000 AXPZ20 KNHC 181605 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Nov 18 2021 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front is forecast to move through the Gulf of Mexico today through Fri with high pressure building behind it across eastern Mexico. The building high combined with lower pressure south of southern Mexico will support a gale-force northerly gap wind event from early Fri through Sat morning. Seas will build to around 12 ft during the event. Please see the latest NWS High Seas Forecast issued by the National Hurricane Center at website://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more information. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1011 mb low off northwest Colombia near 11N77W to across southern Costa Rica and to 09N104W to low pressure near 10N121W 1011 mb. The ITCZ begins west of this low near 10N122W and continues to 09N130W, where it pauses west of trough that extends from 10N130W to 07N132W, It resumes at 08.5N133W to beyond 08N140W. Scattered moderate to isolated strong convection is within 60 nm of the ITCZ between 124W-127W. Scattered moderate convection is within 120 nm south of the trough between 96W-101W, within 120 nm north of the trough between 114W-120W, and also within 60 nm south of the trough between 96W-102W and between 111W-114W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details on an upcoming Gulf of Tehuantepec Gale Warning. Fresh north to northeast winds are across the Gulf of Tehuantepec with seas to 6 ft. A surface ridge extends across the offshore waters with mainly gentle to moderate winds across the waters outside of the Tehuantepec region. Seas are in the 4-6 ft range across the open waters. Seas are 2-4 ft in the southern Gulf of California, and 3 ft or less in the central and northern Gulf of California. For the forecast, moderate to fresh winds prevail across the Tehuantepec area today. A gale-force northerly gap wind event is forecast in the Gulf of Tehuantepec beginning early on Fri and through Sat morning. Fairly tranquil conditions are forecast elsewhere through the upcoming weekend. Gap winds may approach gale-force again in the Gulf of Tehuantepec early next week. Fresh to strong northwest to north winds may develop in the northern Gulf of California early next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR Moderate to fresh winds prevail across the Papagayo region. Otherwise, light to gentle winds are noted north of the monsoon trough. Gentle to moderate southerly winds prevail south of the monsoon trough. Seas are in the 4 to 7 ft range across the majority of the offshore waters, highest south of Panama and west of Colombia and Ecuador. Scattered showers and thunderstorms are noted south of Panama and Costa Rica, and west of Colombia. For the forecast, moderate to fresh winds prevail across the Tehuantepec area today. A gale-force northerly gap wind event is forecast in the Gulf of Tehuantepec beginning early on Fri and through Sat morning. Fairly tranquil conditions are forecast elsewhere through the upcoming weekend. Gap winds may approach gale-force again in the Gulf of Tehuantepec early next week. Fresh to strong northwest to north winds may develop in the northern Gulf of California early next week. REMAINDER OF THE AREA... A broad and weak ridge extends from a 1021 mb high centered 30N129W to near 20N112W. Low pressure of 1011 mb is along the monsoon trough near 10N121W. A trough extends from 12N119W to the low pressure and to 08N123W. A trough is west of this low from 10N131W to 06N133W. An overnight ASCAT pass highlighted and area of mainly fresh east to southeast winds within 180 nm north and northeast of the low. Similar winds are near the northern part of the trough that is west of the low pressure. Satellite imagery shows scattered moderate convection from 14N to 18N between 131W and 136W, and also within 60 nm of 10N131W. Moderate to locally fresh trades are noted north of the convergence zone to 21N, with gentle to moderate winds north of there under the ridge. Gentle to moderate southerly flow prevails south of the monsoon trough. Seas of 5-7 ft prevail south of 21N, locally to 7 ft near 12N118W, with 4-6 ft north of 22N, highest along 30N between 120W and 130W. For the forecast, little change is expected through Fri. A cold front may drop south into the far northern waters Fri night. High pressure may build behind the front with freshening winds for the end of the weekend into early next week. Seas may build to around 8 ft in the west-central waters north of the ITCZ this weekend with the freshening winds and lengthening fetch. $$ Aguirre