000 AXPZ20 KNHC 092205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Mon Mar 9 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... Gulf of Tehuantepec Gale Warning: The earlier gale force north to northeast winds across the Gulf of Tehuantepec have diminished to just below gale this afternoon, however wave heights are still rather high peaking to around 12 ft just downstream of the Gulf. Winds are expected to pulse back up to gale force tonight as the pressure gradient over southeastern Mexico tightens slightly and while local drainage flow is occurring. Model guidance indicates that the gale force winds will continue through early Wed before diminishing to mainly strong speeds as the high pressure over the western Atlantic weakens and shifts eastward. A large area of south to southwest is located well to the south and southwest of the Tehuantepec from 01N to 14N and between 93W and 117W and with wave heights in the range of 8-10 ft. These area of swell will gradually decay through Wed, with wave heights lowering to 8 ft by that time. For more information please read 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 further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from just southwest of southern Costa Rica near 08N84W to 03N93W and to 02N101W, where latest scatterometer data indicates that it transitions to the ITCZ axis and continues to 05N116W and to 09N130W, where it its briefly interrupted by a trough that extends from 20N114W to 14N120W. It resumes at 08N136W and to beyond the area at 07N140W. A second ITCZ axis extends from 07S84W to 07S90W to 04S98W to 04S108W and to 01S112W. Scattered moderate convection is noted within 120 nm south of the second ITCZ between 95W and 99W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details on a gap wind event in the Tehuantepec region. Weakening high pressure is located over the offshore waters of the Baja California Peninsula. This is maintaining light to gentle southeast to south winds within about 90 nm of the Baja California Peninsula coast, with wave heights in the 5-7 ft range due to long-period northwest swell combination combining with long period south to southwest swell. Beyond 90 nm, stronger southeast to south winds of fresh to strong speeds are present ahead of an approaching frontal system. Wave heights in these waters are higher, in the 6-8 ft range. Abundant upper-level moisture in the form of overcast multilayer clouds are streaming east-northeastward over these offshore waters to across the Baja California Peninsula and northern and central Mexico. This is due to a very dynamically active jet stream branch that stretches from well west of the area in the central tropical Pacific east-northeastward to across central Baja California. Areas of rain along with embedded scattered showers and isolated thunderstorms are possible underneath these clouds. Looking ahead, the aforementioned weakening high pressure will continue to shift eastward in response to an approaching frontal system and associated low pressure of 1007 mb presently analyzed near 30N131W. this low is forecast to lift northeastward through Wed as it weakens. The attendant cold front will begin to weaken as it moves over the water just west of northern and central Baja California on Wed. The interaction between a ridge of high pressure in the wake of the front and the typical Baja California thermal trough should help induce fresh to strong northwest over the southern Gulf of California and over the waters between Los Cabos and Cabo Corrientes from late Tue night through Wed night along with wave heights there building to a peak of 8 or 9 ft. Farther south, long period southerly swell will dominate the Mexican offshore waters south of 20N through late week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: A tight pressure gradient between high pressure north of the area and lower pressure to the south continues to support northeast 20-30 kt winds across the Papagayo region. This flow tends to be the strongest during the early morning hours enhanced by drainage flow across the area. These winds will continue across the region through the middle of the week, with winds pulsing to near gale force each night and into the early morning hours. Wave heights will peak around 10 ft downstream of the Gulf each morning during the next few days. As the high pressure slides eastward and weakens over the western Atlantic, these winds should subside late in the week. Gulf of Panama: High pressure north of the area will maintain fresh to strong north to northeast winds over and downstream of the Gulf of Panama for the next few days. Wave heights with these winds are expected to reach up to 10 ft well downstream of the Gulf, mixing with a component of longer period southerly swell. Elsewhere, mixed northeast and southwest swell is resulting in a large area of high seas, up to 11 ft, across much of the waters off the coast of Central America. These wave heights are expected to only slowly subside during the next couple of days. REMAINDER OF THE AREA... A cold front, associated with a large low pressure system near 30N131W with a pressure of 1007 mb is analyzed from near 32N124W to 22N130W and to 20N140W. Earlier scatterometer and ship data indicate that strong NW winds, up to 30 kt, were occurring behind the front over the northwestern waters. Latest altimeter satellite data from this afternoon showed wave heights in the 11-17 ft range behind the front, likely with a component of NW swell. A few showers and thunderstorms are occurring near the front, north of 28N and on the south side of the low north of 28N between 130W and 134W. An area of fresh to strong southeast inds and seas to 9 ft are likely still occurring between high pressure off Baja California Norte and a trough in the deep tropics from 08N to 15N along 129W/130W. These winds and seas should diminish early tonight. Elsewhere, the weaken that normal subtropical ridge is resulting in light to moderate trades across the deep tropics. The surface low and associated front will weaken as they continue eastward during the next few days, reaching 120W by late Wed. This will allow winds to diminish over waters north of 25N. Northwest swell in excess of 8 ft will cover most of the area north of 10N and west of 120W by the middle of the week before subsiding. By late week, high pressure will build north of the area in the wake of the front and low, supporting fresh trades wave heights and wave heights to a peak of 8 ft in mixed swell over the deep tropics west of 120W. Farther east, wave heights in the range of 8-10 ft cover a large area generally south of 12N between 90W and 115W. This is associated with confused seas related to a mix of longer period southerly swell and components of shorter period northeast and east swell related to the persist gap wind events in Tehuantepec and Papagayo. These seas will gradually subside during the next few days as the gap winds diminish. $$ Aguirre