000 AXPZ20 KNHC 130957 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Fri Jan 13 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 0600 UTC surface analysis and satellite imagery through 0930 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec gale warning: The pressure gradient is increasing over southeastern Mexico. The resulting surge of strong to near gale north to northeast winds, aided by nocturnal drainage flow, has just recently begun to funnel southward through the Isthmus of Tehuantepec. These winds will increase to gale force this evening. Gale force winds may then briefly diminish during the early afternoon hours on Saturday before returning again Saturday night into early Sunday, then diminishing below gale force. Northerly winds will then be fresh to strong into early Monday before diminishing and shifting to the south-southwest through the early part of next week. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough is not presently identifiable. A trough extends from 03N81W to 04N87W to 03N96W. The intertropical convergence zone axis extends from 03N96W to 07N107W to 07N119W to low pressure near 06N124W 1011 mb to 03N130W and to beyond 09N140W. Scattered moderate isolated strong convection is occurring within 60 nm north of the axis between 121W and 124W, and also between 127W and 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features section for information on the Gulf of Tehuantepec gale warning. Elsewhere, moderate northwest to north winds prevail over the waters adjacent to the Baja California peninsula, and winds will shift to the southwest ahead of a cold front moving across the the waters west of northern and central Baja California. The front is supported by a very pronounced upper trough that digs southward into the area to north of 20N. The upper trough will quickly shift eastward to inland the southwest U.S. on Saturday with rather transit upper ridging building across these waters Saturday evening into Sunday. The cold front will then weaken as it crosses Baja California Sur Saturday through late Saturday night while weakening to a frontal trough. Seas are in the 4 to 6 ft, but will build to 6 to 8 ft west of Baja California Norte behind the trough by Friday night. Surface high pressure, associated with the upper ridge, will build in the wake of the trough this weekend while low pressure troughing sets up across southern California and the northern Gulf of California. This will increase the pressure gradient offshore of southern California generating fresh northerly swell which will propagate back into the waters offshore of Baja California Norte Sunday night through Monday, then will decay thereafter once the gradient slackens. Combined waveheights from this swell are expected to be in the 7-9 ft range before subsiding. In the Gulf of California, mainly light and variable winds and seas of 2 ft or less will prevail south of 30N, with moderate to fresh south-southwest winds north of 30N east of the above describe cold front, which is analyzed along a position from southern California southwest to 32N117W southwest to near 25N126W, where seas are also 2 to 4 ft. Little change is anticipated across the Gulf of California through the upcoming weekend and early next week, except on Saturday night when winds will become fresh from the northwest in direction over the southern portion as the aforementioned front passes through this area. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, fresh to strong northeast flow will continue to pulse through early next week, approaching near gale force by daybreak this morning then diminishing to strong this afternoon. Model wind guidance suggests that these winds then increase back to near gale force again tonight and into Saturday morning before diminishing back to strong through Monday. Seas will build to 8 to 10 ft during the strongest winds. Winds will also pulse to fresh to strong across the offshore Gulf of Fonseca waters into early this afternoon, then diminishing thereafter. In the Gulf of Panama fresh to strong northerly winds will diminish to moderate to fresh later this morning, and remain at this category through Monday. REMAINDER OF THE AREA... A cold front extends into the northeast portion of the discussion area from surface trough is passing through the northern waters from 30N117W southwest to near 25N126W. Associated winds are 20 kt or less, however a set of accompanying northwest swell with assocaited combined waveheights in the range of 8 to 10 ft continues to follow in behind the front. These seas will gradually subside to 8 ft by late Saturday night, and to 6 to 7 ft on Sunday. High pressure ridging is building in the wake of the cold front supporting moderate to fresh trades to the southwest of the ridging across the west-central waters. Combined seas are 8 to 10 ft north of the ITCZ west of 120W in mixed northeast and northwest swell. The high pressure ridging will gradually strengthen this weekend and through Monday, increasing trades to fresh to strong while expanding the stronger trades in coverage. Combined waveheights will also build up to 11 ft as a result of the increasing and expanding trades. $$ AGUIRRE