000 AXPZ20 KNHC 211003 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 916 UTC Mon Nov 21 2016 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 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec gale warning: Earlier scatterometer data clipped the offshore Gulf of Tehuantepec area indicating gale force winds, while a ship with call-sign A8PX5 traversing the southern portion of the area reported elevated winds of 45 kt, and seas of 19 ft which verified local wave model output. These winds are occurring with high pressure ridging nosing down eastern Mexico behind a strong cold front, which has passed across the Gulf of Mexico north of the area. Winds are forecast to diminish below gale force this afternoon, then will pulse at strong to near gale force through Wednesday morning. Winds are then forecast to increase back to gale force Wednesday night, pulsing to gale force into the upcoming weekend, with the strongest winds anticipated during the overnight and early morning hours. Newly formed Tropical Depression Sixteen in the southwest Caribbean Sea near 11.5N 79.4W at 21/0900 UTC or about 261 nm east of Bluefields, Nicaragua nearly stationary. Estimated minimum central pressure is 1002 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. The official forecast calls for the tropical depression to move across southern Nicaragua or near northern Costa Rica as a minimal hurricane late Thursday, emerging into the northeast Pacific near the Gulf of Papagayo Friday as a remnant low. Interpolation of the day 4 and day 5 forecast points results in winds of 35 kt or greater near the Gulf of Papagayo, and these winds combined with 34 kt wind speed probabilities around 20 percent is enough to result in tropical storm conditions being possible Thursday night and Friday for the offshore waters zone PMZ113, which is within 250 nm of El Salvador to north Costa Rica. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N80W to 07N92W. The intertropical convergence zone axis extends from 07N92W to 10N116W, where it is disrupted by an embedded surface trough, then resumes from 10N120W to low pressure near 09N130W to 06N140W. Scattered moderate convection is from 07N to 09N between 81W and 86W. Scattered moderate and isolated strong convection is from 08N to 11N between 111W and 116W, from 10N to 12N between 118W and 122W, and also within 75 nm north of the axis between 128W and 133W. Scattered moderate convection is from 13N to 17N between 115W and 122W, as well as from 17N to 24N between 115W and 120W where the surface trough embedded in the ITCZ is underneath an area of upper level diffluence. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the special features section for information on the gale warning in the Gulf of Tehuantepec. In the Gulf of California, a weakening cold front is approaching Baja California Norte with a weak mesoscale low pressure area developing in the northern Gulf of California. Southerly winds on the southeast side of the low have increased to fresh to near gale force, but will diminish as the front itself moves across the area tonight. Seas will build to up to 8 ft later this morning into the early afternoon. Winds will shift to northerly behind the front, and are forecast to increase to fresh to strong across the majority of the gulf waters Thursday into Friday as the pressure gradient across the region tightens. Elsewhere, northwest swell of 8 to 12 ft is outrunning the mentioned weakening cold front. This swell will continue to propagate toward the Baja California peninsula early this week with high pressure surging in the wake of the front. Seas will gradually decay to less than 8 ft from north to south through Tuesday night. The pressure gradient will then tighten across the region thereafter, with fresh to strong winds developing offshore of Baja California Norte and southern California Wednesday through Thursday, diminishing then through Friday. These winds will send fresh northerly swells into the area, while a new set of reinforcing northwest swell for the end of the week building seas back up to the 8 to 12 ft range. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... See the special features section for information on newly formed Tropical Depression Sixteen in the southwest Caribbean Sea, which may impact Central America through the week. In the Gulf of Fonseca, a narrow and brief pulse of fresh to strong north to northeast winds will diminish in the next few hours. In the Gulf of Papagayo, strong to near gale force northeast winds will continue to pulse through Tuesday morning. Fresh seas will be 7 to 9 ft through that time. In the Gulf of Panama, guidance is suggesting that the southwesterly monsoon flow will be fresh levels through tonight. Elsewhere, gentle to locally moderate northerly winds, and combined seas of 3 to 6 ft are occurring north of the monsoon trough, which will continue to meander between 07N and 09N through the week. Moderate to fresh southwest flow is observed to the south of the monsoon trough, with combined seas of 4 to 7 ft in long-period southwest swell. Little change forecast through early next week. REMAINDER OF THE AREA... A cold front extending from 30N119W to 25N122W to 21N130W will weaken as it continues to move to the southeast and south. Altimeter data sampled large northwest swell outrunning the front, up to 14 ft along 30N. These seas will gradually decay through Tuesday. High pressure is surging in behind the front, and ridging combined with an embedded ITCZ surface trough has resulted in fresh to strong trades across the west-central waters. A new cold front will dive southward, weakening as it shifts into the northern waters Tuesday night into Wednesday. This front will bring a new and reinforcing set of northwest swell into the area for the remainder of the week, while high pressure ridging continues to force fresh to strong trades across the west-central waters through Friday. $$ LEWITSKY