393 AXPZ20 KNHC 170317 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0317 UTC Tue Dec 17 2019 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 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 0200 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: a strong cold front has entered the northwestern Gulf of Mexico tonight and will continue moving SE across the basin. High pressure will build southward across the Sierra Madre Oriental in the wake of the front. The pressure gradient between this building high pressure and the equatorial trough in the eastern north Pacific will usher in the next gale force gap wind event on Tue night across the Gulf of Tehuantepec. This will be a strong gap wind event, with wind speeds possibly reaching minimal storm force on Wed night. Seas will build in excess of 20 ft during this time. Conditions will weaken slightly on Fri, but winds will quickly pick up speed again to gale-force and prevail through the weekend. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 06N77W to 08N88W. The ITCZ continues from 08N88W to beyond 07N140W. Scattered moderate convection is noted from 06N to 11N between 104W and 122W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details on a gap wind event with winds possibly reaching storm force by early Thu over the Gulf of Tehuantepec. A surface ridge extends from a 1025 mb high pressure centered near 35N126W to near the Revillagigedo Islands. The pressure gradient between this ridge and a surface trough across the Gulf of California is supporting moderate to fresh winds off the coast of Baja California Norte. Northerly swell continues to propagate across the forecast area, with seas near 10 ft off the coast of Baja California Norte. Seas greater than 8 ft are covering the offshore waters W of 105W. The area of high pressure will weaken by late Tue and will loosen the pressure gradient, diminishing winds off most of Baja California offshores. High pressure building over the Great Basin region is supporting fresh to strong force NW winds across the Gulf of California. These winds will increase to near gale through through early Wed. Strong winds will funnel through the mountain passages of Baja California Norte into the Sebastian Vizcaino Bay tonight through Tue night. The NW swell will slowly subside, and seas will fall below 8 ft by late Tue. A fresh set of NW swell will propagate into the waters off Baja California Norte Wed evening and propagate SE to near the Revillagigedo Islands through the upcoming weekend. Seas will build to near 10 ft off Baja California Norte with this new set of NW swell. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh winds are expected across the Gulf of Papagayo, increasing to fresh to strong Wed, and continuing through the upcoming weekend. Elsewhere, gentle to moderate south to southwest monsoon flow will persist across the offshore waters of Costa Rica, Panama, Colombia, and Ecuador, while light to gentle flow will dominate across the Gulf of Panama. REMAINDER OF THE AREA... High pressure of 1025 mb is centered near 35N126W. The pressure gradient between this area of high pressure and lower pressure in the vicinity of the ITCZ is supporting moderate trade winds N of the ITCZ to near 20N and W of 120W. Subsiding NW swell continues across the forecast waters. Seas 8 ft or greater cover much of the waters N of 07N and W of 105W. The NW swell will continue to gradually subside over the next couple of days, and areal coverage of seas 8 ft or greater will decrease. A cold front will move from the north central Pacific into the region tonight to weaken from near 31N123W to near 25N127W by early Wed. While the front will initially weaken the subtropical ridge as it moves into the area, high pressure building behind the front will allow trade winds to increase west of 130W by mid week. A new round of long-period NW swell in excess of 8 ft will accompany the front with seas building to 12 ft N of 25N W of 124W. $$ ERA