AXPZ20 KNHC 160938

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sat Dec 16 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 0830 UTC.


Gulf of Tehuantepec Gale Warning: A cold front has stalled across the western Gulf of Mexico this morning and is extends across the central Bay of Campeche and through the Chivelas Pass. Recent ASCAT data prior to 0400 UTC showed northerly winds to around 30 kt across the Gulf of Tehuantepec northward of 15.5N. Winds are assumed to have increased to gale force over the Gulf of Tehuantepec since this time. The cold front will weaken during the day Saturday, and begin to drift northward by afternoon. This will diminish winds funneling across the Gulf of Tehuantepec with gales expected to end by late morning, or around 1500 UTC, then continue to gradually diminish during the afternoon.


A weak trough extends from the Gulf of Panama westward to 90W. The ITCZ extends from 06.5N91W to beyond 10N140W. Scattered moderate to strong convection is noted within 120 nm N of the ITCZ between 96W and 99W, and from 110W to 113W.



Gulf of California: A cold front is moving SSE into Southern California and the offshore Pacific waters tonight and will move into the northern Gulf of California today, before stalling and dissipating over the central Gulf on Sun. Winds over the northern Gulf will shift SW early today ahead of the front, and increase to strong by afternoon as associated low pressure deepens over the lower Colorado River basin. The main issue by Sat night will be the possibility of strong W to NW winds over the northern Gulf as the low pressure shifts eastward into the Sonora Desert. While the fetch across the northern Gulf will be too limited to develop large seas, mariners should be aware of the possibility of sudden strong winds through low lying areas of Baja California Norte through early Sun. Winds diminish through early next week after the low pressure dissipates. By weeks end, another cold front sweeping across the region will force strong to near gale force winds spreading the length of the Gulf, with large seas developing.

This same cold front will move through the waters off Baja California Norte through this morning followed by strong NW winds and seas building to 8 to 12 ft late today. Seas of 8 to 10 ft will cover most of the waters beyond 60 nm of the Baja coast through early next week in NW swell. Elsewhere gentle to moderate winds and 3 to 5 ft will persist along the coast of Mexico outside of the Gulf of Tehuantepec through mid week.

To the SE, and upper level trough extends from Sinaloa SW to the tropics near 11N120W. A broad low level convergence zone extends from near 10N120W to the coast of Mexico between Cabo Corrientes and Manzanillo, where scattered moderate to strong convection is active tonight under strong upper level SW winds occurring to the SE of the upper trough. Weather across this zone is expected to remain active today and shift slightly northward along the coast tonight and Sunday ahead of the front moving across Baja California.

Please see Special Features section for more information on the latest Gulf of Tehuantepec gale warning.


Fresh winds forecast to develop across the Gulf of Papagayo today are expected to strengthen to 20-25 kt tonight. Fresh N winds will funnel into the Gulf of Panama through late this morning.


Fresh to strong tradewinds prevail from 11N to 21N west of 128W. Moderate to fresh winds prevails elsewhere over the forecast waters north of the ITCZ to 20N and west of 120W. Seas associated with a fresh pulse of NW swell are reaching 13-14 ft in the area of strong trades W of 135W. Seas will slowly subside as the swell propagates southeast the next few days. A cold front will move into the far northern waters Saturday. This will usher in another set of northerly swell into the area.