000 AXPZ20 KNHC 290254 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Fri Jun 28 2019 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 0000 UTC surface analysis and satellite imagery through 0200 UTC. ...SPECIAL FEATURES... Tropical Storm Alvin IS centered near 20.1N 119.3W at 0300 UTC moving NW at 11 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. Scattered moderate convection is present within 240 nm across the N semicircle of the center. Alvin continues to be impacted by strong upper level wind shear and is ingesting dry and stable air. Steady weakening is forecast, with Alvin expected to become a tropical depression Sat morning and a remnant low by Saturday afternoon, then dissipate on Sunday. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. Gulf of Tehuantepec Gale Warning: High pressure over the NW Gulf of Mexico combined with a tropical wave passing south of Tehuantepec is causing a strong Gulf of Tehuantepec gap wind event. Minimal N to NE gale conditions are expected to continue through Sat night then slowly diminish Sun and Mon. Peak seas occurred at around 16 ft this morning, and will fluctuate around 12 ft through early Sun morning. Please see the latest High Seas Forecast issued by the National Hurricane Center under AWIPS/WMO headers FZPN03 KNHC/HSFEP2 or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for details. A pair of tropical waves are moving westward through the tropical eastern Pacific this evening, and passing S and SW of the Gulf of Tehuantepec. One wave is along 106W and the second along 92W-93W, and are provoking very active weather along the monsoon trough between NW Costa Rica and 114W, where scattered to locally numerous convection is occurring. Environmental conditions are expected to be conducive for continued active weather and the potential development of a tropical cyclone over the next several days. A tropical depression is likely to form late this weekend or early next week while these two disturbances moves W to WNW and remain well away from the coast of Mexico. This system has a medium chance of becoming a tropical depression during the next 48 hours and a high chance of becoming a tropical depression during the next 5 days. ...TROPICAL WAVES... A tropical wave along 137W-138W from 01N to 19N is moving W around 10 kt. Scattered moderate isolated strong convection is seen from 06.5N to 12N between 127W and 138W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N75W to low pres near 07N106.5W to 10.5N115W TO 09.5N125W. The ITCZ extends from 09.5N125W TO 08.5N135W. Scattered to locally numerous moderate scattered strong convection is seen about the monsoon trough from 04N to 11N between 82W and 120W. Scattered moderate isolated strong convection is from 11N to 13N between 96W and 113W, and from 127W to 138W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for more details about the Gulf of Tehuantepec Gale Warning. Relatively tranquil marine conditions are expected for the next several days over the Gulf of California, and the offshore waters of Baja California. Late afternoon and evening winds along the Pacific coast of the Baja Peninsula will reach around 20 kt for the next few days, but otherwise typical early summer conditions will prevail under modest high pressure. Tropical Storm Alvin is moving NW away from the area and not expected to significantly impact the Mexican offshore zones. Small to moderate southerly swell from Alvin will move through the offshore waters N of 20N tonight through late Sat, but with seas generally remaining at 6 ft or less. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... A tight north to south pressure gradient across Central America is causing a significant Gulf of Papagayo gap wind event. Fresh to strong NE winds are expected to extend from the coast of Central America to 95W through Sat, then diminish by Sat night as the pressure gradient relaxes. The unusual length of this plume of strong offshore winds extending from the Papagayo area will generate a broad zone of seas 7 to 10 ft through Sat that will combine with N swell from Tehuantepec to produce a large area of high seas between 90W and 100W through Sun. Elsewhere moderate offshore winds will prevail north of the monsoon trough, with moderate S- SW winds south of the trough axis the next few days. New S to SW long-period swell will reach the equator beginning on Sun and raise offshore wave heights to near 7 ft north of the equator, and to 8-9 ft by late Mon. REMAINDER OF THE AREA... Please see the Special Features section for more details about Tropical Storm Alvin. A broad weak ridge extends from high pressure NNW of the area. Moderate trades prevail south of this ridge and west of 125W. Seas are mainly running 5 to 8 ft in mixed northerly and southerly swell. Little change in the overall pattern is expected for several more days. Trades will strengthen slightly in the W central waters this weekend into early next week, with seas building to between 8 and 10 ft. SW and SE swell along the equator will gradually decay. $$ Stripling