Tropical Weather Discussion
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000
AXPZ20 KNHC 201607
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Fri Apr 20 2018

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
1515 UTC.

...SPECIAL FEATURES...

Minimal gale force winds continue across and downstream of the
Gulf of Tehuantepec to near 12.5N96.5W this morning. Winds will
further diminish throughout the day and fall below gale force by
around noon today and then to 20-25 kt within about 90 nm of the
coast by this evening. Supporting high pressure across the
southern U.S. behind A stalled cold front over the northern Gulf
of Mexico is shifting slowly eastward, and is allowing the
pressure gradient across the Isthmus of Tehuantepec to gradually
weaken. Winds will become light and variable and seas will
subside below 8 ft by Sat evening.

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

A surface trough extends from 07.5N76W TO 05N90W TO 08N106W TO
06N118W. The ITCZ continues from 06N118W TO 07.5N124W  to beyond
06.5N140W. Scattered moderate to strong convection is present
from 04N TO 07.5N E OF 85W to the coast of Colombia, within 150
nm of the trough between 91W and 109W, and from 05N to 11.5N
between 100W and 128W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Fresh to strong NW winds and seas of 5 to 8 ft prevail across
the offshore waters of Baja California. The weakening cold front
that was crossing Baja California Norte and the adjacent waters
has dissipated overnight. Fresh to strong NW winds can be
expected over the waters W of Baja California today as a tight
pressure gradient sets up between a ridge building in behind the
front over the northern waters and lower pressure over the SW
United States and NW Mexico. NW swell following the front will
maintain seas at 5-8 ft through tonight. Winds and seas W of the
peninsula will then diminish Sat through Mon as the high to the
N weakens in response to low pres and an attendant cold front
approaching from the NW. Moderate NW winds over the Gulf of
California will strengthen today and become fresh over the
northern and central Gulf. Winds will subside over the Gulf Sat
and Sun as the high weakens slightly and the area of low
pressure moves east.

See the special features section for details concerning the gale
force winds affecting the Gulf of Tehuantepec.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Gulf of Papagayo: Fresh NE to E winds across the region area
expected to pulse at night through morning to 20-25 kt across
and downstream of the Gulf of Papagayo through at least Tue
night with seas peaking each night between 7 and 9 ft.

Gulf of Panama: Fresh northerly winds and seas of 5 to 7 ft in
SW swell prevail across the Gulf of Panama and offshore of
Panama and Colombia to 250 nm this morning. Very active
convection overnight has become concentrated from 04N TO 07.5N E
OF 85W to the coast of Colombia, and is likely producing strong
gusty winds and very rough seas to 8 ft or greater this morning.
Northerly winds will become moderate today through Sun across
the Gulf of Panama, while farther offshore and SW, gentle to
moderate SW winds will develop. Seas will generally run between
4 and 6 ft.

Elsewhere, mainly light to gentle winds are expected S of 05N
through Tue. Cross-equatorial swell will mix with residual swell
downwind from Papagayo through Tue, and maintain seas in this
area between 5 and 7 ft. Elsewhere seas will subside to 3-5 ft
by Sun as long period SW swell from the Southern Hemisphere
decay.

REMAINDER OF THE AREA...

A 1029 mb high pressure center was located north of the forecast
area near 36N132W. The high ridges SE across the northern
forecast waters to near the Revillagigedo Islands. The ridge has
been weakened temporarily by cold front that dissipated
overnight over the NE waters. The high will be reinforced by
stronger high pressure building in behind the dissipated cold
front today through Sat.

Cross equatorial SW swell moving into the southern forecast
waters will affect the waters near the equator between 98W and
120W this morning. Seas will subside to 8 ft or less across most
of this area today by this evening. Another round of SW swell
could cause waters near the equator to build to 8 ft or above by
early next week.

The pressure gradient between the ITCZ and building high
pressure to the north will support fresh to strong NE trades N of
the ITCZ generally between 10N and 15N W of 125W through
Saturday. The combination of these winds, NW swell and SW swell
will support combined seas of 8 to 12 ft over these waters into
Saturday, expanding N to 30N by Sunday as NW swell propagates
into the northern waters. The swell will begin to decay below 8
ft Sunday night before becoming reinforced by another pulse of
NW swell by Monday night.

$$
Stripling



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