000 AXPZ20 KNHC 090959 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Thu Sep 9 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 0600 UTC surface analysis and satellite imagery through 0945 UTC. ...SPECIAL FEATURES... Tropical Storm Olaf is centered near 20.5N 108.0W 1000 mb at 2 AM PDT moving NNW at 5 kt. Estimated minimum central pressure has decreased to 993 mb. Maximum sustained wind speed has increased to 55 kt with gusts to 65 kt. Satellite imagery shows that the cyclone is becoming more symmetrical in appearance, with wide banding features containing deep convective activity. This convective activity is observed as the numerous moderate to strong type intensity within 180 nm of the center in the NE quadrant. Scattered moderate to strong convection is within 180 nm of the center in the NW quadrant. Scattered moderate to isolated strong convection is within 120 nm of the center in the S semicircle. Scattered moderate convection is within 60 nm of 20N105W. Presently maximum seas reach a peak of 20 ft, but are forecast to build to near 25 ft today through Fri as the cyclone approaches southern Baja California. Overnight altimeter data passes revealed that the 12 ft sea radii extends outward about 75 nm from the center in the SE quadrant. Additional strengthening is forecast during the next day or so, and Olaf is expected to become a hurricane later today. Weakening is forecast to start on Fri when Olaf begins to move away from Baja California Sur. Olaf is expected to produce total rainfall amounts of 3 to 6 inches with maximum amounts of 10 inches across portions of far southern Baja California Sur through Fri. This rainfall may trigger flash flooding and mudslides. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPEP5.shtml and Forecast/ Advisory at https://www.nhc.noaa.gov/text/MIATCMEP5.shtml for more details. ...TROPICAL WAVES... A tropical wave has its axis along 96W north of 04N to inland southeastern Mexico. It is moving westward at 10 kt. Scattered moderate to strong convection is within 120 nm east of the wave axis from 12N-15N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from just offshore northwestern Colombia to across southern Panama and northern Costa Rica to 11N86W to 11N96W to 10N105W to 11N113W to 08N125W. It resumes at 16N133W to low pressure of 1012 mb at 15N136W and to 15N140W. Aside from the convection associated with Tropical Storm Olaf and the tropical wave, scattered moderate to isolated strong convection is noted within 180 nm south of the trough between 98W-100W. Scattered moderate convection is within 180 nm south of the trough between 86W-87W, between 100W and 104W, and within 120 nm south of the trough between 106W-109W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details on Tropical Storm Olaf. A weak 1013 mb low is centered near 25N127W. No convection is occurring with this low as it is surrounded by a very dry and stable environment. Latest ASCAT data showed gentle to moderate northwest winds off the Baja California peninsula, except for moderate to fresh winds within about 180 nm west of Baja California Norte. Seas over these waters are in the 4-5 ft range in long-period south swell. Latest ASCAT data revealed light to gentle variable winds across the Gulf of California. Seas are less than 3 ft, except 3-4 ft just south of the entrance to the Gulf. Scattered moderate to isolated strong convection occurring in an outer rain band from Olaf is along and just inland the coast from Jalisco to Nayarit. Tropical Storm Olaf is forecast to turn toward the northwest is forecast by tonight, followed by a slower westward motion Friday night and Saturday. On the forecast track, the center of Olaf will approach southern Baja California Sur today, move near or over the southern part of the peninsula tonight and on Fri, and then move westward away from land Fri night and Sat. Swells generated by Olaf are beginning to reach portions of the coasts of southern Baja California Sur, Nayarit, and Sinaloa, and will spread northward along the west coast of Baja California Sur through Sat. In the Gulf of California, light and variable winds will continue through Thu night, then become gentle to moderate southeast winds through Sat. Light to gentle winds will continue across southern Mexico. Fresh to strong gaps winds are expected to develop across the Gulf of Tehuantepec beginning Fri afternoon and continue into the upcoming weekend. An area of low pressure is expected to form in a few days to the south of the southern coast of Mexico. Environmental conditions appear favorable for development of this system, and a tropical depression could form late this weekend or early next week while it moves west-northwestward near the coast of southern and southwestern Mexico. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Moderate south to southwesterly winds is noted south of the monsoon trough with light and variable winds north of the monsoon trough. Seas are 3-6 ft in the Central American offshore waters and 6-7 ft seas off of Ecuador and the Galapagos Islands. Satellite imagery shows numerous showers and thunderstorms along and just offshore the coast of El Salvador and most of the offshore waters of Nicaragua. Seas are 3-6 ft in the Central American offshore waters, except for higher seas of 5-7 ft over the waters between Ecuador and the Galapagos Islands due to a southwest swell. These seas will build to 6-8 ft due to a southwest swell beginning today Thu. Winds in Papagayo region will increase to fresh speeds Sat. Moderate to fresh southwest winds are expected along the offshore waters of Costa Rica, Panama, Colombia, Ecuador and Galapagos Islands through the weekend. Strong south to southwest winds are expected over the offshore waters of Guatemala and El Salvador late Sat through late Sun as low pressure develops south of the southern coast of Mexico. Seas in these waters will remain in the 6-7 ft range, except near 8 ft seas in the region west of Ecuador. Seas offshore Guatemala, Honduras and El Salvador are expected to build to possibly 9 ft during Sat and Sat night due to the expected strong south to southwest winds combining with southwest swell that will be propagating through those same offshore waters. REMAINDER OF THE AREA... Broad high pressure dominates the waters north of the monsoon trough. The gradient between the high and the lower pressure to the south in the monsoon trough region is allowing for moderate to fresh north-northeast winds and seas 7 ft south of 21N and west of 134W, especially in the vicinity of the 1012 mb low pressure near 15N136W. Moderate southerly winds remain south of the monsoon trough, with seas to 7 ft. Seas to 8 ft due to a southwest swell continue south of the Equator and west of the Galapagos Islands tonight before another set of southwest swell begins to propagate through the waters west of the Galapagos Islands from Thu through the upcoming weekend. Seas will range between 8-9 ft through early next week. $$ Aguirre