Pacific Discussion

  • NHC East Pacific Tropical Weather Discussion
    by nhcwebmaster@noaa.gov (nhcwebmaster) on August 16, 2018 at 9:41 AM

    341 AXPZ20 KNHC 160941 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Thu Aug 16 2018 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 0800 UTC. ...SPECIAL FEATURE... Tropical Storm Lane is centered near 10.4N 126.4W at 0900 UTC, moving W at 10 kt. Estimated minimum central pressure is 1003 mb. Maximum sustained wind speed remains 45 kt with gusts to 55 kt and extend outward to 15 nm across the E semicircle. Peak seas are about 17 ft just NE of the center. Scattered to numerous moderate to strong convection is occurring within 75 nm across the NW and 120 nm across the SE semicircles, while bands of scattered moderate to strong convection is elsewhere within 300 nm across the NW and 210 nm across the SE semicircles. The convective pattern of Lane appears to be improving per overnight satellite imagery. However, a 0605 UTC ASCAT pass suggested that winds still remain in the 40-45 kt range attm. It is expected that the wind speed will begin to increase soon. Lane is expected to continue moving westward through Thu morning and gradually intensify, reaching hurricane strength this afternoon, then begin to veer more WNW and intensify further to major hurricane status late Fri. The small size of Lane is anticipated to retain gale force winds of less than 100 nm radius for the next few days and will limit the extent of 12 ft seas during that time. See latest NHC forecast/ advisory under AWIPS/WMO headers MIATCMEP4/WTPZ24 KNHC for more details. The Fuego Volcano in Guatemala near 14.3N90.5W emitted an ash cloud or plume Thu afternoon around 1916 UTC, and spread potential ash westward in the prevailing easterly low level winds over the Pacific waters to the west and across the Gulf of Tehuantepec tonight, generally from 14N to 16N between 91W and 95W. However, no further ash emissions have occurred overnight, and showers and thunderstorms occurring across the Gulf of Tehuantepec in recent hours have likely washed the atmosphere clean of ash. ...TROPICAL WAVES... A tropical wave extends from the northwestern Caribbean, across Central America, and into the Pacific down to about 06N along 85W-86W. Scattered moderate to strong convection is occurring ahead of the wave along the monsoon trough from 05N to 09N between 90W and 96W, while scattered moderate to strong convection is seen behind the wave from 04.5N to 09N between 84W and 90W and along the Pacific coasts of Costa Rica and Panama. A tropical wave along 103W-104W extends from 05N to 18N moving W 10-15 kt. Scattered moderate to strong convection is observed about the wave from 08N to 14.5N between 97W and 108W. A 1011 mb surface low is lingering along the monsoon trough ahead of the wave near 09.5N110W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N74W TO 07.5N91W TO LOW PRES NEAR 09.5N110W TO 11N117W. The ITCZ extends from 12N134W TO beyond 11N140W. Scattered moderate to strong convection is seen in satellite imagery from 05N to 10N between 82W and 97W, and from 08N to 14.5N between 97W and 120W. Scattered moderate to strong convection is observed within 120 nm SE of the ITCZ west of 138W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Weak surface ridging extends from the NE Pacific Se into the area from around 30N134W to near las Islas Revillagigedo. A weak trough associated with the remnants of tropical cyclone John lingered across the coastal waters near Punta Eugenio, and is aiding in producing gentle N to NW winds across the near shore waters of Baja California, with moderate NW winds further offshore. NW winds should remain moderate or weaker through Sat until th ridge strengthens slightly and freshens the winds Sat afternoon through Sun. No significant gap wind events are expected in the Gulf of Tehuantepec, although nocturnal northerly drainage flow to around 20 kt is expected there each night. Long-period S to SW swell originating south of the equator is impacting the Mexico offshore zones from Cabo Corrientes southeastward, producing seas of 7 to 10 ft. This swell is generating very large and dangerous surf conditions along the coastlines and outer reefs with localized breaking waves of 15 to 20 ft expected through late this morning. These swell will gradually be diminishing during the next two to three days. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough should remain near 10N during the next few days. Easterly winds north of the trough will be moderate or weaker, while southwesterly winds south of the trough will also be moderate breeze or weaker. Long-period SW swell originating south of the equator is also impacting the Central America, Colombia, and Ecuador offshore zones, producing seas of 6 to 9 ft. Large breaking waves are also occurring across these coastlines and outer reefs with localized breaking waves of 10-15 ft expected through late this morning. These swell will gradually be diminishing during the next two to three days. REMAINDER OF THE AREA... See discussion above for Tropical Storm Lane. A weak 1013 mb low pressure center is located near 18N139W and moving westward near 12 kt. Scattered moderate isolated strong convection is observed within 120 nm across the NW semicircle. Fresh to strong easterly winds are occurring across the northern periphery of the low center, due to the pressure gradient imposed by the ridge centered north of the area. Seas within this area of winds are 7-9 ft. Building high pressure north of the area will maintain this area of fresh easterly winds today, even as the low pressure opens into a trough over the next 12-24 hours, and moves to the west of 140W late today. Long-period cross-equatorial southerly swell, in the form of 7 to 9 ft seas, will propagate N across the tropical waters S of 20N E of 125W overnight through today, and then subside to less than 8 ft on later tonight. $$ Stripling […]

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