000 AXPZ20 KNHC 170352 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Thu Jan 17 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 0000 UTC surface analysis and satellite imagery through 0215 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough extends from low pres over central Colombia to the coast at 03N79W and continues to 03N88W, where latest scatterometer data indicates the ITCZ begins. The ITCZ continues to 03N100W and northwestward to 06N101W, where it is briefly interrupted by low pressure near 07N110W. The ITCZ resumes at 06N113W to 07N130W and to beyond the area at 06N140W. Scattered moderate convection is within 180 nm north of the ITCZ between 100W and 107W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec: The pressure gradient is gradually relaxing over southeastern Mexico. North to northeast winds funneling out from the Chivela pass and out across the Gulf have diminished to strong to near gale force, with seas up to 12 ft reaching southward from the Gulf to near 13N. Winds will diminish to fresh speeds by early Fri evening and become light and variable on Sat. In the long term, the global models depict that a powerful cold front will move across the western Gulf of Mexico, across southern Mexico and over the Gulf of Tehuantepec by Sat night. Strong high pressure will ridge southward over the western Gulf of Mexico and eastern Mexico. The resultant tight pressure gradient is expected to bring a surge of northerly storm force winds across the Gulf of Tehuantepec as well as downstream from the Gulf beginning on Sun. Very large seas reaching the lower 20s in values are expected with these winds. This upcoming significant event will most probably be similar to a recent significant one that occurred in December. The model guidance suggests that the storm force winds will continue through Sun night, before diminish slightly to strong gale force through Mon. Marine interests transiting through the Gulf of Tehuantepec Sun into early next week should be aware of this upcoming gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Light to gentle northwest to north winds are offshore Baja California and across the Gulf of California. Moderate north winds persist off Cabo Corrientes, and light breezes elsewhere off the Mexican coast outside of Tehuantepec. Northwest swell producing seas of 8-10 ft are present in the offshore waters of Baja California and the Revillagigedo Islands. Little change is expected until late Thu with the arrival of a weakening cold front into northern Baja California Norte. While the front will dissipate as it moves across Baja California and the Gulf of California through Fri, it will be accompanied by a new round of long-period northwest swell composed of 12-17 ft seas across the waters off Baja California. This swell will start to impact the waters off Baja California Norte starting Thu night, bringing dangerous surf and large breaking waves across Baja California Norte through Fri. Over the Gulf of California, high pressure building over the Great Basin north of the area will support fresh to strong northwest winds extending the length of the Gulf from Fri night through Sat. The strength, fetch and duration of the winds will support wave heights to 8 ft in the southern Gulf of California by Sat night. Winds and seas will diminish by Sun as the high pressure weakens and shifts east. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The pressure gradient between high pressure northeast of the area over the Gulf of Mexico and western Caribbean Sea will maintain fresh to strong northeast gap winds across Papagayo and Panama through the next few days. The winds across the Gulf of Papagayo may possibly reach gale force on Mon, otherwise they are forecast to pulse to near gale force during the overnight and early morning hours. Seas will build to 8 to 10 ft. Over and near the Gulf of Panama, fresh to strong northeast winds reaching southward to near 03N by Thu evening with seas of 8-9 ft are forecast to diminish late Fri along with seas lowering to less than 8 ft. REMAINDER OF THE AREA... A cold front has moved over the northwest part of the area, and as of 00Z it extends from near 32N131W to 28N140W. The front marks the leading edge of a rather extensive set of long period, northwest swell that is producing seas in the 12 to 19 ft range. As the front continues eastward through early Thu tonight, the swell train will propagate through the rest of the northwest and north-central waters, with seas building to 19 to 23 ft north of 27N between 131W and 135W. The front is forecast to reach from near 32N127W to 28N132W by early Thu afternoon as it weakens and dissipate from northern Baja California to 28N122W by early Fri. The northwest swell is forecast to propagate through the remainder of the northwest section of the area through Fri, while it gradually loses energy allowing for the resultant maximum seas to lower to around 15 ft by then. Elsewhere, seas of 8 ft and higher will exist over much of the forecast waters west of 95W. Low pressure of 1009 mb is centered near 07N110W. Fresh to strong winds are noted from 07N to 10N between 107W and 111W, with seas of 10-12 ft. Latest satellite imagery shows scattered moderate to strong convection within 180 nm of the low in the east and southeast quadrants. Scattered moderate isolated strong convection is occurring from 12N to 16N between 115W and 119W, and also within 30 nm of a line from 12N110W to 12.5N115W due to a very sharp mid-upper level trough. This convection activity will remain quite active into Thu morning. Upper debris cloudiness from this activity is streaming toward Mexico and the central and southern sections of Baja California as observed in satellite imagery. A ridge will build cross the waters north of 25N in the wake of the front. This will support a broad area of fresh to strong trade winds developing over the tradewind belt north of the ITCZ by Fri along with seas of 9-12 ft. $$ Aguirre