FT BY FRI MORNING. 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 7-10 FT THIS AFTERNOON IN
MIXED NE WIND SWELL AND BUILDING S SWELL. THE HIGH IS EXPECTED
TO COLLAPSE OVERNIGHT AS THE COLD FRONT APPROACHES 135W...WITH
STRONGER HIGH PRES BUILDING ACROSS THE NW HALF OF THE AREA OVER
THE WEEKEND. THIS WILL STRENGTHEN THE TRADEWINDS MODESTLY...WITH
AN AREA OF 20-25 KT TRADES EXPECTED FROM 13N TO 20N W OF 136W BY
FRI AFTERNOON AND GENERALLY CONTINUING THROUGH SAT.

ELSEWHERE E OF 115W...WINDS AND LIGHT TO MODERATE...WITH NO
SIGNIFICANT GAP WINDS OCCURRING. A STRONG PULSE OF CROSS
EQUATORIAL S SWELL HAS REACHED THE COASTS OF CENTRAL AMERICA AND
MEXICO TODAY...AND WILL BUILD DURING THE NEXT 24 HRS TO GENERATE
STRONG AND DANGEROUS SURF ALONG THE LOCAL COASTLINES AND REEFS.
SEAS TO 8 FT AND GREATER WILL REACH WITHIN 200 NM OF THE CENTRAL
MEXICAN COAST ON FRIDAY...AND ALSO PASS BETWEEN THE GALAPAGOS
AND ECUADOR. THIS SWELL EVENT WILL SLOWLY SUBSIDE OVER THE
WEEKEND.

$$
STRIPLING


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