000 AXPZ20 KNHC 241008 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Mon Oct 24 2016 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 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 0900 UTC. ...SPECIAL FEATURES... Tropical storm Seymour is located near 14.9N 108.5W at 0900 UTC, about 345 nm, or 640 km, SW of Manzanillo Mexico, moving W- NW or 290 deg at 13 kt. Maximum sustained winds have increased to 55 kt with gusts to 65 kt. Minimum central pressure is 999 mb. Cloud tops have cooled overnight near the center of Seymour, where numerous strong convection is occurring within 90 nm of the center. Conditions appear favorable for continued strengthening during the next few days as Seymour continues moving W-NW to NW, and hurricane force winds are expected later this afternoon. In fact, some computer model guidance suggests rapid intensification during the next 24 to 48 hours, and winds with Seymour are forecast to strengthen to 100 kt within 48 hours. Although the forecast track keeps Seymour just outside of the Mexican offshore zones, fresh to strong winds and seas in the 8-10 ft range are expected to affect the southern part of zones PMZ023 and PMZ025 through late Monday, then PMZ015 tonight and Tue. For additional details, refer to the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25. A gale warning will remain in effect for the Gulf of Tehuantepec during the next 48 hours, as strong northerly winds will persist throughout the week across this region. Marine guidance continues to suggest minimal gale force winds during the overnight and early morning hours each day, probably through the end of the week. By Thu night into early Fri morning, the aerial extent of the gale force winds will increase as high pres builds across the western Gulf of Mexico. At that time, seas are expected to build to 10-14 ft. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N74W to 09.5N84W to 07N93W to 11N102W, where it has fractured away from Seymour, then resumes W of Seymour from low pres near 17N116W to low pres near 14N126.5W to 09N133W to beyond 12N140W. Widely scattered to scattered moderate isolated strong convection is noted within 150 nm S of the trough between 77W and 86W, and between 95W and 100W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See special features for details on Seymour and for the Tehuantepec area. High pres of 1017 mb is centered near 27N123W and is producing light anticyclonic winds across the waters W of the Baja California Peninsula. Combined seas there are 4-6 ft across southern portions of the peninsula, and 5 to 8 ft N of 27N due to long period NW swell moving into the region. Seas here will subside below 8 ft by Tuesday. The high pres will shift slightly N-NE during the next 24 hours, allowing for an increase to moderate NW winds across the offshore waters. Inside the Gulf of California, mainly gentle southerly winds were detected by scatterometer and surface observations across the north half, while gentle N to NW winds had developed across far southern portions. This general wind pattern will persist today. By this evening, gentle to moderate NW winds will dominate all the waters S of 27N extending SE to between Los Cabos and Las Tres Marias Islands. Then on Tuesday as the high center shifts farther N-NE, NW winds will spill down then entire length of the Gulf of California. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: moderate to fresh NE winds and seas to around 6 ft are expected across and just downstream of the Gulf of Papagayo through this morning before winds and seas subside modestly this afternoon. Look for ENE winds to increase to near 20 kt again late tonight through Tuesday morning. Gentle to moderate S to SW winds are noted S of 06N, while gentle to moderate W to NW winds are N of 06N, with the exception of moderate to fresh southerly winds from 05N to 07N E of 80W. Combined seas of 4 to 6 ft, primarily in long- period SW swell dominate the offshore waters. These marine conditions will persist over the few days. REMAINDER OF THE AREA... A weak NE to SW ridge dominates most of the north waters N of 20N, and is producing mainly light and variable winds between 20N and 30N. Outside Seymour, two weak low pres centers of 1010 mb are noted along the monsoon trough near 17N116W and near 14N126.5W. Overnight scatterometer data suggested that winds were 20 kt or less surrounding these lows, and computer models do not indicate any strengthening during the next few days as they shift slowly W to NW. Seas of 8-10 ft in NW swell are noted per altimeter data N of 15N between 117W and 134W, and area forecast to subside to less than 8 ft across by Tuesday afternoon. A cold front will enter the NW waters near 30N140W this morning and will move across the NW waters, becoming stationary from 30N134W to 27N140W by this evening. This front will be reinforcing by a second cold front reaching the same area on Tue. The merging cold front is forecast to extend from 30N132W to beyond 26N140W by Tue night. Expect increasing SW winds to 20- 25 kt within 90 nm ahead of the front and building seas of 8-10 ft across most of the NW waters with these fronts on Tue. $$ Stripling