000 AXPZ20 KNHC 172205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Tue Nov 17 2020 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...SPECIAL FEATURES... Newly formed Tropical Depression Twenty-One-E is centered near 15.2N 113.3W at 17/2100 UTC or about 500 nm south-southwest of the southern tip of Baja California moving WNW at 10 kt. The estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. The overall cloud pattern of what earlier was a low pressure system has become more symmetrical in its shape during the course of the day, and associated cyclonic has become better defined as well. Latest satellite imagery shows that scattered moderate to isolated strong type convection has increased during the day within 240 nm of the center in the NE quadrant and within 210 nm of the center in the NW quadrant. Scattered moderate convection is noted within 150 nm of the center in the SE quadrant. The depression is forecast to become a tropical storm tonight near 15.6N 114.9W, with maximum sustained winds 35 kt gusts 45 kt and maintain that intensity through Wed before it begins to weaken Wed night as it moves into an environment of upper-level westerly shear and cooler sea surface temperatures. It is expected to become a remnant low within two to three days. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website- https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest Tropical Depression Twenty-One-E NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Gale Warning: A tight pressure gradient resulting from strong high pressure surging southward along the eastern slopes of the Sierra Madre Oriental mountains of Mexico and over the western Gulf of Mexico is ushering strong northerly gale force winds through the Chivela Pass and out into the Tehuantepec region. This event will be a long-lived with gale force winds forecast to reach near storm force late tonight into early Wed and again Wed night into early Thu. Wave heights are forecast to build to the range of 14-20 ft by early Wed. Wave heights downstream of the Gulf of Tehuantepec are forecast to build slightly large, possibly peaking to around 22 ft late Wed night into early Thu, with the leading edge of 8 ft or greater wave heights expected to reach near 04N100W on Thu and to near 03N107W on Fri. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from just west of northern Nicaragua near 13N88W to 15N100W to just east of Tropical Depression Twenty-One-E. It resumes just southwest of Tropical Depression Twenty-One-E near 14N113W and continues southwestward to low pressure near 12N119W 1013 mb and another low pressure near 10N126W 1013 mb and to 08N136W, where overnight scatterometer data indicates that the ITCZ begins and to continues to beyond the area at 09N140W. Scattered moderate convection is within 120 nm south of the trough between 87W-90W and within 60 nm south of the trough between 117W-119W and also within 60 nm south of the low pressure near 10N126W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A Gale Warning remains in effect for the Gulf of Tehuantepec. Please, see the Special Features section above for details. A ridge extends across the offshore forecast waters west of Baja California producing mainly gentle to moderate winds. Wave heights are in the 5-7 ft range south of Punta Eugenia, and 7-9 ft north of Punta Eugenia due to long-period northwest swell. The swell will slowly decay through Wed allowing for wave heights north of Punta Eugenia to lower to 5-7 ft. The latest Ascat pass shows lighter wind speeds in the light to gentle range over the southern part of the Gulf. The earlier moderate to fresh northwest winds over the northern part of the Gulf of California have become light and variable winds, and little change is expected with these winds through Thu. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Enhanced southwesterly flow of moderate to fresh speeds is occurring south of the monsoon trough portion offshore Panama as depicted by a recent ASCAT pass. In addition, ship with call letter ID "A8PQ4" at 11N88W is reporting west winds of 25 kt and combined wave heights of 7 ft. This enhanced flow is due to the broad cyclonic circulation that is occurring around Tropical Storm Iota now inland northern Nicaragua. Elsewhere, moderate to fresh southwest winds are present south of the monsoon trough east of 100W, with mainly gentle west to northwest winds north of the monsoon trough. Wave heights are in the 5-7 ft range. Wave heights generated in the Tehuantepec region will propagate across the offshore waters between 89W and 95W through late Wed. Scattered showers and thunderstorms in a wide band ahead of Iota are offshore the coasts of southeastern Honduras, El Salvador and Nicaragua. This activity will continue to spread westward out across the eastern half of offshore waters through Thu. The shower and thunderstorm activity may contain strong gusty winds. REMAINDER OF THE AREA... See the Special Features section above for the details on newly formed Tropical Depression Twenty-One-E that is located roughly 500 nm south-southwest of the southern tip of Baja California. A 1019 mb high is centered near 25N117W. The associated ridge dominates the waters north of about 16N and west of 110W. Gentle to moderate trades are along the southern periphery of the ridge west of 115W as were noted in a recent ASCAT pass. Wave heights are in the 6-7 ft range within that region. The recent ASCAT passes suggested that weak lows of 1013 mb are along the monsoon trough near 12N119W and 10N126W respectively. Scattered moderate convection is within 120 nm in the SE quadrant of the low near 12N119W. The ridge to the north of these lows will continue to weaken through Wed as a cold front that extends from near 32N128W to 27N124W and to 25N140W also weakens and dissipates as it reaches the northeast forecast waters by Thu. Large northwest swell, producing wave heights in the range of 8-10 ft, will follow in behind the front through Wed, then slowly decay through Thu. $$ Aguirre