000 AXPZ20 KNHC 112121 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2121 UTC Fri Aug 11 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Low pressure 1006 mb is about 180 nm W of Manzanillo, Mexico near 18.5N108W moving W-NW at around 15 kt. Plentiful convection extends far away from the low center, but little organized convection is near the actual center. Scattered moderate and isolated strong convection is within 300 nm in the SE quadrant, and within 240 nm in the W semicircle, with additional convection to the S and SW along a very active monsoon trough. Afternoon scatterometer data indicated an area of gale force winds being funneled offshore along the coast of Mexico, while surface observations at Manzanillo, Mexico have been sustained at 35 kt for a couple of hours. There has also been a recent elevated ship observation in the vicinity of the low of sustained 40 kt winds along with seas to 12 ft. The low is forecast to continue to move to the W-NW to the N of the Revillagigedo Islands through the weekend. This low has a high chance of becoming a tropical cyclone during the next 48 hours before it moves over cooler waters on Sunday. ...TROPICAL WAVES... A tropical wave is N of 06N with axis along 97W, moving W at 15 kt. Widely scattered moderate convection is observed N of 05N between 92W and 100W. This tropical wave will continue to move to the W-NW during the weekend. .INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from low pressure near 10.5N76W to 08N80W to low pressure near 11N94W, then resumes from 15N107W to 11N120W to 10N135W. The intertropical convergence zone axis extends from 10N135W to 10N140W. Scattered moderate and isolated strong convection is N of 03N and E of 83W, within 75 nm either side of the axis between 85W and 93W, and also within 150 nm either side of the axis between 107W and 130W. Scattered moderate convection is within 120 nm S of the axis between 130W and 138W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on developing low pressure W of Manzanillo, Mexico. Otherwise, a gentle to moderate breeze will prevail off the northern and central Baja California Peninsula through early next week. Overnight gap winds through the Gulf of Tehuantepec will increase to fresh tonight through Saturday morning, then again Saturday night through Sunday morning, as high pressure builds N of the area in the wake of a tropical wave. Long period southerly swell will propagate into the coast of southern Mexico from Sunday morning through Monday with seas building to 7 to 9 ft, gradually decaying through Tuesday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate S to SW winds are expected S of the monsoon trough, with mainly light to gentle variable winds N of the monsoon trough anticipated through Sunday. A new and more robust set of Southern Hemisphere swell is forecast by wave model guidance to cross the equator by early Saturday, bringing seas to 9 ft along the Central American coast Saturday through Monday, decaying thereafter. REMAINDER OF THE AREA... Weak 1012 mb low pressure centered near 11N94W is forecast to move W to near 11N97W by Saturday morning, possibly merging with the tropical wave just to the W. Otherwise, a broad surface ridge dominates the waters N of the monsoon trough. Gentle to moderate NE winds persist N of the monsoon trough, with moderate to locally fresh flow converging into the monsoon trough from the S-SW, supporting plentiful scattered showers and a few thunderstorms. No major changes are anticipated through the weekend. $$ Lewitsky