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Tropical East Pacific Satellite

NHC Tropical Weather Discussion (East Pacific)

National Hurricane Center – Tropical Weather Discussion (East Pacific)

NHC East Pacific Tropical Weather Discussion

AXPZ20 KNHC 200930
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
645 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 0600 UTC surface analysis and satellite imagery through
0845 UTC.


A cold front stalling over the northern Gulf of Mexico is ushering in reinforcing high pressure over the Gulf of Mexico. This has tightened the pressure gradient across the Isthmus of Tehuantepec and causing very strong winds over the Gulf of Tehuantepec. N winds there are currently peaking around 40 kt and
will produce 10 to 15 ft seas as far downstream as 11N97W. 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 08N81W to 06N92W. The ITCZ continues from 06N92W to 07N101W to 07N118W to 06N132W to beyond 06N140W. Scattered moderate and isolated strong convection is present within 60 nm either side of a line from 08N75W to 03N79W,
from 04N to 08N between 94W and 98W and from 06N to 12N between 111W and 126W. Isolated moderate and strong convection is found from 04N to 08N between 81W and 85W.



Fresh to strong NW winds and seas of 5 to 8 ft are evident in the offshore waters. The weakening cold front that was crossing Baja California Norte and the adjacent waters has dissipated. 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 cause seas to build along the length of the peninsula through tonight. Winds and seas
W of the peninsula will 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: Pulsing fresh to strong nocturnal NE to E winds are expected across and downstream of the Gulf of Papagayo through at least Tue night with seas peaking each night between 8
and 9 ft.

Gulf of Panama: Fresh northerly winds and seas of 5 to 7 ft are
evident across the Gulf of Panama this evening. Winds will become moderate Fri through Sun, with seas generally running 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… High pressure measuring 1030 mb is centered 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 95W and 120W this morning. Seas will subside to 8 ft or less across most of this area today by midday. 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 set of NW swell by Monday night. $$