000 AXPZ20 KNHC 080924 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Tue Aug 8 2017 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 0822 UTC. ..TROPICAL WAVES... A tropical wave is along 106W/107W, from 19N southward, moving westward 10 knots. The latest satellite derived high density winds were showing cyclonic turning in this area. No significant deep convective precipitation is apparent just with the tropical wave. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough is along 13N102W 11N110W 10N120W 07N129W. Another segment is along 13N130W, to a 1013 mb low pressure center that is near 13N137W, beyond 11N140W. Convective precipitation: scattered strong from 14N to 17N between 94W and 96W including in the Gulf of Tehuantepec. Scattered moderate to isolated strong from 02N to 11N from 90W eastward, from 07N to 17N between 98W and 116W, within 30 nm to the north of the monsoon trough between 122W and 125W, and from 12N to 14N between 137W and 139W. Scattered moderate to strong along the coast of Mexico from 24N to 27N between 107W and 110W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A 1011 mb low pressure center, remnants of recent Tropical Depression Eleven-E, is near 20N112W and remains nearly stationary. Latest satellite imagery shows a swirl of low level to middle level clouds within 75 nm radius of the low center. Rainshowers are possible with these clouds. A scatterometer pass at 08/1700 UTC showed moderate winds within 120 nm of the center in the NW quadrant, and gentle winds elsewhere. The low center is forecast to become a trough by Wednesday as it drifts southeastward near the Revillagigedo Islands. A weak surface ridge extends along 27N. The gradient between the ridge and lower pressure in the Colorado River basin is supporting moderate to fresh northerly winds off the northern coast of Baja California Norte. The ridge is maintaining generally light to gentle winds elsewhere with 4 to 6 ft seas in southerly swell. Wave models are indicating that a reinforcing round of long period southerly swell may move into the region by Friday into Saturday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate southerly winds are expected to the south of the monsoon trough, with gentle and variable winds to the north of the monsoon trough. Sea heights generally will range from 4 feet to 6 feet. A set of long-period southerly swell, with a leading edge period of 20 to 21 seconds, is imminent in the coastal areas of Costa Rica and Panama, from today until Wednesday and possibly into Thursday. Wave model guidance is suggesting that wave heights will build to the range of 6 to 7 ft mainly in the the offshore waters of Costa Rica and Panama on Tuesday, with some potential for large breaking waves as it reaches shallow waters along the coast. Scattered moderate to isolated strong convective precipitation is in the inland areas and coastal areas of Colombia from 02N to 08N between 76W and 79W. This activity is expected to last during the next 24 to 48 hours. REMAINDER OF THE AREA... A surface ridge is forecast by the global models to build southeastward through Wednesday as the parent high, that is located well to the northwest of the area, drops southeastward. This will push the remnant low of Tropical Depression Eleven-E southeastward toward the Revillagigedo Islands, that are to the west of central Mexico, as it weakens and becomes a surface trough. The pressure gradient between the ridge and lower pressure near the monsoon trough region will allow for moderate to locally fresh trade winds from about 12N to 19N and west of 125W, along with resultant seas in the range of 5 to 6 ft until Saturday night. The same wind and sea height conditions will continue from Saturday night until Monday night, but from 13N to 30N from 125W westward. A first 1012 mb low pressure center is forecast in 24 hours near 13N132W along the monsoon trough. A second 1012 mb low pressure center is forecast to develop along the monsoon trough near 13N138W, also in 24 hours. Each low pressure center is forecast to dissipate by 48 hours. No significant organization is expected with either of these lows. Model guidance is forecasting an event of 8 foot sea heights crossing 03.4S from 120W eastward on Friday evening in 3 days, and moving northward and reaching the Equator just after midnight on Sunday. Sea heights ranging from 8 feet to 9 feet are forecast to reach the coastal waters of Panama and Costa Rica between 79W and 87W, and the coastal waters of Guatemala, around sunrise on Sunday. The overall areal coverage by late Monday will be from 02N to 07N between 81W and 86W, and from 05N to 16N between 90W and 114W. $$ mt