000 AXPZ20 KNHC 150957 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 930 UTC Thu Mar 15 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 0600 UTC surface analysis and satellite imagery through 0930 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: An earlier scatterometer satellite pass confirmed gale force gap winds across the Gulf of Tehuantepec. The gale is due to strong high pressure lingering over the north central Gulf of Mexico and east central Mexico. Overnight drainage effects are also contributing to the gales. The plume of strong winds and high seas is reaching downstream of the Gulf of Tehuantepec to 14N96W. Associated seas are likely reaching 8 to 12 ft. The gradient will start to weaken through late today as the supporting high pressure shifts eastward, allowing winds and seas to diminish substantially thereafter. Please see the latest Pacific Ocean High Seas Forecast product under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 08N84W to 06N90W to 04N100W. The intertropical convergence zone continues from 04N100W to 03N140W. Scattered showers and a few thunderstorms within 180 nm north of the intertropical convergence zone between 112W and 117W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for details on an ongoing Gulf of Tehuantepec gale event. A cold front reaching from the northern Gulf of California across central Baja California Norte to 20N130W will move across the region through this morning and dissipate. Areas of light rain probably ongoing over the northern portion of Baja California Sur ahead of the front. An earlier scatterometer pass showed fresh to strong gap winds south of San Felipe. These winds will diminish through the morning and veer more NW. A second weak cold front will move through the region late today and tonight while dissipating. Looking ahead, a third cold front will move across the region late Sat into Sun, possibly allowing another pulse of strong gap winds into the northern Gulf of California Fri night ahead of the front and again Sat night. Meanwhile long period NW swell in excess of 9 ft will move into the waters off Baja California following the front. The swell will propagate to the waters of Baja California Sur late today before decaying below 8 ft into Sat. Winds and seas will continue to diminish into early next week as high pressure builds over the region. Farther south, strong gap winds are possible off Cabo Corrientes by early Mon as the high pressure builds eastward into the region. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Over Gulf of Papagayo, high pressure ridging over the Caribbean will bring fresh to strong NE to E winds mainly at night and in the early morning hours through early next week as the pressure gradient re- strengthens in response to high pressure building southeastward over the northern Caribbean from the Gulf of Mexico. Over the Gulf of Panama, moderate to fresh winds will increase to fresh to strong to night with 4 to 6 ft seas building to 5 to 7 ft due to an added component of 5 to 7 ft by late Fri. Elsewhere, expect gentle to moderate winds and 4 to 6 ft to persist. REMAINDER OF THE AREA... A cold front reaching from northern Gulf of California across central Baja California Norte to 20N130W will move east of the region and dissipate this morning. This will be followed by a weak reinforcing front from 32N120W to 27N127W to 28N140W that will shift east of the region and dissipate through late today. A third, slightly stronger cold front will approach the area tonight and move eastward over the waters north of 25N through Sun. Looking ahead, global models are showing a more powerful front related to a deep layer low approaching the region from the north central Pacific. Southerly flow may increase to fresh to strong north of 25N west of 130W ahead of this front Sun night, shifting NW Mon as the front enters the area and reaches from 32N130W to 20N140W by late Mon followed by 8 to 12 ft seas. Farther south into the deep tropics, a broad upper low is centered near 10N118W. Divergence aloft on the southeast side of the upper low along with modest trade wind convergence in the lower levels are supporting scattered convection within 180 nm norht of the ITCZ. Various altimeter satellite passes indicate 8 to 9 ft seas mainly due to NW swell, and this is expected decay below 8 ft through early Fri. The subtropical ridge north of the area will not get a chance to build substantially due to the frequency of passing cold fronts, keeping trade wind flow minimal through early next week. $$ Christensen