000 AXPZ20 KNHC 181631 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sun Aug 18 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 1200 UTC surface analysis and satellite imagery through 1445 UTC. ...SPECIAL FEATURES... A 1010 mb low pressure center remains about 100 nm SW of the Pacific coast of Guatemala, located near 12N92W moving WNW near 5 kt. Scattered moderate to strong convection is noted within 75 nm SE and 120 nm across the NW semicircle of the low, and also from 1N to the coast of San Salvador between 87.5W and 90.5W. Additionally, scattered to numerous moderate to strong convection is occurring to the W of the low from 08N to 16.5N between 95W and 100W, affecting coastal portions from Salina Cruz to Puerto Escondido, Mexico, with heavy rainfall. This low is expected to move W-NW through the next couple of days and has a medium chance of tropical cyclone formation. Heavy rainfall and the potential for flash flooding will continue along the coastal zones through Tuesday from El Salvador to SE Mexico as this system shifts westward. Winds and seas are expected to increase as the low generally tracks parallels to the coast. Refer to the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOEP/ABPZ20 KNHC for more information. ...TROPICAL WAVES... A tropical wave extends from the Yucatan Peninsula SSE to the coastal waters of western Costa Rica and Nicaragua. This wave is moving W at 10-15 kt. Convection noted with this wave is mostly occurring E of the wave across the W Caribbean and Central America. A tropical wave extends from the Cabo Corrientes area SSW near 05N108W, moving W at around 10 kt. Convection is noted well W of this wave, where scattered moderate to strong is noted from 09N TO 16.5N between 108W AND 113W. A tropical wave is along 118W-119W, moving W at around 5-10 kt. Overnight scatterometer data showed an elongated area of low pressure associated with this wave between 112W and 119W. A 1009 mb surface low is estimated to currently be located near 12.5N117.5W. Scattered to locally numerous moderate to strong convection is noted within 270 nm across the SW semicircle, where fresh SW to W surface winds are occurring. A tropical wave is along 128W, with a 1010 mb low pressure center near 14N128W, moving W at around 5 kt. Scattered moderate to strong convection is within 150 nm in the N quadrant of the low. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09.5N74W TO 08.5N86W to low pres near 12N92W to low pres near 12.5N117.5W to low pres near 14N128W TO 12N133W. Scattered moderate to strong convection is noted FROM 08N TO 11N BETWEEN 93W AND 99W. Scattered to locally numerous moderate to strong convection is noted from 08N TO 16.5N between 95W AND 100W and also from 09N TO 16.5N between 108W AND 113W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for more details about the low pressure area south of Guatemala and approaching the Gulf of Tehuantepec. A weak high pressure ridge extends SE from the north-central Pacific into the Baja California offshore waters, bringing gentle to moderate NW winds to these waters. This ridge will slowly shift SE into the middle of the week, causing the pressure gradient to increase Monday through early Wednesday. This will support moderate to fresh NW winds offshore of Baja California Norte, becoming fresh to locally strong Tuesday afternoon and evening. A low pressure trough along the Baja California peninsula will support fresh S to SE winds over the northern Gulf this morning before tonight. This trough will redevelop again late Wed into Thu to again produce fresh southerly wind flow across the northern Gulf. As mentioned above, the low pressure system located SW of Guatemala will shift generally WNW for the next few days, with winds gradually increasing to 20-25 kt and seas near 8 ft across the northern semicircle of the low. Additionally, very active weather will accompany this feature and across SE Mexico and the coastal zones through Tue or Wed, and could produce periods of very heavy rainfall and lead to flash flooding. See the latest statements issued by your local meteorological service. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please see the Special Features section for more details about the low pressure area SW of Guatemala. Fresh offshore winds prevail across the Gulf of Papagayo region and Nicaragua waters this morning, behind a tropical wave and low pressure offshore of Guatemala. Winds across the Papagayo region will remain offshore and pulse at times to fresh through the early part of the week. Southerly swell with seas of 5 to 7 ft offshore of Ecuador and the Galapagos Islands will subside today, with new long period SW swell arriving by mid-week. Otherwise, mainly moderate W to SW winds will prevail S of 10N, along with seas of 4 to 6 feet. REMAINDER OF THE AREA... A weak ridge extends SE from 1023 mb high pressure near 41N143W. Scatterometer data showed gentle to moderate trades outside of any deep convection, while altimeter data sampled 4-7 ft seas, except N of 28N between 120W and 128W where seas were up to 8 ft in northerly swell. The swell will subside through today. A weak cold front or pre-frontal trough is forecast to breach SE of 30N140W by the end of the forecast period with a wind shift and building seas to 7 ft behind it. This will force the ridge ahead of it to shift ESE, and gradually tighten the pressure gradient to the south across the tradewind belt. E to NE tradewinds will freshen W of 120W Tue through the end of the week due to this pattern shift. $$ Stripling