000 AXPZ20 KNHC 210401 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sat Sep 21 2024 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 0000 UTC surface analysis and satellite imagery through 0320 UTC. ...SPECIAL FEATURE... A Central American Gyre is gradually developing this weekend and will continue through the middle of next week. This scenario, combined with daytime heating and orographic lifting, is expected to generate periods of excessive rainfall over southern Mexico and Central America, as well as the adjacent W Caribbean and E Pacific waters between 80W and 95W. This activity could produce dangerous flooding and mudslides across the area. Furthermore, strong to near gale force winds, rough seas and tstms are forecast to affect the offshore waters between Costa Rica and El Salvador from Mon night through mid week. Please follow the forecasts from your local weather offices for more detailed information. ...TROPICAL WAVES... A tropical wave moves across the Yucatan Peninsula, Guatemala and its E Pacific offshore waters. The wave axis is near 90W and is moving westward at about 10 kt. Scattered moderate convection is noted from 06N to 15N between 83W and 97W. A tropical wave has its axis along 107W from 05N to 18N, and is moving westward at 10-15 kt. Scattered moderate isolated strong convection is from 09N to 16N between 100W and 114W. A tropical wave has its axis along 124W from 04N to 16N moving westward at about 10 kt. Scattered moderate convection is from 09N to 14N between 114W and 127W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N85W to a 1007 mb low near 14N107W to 09N130W to 10N137W. The ITCZ continues from 10N138W and then beyond 10N140W. Aside from the convection associated with the tropical waves described above, scattered moderate convection is N of 03N and E of 83W. Scattered moderate convection is also from 07N to 14N W of 135W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad surface ridge extends southeastward into the region. Moderate to fresh northwest winds are over the Baja California offshore waters with moderate seas. Along the Gulf of California, light to gentle winds are ongoing, except for moderate to fresh SW winds in the northern Gulf N of 29N. Light to gentle winds and slight seas are elsewhere, except for moderate to locally fresh W winds over the outer southern Mexico offshore waters. For the forecast, the surface ridge will remain in place and fluctuate into the weekend. Moderate to fresh NW winds will continue over the Baja California offshore waters through late Sat night, then diminish to gentle to moderate speeds afterward into Mon night. Ongoing moderate to fresh SW winds in the northern Gulf of California will diminish to gentle speeds Sat and then prevail through Wed night. An active monsoon trough will support moderate to fresh W to SW winds across the outer SW Mexican offshore waters tonight through Tue night. Looking ahead, an area of low pressure could form well to the southwest of the southwestern coast of Mexico this weekend. Environmental conditions appear conducive for some slow development of this system, and a tropical depression could form during the next few days while it slowly moves generally north to northeastward. Regardless of development, strong to near-gale force winds and rough seas are forecast to affect the S and SW Mexican offshore waters starting Tue evening and continuing through the end of the week. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh southwest to west winds are ongoing south of the monsoon trough and across the offshore waters from Colombia to Costa Rica along with moderate seas. Gentle to moderate winds and slight to moderated seas prevail elsewhere. Scattered heavy showers are over the majority of the Central America offshore waters. For the forecast, moderate to fresh southwest to west winds south of the monsoon trough will change little through the weekend, then increase to fresh to near gale force speeds across the offshore waters from Costa Rica to Guatemala late Mon through Wed night. Seas will build during this time in mixed swell. The monsoonal flow is expected to become very active, and dominate the region through early next week. This pattern will generate increasing westerly wind waves moving into the area waters. Periods of very active weather are also expected across the Central America offshore waters through mid week. ...REMAINDER OF THE AREA... Surface ridging extending from a pair of high pressure centers located well NW of the area reaches ESE to the Baja California Peninsula offshore waters and south to about 20N. The pressure gradient between the ridge and the monsoon trough to the south is resulting in moderate to fresh NE trade winds and moderate seas from 10N to 20N and W of 132W. Gentle to moderate NE to E winds and moderate seas are elsewhere N of 10N. South of the monsoon trough and between 102W and 120W SW winds are fresh to strong and seas are 7-8 ft. Between 82W and 102W, SW winds are moderate to fresh and seas are 5-7 ft. For the forecast, fresh to strong winds and rough seas to 10 ft are forecast to develop tonight in association with a 1010 mb low located near 10N138W. The low will prevail in that region Sat and then move W of 140W Sat night. SW monsoonal winds will continue to become well established through the weekend as the monsoon trough lifts slowly northward. Looking ahead, an area of low pressure could form well to the southwest of the southwestern coast of Mexico this weekend. Environmental conditions appear conducive for some slow development of this system, and a tropical depression could form during the next few days while it slowly moves generally north to northeastward. Regardless of development, strong to near gale force SW to W winds will develop and amplify, covering the open waters between 90W and 110W Mon night through Wed night. $$ Ramos