000 AXPZ20 KNHC 191524 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Oct 19 2023 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 1430 UTC. ...SPECIAL FEATURES... Major Hurricane Norma is centered near 17.4N 107.6W at 19/1500 UTC, moving north at 6 kt. Estimated minimum central pressure is 946 mb. Maximum sustained wind speed is 115 kt with gusts to 140 kt. Peak seas are currently around 32 ft. Numerous moderate scattered strong convection is noted within 150 nm of the center of Norma. Scattered moderate and isolated strong convection is elsewhere from 14N to 22N between 104W and 111W, and from 10N to 14N between 101W and 107W. A northward to north-northwestward motion at a similar forward speed is expected for the next couple of days. A slower northward to northeastward motion is forecast over the weekend. On the forecast track, Norma is forecast to approach the southern portion of Baja California on Friday night and Saturday. Norma is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Small intensity fluctuations are possible today, followed by gradual weakening beginning Friday and continuing into the weekend. Heavy rains from Norma will begin to impact the far southern portions of California Baja Sur on late Friday, continuing through Sunday. This rainfall may produce flash and urban flooding, along with possible mudslides in areas of higher terrain. Swells generated by Norma are affecting portions of the coast of southwestern Mexico, and will spread northward along the coast of western Mexico and toward Baja California Sur during the next couple of days. These swells are likely to cause life- threatening surf and rip current conditions. Please consult products from your local weather office. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website - https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest Norma NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. NW Swell in the NW waters: Large NW swell is propagating across the NW waters. Peak seas have started to subside somewhat, currently 12-13 ft W of a line from 30N129W to 20N140W. Seas of 8 ft or greater will continue to propagate SE, and will cover the majority of the waters W of 100W by early Fri. By that time, peak seas should also subside to just below 12 ft. Confused and hazardous seas will result from the combination of the NW swell, SW swell moving N of the Equator, and swells generated by Norma by the end of the week. Seas will gradually decay from west to east Fri night through the upcoming weekend. Please read the latest NHC High Seas Forecast at website www.hurricanes.gov/marine for more details. South of Southern Mexico (EP91): Shower and thunderstorm activity has increased since yesterday in association with a broad 1007 mb area of low pressure located several hundred nautical miles south of the Gulf of Tehuantepec near 08.5N94.5W. Numerous moderate isolated strong convection is noted within 240 nm in the NE semicircle and 360 nm in the SW semicircle of the low. Associated winds are currently around 20 kt with seas of 6-8 ft. Gradual development is expected, and a tropical depression is likely to form during the next few days while the system meanders or drifts generally northward over the far eastern portion of the basin. This system has a medium chance of tropical cyclone formation through 48 hours, and a high chance through 7 days. Please read the latest NHC Tropical Weather Outlook at www.hurricanes.gov for details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N76W to low pressure near 08.5N94.5W to 10N102W, then resumes well SW of Norma near 10N117W to low pressure near 10.5N122W to 07N128W to beyond 09.5N140W. Scattered moderate isolated strong convection is noted from 01N to 09N between 77W and 89W, including the Gulf of Panama, and from 05N to 10N between 107W and 127W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the SPECIAL FEATURES section above for more details on Major Hurricane Norma, and on low pressure (EP91) near 08.5N94.5W. Fresh to strong winds prevail in the Gulf of Tehuantepec, with seas of 6-8 ft. Aside from Hurricane Norma, a ridge extends across the Baja California offshore waters. Gentle to moderate winds prevail across the remainder of the offshore waters. Seas are in the 6-8 ft range in arriving NW swell offshore Baja California Norte, and 4-7 ft elsewhere over the open waters off Mexico. Seas of 1-3 ft are noted over the Gulf of California, however building near the entrance due to Norma. For the forecast, other than the low pressure area (EP91) near 08.5N94.5W, Norma will move to 18.1N 107.7W this evening, 19.3N 108.3W Fri morning, 20.5N 108.8W Fri evening, 21.9N 109.2W Sat morning, 23.0N 109.3W Sat evening, and weaken to a tropical storm near 23.6N 109.0W Sun morning. Norma will change little in intensity as it moves to 24.2N 108.3W early Mon. Elsewhere, fresh to strong N winds will continue to pulse over the Tehuantepec region through Sat morning. Gentle to moderate winds will prevail elsewhere through the end of the week. Fresh to strong winds offshore Baja California may develop this weekend. Large NW swell is forecast to spread offshore Baja California later today into the weekend, resulting in confused and hazardous seas as it mixes with swells generated by Norma. A new set of NW swell may spread offshore Baja California early next week. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please see the SPECIAL FEATURES section above for more details on low pressure (EP91) near 08.5N94.5W. Moderate to fresh gap winds are over the Papagayo region, extending downstream of Papagayo to near 11N94W. Light to gentle winds are noted elsewhere N of the monsoon trough. Gentle to moderate winds are S of the monsoon trough. Seas are in the 3-5 ft range offshore Colombia, Panama, and Costa Rica, and 4-6 ft in SW swell elsewhere. Numerous showers and thunderstorms are offshore Colombia and Panama as detailed above. For the forecast, other than the low pressure area (EP91) near 08.5N94.5W, gentle to moderate winds over and downstream of Papagayo will diminish today, with light to gentle winds then prevailing north of the monsoon trough through the weekend. Gentle to moderate winds will prevail south of the monsoon trough. Seas may build slightly in SW swell offshore Ecuador to the Galapagos Islands by the end of the week into the weekend, then build slightly across the waters from W to E by the end of the weekend as NW swell arrives. ...REMAINDER OF THE AREA... Please see the SPECIAL FEATURES section above for more details on Major Hurricane Norma, a large NW swell event over the NW waters, and on low pressure (EP91) near 08.5N94.5W. A weak trough extends from 24.5N123W to 17N118W, and a weak 1009 mb area of low pressure is embedded in the monsoon trough near 10.5N122W. Otherwise, ridging dominates the waters N of the monsoon trough. Light winds are over the far NW waters. Gentle to moderate winds are elsewhere over the discussion waters. As described above, NW swell is beginning to dominate the waters W of 100W while the remainder of the open waters are now 6-8 ft in a mix of swell. For the forecast, other than the large NW swell event and low pressure (EP91) near 08.5N94.5W, Norma will move to 18.1N 107.7W this evening, 19.3N 108.3W Fri morning, 20.5N 108.8W Fri evening, 21.9N 109.2W Sat morning, 23.0N 109.3W Sat evening, and weaken to a tropical storm near 23.6N 109.0W Sun morning. Norma will change little in intensity as it moves to 24.2N 108.3W early Mon. Elsewhere, a weak pressure pattern will support mainly gentle to moderate winds across the open waters through the weekend. Winds may increase slightly early next week as high pressure builds N of the area and tightens the pressure gradient. Meanwhile, a new set of NW swell generated offshore California, is forecast to spread S of 30N to the E of 130W by early next week, potentially building seas to 7-10 ft N of 25N. $$ Lewitsky