- NHC East Pacific Tropical Weather Discussion
by nhcwebmaster@noaa.gov (nhcwebmaster) on September 20, 2020 at 9:20 AM000 AXPZ20 KNHC 200920 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sun Sep 20 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 0600 UTC surface analysis and satellite imagery through 0915 UTC. ...SPECIAL FEATURES... Broad low pressure is located a couple of hundred nm south- southwest of Manzanillo, Mexico. The surface low center is centered along the monsoon trough near 15N107W, or approximately 300 SSW of Manzanillo, Mexico. Its estimated pressure is 1007 mb. Satellite imagery shows scattered moderate to isolated strong convection from 10N to 14N between 100W-104W and from 10N to 13N between 104W-112W. Recently developed scattered moderate to strong is within 90 nm of the low in the SW quadrant. Scattered moderate convection is within 60 nm of the low in the SW quadrant. Atmospheric conditions are forecast to be conducive for additional development, and a tropical depression is expected to form early next week while the system moves in a general west-northwestward track. This system has a high chance of becoming a tropical cyclone during the next 48 hours. Please refer to the latest NHC Tropical Weather Outlook at www.hurricanes.gov for more details. ...TROPICAL WAVES... A tropical wave has its axis along 131W from 03N to 17N. It is moving westward 10 to 15 kt. Only isolated showers and thunderstorms are seen within 120 nm east of the wave from 08N to 10N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A segment of the monsoon trough extends from 11N86W to 13N96W to low pres near 15N107W 1007 mb to 12N116W to 11N128W to low pres near 10N131W 1008 mb and to 09N140W. Scattered moderate to isolated strong convection is from 10N to 14N between 100W-104W and from 10N to 13N between 104W-112W. Scattered moderate convection is within 120 nm north of the trough between 131W- 133W and within 30 nm south of the trough between 126W-128W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Weak deep layer ridging observed between Baja California and 125W is supporting moderate to fresh winds off Baja California Norte with combined seas to 7 ft. A 00436 UTC ASCAT showed northwest to north 15-20 kt winds mainly north of 28N. Winds and seas will diminish into early next week as the ridge weakens. Farther south, fresh to strong winds will pulse in the Gulf of Tehuantepec region, starting tonight. Elsewhere, a weak pressure pattern across the region will result in mainly gentle to moderate winds and slight seas. A large cluster consisting of scattered moderate to strong convection has formed over the Gulf of Tehuantepec region from 14N to 16N and between 93W and 95W. This activity contains frequent lightning and most likely strong gusty winds. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Gentle to moderate south to southwest winds continue south of the monsoon trough. Elsewhere, gentle winds prevail north of the monsoon trough. Combined seas are currently in the 5-6 ft range in a mix of wind waves and southerly swell. Clusters of nocturnal scattered moderate to isolated strong are developing along and just inland the majority of the Central American coast. REMAINDER OF THE AREA... A surface trough along 132W from 16N to 25N is breaking up the subtropical ridge and supporting only gentle moderate trade winds farther south into the deep tropics. The ridge will gradually build eastward north of 20N through early next week, and trades will strengthen somewhat between the ridge and the monsoon trough. Farther east, seas are in the 7-8 ft range in an area along the monsoon trough between 105W and 115W. These seas are within 240 nm of the new low pressure centered near 15N107W and are due to a combination of moderate to fresh southwest winds and longer period SW swell. Over and just of this low pressure system, seas are lower, in the 5-7 ft range, as revealed by a recent altimeter data pass. $$ Aguirre