000 AXPZ20 KNHC 062145 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2023 UTC Fri Jan 6 2017 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... A storm warning is in effect for the Gulf of Tehuantepec. This upcoming event is forecast to be the strongest of the events so far this season. A strong cold front is forecast to move across the Gulf of Mexico through Saturday with very strong high pressure of 1043 mb expected to be located over north-central Texas on Saturday. The associated ridge will press southward along the Sierra Madre Oriental mountains of Mexico through the weekend with a very tight pressure setting up over southeastern Mexico and the Isthmus of Tehuantepec. Northerly winds of 20-30 kt will rapidly surge into the Tehuantepec area early Saturday. Winds will quickly increase to strong gale force by early Saturday afternoon, with seas building to 10-15 ft. Winds will continue to increase to storm force of about 55 k with possible higher gusts on Saturday night with seas building rapidly to the range of 15-24 ft. Model guidance shows the gale force winds, surrounding the storm force wind area expanding well to the south and southwest of the Isthmus of Tehuantepec through Sunday evening. As the very strong high pressure slides eastward through Monday, the pressure gradient will respond by relaxing. This will allow for the aforementioned winds to diminish below storm force late Sunday night. The gale force winds, however, are expected to continue across the Tehuantepec region through late Tuesday. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from A 1010 MB low pressure near 06N89W to 06N100W to 1011 low pressure near 06N110W to 1011 MB low pressure near 08N118W to 07N125W. The ITCZ axis continues from 07N125W to beyond 08N140W. There is no significant convection noted. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more details on the Gulf of Tehuantepec storm force gap wind event. Outside of the Gulf of Tehuantepec region, a 1018 mb high pressure persists west of the forecast waters near 27N122W, extending a ridge to near 21N113W. The pressure gradient between this area of high pressure and surface troughing over Mexico is producing gentle to moderate northwest winds across the Pacific waters off the coast of Baja California, with seas in the 3 to 5 ft range. The area of high pressure will shift northeastward over the next 24 hours. This will increase surface pressures slightly over the waters off the western coast of the Baja California peninsula while a surface trough prevails over the Gulf of California. The tightening of the pressure gradient between the high pressure and the trough is expected to bring an increase to the northwest winds over the central and southern portions of the Gulf of California tonight through Saturday night. The ridge will weaken by Sunday. This will allow for these winds to diminish to fresh intensity. Elsewhere between Cabo Corrientes and the Tehuantepec region, light to gentle breezes and seas in the 3 to 5 ft range, primarily in northwest swell, will prevail over the next several days. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The very strong high pressure building behind the cold front responsible for the Gulf of Tehuantepec storm event will help for strong northeast gap winds to materialize across the Gulfs of Papagayo and Fonseca late Saturday night into Sunday. Winds are forecast to reach near gale force in the Papagayo area late Sunday night into Monday with resultant seas building up to around 11 ft. In the Gulf of Panama, fresh nocturnal northerly flow is expected through Sunday night. Winds will further increase to 20-25 kt on Monday as strong winds funnel from the SW Caribbean into the Gulf of Panama as high pressure behind the cold front over the Caribbean waters helps tighten the pressure gradient. These gap wind events, along with a possible storm force wind event in the Gulf of Tehuantepec, will generate a large area of 8 ft seas or greater that will eventually extend from Tehuantepec and Papagayo regions southward to near 4N-5N and westward to near 111W by early Monday. Elsewhere, light to moderate south to southwest winds will prevail south of the monsoon trough region, with seas 5 ft or less through the upcoming weekend. REMAINDER OF THE AREA... A series of cold fronts will move across the northwest portion of the forecast region during the next few days. Presently, a weak cold front extends from 30N132W to 24N140W. A scatterometer pass showed fresh to strong winds ahead and behind the front. A stronger cold front will reach the northwest waters on Saturday afternoon reaching a position from 30N137W to 27N140W. Yet another front will quickly move in behind this front on Sunday, with a large area of strong southwest to west winds becoming established over much of the northwest and north-central waters. A weak pressure gradient prevails over the forecast waters north of the ITCZ to near 20N with gentle to moderate winds prevailing. The pressure gradient will remain weak over this area through the forecast period with winds and seas expected to remain below advisory criteria through at least Monday. $$ GR