Tropical Weather Discussion

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Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Thu Dec 18 2025 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 0000 UTC surface analysis and satellite imagery through 0230 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N85W to 09N95W. The ITCZ continues from 09N95W to beyond 07N140W. Scattered moderate convection is noted from 06N to 12N between 92W and 116W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A 1025 mb high center is analyzed just N of the area near 33N130W with the associated ridge extending to near the Revillagigedo Islands. The related pressure gradient is allowing for gentle to moderate northwest to north winds and slight to moderate seas over the Mexican offshore waters including the Gulf of California. In the far outer Baja California Norte waters and beyond, fresh NW winds and rough seas are present due to a tight pressure gradient mainly N of the area with a high pressure inland of the San Francisco Bay area and troughing just to the S over the Channel Islands. For the forecast, moderate to fresh winds will pulse near Cabo Corrientes through tonight, then again this weekend. Similar winds will be well offshore Baja California Norte through the end of the week, along with rough seas due to a tight pressure gradient mainly N of the the area. Fresh to strong gap winds and associated rough seas may develop in the Gulf of Tehuantepec Fri through the upcoming weekend and into early next week as the pressure gradient tightens in the area. Moderate or weaker winds and slight to moderate seas are forecast elsewhere for the next several days. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh NE winds prevail in the Gulf of Papagayo extending downwind to near 09N92.5W with as high pressure over northern Central America and lower pressures along the monsoon trough over southern Costa Rica and Panama. Light to gentle winds and moderate seas are elsewhere N of 06N. S of 06N, gentle to moderate southerly winds and moderate seas prevail per earlier ASCAT scatterometer data, except slight seas nearshore Colombia, eastern Panama, and southern Costa Rica per an altimeter pass. Isolated to widely scattered showers and thunderstorms are present offshore Colombia northward per conventional satellite imagery. For the forecast, high pressure over interior northern Central America and lower pressures near the monsoon trough will support pulsing moderate to fresh easterly trade winds and moderate seas across the Gulf of Papagayo through Fri while extending well downwind to the far outer offshore waters of El Salvador and Guatemala, then increasing to fresh to strong in the Gulf of Papagayo Fri afternoon through the upcoming weekend and into early next week as the gradient tightens. Moderate to fresh northerly winds will pulse at times in the Gulf of Panama through the next several days. Gentle to moderate winds and slight to moderate seas will prevail elsewhere. ...REMAINDER OF THE AREA... A 1025 mb high center is analyzed just N of the area near 33N130W with the associated ridge extending to near the Revillagigedo Islands. The pressure gradient between the high and relatively lower pressures near the ITCZ/Monsoon Trough is bringing moderate to fresh trade winds from 08N to 22N and W of 120W where seas are 6-9 ft per multiple earlier altimeter passes. A tight pressure gradient over southern California and offshore supports fresh to strong winds and locally rough seas extending over our waters N of 2118W and 126.5N. Gentle to moderate winds and mainly moderate seas prevail across the remainder of the open waters, including S of the monsoon trough and ITCZ. For the forecast, high pressure will continue over the northern waters tonight leading to fresh easterly winds and rough seas over much of the tradewind belt west of 125W. A tight pressure gradient will persist over and offshore southern California leading to fresh to locally strong winds and rough seas in the N-central waters through the remainder of the work week. Marine conditions should improve overall during the upcoming weekend as the pressure gradient slackens due to a cold front approaching 30N140W. That front may move SE into the NW and N-central waters early next week with the potential for fresh to strong NE winds and rough seas behind it.