AXPZ20 KNHC 202158

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2158 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 1800 UTC surface analysis and satellite imagery through 2100 UTC.


The monsoon trough extends from 08N78W to 06N105W. Intertropical convergence zone extends from 06N105W to 12N140W. Scattered moderate convection is observed within 60 nm of the intertropical convergence zone between 125W and 140W.



An earlier scatterometer satellite pass indicaated strong gap winds still active into the Gulf of Tehuantepec, with a 60 nm wide plume extending as far as 450 nm offshore. Seas are estimated to be 13 ft in the area of strong winds. The strong high pressure north of the area that has been supporting gale force winds in Tehuantepec is weakening, allowing winds to diminish through early Tue. Seas to 8 ft will linger well offshore with the assistance of long period southwest swell. These seas will subside through late Tue as the swell decays. The window of relative diminished winds will be short, as another front moving through the Gulf of Mexico will initiate a new round of strong winds into the Gulf of Tehuantepec late Wed, reaching gale force Wed night with seas building 12 to 17 ft.

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.

$$ Christensen/MT