Tropical Weather Discussion
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AXPZ20 KNHC 201600

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Sun May 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
1500 UTC.


The monsoon trough extends from 09N73W TO 08N83W TO 11.5N102W TO
09N127W. The ITCZ continues from 09N127W to beyond 08N140W.
Widely scattered moderate to strong convection is noted from
04.5N to 11N between 83W and 108W. Scattered moderate to strong
convection is noted from 02N to 07N e of 80W, from 07N to 12N
between 110W and 115W, and within 210 nm N and 150 nm S of
axis between 114W and 136W.



Fresh NW winds continue across the offshore waters of Baja
California this morning, and are maintaining seas of 5 to 7 ft
across these waters. Generally light to gentle variable winds
are noted over the Gulf of California, with slightly stronger
westerly gap winds near low level areas over the peninsula.
Light NW to W winds are noted farther south across the Mexican
coastal waters. The main forecast issue ahead will be the onset
of long period SW swell in excess of 8 ft moving into the open
Pacific waters off Mexico late today. Large SW swell will reach
waters of southern Mexico by early Mon, and into the open waters
off Baja California Mon night and Tue, mixing with NW swell off
Baja California Norte. Seas across the region will build to 7-8
ft in this mixed swell by Mon afternoon and spread into the
mouth of the Gulf of California early Tue.

In the Gulf of Tehuantepec, light winds will persist into Tue,
then moderate to fresh gap winds will pulse briefly as sharp
troughing moves through southeast Mexico.


Gulf of Papagayo: Light to gentle winds will dominate the gulf
the entire forecast period as weak pressure will prevail across
Central America. Seas of 5-8 ft are forecast over the Gulf and
nearby waters through mid week due to strong long period SW

Gulf of Panama: Gentle to moderate S to SW winds are forecast
through Wed with seas of 4-6 ft in long period SW swell,
building to 5-7 ft on Mon as the swell reaches the coasts of
Panama and Colombia.

Elsewhere, gentle to moderate SW winds are expected to the south
of the monsoon trough with light to gentle variable winds north
of trough as a weak pressure pattern remains over Central
America. Seas of 6-7 ft in building long period SW swell west of
the Galapagos Islands are expected to propagate northward
tonight through late Tue next week, building 8 to 9 ft tonight
through Mon.


A ridge extends from 1026 high pressure centered near 32N141W
through the Revillagigedo Islands. The ridge is supporting
moderate to fresh trade winds farther south into the deep
tropics north of the monsoon trough. Convergence of the moderate
to fresh NE trades with light to moderate SW flow on the south
side of the monsoon trough is supporting clusters of showers and
thunderstorms near the monsoon trough west of 114W.
Various recent altimeter satellite passes indicate 4 to 6 ft seas
north of 20N where winds are lighter, and 7 to 9 ft seas in the
trade wind belt between the monsoon trough as far north as 20N
as SW swell begins to move into the region.

The ridge will build north of 20N through early in the week,
enhancing trade winds especially near a developing low pressure
along the monsoon trough near 10N134W. A new round of SW swell
in excess of 8 ft is noted south of 05N, propagating northward.
This will overtake the region mainly east of 130W late today
through Tue. Looking ahead, the upper pattern will amplify by
mid week, supporting development of another weak low along the
monsoon trough west of 125W.

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