000 AXPZ20 KNHC 132133 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2130 UTC Thu Apr 13 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 2130 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The northern Intertropical Convergence Zone extends from 06N89W to 02N105W to 04N140W. The southern ITCZ extends south of 3.4S between 105W and 130W. Scattered moderate convection is within 60 nm of the axis between 89W and 97W and another area prevails between 120W and 140W. 124W and 129W. Isolated showers along the southern ITCZ extend along 02S between 117W and 125W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... The combination of high pressure over the eastern and southeastern sections of Mexico, and lower pressures present to the south of the Tehuantepec region will support fresh to strong northerly winds across the Isthmus of Tehuantepec. These winds will pulse during the overnight and early morning hours through the end of the week and upcoming weekend. A surface ridge extends from northwest to southeast across the offshore waters. Latest scatterometer data depicted northwest fresh to strong winds offshore of Baja California Norte where seas are up to 8 ft. The pressure gradient will remain tight enough to support these conditions through Friday night, then will weaken thereafter. In the Gulf of California, mainly light to gentle variable flow will prevail through the upcoming weekend, with seas mainly 2 ft or less, except 3 to 4 ft near the entrance to the Gulf. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, fresh to locally strong nocturnal drainage winds expanded to the north early this morning reaching the Gulf of Fonseca based on latest observations. These winds are forecast pulse back up to the strong range late tonight and diminish to the fresh range early in the afternoon on Friday. Seas are expected to build to 8 ft with these winds. These conditions will continue through at least Saturday. In the Gulf of Panama, moderate to fresh nocturnal northerly flow is expected during the overnight hours through the upcoming weekend. Seas will be in the range of 5 to 6 ft downstream of the Gulf. Elsewhere, light to gentle winds and combined seas of 3 to 6 ft will change little through the weekend. REMAINDER OF THE AREA... A cold front has transitioned to a surface trough currently extending from 30N120W to 23N140W. A large set of northwest swell producing seas of 8 to 10 ft will propagate into the northwest portion of the basin tonight, and through the north- central and northeast portions Friday through Saturday while losing energy. This swell will merge with the one currently affecting the waters west of Baja California Norte during this weekend. Models are suggesting that another cold front will approach the far northwest corner on Saturday, then move over that area by late Saturday/early Sunday. Southerly winds ahead of the front are expected to be in the range of 20 to 25 kt mainly north of about 29N. Wave model guidance indicates that this next front will usher in a new set of northwest swell that will build seas to the range of 8 to 10 ft in the far northwest portion of the area by late Saturday, but then slowly subside late on Sunday as the swell energy decays. Elsewhere, a ridge axis extends from a 1028 mb high pressure center analyzed north of the area near 35N143W. The weak pressure gradient between the ridge and lower pressures found to the southwest of the ridge is allowing for generally moderate to fresh northeast trades to exist from about 05N to 16N west of 117W. Seas will range between 8 to 10 ft in this area. Another area of high pressure will build across the area during Friday, but will be shunted to the east with the approach of deep layer troughing from the west and the associated aforementioned cold front. This process will bring a further weakening to the trades Saturday and Saturday night, with model guidance showing mostly gentle to moderate trades over the western and central waters from about 05N to 20N. Seas will range between 8 and 9 ft under these conditions. $$ ERA