AXPZ20 KNHC 190242

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0242 UTC Thu Oct 19 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 0000 UTC surface analysis and satellite imagery through 0215 UTC.


Gulf of Tehuantepec Gale Warning: Gale force winds continue over the Gulf of Tehuantepec and will persist through tonight, diminishing after sunrise Thursday once the pressure gradient relaxes. Seas are up to 14 ft but will gradually subside through Thursday. Expect winds to pulse to fresh to strong, especially during the overnight hours, through the upcoming weekend, with another gale force wind event possible early next week as the gradient tightens once again.


A tropical wave is N of 04N along moving W at 10 to 15 kt. Scattered moderate and isolated strong convection N of 05N and E of the tropical wave axis.


The monsoon trough axis extends from 09N74W to 10N85W to 07N103W to 08N117W. The intertropical convergence zone axis extends from 08N117W to 10N125W to 08N140W. Scattered moderate and isolated strong convection is within 75 NM S of the axis between 90W and 93W, from 08N to 09N between 96W and 100W, from 08N to 10N between 118W and 120W, and within 120 nm N of the axis between 135W and 139W.



Please see the Special Features section above for information about the ongoing Gulf of Tehuantepec gale event.

A surface ridge extends SE into the waters off Baja California, producing mainly gentle to moderate NW to N winds and seas of 5 to 7 ft. The ridge will remain in place during the next few days with little change in winds and seas over the offshore waters aside from the Gulf of Tehuantepec region as described above. By Friday evening a weakening cold front and accompanying set of large NW swell will propagate into the waters W of Baja California, causing seas to build to between 8 and 12 ft across the waters N of 26N. Seas will continue to build to 14 to 16 ft in NW swell N of 27N Friday night. This swell event will continue propagating SE across the remaining offshore forecast waters W of Baja on Saturday. Also on Friday, expect increasing winds of 20 to 25 kt over the waters adjacent to Baja California Norte as high pressure building in the wake of the front tightens the pressure gradient over the northern forecast waters. These winds will diminish on Saturday.

Mainly light and variable winds are expected over the Gulf of California through Friday night. Winds will become northerly and increase to moderate to fresh in the northern Gulf Saturday, then increasing to fresh to strong Sunday as the local pressure gradient tightens. The fresh to strong winds will then spread southward through the Gulf into early next week. Seas will stay mainly 2 ft or less, except for higher seas of 3 to 4 ft at the entrance to the gulf in SW swell, subsiding to 2 to 3 ft by Friday. The fresh to strong winds this weekend will build seas to 4 to 7 ft across the majority of the basin by early next week.


Moderate to fresh offshore winds will develop across the Papagayo region each night through tonight, accompanied by seas of 5 to 7 ft. Otherwise, light and variable winds and seas of 4 to 6 ft in SW swell will prevail N of the monsoon trough, while gentle to moderate SW to W winds and seas of 5 to 7 ft in SW swell will prevail S of the trough.

Long period S to SW swell will reach the area between Ecuador and the Galapagos Islands Thursday evening through Friday evening, building seas to 7 to 8 ft on Friday.


Gentle to moderate winds are noted across the northern forecast waters under the influence of a ridge being weakened by an approaching cold front. Seas continue to subside across most of the region W of 110W. An area of 8 ft seas primarily in SE swell is present across the SW corner. A new set of long period S to SW swell is forecast to cross the Equator on Thursday and propagate across the far southern waters with resultant combined seas building back to 8 to 9 ft in the SW corner and far S central waters through Friday. The swell will then decay with seas subsiding to less than 8 ft during the upcoming weekend.

Models agree in bringing the cold front to the far NW corner of the discussion area by Thursday evening in a weakened state. A significant swell event will follow the front as it weakens and dissipates while moving across the area N of 28N. Seas will build to 10 to 17 ft over the NW waters Thursday night and Friday. The seas will spreading across all of the waters N of 08N and W of 110W by Fri evening, then across all of the waters N of the Equator and W of 108W by Sunday night. Seas of 8 ft or greater will reach all the way to 110W by early Sunday then continue to propagate SE, but begin to gradually decay thereafter through early next week.

$$ Lewitsky