Pacific Discussion

  • NHC East Pacific Tropical Weather Discussion
    by (nhcwebmaster) on December 11, 2018 at 9:05 AM

    000 AXPZ20 KNHC 110905 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Tue Dec 11 2018 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: A tight pressure gradient over the Isthmus of Tehuantepec is producing a large area of strong gales across the Gulf of Tehuantepec. A scatterometer pass at 0400 UTC showed 40-45 kt winds extending from 16N95W to 14N95.5W and 30-40 kt winds between 94W and 97W north of 12.5N. The large area of strong gales will generate very large seas to 21 ft for the next several hours. Gale force winds will continue today and tonight, then rapidly decrease and become gentle to moderate by Wed evening as high pressure over the Gulf of Mexico weakens and shifts east. Large N to NE swell will propagate well away from the source region, with the leading edge of 8 ft seas expected to reach to 110W and 02N by early Wed, and merge with a larger area of 8 ft seas approaching from the northwest. Please refer to the Eastern Pacific High Seas Forecast under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for more specific marine details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough is analyzed from 05N77W to 04N91W. The ITCZ extends from 04N91W to 08N108W to 08N119W. The ITCZ resumes west of a surface trough from 08N124W to 07N140W. Scattered moderate isolated strong convection is occurring from 07N to 10N between 116W and 131W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec...After the ongoing high wind event tapers off on Wed, light to gentle winds are expected through Thu night. A strong cold front moving into the Gulf of Mexico will initiate another gale force wind event Fri and Sat. High pressure NW of the area extends a ridge southeast to the Revillagigedo Islands. The pressure gradient between the high and troughing in the Gulf of California is supporting gentle to moderate NW winds across the entire Gulf of California. Model guidance suggests that the gradient will tighten early Thu, with fresh to strong winds expected over almost all of the Gulf of California through Fri morning. 5 to 9 ft seas west of Baja California will spread eastward through tonight, then subside below 8 ft through Wed evening. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo...Winds will pulse to near gale force tonight, remain fresh to strong Wed night, then diminish to 10-15 kt Thu. Elsewhere, gentle to moderate winds will persist on either side of a weakening monsoon trough, with seas in the 4-6 ft range. REMAINDER OF THE AREA... A weakening cold front extends from 31N121W to 25N134W. NW swell associated with the front supports seas in excess of 8 ft across most of the area west of 120W. A tighter pressure gradient that will build east-southeast behind the front will support fresh to strong NE trade winds from 08N to 27N west of 128W through Thu. Wave model guidance suggests a rather large area of 8 ft seas will stretch from about 02N to 15N between 92W and 110W as a result of long-period northwest swell mixing with shorter period northeast swell from the Gulf of Tehuantepec, and to a lesser extent those from the Gulf of Papagayo. This area of swell will merge into a larger area of seas associated with northwest swell which will cover most of the forecast area west of 92W on Wed. A surface trough is analyzed from 15N120W to 07N122W. Associated winds are moderate to fresh, with seas to 8 ft. The trough is E of a pronounced upper-level trough as seen in water vapor. The upper trough will amplify southward, but the surface trough will gradually loses its identity and continue westward. $$ Mund […]