000 AXPZ20 KNHC 180906 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 906 UTC Sun Jun 18 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 0845 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10.5N83W to the NW across Central America to Guatemala near 15N92W, then resumes from 14N101W to 10N120W to 10N127W. The intertropical convergence zone axis extends from 10N127W to 07N140W. Scattered moderate and isolated strong convection is from 09N to 13N between 90W and 97W, and also within 180 nm S of the axis between 101W and 125W. Broad surface low pressure is forecast to continue for the next few days across most of Central America and Eastern Mexico under a diffluent upper ridge. Additionally, a surface low over the Gulf of Honduras is expected to drift NW across the Yucatan Peninsula during the remainder of the weekend, and into the S central Gulf of Mexico early next week. Locally heavy rainfall accumulations are possible as large clusters of TSTMs develop. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A NW to SE orientated ridge will meander across the EPAC waters well to the W of the offshore zones through Wed night, while a NW to SE orientated trough will meander across the Baja Peninsula and Gulf of California. A gentle to locally moderate NW breeze is forecast across the offshore waters W of 112W through this evening, then the pressure gradient will tighten with the NW flow increasing to a moderate to locally fresh NW breeze that will persist through late Mon, with these conditions continuing to the W of 113W on Tue and Wed as a N to S trough develops along 112W. Strong northerly drainage winds are expected in the Gulf of Tehuantepec on Mon night into early Tue, and then again Tue night into early Wed. Large SW swell across the waters S of 13N will linger through Mon, subsiding thereafter. A moderate W to NW breeze is expected elsewhere across the open Pacific waters through early Mon when the flow will diminish to a gentle westerly breeze. Large NW swell will reach 30N120W on Tue and reach 25N118W on Wed and Thu. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Broad low pressure is forecast across Central America and the adjacent offshore waters for the next few days. A moderate to locally fresh SW to W breeze is expected to dominate the entire forecast area through Mon, then the pressure gradient will relax with a gentle to moderate SW breeze forecast to continue through Thu night. Long period SW swell of 6 to 9 ft will spread across the entire offshore waters by the afternoon. These seas will begin to subside from the N late tonight, with seas less than 8 ft everywhere by Tue night. Seas will then continue to subside through Thu night. REMAINDER OF THE AREA... An area of 6 to 9 ft seas, primarily due to SW swell, is observed to the S of 15N and E of 130W. These seas will linger through the early part of the week, subsiding thereafter. Expect 3 to 6 ft seas to the lee of the Galapagos Islands. A ridge axis extends from 1025 mb high pressure N of the area near 35N137W to the SE, terminating near 15N113W. This ridge will gradually shift westward over the next few days terminating near 12N124W by early Tue. The ridge axis is forecast to move W of 140W Wed night into early Thu. A surface trough will extend S from the Baja California Peninsula to 17N114W on Mon night, and then shift W on Tue with a surface low developing along the trough near 18N118W by Wed night. The low should reach near 16N123W by Thu night. This pattern will result in the pressure gradient tightening across the NW and N central waters through mid-week, then diminishing S of 30N thereafter. Large N swell will build combined seas to 8 to 12 Ft to the N of 20N W of 120W by Thu. $$ Lewitsky