AXPZ20 KNHC 250929

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sat Nov 25 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 0900 UTC.


A ship crossing now the Gulf of Tehuantepec is reporting sustained winds of 24 kt. Winds will diminish to 20 kt or less late this morning, and increase again to 20 to 25 kt tonight. The next Gulf of Tehuantepec gale event is forecast to begin by mid-day Sunday. As a result, a gale warning has been issued. A building ridge across the western Gulf of Mexico and the eastern slopes of the Sierra Madre Mountains will allow northerly winds to begin to spill through the Isthmus of Tehuantepec and across the Gulf of Tehuantepec by early Sun morning. The latest computer model guidance is suggesting another 30 to 40 kt gap wind event on Sun night, with seas building to 16 or 17 ft. Gale conditions will persist on Mon, with the area of fresh to strong winds extending downwind of the gulf to near 10N99W. Winds should diminish below gale force by late Tue morning.


The monsoon trough extends from 09N84W to 07N90W to 09N95W to 08N105W. The ITCZ continues from 08N105W to 10N120W to 11N130W to beyond 10N140W. Scattered moderate convection is occurring within about 75 nm south of ITCZ axis between 110W and 133W. Similar convection is noted from 13N to 16N between 110W and 113W.



See Special Features paragraph above for information on the Gulf of Tehuantepec Gale Warning.

A weak ridge continues across the offshore waters of Baja California producing mainly light and variable winds. Seas are in the 4 to 7 ft range in NW swell. Seas are forecast to subside some today into Sun. Another set of long-period NW swell in the form of 7 to 9 ft seas will reach 30N120W by Mon morning, and spread S across the offshore forecast waters W of Baja with 8 to 13 ft seas at 17 to 19 seconds Mon night and Tue.

Winds will increase very slightly over the weekend, mainly due to daytime heating. However early on Monday, stronger high pressure will begin to build across the region from the NW and act to increase NW winds to 20-25 kt across the waters N of 26N, including the Sebastian Vizcaino Bay, by the late afternoon and evening hours.

Gulf of California: light southerly winds are noted across the entire Gulf. The pressure gradient will relax further, with light and variable winds expected through Mon. Strong to near gale force NW flow is expected to develop across the northern Gulf Mon night, with fresh to locally strong winds spreading southward across the central and southern portions of the Gulf through Tue night. Seas will quickly build to near 8 ft across the northern Gulf by Tue morning and then 5-7 ft through central portions by Tue night.


Fresh to locally strong NE winds are occurring across and downstream of the Gulf of Papagayo early this morning, with the assistance of the nocturnal drainage flow. Seas have built to 6- 7 ft downstream of the gulf. Expect a typical nocturnal maximum of around 25 kt across the region through early Tue morning, diminishing to 15-20 kt by mid afternoon. Seas will maximize to around 7 ft each morning near sunrise, and will likely build to 8 ft early Monday morning, and early Tue morning. Moderate to locally fresh NE winds are expected across the Gulf of Fonseca each night through Tue.

Light to gentle N to NE winds, and 3 to 5 ft seas are expected elsewhere through Sun night to the N of the monsoon trough which has been meandering between 09N and 11N. Moderate southerly winds, and 4 to 6 ft seas, are forecast S of the monsoon trough.


A cold front is over the NW waters and extends from 30N136W to 21N140W while a reinforcing or secondary cold front is approaching 30N140W. Fresh to strong S to SW winds are noted N of 27N W of 135W. The secondary front will reach the far NW corner of the area this morning followed by fresh to strong NW winds and seas up to 10 or 11 ft. The fronts are forecast to merge on Sun as they move eastward and approach 125W.

The most recent altimeter data indicated seas of 8 to 11 ft N of 20N W of 128W, and seas of 8 to 10 ft from 12N to 20N W of 128W. Seas of 8 ft or greater in long period NW swell are propagating across the waters NW of a line from 20N125W to 05N140W. This swell event will begin to subside, with seas 8 ft or greater mainly S of 14N and W of 125W by tonight. At that time, another set of NW swell is expected to reach the far NW waters.

$$ GR