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Anticipating Aviation Weather Hazards in the Southwest

Anticipating Aviation Weather Hazards in the Southwest. Dr. Curtis N. James Department of Meteorology Prescott, Arizona. Overview. What are some general characteristics of the climate of the Southwest? How is aviation affected by this climate?

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Anticipating Aviation Weather Hazards in the Southwest

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  1. Anticipating Aviation Weather Hazards in the Southwest Dr. Curtis N. James Department of Meteorology Prescott, Arizona

  2. Overview • What are some general characteristics of the climate of the Southwest? • How is aviation affected by this climate? • How can the aviation weather hazards be anticipated and avoided? • Why is an understanding of the vertical structure of the atmosphere necessary?

  3. General Climate of the Southwest • Located in a latitude belt (~30°) where air generally sinks and warms (usually clear & dry; 300+ flying days / year) • Rugged terrain (clouds/precip usually more frequent over windward slopes w/ lee rain shadowing & waves) • Continental climate, isolated from oceans by terrain (generally dry air w/ high temperature variability) • Prevailing surface wind generally southwesterly (except where terrain generates local winds) • Prevailing wind aloft westerly in cold season, southerly in summer (associated with the SW monsoon) • In warm season, deep convective layer near the ground

  4. Related to the vertical structure of atmosphere Aviation Hazards of the Southwest • Deep convective boundary layer • Low-level turbulence and dust devils • Thunderstorms (esp. July – September) • Downbursts (especially dry microbursts) • Hail, lightning, turbulence near thunderstorms • Mountain waves / shears & lee turbulence • Other (icing, low clouds, IMC, LLWS, etc.)

  5. thermal thermal dust devil Deep convective boundary layer (more stable air above) 20,000’ MSL or more Hot, dry, unstable air

  6. Convective boundary layer (Prescott, AZ) Fall 2000—Photo by Joe Aldrich

  7. Dust Devil in Arizona www.nasa.gov www.nasa.gov

  8. Mountain waves ACSL clouds Strongest wind speed Roll cloud Cap cloud Cloudy, cooler, possible fog & precip Lee waves Mountain Dust may be visible Clear, warm, dry & windy

  9. Mountain wave clouds (PRC) 2000—Photo by Ben Small

  10. Lenticular clouds (near Denver) 2000—Photo by Josh Richmeier

  11. 45 kt downburst Flight path of plane 45 kt headwind 45 kt tailwind Dry microbursts • When precipitation falls through unsaturated air, evaporative cooling may produce dry microbursts • Result in very hazardous shear conditions • Visual clue: fallstreaks or virga (fall streaks that don’t reach the ground)

  12. Downburst (Phoenix, AZ) July 2003—Photo by Phillip Zygmunt

  13. Downburst (Prescott Valley, AZ) 1999—Photo by Jacob Neider

  14. ERAU Aircraft #N519ER 08 June 2003 Virga KPRC 081953Z 19008G15KT 160V220 10SM CLR 29/01 A2999 RMK AO2 PK WND 13027/1921 SLP060 VIRGA N-E TCU W-SE T02890006 KPRC 082053Z 25011G17KT 10SM CLR 32/M01 A2998 RMK AO2 SLP052 T03221011 56010 KPRC 082153Z 25013G18KT 10SM CLR 32/M01 A2996 RMK AO2 SLP048 ACFT MISHAP T03171006

  15. ERAU Aircraft #N518ER 29 November 2003 Stable air over less stable air, increasing wind speed with height Kingman, AZ Downslope wind?

  16. Vertical structure of atmosphere The following three parameters can be used to anticipate most of the hazards in a forecast vertical sounding: (Analysis Tool: http://meteo.pr.erau.edu/links.php)

  17. (http://rucsoundings.noaa.gov/gifs/)

  18. Convectively unstable layer Dry thermals

  19. WSR-88D Radar Images NM/Holloman AFB

  20. Summary • The Southwest has a fascinating climate, with a number of aviation hazards • Many hazards may be anticipated using a vertical profile of the atmosphere • Suggest analyze forecast sounding prior to flight (http://rucsoundings.noaa.gov/gifs/) • Spreadsheet tool is available on the ERAU Department of Meteorology website (http://meteo.pr.erau.edu/links.php) Questions?

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