AXPZ20 KNHC 201558

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Mon Nov 20 2017

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 1430 UTC.


Gulf of Tehuantepec Gale Warning: Gale force 30 to 40 kt northerly winds will continue until midday today, with maximum seas of 17 ft downstream of the gulf waters near 13.5N96W at sunrise earlier today, and forecast to subside during the next 24 hours. The wind speeds will diminish gradually during the next 24 hours, and to 20 knots or less just after sunrise on Tuesday. The associated NE swell will propagate SW mixing with long-period cross-equatorial swell, resulting in an area of 8 ft and greater seas of across the waters from roughly 09N to 14N between 94W and 103W on Mon in the early evening. Two areas of 8 foot sea heights will remain just after sunrise on Tuesday... one from 14N to 15.5N between 94.5W and 95.5W, and the other one from 08N to 11N between 102W and 105W. The areas of 8 foot sea heights are forecast to disappear completely late in the afternoon on Tuesday. Strong N winds are expected to resume on Wed afternoon, with gale conditions from Wed evening until midday on Friday, with maximum sea heights of 18 feet near 13.5N95.5W on Thursday morning.


The monsoon trough passes through Panama near 08N81W, to 06N90W, to 07N106W. The ITCZ continues from 07N106W to 10N120W to 10N140W. Precipitation: scattered moderate to strong within 120 nm to the S of the ITCZ between 131W and 135W, and within 120 nm to 240 nm to the N of the ITCZ between 138W and 140W. Scattered moderate to isolated strong within 180 nm to the N of the ITCZ between 121W and 130W, and within 150 nm to the S of the ITCZ between 127W and 129W. Widely scattered moderate to isolated strong from 02N to 07N from 80W eastward.

A dissipating cold front is just to the west of the area. Precipitation: widely scattered moderate to isolated strong from 22N northward from 135W westward.



Please read the Special Features paragraph for the GALE WARNING in the Gulf of Tehuantepec.

A NW to SE orientated ridge just beyond 250 nm seaward will maintain moderate NW flow W of the Baja Peninsula through mid morning when the pressure gradient will relax, supporting light northerly winds through late wed when a trough will form SW from the central Baja Peninsula to near 22N116W and continue through early Fri before filling. Expect seas in the 3 to 5 ft range through Thu building to 5 to 7 ft N of 25N late in the week.

Gulf of California: The earlier moderate NW flow has been diminishing this morning. This situation will continue, until reaching light breezes from later today until Tue morning. Moderate to locally fresh conditions will develop,again, on Tuesday morning, and continue until early Wed. Light to moderate NW flow is expected on Thu and Fri, becoming light and variable on Fri night.


Gulf of Papagayo: Moderate to locally fresh NE drainage winds are forecast during the overnight hours tonight, then light drainage flow expected during the overnight hours through Thu night, with fresh to locally strong nocturnal drainage possible on Fri and Sat nights.

Light and variable winds, and 3 to 5 ft seas, are expected elsewhere to the N of the monsoon trough which has been meandering from 09N to 11N, while moderate to locally fresh southerly winds, and 4 to 7 ft seas, are forecast S of the monsoon trough this week.


A NE to SW aligned ridge will meander from 32N125W to beyond 20N140W for the next several days. Strong to occasionally near gale force southerly winds, that are currently across the waters N of 28N W of 138W, will spread E across the waters generally W of a line from 32N130W to 22N140W through late tonight before the pressure gradient relaxes. Associated seas are expected to build to 8 to 12 ft across the waters S of 30N, while 10 to 14 ft seas are forecast from 30N to 32N. A series of cold fronts will approach, but stall just W of 140W through Tue night. Model guidance is suggesting a cold front will arrive at 32N140W on Wed, and stall from 32N136W to 23N140W on Thu, with seas building 12 to 17 ft W of the front through Thu.

Moderate anticyclonic flow expected across the tropics N of the ITCZ and W of 120W through the middle of next week, with seas of 4 to 7 ft. Long period NW swell will propagate E across the discussion waters W of 120W from mid to late week, and subside during the upcoming weekend.

$$ mt