Tropical Weather Discussion

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Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...SPECIAL FEATURES... Western East Pacific: Low pressure, Invest EP98, is centered near 11N118W with a pressure of 1009 mb. This feature is part of a rather broad area of cyclonic circulation. Satellite exhibits numerous moderate to isolated strong convection from 08N to 13N between 117W and 120W. Environmental conditions appear conducive for 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 low has a high chance of tropical cyclone formation through the next 48 hours. South of Southwestern Mexico: A tropical wave, Invest EP99, has its axis extending from near 16N105W to 06N106W, with low pressure of 1010 mb, near 07N106W. This feature 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 from 07N to 12N between 103W and 108W. 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 northwestward off the coast of southwestern Mexico. This system has a medium chance of tropical cyclone formation through the next 48 hours. Please refer to the latest NHC Tropical Weather Outlook at website: www.hurricanes.gov for more details on these Invests. ...TROPICAL WAVES... The southern portion of the axis of a western Caribbean Sea tropical is along 79W north of about 05N. It is moving westward near 15 kt. Numerous moderate to strong convection is within 180 nm west of the wave, and also from 03N to 05N between 79W and 81W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northwest Colombia westward to across northern Costa Rica, and southwestward to 09N86W to 09N100W to 06N101W to 06N111W to 10N114W to low pressure, Invest EP98, near 11N118W and to 12N126W. It resumes at 13N138W to beyond 12N140W. Scattered moderate to isolated strong convection is within 300 nm north of the trough between 93W-103W, also within 300 nm south of the trough between 90W-102W and within 120 nm south of the trough between 120W-126W. ...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 as was evident in satellite scatterometer from throughout the day. Seas with these winds are 6 to 8 ft. Scattered to numerous showers and thunderstorms are over most of the offshore waters, especially east of about 101W. 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 pulse to fresh to strong speeds in the Gulf of Tehuantepec tonight becoming moderate north to northeast winds Sat afternoon. Fresh to strong northwest winds offshore Baja California will diminish Sat afternoon. Northwest winds over these waters are expected to briefly reach fresh speeds Mon night into Tue. Otherwise, the environmental conditions of the tropical wave that extends from 6N105W to 06N106W, with low pressure of 1010 mb, Invest EP99, near 07N106W are conducive for development, and a tropical depression is likely to form late this weekend or early next week while it gradually moves 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 the middle part of next week. ...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 over the offshore waters are of moderate state due to a long-period southwest 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 speeds through early Sun. Moderate winds and seas will prevail elsewhere. ...REMAINDER OF THE AREA... The remnant 1008 mb low of former Tropical Depression Fifteen-E is located near 17N137W. A tight gradient between the low and high pressure to its north is bringing fresh to strong northeast to east winds over the waters from 19N to 27N west of 129W. Seas are 6 to 9 ft within this area of winds as interpreted from earlier satellite altimeter data passes. Satellite imagery shows numerous moderate convection within 180 nm of the low in the NE quadrant and 90 nm of the low in the SE quadrant. Elsewhere, winds are moderate or weaker and seas are of moderate state, except for rough state seas in the vicinity of Invest EP98. For the forecast, see the Special Features section. Otherwise, environmental conditions appear conducive for some development of the remnant low of former Tropical Depression Fifteen-E 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.