000 AXPZ20 KNHC 200900 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0900 UTC Fri Dec 20 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong gale force northerly gap winds prevail across the Tehuantepec region with seas up to 16 ft. Similar marine conditions are expected to persist through the weekend and into early next week. Swell generated from this event is currently producing a large plume of 12 ft or greater seas that extends beyond 100W, as depicted by overnight altimeter passes. Seas are forecast to subside slightly today before rebuilding late this weekend. Marine interests transiting across or in the vicinity the Gulf of Tehuantepec over the next several days should be aware of this strong gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Please see the latest High Seas Forecast issued by the National Hurricane Center under AWIPS/WMO headers HSFEP2/FZPN03 KNHC or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N78W to 06N92W to 06N95W. The ITCZ continues from 06N95W to 09N112W to 09N128W to 08N140W. Scattered moderate convection is noted from 06N to 08N between 90W and 94W, from 08N to 10N between 110W and 122W, and from 08N to 10N between 135W and 140W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details about the ongoing gale force gap wind event across the Gulf of Tehuantepec. Gulf of California: The pressure gradient between high pressure of 1039 mb over the U.S. Great Basin region and a surface trough over Baja California is supporting fresh to strong NW winds across the Gulf of California. An overnight ASCAT B pass depicted these strong winds over the Gulf of California. The fresh to strong winds will continue today. The area of high pressure will shift E of the Great Basin region today through Sat. This will loosen the pressure gradient across the Gulf of California, and diminish winds Sat. With persistent fresh to strong winds today, seas will build to around 8 ft by this evening. NW swell is propagating across the offshore waters of Baja California, with seas in the 8 to 11 ft range. Seas will subside to 7-8 ft late today. Another set of NW swell will propagate into the area late tonight, which will help maintain seas in the 7-8 ft range through this weekend into early next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Seas generated by a gale force gap wind event in the Tehuantepec region will continue to propagate across the offshore waters of Guatemala and El Salvador through early next week. Fresh to strong winds are expected across the Gulf of Papagayo and downwind to near 90W through early next week, pulsing to near gale force at night. 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 1026 mb is centered N of the area near 33N125W. The pressure gradient between the area of high pressure and lower pressure in the vicinity of the ITCZ supports an area of moderate to fresh trades N of the ITCZ to 22N and W of 120W. Long period NW swell propagating across the area is mixing with shorter period wind waves, supporting seas in the 8 to 11 ft range over this area. The NW swell is also helping to maintain seas of 8 ft or greater over much of the remaining waters N of 05N and W of 113W. A cold front will move into the NW corner of the forecast area today, and extend from 30N136W to 27N140W by this evening. Fresh to strong winds are expected on either side of the front, forecast to gradually dissipate as the front moves eastward during the weekend. This front will usher in a new set of long period NW swell, with seas peaking near 15 ft later tonight. High pressure will build in the wake of the front. This will tighten the pressure gradient, and increase trades across the west- central waters into early next week. $$ AL