000 AXPZ20 KNHC 181605 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 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 1200 UTC surface analysis and satellite imagery through 1445 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 11N75W TO 09.5N82W to low pres near 14N91W 1007 MB to low pres near 09N118W 1010 MB to low pres near 10N128W 1010 MB. The ITCZ extends from 10N128W to beyond 06N140W. Scattered moderate to strong convection is noted from 04.5N TO 08.5N between 78W AND 82W...from 07.5N TO 16N between 87W AND 97W...and within 210 NM S of trough between 104W AND 122W. A broad cyclonic circulation in the lower atmosphere is forecast to continue for the next few days across most of Central America and Eastern Mexico and adjacent oceanic areas. An upper level ridge is also forecast to persist across this area and will provide favorable upper atmospheric conditions for sustained deep convection. A surface low currently along the coast of Mexico between Cancun and Belize City 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 likely during the next 2-3 days as large clusters of TSTMs develop around the periphery of this broad circulation. ...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. Moderate to fresh northerly drainage winds are expected in the Gulf of Tehuantepec on Mon night into early Tue, and then again Tue night into early Wed associated with the broad low pressure across Central America and the Yucatan Peninsula. Large S swell across the waters S of 13N will maintain seas at 8 ft and higher 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, the Yucatan Peninsula, and the adjacent offshore waters for the next few days, as it shifts slowly NW. This will maintain moderate to locally fresh SW to W breeze monsoonal winds across the area waters through Mon, then the pressure gradient will relax with a gentle to moderate SW breeze forecast to continue through Thu night. Long period S swell of 6 to 9 ft will spread across the entire offshore waters today. This S swell will then begin to slowly subside tonight, with seas less than 8 ft area wide 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 SSW swell, is observed to the S of 15N and E of 130W. These moderate 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 36N135W to the SE, terminating near 18N117W. 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. $$ Stripling