000 AXPZ20 KNHC 140931 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Thu Mar 14 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 0600 UTC surface analysis and satellite imagery through 0915 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: The next gale force gap wind event to impact the Gulf of Tehuantepec region is forecast to begin late Fri night or near daybreak on Sat as strong high pressure builds southward over eastern Mexico along the eastern slopes of the Sierra Madre mountains in the wake of a strong cold front that will move across the Gulf of Mexico. Presently, model guidance indicates that this next event of gale winds will last into Sun. Seas will quickly build with these winds, with resultant northeast swell forecast by Wave model guidance to propagate well away from the Gulf of Tehuantepec through late Sun. Prior to the onset of the gale force winds, expect for near gale force north winds to surge out across the Gulf of Tehuantepec on Fri night. Please read future High Seas Forecasts issued by the National Hurricane Center under the AWIPS/WMO header MIAHSFEP2/FZPN03 KNHC or the website https://www.nhc.noaa.gov /text/ MIAHSFEP2.shtml that will contain specific marine details on this upcoming event. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from near the border of Costa Rica and Panama near 08N83W to 04N97W. The intertropical convergence zone (ITCZ) continues from 04N97W to 03N112W to 01N125W to beyond 04N140W. Scattered moderate convection is seen within 120 nm north of the ITCZ west of 137W, within 60 nm of the ITCZ between 134W and 137W and within 30 nm south of the trough between 86W and 88W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... In the wake of a recent cold front passage, high pressure has again taken control of the weather regime over these waters. A recent overnight Ascat pass revealed mainly fresh northwest winds offshore Baja California Norte, while moderate north to northeast were west of Baja California Sur and mainland Mexico. Recent altimeter data showed seas of 10 to 14 ft over the waters west of Baja California Norte and seas in the range of 8 to 12 ft west of Baja California Sur, and south-southwest from there to 14N and west of 106W. Strong high pressure will build over the Great Basin today and support fresh to strong northwest winds across the Gulf of California beginning this afternoon, and are expected to continue through Fri night before diminishing to fresh winds on Sat as the culprit tight gradient relaxes. It does not happen too often, but seas are forecast to build to 8 to 9 ft on Fri in the central section of the Gulf of California before subsiding to less than 8 ft by late Fri night or a little sooner. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fairly strong high pressure ridging north of the area will continue to support fresh to strong northeast winds pulsing across the Gulf of Papagayo through the upcoming weekend and into early next week. The strongest winds, expected to reach near gale force intensity, will occur during the overnight and early morning hours early next week with the assistance of nocturnal drainage flow. Elsewhere, ongoing fresh to strong north to northeast winds through the Gulf of Panama will diminish to moderate speeds this afternoon, then increase to fresh winds tonight into early Fri and diminish back to moderate speeds on Fri afternoon. These winds will pulse to moderate to fresh speeds through the weekend, then increase back to fresh to strong early next week. Gentle to moderate northeast to east winds along with seas in the general range of 5 to 7 ft will continue elsewhere through Mon night. REMAINDER OF THE AREA... Strong high pressure ridging extends northwest to southeast across the northern waters to the east of 130W, with the parent high center of 1030 mb north of the area at 36N128W. Ascat data from the overnight hours along with a few ship observations revealed fresh to locally strong northeast trade winds between the ITCZ and 20N, with the locally strong winds confined from 09N to 16N between 123W and 131W. This is where an earlier altimeter pass indicated seas to 12 ft. These winds will soon diminish to moderate to fresh speeds as the strong high pressure center north of the area begins to weaken slightly and slowly shift eastward. Long-period northwest swell persists over much of the region west of 105W. The northwest swell will continue to propagate southward across much of the region west of 97W by late Fri while gradually decaying. The swell will continue decaying through Sat night with significant wave heights subsiding to 8 ft or less west of 120W. Farther east, 8 to 9 ft seas will persist through Sun in mixed northwest and southwest swell with some shorter period northeast wind waves as well. Beyond Sat, a strong cold front approaching from the northwest on Sun will be preceded by strong to near gale south to southwest winds through Sun night north of 26N. Presently, global model mean ensemble probabilities for these winds to attain gale force intensity appears low, however, future probability guidance will have to be closely monitored for any signs of an upward trend to higher chances for gale force winds ahead of the aforementioned cold front. Associated long period northwest swell will begin to move through part of the area on Sun with seas to 12 ft near 30N140W by Sun night, then building to around 19 ft near 28N140W by Mon night. $$ Aguirre