000 AXPZ20 KNHC 212158 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2001 UTC Fri Dec 21 2018 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 2100 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A ridge across the eastern slopes of the Sierra Madre mountains supports a strong gap winds event across the Gulf of Tehunatepec. The most recent scatterometer pass shows an area of 30-40 kt winds extending downwind to about 12N96W while winds of 20-30 kt are covering a large area N of 10N between 93W and 99W. Seas of 10-17 ft are associated with these winds. The gales will persist through tonight, then diminish on Sat as high pressure north of the area shifts eastward. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZNPN03 for more specific marine details. Gulf of Papagayo Gale Warning: High pressure building in behind a cold front that currently extends from eastern Cuba to Nicaragua is tightening the pressure gradient over northern Central America. This will allow for northeast winds to soon increased to strong speeds over the Gulf of Papagayo. As the gradient continues to tighten, these winds will further increase to near gale force by early this evening and to gale by late tonight, with seas building in the 9 to 12 ft range. These winds are then forecast to diminish to below gale force by early Sat afternoon, then increase again to minimal gale force by Sat night. Extended model outlook indicates that strong gap winds will continue flowing over the Gulf of Papagayo through the middle of next week. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from the coast of Colombia near 07N77W to 06N95W. The ITCZ continues from 06N95W to 06N110W to beyond the area at 06N140W. Isolated moderate convection is near 10.5N114W, near 13N109W, and also within 90 nm N of the ITCZ between 125W and 127W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features Section above for information on the ongoing strong gale force gap wind over the Gulf of Tehuantepec. Long period NW swell continues to propagate across the offshore forecast waters. Seas of 8 ft or greater cover much of the open ocean waters in the discussion area. Seas, everywhere outside the Gulf of Tehunatepec, will begin to subside late tonight into Sat. The next round of large swell is forecast by Wave model guidance to reach the offshore waters of Baja California Norte by early on Mon and the remainder of the Baja California Peninsula offshore waters by early on Tue. The guidance depicts seas to build to the range of 10 to 14 ft offshore Baja California Norte on Tue. Elsewhere, weakening high pressure over the Great Basin supports fresh northwest winds in the central Gulf of California, which will become light and variable by tonight. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please the Special Features Section for more on the upcoming gale force gap wind event over the Gulf of Papagayo. Strong north winds will begin to over the Gulf of Panama beginning late tonight and are expected to last through Sun night, with seas starting at less than 8 ft but building to 8 ft by early on Sun. Elsewhere, gentle to moderate winds will persist, with seas in the 4 to 7 ft range. REMAINDER OF THE AREA... A weakening stationary front is analyzed from near 30N3132W to 25N140W. The front is located over a large area of 9 to 10 ft seas due to a northwest swell that is presently decaying. The front will slowly become diffuse through this evening as high pressure behind builds southeast and south. The pressure gradient between the high pressure and lower pressure present in the tropics has initiated an area of fresh to strong northeast trades from 09N to 14N west of 136W along with seas in the range of 10 to 12 ft due to the northwest swell combining with the wind waves. This area of trades will change little through late tonight, then expand north and east Sat through early next week. Seas of 9 to 12 ft will persist in association with the area of trade winds combined with the long period NW swell. Northwest swell propagating through the discussion area is decaying making seas north of 20N and W of 120W to lower through Sat. An area of mixed swell will develop south of about 14N or 15N between 90W and 110W on Sat as lingering NW swell mixes with shorter period northeast swell from the Tehuantepec and Papagayo gap wind events. $$ GR