AXPZ20 KNHC 200949

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 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 0600 UTC surface analysis and satellite imagery through 0945 UTC.


Gulf of Tehuantepec Gale Warning: Gale force 30 to 40 kt northerly winds will continue through sunrise this morning, with maximum seas of 17 ft downstream of the gulf waters near 14N95.5W just before sunrise. Winds will gradually diminish to 20 kt or less on Tue morning. 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 13N between 94W and 103W on Mon night, with a small area of 8 ft seas subsiding near 10N104W on Tue morning. Strong N winds are expected to resume on Wed afternoon, with gale conditions on Wed evening through Fri morning with max seas of 15 ft near 13N96W on Thu.


The monsoon trough extends W-SW across the southern Gulf of Panama from 08N78W to 06N90W to 08N104W where scatterometer winds indicate a transition to an ITCZ, which continues W-NW to 11N114W to 10N131W to beyond 11N140W. Scattered moderate isolated strong convection is noted within 240 nm of 11.5N121W, and along the ITCZ within 75 nm either side of a line from 09N128W to 14N140W.



See Special Features paragraph for Gulf of Tehuantepec Gale Warning.

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: Moderate NW flow will diminish to a light breeze later this morning and continue through Tue morning when moderate to locally fresh conditions will develop, and continue through early Wed. Light to moderate NW flow 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 between 09N and 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 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 front 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 over the upcoming weekend.

$$ Nelson