000 AXPZ20 KNHC 202123 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Mon Sep 20 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...TROPICAL WAVES... The axis of a tropical wave is along 102W/103W and N of 06N, moving west at 10 to 15 kt. Scattered moderate convection is noted from 07N to 14N between 100W and 107W. The axis of a tropical wave is along 112W from 07N to 20N, moving west at 10 to 15 kt. Scattered moderate convection is seen from 12N to 20N between 107W and 115W. The axis of a tropical wave is along 124W from 07N to 17N, moving west at around 10 kt. Convection is limited near the wave axis. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N85W to 11N100W a 1012 mb low pressure near 11.5N116W to 09N131W. The ITCZ continues from 09N131W to 07N140W. Aside from the convection associated with the tropical waves, scattered moderate convection is from 05N to 10N E of 90W to the coast of Colombia, and from 05N to 10N between 90W and 100W. Scattered moderate to isolated strong convection is noted from 10N to 14N between 114W and 121W. The latter convective activity is mainly associated with the above mentioned low pressure. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge dominates the offshore forecast waters of Baja California producing mainly gentle to moderate NW-N winds. Seas are in the 4-6 ft. Light to gentle winds are seen elsewhere offshore of SW Mexico with seas in the 3 to 5 ft range. Light to gentle SE-S winds prevail in the Gulf of California. Some shower activity is still noted over the southern Gulf of California and also near Los Cabos area. Abundant moisture, in a southerly low level flow, will persist in this area tonight and Tue. For the forecast, a ridge will continue to dominate the offshore waters of Baja California. Seas will build to 8 ft in NW swell N of Punta Eugenia tonight. A gap wind event is expected in the Gulf of Tehuantepec beginning late Tue night with gale conditions possible Wed to Thu night. Seas are forecast to build to 9 or 10 ft with this event. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Gentle to moderate southerly winds will prevail across the offshore waters of Costa Rica, Panama, Colombia and Ecuador during the forecast period, with seas of 4-6 ft in SW swell. Mainly light and variable winds are forecast across the offshore waters from Guatemala to northern Costa Rica, with seas of 3-5 ft also in SW swell. In the Papagayo region expect moderate NE-E winds through Tue. REMAINDER OF THE AREA... A dissipating frontal boundary is located just N of area. An earlier altimeter pass indicates seas to 10 ft in the wake of the front. These seas will propagate across the northern forecast waters, mainly between 120W-130W, in NW swell trough late Tue or Tue evening. The northern forecast waters are under the influence of a ridge anchored by a 1029 mb high pressure located near 40N135W. The pressure gradient between the ridge and lower pressures near the monsoon trough/ITCZ supports moderate to locally fresh trades between 10N-20N W of 115W, with seas of 5-7 ft based on altimeter data. Moderate to locally fresh southerly winds are also noted per scatterometer data S of the monsoon trough between 103W- 120W. An area of low pressure is forecast to form several hundred miles southwest of the southern tip of the Baja California peninsula within the next couple of days. Thereafter, some gradual development of this system is possible, and a tropical depression could form by the latter part of this week while it moves west-northwestward to northwestward at 10 to 15 kt. At 1800 UTC, a 1012 mb low pressure is analyzed along the monsoon trough near 11.5N116W. Fresh to strong S-SW winds and seas of 8-9 ft are noted on the SE quadrant of the low center. The latest Tropical Weather Outlook gives this system a medium chance of tropical cyclone formation through 5 days. Please, refer to the latest Tropical Weather Outlook, at www.hurricanes.gov for more details. $$ GR