000 AXPZ20 KNHC 160926 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 701 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 0600 UTC surface analysis and satellite imagery through 0845 UTC. ...SPECIAL FEATURES... The center of Tropical Storm Tara is located near 18.7N 104.5W at 16/0900 UTC or 20 nm SSW of Manzanillo Mexico drifting NNW or 335 degrees at 2 kt. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 50 kt with gusts to 60 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 system is forecast to move slowly toward the northwest during the next day or so. On the forecast track, the center of Tara should pass very close to the coast of southwestern Mexico, or possibly move inland, today or Wednesday. Gradual weakening is forecast as Tara interacts with the mountains of southwestern Mexico. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP2/WTPZ32 KNHC for more details. Gulf of California: Frequent gusts to gale force over the northern Gulf of California have ended as winds begin to subside. A recent ASCAT pass from around 04Z provided observations of 20 to 25 kt sustained winds over Gulf of California N of 27N. These winds are caused by high pressure over the Great Basin of the United States. The fresh to strong winds are expected to subside by Wed morning as the high moves E and weakens. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 17N85W to a 1007 mb low pressure centered over the far SW Caribbean near 16N87W, then across Central America to near the Gulf of Tehuantepec at 17N95W to 12N106W to 12N116W to 09N121W to 10N130W to beyond 08N140W. Numerous moderate and scattered strong convection is found from 04N to 07N E of 78W. Scattered moderate and isolated strong convection is seen N of a line from 07N82W to 11N92W and within 180 nm of the monsoon trough axis W of 95W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Latest scatterometer data indicate moderate to locally fresh NW winds over the offshore forecast waters W of Baja California. A ridge currently extending from 1022 mb high pressure centered near 35N127W to near the Revillagigedo Islands will maintain its influence over the offshore waters W of Baja California Peninsula. Gentle to moderate NW to N winds, and seas generally in the 4 to 6 ft range will prevail through Thu night. Seas are forecast to remain largely unaffected by Tropical Storm Tara. 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 sliding S along the eastern slopes of the Sierra Madre Mountains in Mexico and the western Gulf of Mexico. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... 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. This system retains a high chance of becoming a tropical depression during the next 5 days as it tracks WNW along the southern coast of Mexico. REMAINDER OF THE AREA... The pressure gradient between the high pressure ridge to the W of the Baja Peninsula and a cold front approaching from the W is generating 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 30N138W to 27N140W on Tue, and then from 30N138W to 27N138W to 25N140W as a weakening stationary front on Wed. Long period NW swell will follow the front and cause seas to build to between 8 and 10 ft generally N of 15N and W of 132W. Satellite-derived wind and altimeter data confirmed the presence of moderate to fresh monsoonal flow over the forecast waters N of 07N and S of the monsoon trough. 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 115W. 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 by late Wed. 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