Tropical Weather Discussion

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Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Fri Sep 18 2026 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 1545 UTC. ...SPECIAL FEATURES... Invest EP98: A tropical wave with axis along 119W extends from 07N to 19N. Low pressure of 1009 is along the wave axis near 12N119W. These feature compose a broad area of low pressure that is located well southwest of the southern tip of the Baja California Peninsula. The wave is moving westward at about 10 kt. Satellite imagery reveal disorganized numerous moderate to strong convection from 08N to 17N between the wave and 125W. Environmental conditions appear conducive for additional development of this system, and a tropical depression is likely to form this weekend as it moves westward across the western portion of the eastern Pacific. The wave has a medium chance of tropical cyclone formation chance through 48 hours and a high of formation through 7 days. Please refer to the latest NHC Tropical Weather Outlook at website: www.hurricanes.gov for more details. ...TROPICAL WAVES... A tropical wave, Invest EP99, has its axis extending from 16N103W to 06N105W. It is moving westward at around 10 to 15 kt, and is part of a broad area low pressure that is located about 700 nautical miles south-southwest of the southwestern coast of Mexico. Satellite imagery depicts disorganized scattered moderate to isolated strong convection within 180 nm east of the wave from 06N to 12N. Environmental conditions are conducive for development, and a tropical depression is likely to form late this weekend or early next week while it moves gradually north- northwestward and northward off the coast of southwestern Mexico. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northwest Colombia southwestward to across the border between Panama and Colombia, and continues to 08N78W to 10N86W to 09N91W to 08N101W to 06N108W to 12N115W and to 13N123W. It resumes at 15N135W to beyond 13N140W. Numerous strong convection is seen from 04N to 08N between 77W-80W. Scattered moderate to isolated strong convection is from 03N to 08N between 81W-92W, and within 120 nm south of the trough between 114W-119W. Scattered moderate convection is from 03N to 08N between 95W-102W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... The pressure gradient between a ridge over the Gulf of America and the eastern extension of the Pacific monsoon is supporting strong to near-gale force north to northeast gap winds across the Gulf of Tehuantepec. Seas with these winds are 6 to 8 ft. Scattered to numerous showers and thunderstorms are over most of the offshore waters, with numerous coverage of the activity confined to the offshore waters of Jalisco and Colima. The northern portion of tropical wave extends along 104W, northward to near 17N. The gradient related to high pressure west of the Baja California offshores is supporting moderate to fresh northwest winds N of Cabo San Lazaro. Moderate or weaker winds are elsewhere along with moderate seas, except for slight seas in the Gulf of California. For the forecast, winds will continue to pulse in Tehuantepec at fresh to strong speeds through Sat. The environmental conditions of the tropical wave along 104W are conducive for development, and a tropical depression is likely to form late this weekend or early next week while it moves gradually north-northwestward and northward off the coast of southwestern Mexico. Regardless of development, this system is forecast to bring fresh to strong winds and moderate to rough seas to the Michoacan and Jalisco offshores Tue night into midweek. Otherwise, moderate to fresh northwest winds will persist along the Baja Peninsula offshores, reaching strong speeds at night today and Mon. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to strong northeast to east winds prevail across the Gulf of Papagayo extending downstream to near 90W. Moderate easterly winds from this gap event are affecting the outer offshores El Salvador and Guatemala. Moderate or weaker winds prevail elsewhere, except for moderate to fresh N winds in the Gulf of Panama extending to about 07N. Seas across the offshores are moderate in SW swell. For the forecast, the pressure gradient between the ridge north of the area and the eastern Pacific monsoon will support pulsing fresh to occasionally strong easterly winds and moderate to rough seas across the Papagayo region into early Sat, then pulsing to moderate to fresh thereafter. Moderate winds and seas will prevail elsewhere. ...REMAINDER OF THE AREA... The remnant 1006 mb low of former Tropical Depression Fifteen-E is located near 16N136W. Fresh to strong northeast to east winds are within 480 nm northern semicircle of the low. Seas are 7 to 10 ft with these winds. Satellite imagery indicates numerous moderate to strong convection from 15N to 19N between 131W and 136W. Moderate to fresh northeast northeast to east winds are along the northern portion of the tropical wave. Invest EP98, along 119W. These winds extend northward to near 22N between 115W and 128W. Seas are in the range of about 6 to 9 ft with these winds as suggested by recent satellite altimeter data passes. Elsewhere, winds are moderate or weaker and seas are moderate, except rough in the vicinity of Invest EP98. For the forecast, see the Special Features and the Tropical Waves Section. Otherwise, environmental conditions appear conducive for some development of this system as it moves westward to west- southwestward, and a tropical depression could form well to the south or southeast of the Hawaiian Islands by the middle to latter part of next week.