000 AXPZ20 KNHC 161542 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1542 UTC Fri Sep 16 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Tropical Storm Orlene is centered near 19.8N 125.9W at 1500 UTC moving W at 10 kt. Estimated minimum central pressure is 1003 mb. Maximum sustained winds are 40 kt with gusts to 50 kt. Isolated moderate convection is within 150 nm of the southern semicircle of the storm. Orlene is expected to continue weakening and moving W through Sun. Orlene could become a tropical depression as early as tonight. See latest NHC forecast/ advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. A broad area of low pressure has a center estimated near 12N105W, moving northwestward. This system has a high chance to become a tropical cyclone within the next 48 hours. Scattered moderate and isolated strong convection are within 180 nm of the southern semicircle and 360 nm of the northern semicircle of the low. Some of the northern convection is also associated with nighttime enhancements along the Mexico coastline. A gale warning is being issued beginning Sunday morning in anticipation of increasing winds in association with this low. See the latest high seas forecast under AWIPS/WMO headers MIAHSFEP2/FZPN03 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 11N91W through the 1007 mb special features low pres near 12N105W to 10N120W to 09N140W. Other than convection associated with the special features low, scattered moderate and isolated strong convection are from 07N to 17N between 91W and 102W. Isolated moderate convection is within 180 nm S of the monsoon trough axis between 108W and 124W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Surface ridging extends from 1026 mb high pres near 36N143W to near the southern tip of Baja California at 22N112W. The ridge is supporting mainly moderate northwesterly winds west of Baja California supporting seas of 4 to 6 ft. Winds will diminish by Sunday, with gentle to moderate winds prevailing west of Baja California. A surface trough over the Baja peninsula will maintain light to gentle winds over the Gulf of California through the weekend. Low pressure near 12N105W is forecast to move northwestward and increase in organization the next couple of days. This will lead to gale force winds becoming likely over the offshore zones once this system reaches around 17N latitude Sunday morning. The gale winds are expected to continue as this system likely becomes a tropical cyclone as it moves northwestward, to the west of southern Baja California. In the Gulf of Tehuantepec, N winds will pulse to between moderate and fresh during the overnight and early morning hours Sunday through Tuesday. N winds could become strong Tuesday night through early Wednesday morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds are expected through early next week north of 05N. Mainly moderate SW to W winds are expected over the waters S of 05N. Combined seas of 4 to 6 ft are likely across the entire area through the weekend into next week as long period SW swell continue to propagate across the equator from the southern hemisphere. Scattered showers and isolated thunderstorms are possible at night over the offshore waters. REMAINDER OF THE AREA... Aside from higher winds associated with Tropical Storm Orlene, The ridge over the northern waters will support mainly fresh trades through Saturday N of 14N and W of 128W. This will support seas between 8 and 9 ft from 13N to 24N W of 130W through Saturday. Winds and seas will diminish on Sunday as the ridge weakens and Orlene moves W. Low pressure near 12N105W is forecast to become a tropical cyclone as it passes within several hundred miles of the Mexico coast and Baja California through early next week. Strong winds and large swell will be likely over the open Pacific waters west of our offshore zones as far west as 120W Sunday through Tuesday. $$ Latto