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Meteorology Precipitation, Fog & Thunderstorms. Reference. From the Ground Up Chapter 6.8 & 6.9: Precipitation, Fog & Thunderstorms Pages 147 - 154. Introduction. Precipitation, fog and thunderstorms are weather effects that result from cloudy conditions and high humidity.
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Reference From the Ground Up Chapter 6.8 & 6.9: Precipitation, Fog & Thunderstorms Pages 147 - 154
Introduction • Precipitation, fog and thunderstorms are weather effects that result from cloudy conditions and high humidity. • Precipitation and fog can create visibility problems for aircraft. Thunderstorms can create lots of extreme weather that are dangerous to aircraft.
Outline • Precipitation • Fog • Thunderstorms
Precipitation • When water droplets (visible as a cloud) grow sufficiently in size and weight to fall due to gravity.
Fog • Fog is stratus cloud in contact with the ground • Radiation Fog • Air cooled by cooling ground • Formed on clear nights, with moist air and light winds (2 – 5 kts) • Advection Fog • Forms when warm, moist air moves over cool surface • Upslope Fog • Caused by air moving up slope and expanding
Fog • Steam Fog • Cold air moves over warm water surface and picks up water vapour • Precipitation-Induced Fog (AKA Frontal Fog) • Rain falling from warm air mass saturates cool air mass below • Ice Fog • Forms when water vapour added to air saturated with ice crystals • Usually formed from engine exhaust
Thunderstorms • A weather phenomena whose presence creates extremely serious hazards to flying • Hazards • Turbulence, lightning, hail, icing, pressure, wind, rain • Requirements for Development • Unstable air • Lifting agent • High moisture content • Avoidance • Stay at least 15 miles away and pass to the right • Do not fly under
Thunderstorms Types • Air Mass Thunderstorms • Usually form on hot summer days in warm, moist air from convection • VFR weather around them, east to see and avoid • Frontal Thunderstorms • Normally in cold fronts • Can extend for hundreds of miles, and known as a Line Squall • Can be embedded in warm fronts
Thunderstorm Stages • Initial or Cumulus Stage • Strong updrafts • No precipitation • Mature Stage • Updrafts and downdrafts • Precipitation starts • Dissipating Stage • Downdrafts only • Precipitation ends
Next Lesson 4.8 – Meteorology Icing & Turbulence From the Ground Up Chapter 6.10 & 6.11: Icing & Turbulence Pages 154 - 159