000 AXPZ20 KNHC 171552 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1303 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: The next gap wind event over the Gulf of Tehunatepec is expected to commence this afternoon as a strong cold front moving across the Gulf of Mexico reaches the Isthmus of Tehunatepec. High pressure building behind the front across the eastern slopes of the Sierra Madre Mountains in Mexico will provide a very tight pressure gradient over the area, and bring an increase in winds funneling into the Gulf of Tehuantepec. Winds will rapidly increase to gale force late this afternoon and reach storm force by Wed morning with seas building up to 22 ft. Storm conditions will prevail through early Thu while gale conditions are expected to continue through the weekend. Swell generated from this event will produce a large plume of 12 ft or greater seas that will extent beyond 100W by Thu morning. Marine interests transiting the Gulf of Tehuantepec over the next couple of days should be aware of this upcoming 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. Gulf of California Gale Warning: Strong high pressure over the Great Basin region is supporting strong to minimal gale force winds across the Gulf of California, particularly across the central Gulf with seas currently building to 8 to 10 ft. Winds and seas will gradually decrease to 20 kt or less, with seas less than 8 ft by late Wed morning as the high pressure moves eastward. 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 northern Colombia near 10N74W to 07N90W to 08N108W. The ITCZ continues from 08N108W to 07N125W to 07N140W. Scattered moderate isolated strong convection is noted from 03N to 07N E of 80W to the coast of Colombia. Scattered moderate convection is from 06N to 08N between 123W and 130W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details on the next storm gap wind event across the Gulf of Tehuantepec, and minimal gale force winds over the Gulf of California. A storm warning and a gale warning have been issued respectively. The strong high pressure over the Great Basin region is also supporting fresh to locally strong force NE winds across the Baja California Norte mountain passages and over the offshore waters W of Baja California, particularly from 26N to 29N E of 117W. Winds will diminish 20 kt or less on Wed. However, a new set of long period NW swell, behind a dissipating cold front, will bring seas of 8 to 11 ft across the offshore waters W of Baja and N of Cabo San Lazaro by Thu morning. This swell event will reach the Revillagigedo Islands late this work week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Seas generated by a storm gap wind event in the Gulf of Tehuantepec will reach the offshore waters of Guatemala and El Salvador on Wed. The forecast calls for seas of 12 to 18 ft Wed and Wed night, and seas of 10 to 15 ft on Thu, then diminishing some by Thu night. Fresh to strong winds are expected across the Gulf of Papagayo Wed night through Sat night with seas building to 9 ft. 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... A cold front is over the NW forecast waters, and extends from 30N132W to 26N140W. The front will gradually weaken and extend from 30N122W to 25N130W to 24N140W on Wed before dissipating by Thu. A new set of long period NW swell will propagate across the northern forecast waters in the wake of the front. High pressure behind the front will also bring increasing trade winds across the west-central waters Wed through Thu, mainly from 10N to 20N W of 130W. Seas of 8 ft or greater will dominate the waters W of a line from 30N115W to 20N118W to 10N122W to 05N140W on Thu morning. $$ GR