AXPZ20 KNHC 160405

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
307 UTC Tue Oct 16 2018

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 0245 UTC.


The center of Tropical Storm Tara is located near 18.4N 104.6W at 16/0300 UTC or 60 nm S of Manzanillo Mexico drifting NW or 325 degrees at 2 kt. Estimated minimum central pressure is 1000 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Numerous moderate and scattered strong convection is noted within 60 nm in the NW and within 30 nm in the SE semicircle. Scattered moderate and isolated strong convection is seen elsewhere from 17.5N to 20N between 103.5W and 106W. The future track of Tara is highly uncertain. Tara is forecast to move slowly toward the northwest and then west at a similar speed during the next couple of days. The center of Tara should pass very close to the coast of southwestern Mexico, or possibly move inland, on Tuesday and Wednesday. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP2/WTPZ32 KNHC for more details.

Gulf of California: A Gale Warning remains in effect for the northern Gulf of California until around midnight. A recent ASCAT pass provided observations of near gale force sustained winds across the northern Gulf of California. These winds are the result of robust high pressure building over the Great Basin of the United States. Fresh to strong winds are expected to persist across much of the Gulf through early Wed.


The monsoon trough extends from 16N84W to a 1006 mb low pressure centered over the SW Caribbean near 15N85W, then across Central America to near the Gulf of Tehunatepec at 17N96W to 09N122W to 11N129W to beyond 08N140W. Numerous moderate and scattered strong convection is found within 60 nm either side of a line from 08N82W to 13N85W to 19N99W. Scattered moderate and isolated strong convection is seen elsewhere from 10N to 17N between 90W and 98W. Scattered moderate and isolated strong convection is occurring within 120 nm either side of a line from 13N99W to 11N119W and from 07N to 11N between 128W and 140W.



Latest scatterometer data indicate moderate to locally fresh NW winds N of Punta Eugenia, and gentle to moderate NW to N winds elsewhere across the offshore forecast waters W of Baja california. A ridge will continue to dominate the offshore waters W of Baja California Peninsula producing mainly gentle to moderate NW to N winds, and seas generally in the 4 to 6 ft range, with the exception of moderate to fresh winds N of Punta Eugenia tonight through Tue night. Seas are forecast to increase a foot or so by the end of the forecast period as mixed swell generated by Tropical Storm Tara arrives.

Gulf of Tehuantepec: Next gap wind event is forecast to start early on Wed with seas rapidly building to 10 ft by Wed afternoon. This event will be associated with a ridge building behind a cold front across the eastern slopes of Sierra Madre Mountains in Mexico and the western Gulf of Mexico.


Moderate to fresh SW monsoonal flow will continue across the region through Tue, with showers and thunderstorms expected to continue along the Pacific coast of Central America. Long period cross-equatorial SW swell will maintain 5 to 8 ft seas across the forecast area during this time frame. By Tue night and Wed, marine guidance suggests an increase in winds and seas across the offshore waters from northern Costa Rica to Guatemala. This appears to be associated with an area of low pressure forecast to develop a couple of hundred miles south of Guatemala and the southeastern coast of Mexico around mid-week.


A 1021 mb high pressure located near 30N127W extends a ridge across the northern forecast waters. The pressure gradient between the ridge and a cold front approaching from the W is resulting in fresh to strong southerly winds across the far NW waters, mainly NW of a line from 30N138W to 26N140W. Moderate to locally fresh trades are noted S of 15N and N of the monsoon trough W of 125W. The cold front is forecast to reach a position from 0N138W to 27N140W on Tue, and from 30N138W to 27N138W to 25N140W on Wed, when it is forecast to become stationary. Long period NW swell will follow the front building seas of 8-10 ft.

Satellite-derived wind and altimeter data confirmed the presence of moderate to fresh monsoonal flow across much of the forecast waters. Winds increase near the convection. An area of 7 to 9 ft in long period SW swell is noted south of the monsoon trough and mainly between 100W and 120W.

Looking ahead, an area of low pressure is forecast to develop a couple of hundred miles south of Guatemala and the southeastern coast of Mexico around mid-week. Environmental conditions are forecast to be conducive for development, and a tropical depression is likely to form by late week while the system moves west-northwestward near the southern coast of Mexico. The latest Tropical Weather Outlook gives this system a high change of tropical cyclone formation through 5 days.

$$ CAM