000 AXPZ20 KNHC 172159 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sat Jun 17 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 2145 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends NW across the Gulf of Panama from 08N78W to the Pacific coast of Costa Rica at 11N86w to 14N98W, then turns SW to 10N112W, then continues W to a 1009 mb surface low at 10N127W. Scatterometer winds indicate that the ITCZ forms just to the Sw of the low and continues Sw to beyond 06N140W. Scattered moderate isolated strong convection is observed mainly to the S of the monsoon trough within 120 nm either side of a line from 05N80W to 13N94W TO 08N114W. Similar convection is noted to the E of the surface low, within 60 nm of 10N126.5W, and also along the ITCZ within 60 NM of 06N136W. Broad low pressure is forecast to continue for the next few days across most of Central America and Eastern Mexico. Additionally, a surface low has developed over the Gulf of Honduras within an area favorable for gradual development as the low drifts NW across the Yucatan Peninsula this weekend, and into the S- Central Gulf of Mexico early next week where tropical cyclone formation is likely. 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 E to W 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 Sun evening, then the pressure gradient will tighten with the NW flow increasing to a moderate to locally fresh NW breeze 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 Tue, and strong to near gale force flow is forecast on Tue night into Wed. Large SW swell is forecast across the waters S of 13N beginning on Sun night. 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 through Thu night. Long period SW swell will build seas to 6 to 9 ft across the waters S of 02N through tonight, and across the entire offshore waters by late Sun. These seas will begin to subside on Sun night with seas less than 8 ft everywhere by Wed evening. REMAINDER OF THE AREA... An area of 6 to 9 ft seas, primarily due to SW swell, is currently observed to the S of 06N E of 125W. These seas will continue to propagate NE covering the waters S of 15N E of 120W early this week. Expect 4 to 6 ft seas to the lee of the Galapagos Islands. These seas will begin to subside from the N on Sun night. A quasi-stationary surface high is centered just N of the area near 34N136W with a ridge extending S-SE to near 11N120W. This ridge will shift gradually W over the next few days terminating near 11N124W on Mon night, with the ridge axis to the W of 140W by mid week. 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 20N116W on Wed. The low should reach near 19N120W on Thu night. The will result in the pressure gradient tightening this week, with fresh N winds across the waters N of 29N between 124W and 132W on Mon. These fresh N-NE winds will spread SW across the waters N of 25N W of 120W on Tue and Wed, with large N swell building seas to 8 to 12 Ft to the N of 20N W of 120W on Thu. $$ Nelson