Tropical Weather Discussion

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Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 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 1800 UTC surface analysis and satellite imagery through 2000 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from the coast of Costa Rica from near 09N83W to 09N110W. The ITCZ continues from 09N110W to beyond 07N140W. Scattered moderate convection is noted from 06N-15N east of 100W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A 1026 mb high center centered at 31N129W with lower pressure the SW United States is producing moderate to fresh NW winds west of Baja California Norte. Elsewhere, winds are gentle or weaker. Seas are 6-8 ft west of Baja California Norte, 1-2 ft in the Gulf of California, and 3-5 ft elsewhere. No significant deep convection is occurring. For the forecast, with a weak pressure gradient prevailing, winds across forecast waters should remain moderate or weaker through tomorrow morning. By tomorrow afternoon, a Tehuantepecer gap wind event will begin with fresh to near gale N to NE winds. The winds will dimish some Sat into Sun, but by Sun night they should continue with fresh to near gale over the Gulf of Tehuantepec through mid next week. Elsewhere, winds and seas should remain quiescent for the next several days. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Winds across forecast waters are moderate or weaker with seas 3-5 ft. Scattered moderate convection is occurring within 150 NM of the coasts of Guatemala, El Salvador, Costa Rica, and Panama. For the forecast, a light pressure gradient will continue to only force moderate or weaker winds across forecast waters through Fri. Building high pressure over Central America will drive fresh to locally strong NE winds mainly during late night/early morning hours across the Gulf of Papagayo region from Fri evening through mid next week. Elsewhere, winds and seas will be quiescent. ...REMAINDER OF THE AREA... A 1026 mb high centered at 31N129W north of our waters along with lower pressure over the ITCZ is forcing only moderate to locally fresh NE trades north of the ITCZ. South of the ITCZ/monsoon trough, the SE trades and SW monsoonal winds are gentle to moderate. Seas are 4-7 ft. For the forecast, little change is expected through Sun. Starting Sun night, a surface trough is expected to form along the ITCZ near 120W enhancing deep convection and strengthening winds for a couple of days. At the same time, a cold front is anticipated to reach our NW corner at 30N140W and bring with it moderate to fresh SW ahead of the front and moderate to fresh N winds behind the front on Mon and Tue. A large NW swell of 8-12 ft should also reach our NW waters beginning Mon night.