000 AXPZ20 KNHC 212203 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2105 UTC Thu Dec 21 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 2115 UTC. ..SPECIAL FEATURE... ...Eastern Pacific Ocean Gale-Force Winds... Low pressure developing just east of Hawaii will intensify as it tracks NE, clipping our area of discussion near 30N140W early Saturday morning. Forecast models are in good agreement on gale- force SE to S winds developing East of the low center early Saturday, persisting over our waters N of 27N and W of 138W until Saturday afternoon, when the low will track north of 30N and away from our discussion waters. Seas of 14 to 15 ft will be likely with the gale-force wind conditions. Please read the latest high seas forecast under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH FROM LOW PRES NEAR 05N78W 1008 MB TO 07N86W TO 06N99W TO 08N104W. ITCZ CONTINUES FROM 08N104W TO LOW PRES NEAR 10N111W 1012 MB TO 10N126W TO BEYOND 06N140W. SCATTERED MODERATE ISOLATED STRONG WITHIN 480 NM N OF ITCZ BETWEEN 107W AND 121W. SCATTERED MODERATE ISOLATED STRONG WITHIN 150 NM W SEMICIRCLE OF 1008 MB LOW PRES NEAR 05N78W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: COLD FRONT FROM 30N111W TO 27N113W AND DISSIPATING FROM 271N113W TO 25N120W TO 26N126W TO 28N129W. Fresh to strong NW winds are behind the front. These winds will continue to spread south across the Gulf through tonight, reaching as far S as San Jose del Cabo Friday night. Peak wave heights should range from 7 feet to 8 feet on Friday in the central Gulf. Some fresh-to-briefly strong winds will emerge over the Pacific coast of Baja California in the gaps between the highest terrain. Conditions will improve through Sunday with generally benign conditions thereafter through Tuesday. Gulf of Tehuantepec: A new Tehuantepec gap wind event should start early on Sunday, due to a strong cold front that will be pushing across the Gulf of Mexico. Model consensus indicates that the wind speeds will increase to 20 to 30 kt early Sunday morning, with gale force winds beginning late Sunday night, and continuing through Tuesday afternoon. Winds should peak before daybreak Monday and again Tuesday morning between 35-40 kt. 12 ft seas or greater are likely to occur on Monday and Tuesday in the Gulf with maximum seas around 15 ft early Tuesday. NW near gale winds just offshore of southern California and fresh winds west of Baja California Norte will produce combined seas with embedded NW swell west of Baja California Norte of 8 to 9 ft through tonight. Elsewhere winds are fresh breeze or weaker with seas less than 8 ft. These conditions will prevail through Tuesday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... It is likely that fresh-to-strong NE winds are occurring near the Gulf of Papagayo now, and for the next 24 hours or so. These winds will diminish slightly Friday through Saturday night before returning Sunday through at least Tuesday. Seas should remain under 8 ft through Sunday, and peak near 8 ft Sunday, Monday, and Tuesday nights. NE swell to 9 ft will clip the western offshore waters of Guatemala Monday and Tuesday due to the Gulf of Tehuantepec gap wind event. Elsewhere winds are fresh breeze or weaker with seas less than 8 ft. These conditions will prevail through Tuesday. REMAINDER OF THE AREA... Mainly Moderate to fresh east to northeast winds prevail over the waters from the ITCZ to 30N, driven by high pressure centered north of the region. These winds support 6 to 8 ft seas in a NW swell. Winds become northerly N of 25N and E of 125W as a cold front crosses this region. Seas behind the front N of 27N are building to 7 to 9 ft and will continue over these waters through early Friday morning. To the south of the ITCZ, gentle to moderate SE winds prevail with seas of 5 to 7 ft. High pressure will build SE toward California on Friday while low pressure currently developing west of our waters just east of Hawaii tracks NE. The pressure gradient between these two features will support fresh to strong SE winds north of 20N and west of 135W beginning Friday. Models have trended slightly stronger with this system since yesterday, with SE to S winds of 20 to 30 kt along with a small area of gale force winds now expected late Friday night through Saturday N of 24N and W of 133W, as the low clips the corner of our area of discussion near 30N140W. Seas of 8 to 15 ft are expected during this time period over these affected waters. Please read the special features section for more details. The low will lift well to the north of 30N Saturday night with improving winds over our waters. NW swell of 8 to 10 ft will continue to propagate away from the departing system Sunday through Monday, reaching as far SE as 10N and as far east as 125W by Monday night, before the swell begins to decay below 8 ft. $$ mt