000 AXPZ20 KNHC 192059 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 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 1800 UTC surface analysis and satellite imagery through 1900 UTC. ...SPECIAL FEATURES... Major Hurricane Norma is centered near 17.5N 108.0W at 19/2100 UTC, moving north at 5 kt. Estimated minimum central pressure is 944 mb. Maximum sustained wind speed is 110 kt with gusts to 135 kt. Peak seas are currently around 36 ft. Numerous moderate scattered strong convection is noted within 120 nm of the center, except 90 nm in the N quadrant. Scattered moderate and isolated strong convection is elsewhere from 14N to 23N between 102W and 122W, as well as in a band between 150 nm and 570 nm in the SE semicircle of Norma. A turn to the north-northwest at a similar forward speed is expected during the next couple of days. A slower northward to northeastward motion is forecast later this 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 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some weakening is expected during the next few days, but Norma is forecast to be a hurricane when it moves near the southern portion of Baja California. 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 Baja California Sur, and will spread northward along the coast of western Mexico and the Baja California peninsula 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. South of Southern Mexico (EP91): A broad 1007 mb area of low pressure located several hundred nautical miles south of the Gulf of Tehuantepec near 08.5N94.5W continues to produce a large area of disorganized showers and thunderstorms. Numerous moderate isolated strong convection is noted within 150 nm in the NE semicircle and 420 nm in the SW semicircle of the low. Gradual development of this system 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. NW Swell in the NW waters: Large NW swell is propagating across the NW waters. Peak seas have started to subside somewhat, currently now around 12 ft W of a line from 30N126W to 20N140W per recent altimeter data. 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 through the end of the week and into the weekend. 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N76W to low pressure (EP91) near 08.5N94.5W to 11N101W, then resumes well SW of Norma near 10.5N116W to low pressure near 10N122W to 07N130W to 10.5N140W. Scattered moderate isolated strong convection is noted from 01N to 09N between 77W and 88W, and from 04N to 10N between 110W and 128W. ...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. Hurricane Norma is near 17.5N 108.0W at 2 PM PDT, and is moving north at 5 kt. Maximum sustained winds are 110 kt with gusts to 135 kt, and the minimum central pressure is 944 mb. Aside from Hurricane Norma, a ridge extends W of the Baja California offshore waters. Fresh to strong winds prevail in the Gulf of Tehuantepec. Gentle to moderate winds prevail across the remainder of the offshore waters. Seas are in the 7-10 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 18.5N 108.5W Fri morning, 19.8N 109.1W Fri afternoon, 21.2N 109.6W Sat morning, 22.5N 109.7W Sat afternoon, weaken to a tropical storm near 23.6N 109.4W Sun morning, and 24.2N 108.9W Sun afternoon. Norma will weaken to a tropical depression while moving inland over 25.0N 107.5W Mon afternoon, dissipating by Tue afternoon. 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, except moderate to fresh offshore Baja California. Fresh to strong winds offshore Baja California may develop this weekend. Large NW swell is forecast to continue to spread offshore Baja California 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, Costa Rica, and Nicaragua, 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, moderate to fresh winds over and downstream of Papagayo will diminish this evening, 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, except fresh to strong just offshore Costa Rica and Panama Sat and Sat night. Seas may build slightly in SW swell offshore Ecuador to the Galapagos Islands tonight and Fri, 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, low pressure (EP91) near 08.5N94.5W, and on a large NW swell event over the NW waters. Hurricane Norma is near 17.5N 108.0W at 2 PM PDT, and is moving north at 5 kt. Maximum sustained winds are 110 kt with gusts to 135 kt, and the minimum central pressure is 944 mb. A weak trough extends from 25N124W to 17N118W, and a weak 1010 mb area of low pressure is embedded in the monsoon trough near 10N122W. Otherwise, ridging dominates the waters N of the monsoon trough. Mainly light to gentle winds are N of 20N per recent ASCAT scatterometer data, with gentle to moderate winds elsewhere over the open waters. As described above, NW swell is dominating the waters W of 100W while the remainder of the open waters are now 7-8 ft in a broad 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 18.5N 108.5W Fri morning, 19.8N 109.1W Fri afternoon, 21.2N 109.6W Sat morning, 22.5N 109.7W Sat afternoon, weaken to a tropical storm near 23.6N 109.4W Sun morning, and 24.2N 108.9W Sun afternoon. Norma will weaken to a tropical depression while moving inland over 25.0N 107.5W Mon afternoon, dissipating by Tue afternoon. 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 24N. $$ Lewitsky