000 AXPZ20 KNHC 071602 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon Aug 7 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ..TROPICAL WAVES... A tropical wave axis is along 103W/104W north of 08N, moving west around 13 knots. The 700 mb streamline analysis from the GFS depicts this wave within the same general area. This wave is well noted on long term visible satellite imagery as well as in the total precipitable water (TPW) animation imagery derived from CIMSS. The TPW imagery clearly shows that the wave is embedded within a large deep pool of moisture, and that it also marks the leading the edge of additional deep layer moisture that exists south of central America to 08N. Scattered moderate convection is within 180 nm east of the wave from 09N to 13N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 12N88W to 09N106W to 09N118W to 12N130W to 12N140W. Scattered moderate convection is within 180 nm south and 120 nm north of the axis between 90W and 101W, also within 120 nm south of the axis between 119W and 122W, within 120 nm north of the axis between 129W and 135W and within 120 nm south of the axis west of 135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A 1011 mb low pressure center, remnants of recent Tropical Depression Eleven-E, is centered near 21N112W and is nearly stationary. Latest satellite imagery shows a swirl of low to mid- level clouds within 75 nm either side of the low center. Isolated showers are possible with these clouds. An Ascat pass from 0414Z last night indicated mainly gentle cyclonic winds within about 75 nm of the center, with some moderate wind speeds in the west and northwest quadrants. The low is forecast to become a trough by Wednesday as it drifts southeastward to the vicinity of the the Revillagigedo Islands. The morning satellite imagery shows scattered moderate to strong convection within 60-120 nm offshore the coast of central Mexico from 17N-21N. This activity develop during the overnight hours along the Mexican coast before it moved offshore under upper level strong northeast flow found around the southern periphery of a large upper anticyclone that is centered along the northwestern coast of Mexico at 28N110W per latest water vapor imagery. Recent lightning data indicates frequent strikes with this activity. This convection will continue to push offshore through the morning, then weaken this afternoon. A ridge will dominate the offshore waters to the west of northern and central Baja California. Expect gentle to moderate northwest to north winds, with seas in the range of 4 to 5 ft west of the Baja California peninsula. Mainly gentle southerly flow will continue across the Gulf of California through Wednesday. Gulf of Tehuantepec: winds are forecast to be light to gentle in speed, and variable in direction through Wednesday. Wave model guidance has been suggesting consistently that a new set of long-period southerly swell, with the leading edge containing a period of 20 to 21 seconds, is forecast to reach the coast of Mexico south of Cabo Corrientes on Tuesday. This scenario will bring the potential for large breaking waves as it reaches shallow waters along the coast of Mexico on Tuesday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The Gulf of Papagayo: west to northwest light to gentle winds will continue through Wednesday, with seas of 4 to 5 ft in a SW swell. Moderate southerly winds are expected to the south of the monsoon trough, with gentle and variable winds to the north of the monsoon trough, with seas generally in the 4 to 6 ft range. A set of long-period southerly swell, with a leading edge period of 20 to 21 seconds, is forecast to reach the coastal areas of Costa Rica and Panama beginning this evening and Tuesday. Wave model guidance is suggesting that wave heights will build to the range of 6 to 7 ft mainly over portions of 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 strong convection is just west of Colombia within 30 nm of a line from 03N78W to 06N78W. This activity is expected to last during the next 24 to 48 hours. REMAINDER OF THE AREA... Surface ridging across the area is forecast by the models to build some southeastward through Wednesday as the parent high of located well to the northwest of the area drops southeastward. This will push the remnant low of Tropical Depression Eleven-E southeastward towards the vicinity of Revillagigedo Islands west of central Mexico as it weakens to a trough as mentioned above. 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 128W, along with resultant seas in the range of 5 to 6 ft. Low pressure of 1010 mb is forecast to develop along the monsoon trough near 13N130W in about 24 hours or so. A second 1010 mb low pressure center is forecast to form near 12N137W in 24 hours also. The 13N130W low pressure center is expected to dissipate in 48 hours. The 12N137W low pressure center is expected to move near 12N139W in 48 hours. No significant organization is expected with either of these lows. The pressure gradient between the ridge and lower pressure near the monsoon trough region, including the aforementioned forecast lows, will allow for moderate to locally fresh trade winds from about 12N to 19N and west of 128W, along with resultant seas in the range of 5 to 6 ft. $$ Aguirre