000 AXPZ20 KNHC 290917 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 744 UTC Sat Jun 29 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure over the NW Gulf of Mexico combined with a tropical wave passing south of Tehuantepec is producing minimal N to NE gale conditions over the Gulf of Tehuantepec. Winds are expected to diminish below gale force today. 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 tropical wave is moving westward through the tropical eastern north Pacific, with axis near 106/107W. A Madden Julian Oscillation is currently propagating across the eastern north Pacific forecast waters. The MJO is providing favorable large scale lift and active convection across the area, as noted in the monsoon trough/ITCZ section below. This favorable large scale environment will be conducive for continued active weather, with the tropical wave providing a focus for a potential tropical cyclone to develop over the next several days. There is currently a high chance that a tropical depression will develop along this tropical wave during the next 48 hours. ...TROPICAL WAVES... The axis of a tropical wave is near 93W, moving W around 10 kt. Pre-existing active convection is noted along the monsoon trough as noted in the monsoon trough/ITCZ section below. The axis of a tropical wave is near 139W from 01N to 19N, moving W around 10 kt. Scattered moderate isolated strong convection is noted from 07N to 12N between 135W and 140W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N83W to 10N97W to low pres near 08N106.5W to 09N125W. The ITCZ extends from 09N125W TO 09N136W. A Madden Julian Oscillation that is propagating across the region is helping for an active monsoon trough. Scattered to locally numerous moderate scattered strong convection is seen about the monsoon trough from 05N to 13N between 81W and 120W. Scattered moderate isolated strong convection is from 07N to 12N between 128W and 135W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for more details about the current Gulf of Tehuantepec Gale Warning. Elsewhere 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. Small to moderate southerly swell from Tropical Depression Alvin will move through the offshore waters N of 20N through late tonight, but seas will generally remain at 6 ft or less. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Winds across the Gulf of Papagayo will strengthen late Sun night, then pulse each night through Wed night. Elsewhere moderate offshore winds will prevail north of the monsoon trough, with moderate S- SW winds south of the monsoon trough the next few days. S to SW long-period swell will propagate north of the equator on Sun, increasing offshore wave heights to near 7 ft, and then further to 8-9 ft by late Mon. REMAINDER OF THE AREA... Recently downgraded Tropical Depression Alvin centered near 20.3N 119.9W at 29/0900 UTC moving WNW at 7 kt. Estimated minimum central pressure is 1007 mb. The combination of shear and a more stable environment had helped to weaken the system, and maximum sustained wind speed is 25 kt with gusts to 35 kt. Only scattered moderate convection is noted and well removed to the NE of the low level circulation. Alvin is forecast to become a remnant low today, and dissipate later tonight. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. Outside of Alvin, A broad weak ridge extends from high pressure NNW of the area. Moderate trades prevail south of this ridge and west of 125W, with seas are mainly 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. $$ AL