000 AXPZ20 KNHC 122154 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2013 UTC Sun Nov 12 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 1800 UTC surface analysis and satellite imagery through 2130 UTC. ...SPECIAL FEATURES... GULF OF TEHUANTEPEC GALE: Gale-force winds continue over the Gulf of Tehuantepec. A surface ridge along the Sierra Madre Oriental is combining with an area of low pressure over the western Caribbean to maintain a tight pressure gradient over the Isthmus of Tehuantepec. Model guidance suggests that the current synoptic pattern will remain favorable for gale-force N to NE gap wind flow until early Wednesday morning. Wind speeds will peak between 35 and 40 kt tonight through Mon night. Sea heights will range from 10 feet to 13 feet today, building to 16 feet tonight. This gap wind event will wind down on Wed and Thu as ridging shifts E over the Gulf of Mexico and the area of low pressure over the Caribbean migrates NE. POSSIBLE TROPICAL CYCLONE: A 1008 mb surface low is centered near 15N126W, moving NW. Scattered moderate and isolated strong convection is present from 10N to 19N between 121W and 129W. Only a slight increase in organization would result in the formation of a tropical depression later today or tonight. By Tuesday, however, upper-level winds are expected become quite unfavorable for tropical cyclone formation to occur. This system is forecast to move NW at 15 to 20 mph across the open eastern Pacific during the next few days. The chance of this low developing into a tropical cyclone through 48 hours remains high. Please refer to the East Pacific Tropical Weather Outlook TWOEP for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 07N80W to 08N113W to the special features 1008 mb low near 15N126W to 12N129W to 11N140W. Aside from convection associated with the low, Widely scattered moderate convection is seen from 08N to 13N, west of 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section for information regarding the ongoing Gulf of Tehuantepec gale. A ridge will dominate the waters W of Baja California the next several days. The surface pressure gradient W of Baja California will tighten slightly tonight through Tuesday as high pressure shifts eastward closer to the coast, resulting in fresh to locally strong NW winds N of 25N over the open Pacific waters, with seas building to near 8 ft. NW winds over the Gulf of California during this corresponding time period will increase from light to moderate. Elsewhere, mainly light to gentle winds and seas of 4 to 5 ft will prevail through Wed night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light and variable winds, and seas of 4 to 6 ft, are generally expected N of the monsoon trough, which will be in the vicinity of 10N through mid week. Moderate to locally fresh S to SW winds and seas of 5 to 7 ft are forecast S of the monsoon trough through Tuesday. A slight increase in SW flow over the Gulf of Panama, to the south of the monsoon trough, may result in seas of 8 ft Tuesday through Thursday. REMAINDER OF THE AREA... Low pressure near 15N126W is discussed above in the special features section. The combination of long period NW swell propagating southeastward and the broad wind field associated with the special feature low is maintaining seas of 8 to 11 ft from about 08N to 22N, west of 115W. The swell field greater than 8 ft will decrease in areal coverage as the NW swell decays through Monday. However, the wind field associated with the special feature low will generate seas of 8 to 13 ft during the next few days as the low tracks generally NW towards 19N134W by Wed evening. Another batch of 8 to 9 ft NW swell will reach the NW waters Monday night. Seas affected by these swell will cover the waters N of 23N and W of 128W through Fri. Elsewhere, mainly gentle to moderate winds and seas of 5 to 7 ft will prevail through the next several days. $$ CAM