000 AXPZ20 KNHC 181605 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Apr 18 2019 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 1545 UTC. ...SPECIAL FEATURES... Gulf of Tehunatepec Gale Warning: Gentle to moderate south to southwest across the Gulf will become light to gentle southwest to west winds tonight, then moderate to fresh north winds early Fri, before abruptly increasing to minimal gal-force speeds early Fri and to strong gale-force winds Fri afternoon through Fri night as a very tight pressure gradient sets up over southeastern Mexico. Waveheights will build to the range of 11-18 ft with these winds Fri night. The pressure gradient will begin to slacken on Sat as the culprit high pressure center over eastern Mexico shifts eastward and weakens. Strong winds of 20-25 kt are forecast to reach as far south as 10N and between 96W and 98W by early Sat, with waveheights of 10-14 ft in northeast swell. These winds will diminish to fresh winds early on Sun, with seas lowering to less than 8 ft. Please refer to the Pacific High Seas Forecast under the AWIPS header MIAHSFEP2 and under the WMO header FZPN03 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from the Costa Rican/Panamanian border to 08N94W to 08N100W and to 04N100W, where scatterometer data from last night indicated the ITCZ begins and continues to 04N122W where it is bisected by a trough that extends from near 09N121W to 02N113W. The ITCZ resumes at 04N125W to beyond the area at 02N140W. Scattered to numerous strong convection is seen within 180 nm south of the trough between 83W and 87W. Scattered moderate to isolated strong conevection is within 180 nm south of the trough axis between 90W and 96W. Scattered moderate convection is within 120 nm north of the trough between 107W and 111W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... High pressure of 1025 mb is analyzed north of the area near 37N131W, with a ridge extending southeastward to near 20N114W. The associated gradient supports moderate to fresh north to northeast winds across the offshore waters of Baja California. Waveheights with these winds are in the range of 5-7 ft attributed to northwest swell. Little change in these conditions is expected through Friday, as the ridge drifts westward and weakens. A newer and stronger ridge will replace the aforementioned one on Sat. A slight increase in the gradient will allow for mainly fresh northwest winds to develop over the far northeastern waters from late Sat night through Sun, while strong northwest winds will be just north of the area. A new pulse of northwest swell will begin to propagate through the far northeastern waters early on Sun, bringing seas of 7-9 ft there. This swell will only slightly decay in Mon. Gulf of California: Strong northwest winds are occurring from 23N to 26N, with seas of 4-7 ft. These winds will diminish to mainly fresh winds early this afternoon, then materialize over the Gulf late tonight from about 27N to 28N and diminish to mainly fresh winds early on Fri and to gentle to moderate winds Fri afternoon. Gulf of Tehuantepec: please read the SPECIAL FEATURES section for the details about a gale warning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong northeast to east winds will diminish to mainly fresh speeds this afternoon and gentle to moderate speeds by early this evening. These winds will again reach moderate speeds tonight through Fri, become light and variable Fri night and mainly fresh northeast winds Sat. These winds will increase to strong speeds on Sat night, with waveheights possible building from the present peak heights of 6 ft to 8 ft on Sat night. Gulf of Panama: The earlier observed moderate to fresh north to northeast winds have diminished to mainly moderate speeds through tonight, then become light and variable on Fri and into Sat. Light to moderate wind speeds will prevail elsewhere across the waters west of Ecuador through Sunday night. The sea heights will remain in the range from 6 feet to 7 feet, in S to SW swell through midweek. REMAINDER OF THE AREA... A high pressure ridge extends into the area through 32N126W and continues to near 19N110W. A trough extends from 23N112W to 28N117W. The pressure gradient between the ridge and lower pressure in the subtropics and tropics is resulting in fresh northeast to east trades from 04N to 14N and west of 123W, where waveheights up to 9 ft are from currently mixed swell there. These winds are forecast to increase to strong speeds beginning late tonight as the ridge builds some southward tightening the gradient. These winds will change little in speeds through Sat as the gradient remains in tact as the high pressure is replaced by stronger high pressure on Sat. Waveheights with these winds will reach around 9 or 10 ft Fri night through Sat. A surface trough extends from near 09N121W to 02N123W. An upper- level trough is in the vicinity of this trough, and is helping to produce scattered showers and isolated thunderstorms along and within 180 nm west of the trough from 05N to 09N. An inverted northeast to southwest oriented upper-level trough that stretches from near the Gulf of Tehuantepec region southwestward to the equator at 109W. This feature. along with weak surface troughing nearby, is helping to sustain an area of scattered moderate to isolated strong convection within 30 nm of a line from 06N107W to 07N111W. A weak surface trough is along 129W from 19N to 27N. Scattered showers are possible within 60-90 nm of this trough. $$ Aguirre