000 AXPZ20 KNHC 041605 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sat Nov 4 2023 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Tropical Storm Pilar is centered near 10.2N 109.1W at 04/1500 UTC, moving west at 13 kt. Estimated minimum central pressure is 1002 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Numerous moderate to strong convection is noted within 120 nm W and 75 nm E semicircles of center. Peak seas are currently around 16 ft. Pilar is moving toward the west, and this general motion is expected to continue through Sunday. A slower forward motion toward the west-northwest or northwest is forecast early next week. Small intensity fluctuations are possible during the day or so. Steady weakening is forecast early next week. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest Pilar NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Gulf of Tehuantepec Gale Warning: Gale force winds persist in the Tehuantepec region and downwind to about 13N. The gales are due to cooler, drier air and high pressure over the Gulf of Mexico, and lower pressure farther south into the tropical Pacific. Seas are likely reaching 16 ft downstream in the Gulf of Tehuantepec, with a large plume of rough seas in excess of 8 ft extending beyond 400 nm offshore. Gap winds will diminish below gale force Sun night into Mon morning, but strong gap winds and rough seas will persist until late Tue. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. Potential for heavy rainfall over Central America: Surface observations and overnight satellite-derived wind data indicate that the area of low pressure that we have been monitoring during the past few days over the western Caribbean has reformed about 100 miles east of the Nicaragua/Costa Rica border. Showers and thunderstorms have increased associated with the low pressure system, and surface pressures have fallen during the past several hours. Some gradual development of this system is possible before it moves inland over Central America tonight or Sunday. Regardless of development, this system is expected to bring heavy rains to portions of Central America this weekend. This rainfall could produce flash flooding, along with mudslides in higher terrain areas. For additional information about this system, refer to the local weather services for more information. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 12N86W to 09N104W then continues SW of Pilar from 05N112W to a 1010 mb low pres located near 09N125W to 08N135W. The ITCZ extends from 08N135W to beyond 07N140W. Scattered moderate to isolated strong convection is noted from 06N to 09N between 82W and 86W. Scattered moderate convection is W of the above mentioned low from 08N to 10N between 125W and 128W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section above for details on the Gulf of Tehuantepec Gale Warning. Outside of the Gulf of Tehuantepec gap wind event, surface ridging extends across the Baja California offshore waters anchored by a 1021 mb high pres near 28N132W. The pressure gradient from this high pressure and lower pressure over Mexico is leading to moderate to fresh NW to N winds in the Gulf of California, with 2 to 4 ft seas. Meanwhile, light to gentle winds are noted across the rest of the Mexico offshore waters. Seas range 4 to 6 ft in mixed swell. For the forecast, Gale force gap winds will persist across the Gulf of Tehuantepec into Sun night, related to high pressure north of the area following a cold front that entered southern Mexico a couple of days ago. Very rough seas associated with the gales will continue over the waters off eastern Oaxaca and western Chiapas into Mon morning. The winds and seas will continue to gradually diminish into Tue off southern Mexico. Looking ahead, expect fresh NW winds and large NW swell off Baja California north of Cabo San Lazaro as high pressure builds west of the area behind a cold front that moves into the region and stalls. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate S-SW monsoonal winds prevail across the offshore waters with seas 4 to 6 ft. Seas range 8 to 9 ft across the offshore waters of Guatemala due to the Tehuantepec gap wind event, west of 93W. Mixed swell will persist across the Central American and South American offshore waters. For the forecast, expect large seas off Guatemala through Sun night due to swell generated off southern Mexico from gale force winds in the Gulf of Tehuantepec. Gentle to moderate winds and slight to moderate seas will persist elsewhere. ...REMAINDER OF THE AREA... Please refer to the Special Features section above for details on Tropical Storm Pilar. Surface ridging extends across the region north of 20N anchored by a 1021 mb high pressure near 28N132W, supporting mostly moderate trade winds mainly from 10N to 20N. Earlier scatterometer and recent altimeter satellite passes indicated fresh trade winds with combined seas of 8 to 10 ft from 07N to 12N W of 130W For the forecast, Pilar will move to 10.3N 110.9W this evening, 10.7N 112.8W Sun morning, 11.3N 114.6W Sun evening, 12.0N 115.7W Mon morning, weaken to a remnant low near 12.9N 116.7W Mon evening, and 13.9N 118.0W Tue morning. Pilar will dissipate early Wed. Otherwise, mainly moderate to fresh winds will prevail north of the ITCZ and monsoon trough through early next week. Seas will be mainly 5-7 ft through late Mon, with seas to 8 ft across the trade wind zone. Looking ahead, a weak cold front is expected to push across the waters north of 25N through Mon, accompanied by seas 8 to 9 ft which will cover most of the area north of 10N and west of 120W by mid week. $$ GR