000 AXPZ20 KNHC 290236 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sat Apr 29 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 0000 UTC surface analysis and satellite imagery through 0215 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 10N87W to 06N94W to 06N101W to 04N110W, where the ITCZ axis forms and continues west- southwest to 02N120W to 02N130W to 01N140W. Scattered moderate/ isolated strong convection is within 60 nm of the trough axis between 90W and 95W and also between 97W and 103W. Scattered moderate convection is within 120 nm south of the trough axis between 95W and 97W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Strong to near gale force northwest winds continue across the discussion waters from 28N to 30N and west of the Baja Peninsula to near 125W, with seas of 9 to 13 ft in northwest swell. These winds and seas will persist through Saturday as a strong pressure gradient remains over the area between high pressure to the west, and low pressure over the southwestern United States. Seas of 8 to 10 ft in northwest swell will propagate as far south as 20N between 114W and 130W on Saturday before conditions begin to slowly improve over these waters Saturday night into Sunday. Gulf of California: Mostly gentle to moderate southwesterly flow is expected through tonight, with brief fresh to locally strong northerly winds possible over the gulf waters north of 30N briefly this afternoon and evening, and then Sat as a cold front passes across the area. The fresh to strong NW winds with and behind this front will shift southward into the central portions Sat through Sat night and gradually build seas 5 to 8 ft. Winds and seas will decrease early on Sunday. Gulf of Tehuantepec: Gentle to moderate south to southwest flow expected this weekend with fresh to strong north winds possible near daybreak on Monday as the gradient tightens over southeastern Mexico as high pressure builds over the western Gulf of Mexico in the wake of cold front. Seas will be in the range of 3 to 5 ft through Saturday night, then build to 5 to 7 ft Sunday through Monday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Mostly a gentle onshore breeze is expected during the next few days becoming offshore along the coasts at night. Combined seas of 4 to 5 ft in mainly southwest swell will continue through these waters through tonight. Wave model guidance forecasts large long-period southern hemispheric southwest swell of 6 to 8 ft to approach the offshore waters of Ecuador on Saturday through Sunday, then subside slightly before increasing again to 6 to 8 ft early next week. REMAINDER OF THE AREA... A nearly stationary 1030 mb high pressure system well north of the area near 37N135W has a ridge extending southeastward to 26N127W and to near 19N120W. This high pressure system covers the area north of the ITCZ and west of about 115W. A tight pressure gradient between the high and a thermal trough along the coast of California will continue to support strong northwest winds along with seas of 10 to 13 ft north of 28N east of 125W through Saturday, before they begin subside through the remainder of the weekend as the gradient slackens. Fresh northeast trades are expected between the ridge and the ITCZ W of 125W over the next several days, with seas of 6 to 8 ft in mixed northeast and northwest swell expected through Saturday afternoon. Southern hemispheric swell will continue to propagate across the waters south of a line from the equator at 128W to 08N123W to 03N113W to 03.4S97W through Saturday, and south of 05N between 109W and 125W on Sunday, resulting in combined seas in the general range of 8 to 10 ft. These seas will subside to 8 ft on Sunday. Weak low-level westward moving perturbations continue across the tropical belt under mid/upper level ridging. The combination of this and a series of disturbances aloft riding along a relatively pronounced jet stream branch is allowing for clusters of scattered showers and thunderstorms to develop from time to time across this area. Latest satellite imagery shows that the most concentration of this activity is confined to the eastern portion of the tropics between 90W and 103W as described above under the ITCZ/Monsoon Trough section. Upper level diffluent flow is occurring over this portion of the area as noted in upper level streamline analysis as well as in the trajectory of high level clouds within this area. This activity is likely to persist into the weekend, with the activity west of 103W, that although is has diminished during the past few hours in diurnal minimum cycle, is expected to pulse back up late tonight or Saturday morning. It should then continue to pulse through Sunday. $$ Aguirre