AF111 - Meteorology - November 18th, 2014
Wind Shear:
➢ Positive Wind Shear
○ Increasing Headwind OR Decreasing Tail Wind
■ Inertial delay with A/C movement results in increasing A/S
■ Other than a reduced G/S, and steeper Apch, rel. safe.
➢ Negative Windshear
○ Increasing Tailwind OR Decreasing Headwind
■ Inertial delay causes A/C to lose A/S
■ Stall/Bunch of bad shit.
Standing Mountain Wave
● Minimum Windspeed = 25kts, indicated by Lenticular or Rotor clouds.
● Severe Turbulence on lee side at mountain peak level and below.
● -5000 fpm downdraft
● 3.00’’ hg drop (Overreading altimeter)
Mountain Wave Clouds
Cap Cloud: Formed by rising updrafts from low altitude up to mountain tops.
Rotor Cloud: Formed on the lee side of a mountain, often in rows.
Lenticular Cloud: Similar to cap cloud, but along the lee side of the mountain.
Fog types and conditions
Radiation Fog: Formed on clear nights or daybreak with light winds (3-5 kts). Ground cools,
losing heat through radiation. If the air is moist, and air temperature falls below dew point
on ground, fog will form. Dissipates within a few hours after sunrise.
➢ Needed Elements:
○ High Relative Humidity
○ Clear Skies at Night/Daybreak
○ Light Winds
Advection Fog: Caused by the drifting of warm, moist air over a colder land or sea surface,
cooling the air to its DPT and forming fog. May persist for days and cover wide areas, since
sea surface is relatively unaffected by daytime heating.
➢ Needed Elements
○ High Relative Humidity
○ Moderate Winds (13-15 kts)
○ Flows of warm, moist air over a cold land surface
Upslope Fog: Caused by moist air flowing upslope, then cooling to its DPT.
➢ Needed Elements
○ High Relative Humidity
○ Airflow going upslope
○ Moderate upslope winds
Frontal Fog: Evaporation of rain or drizzle causes the air below to become saturated (rising
its DPT). If the OAT is at the dewpoint temperature, fog will likely form. Most often
associated with warm fronts.
➢ Needed Elements
○ High Relative Humidity
○ Warm front (typically)
Steam Fog: Cold air passing over a warm sea surface. The evaporation of the water saturates
the lower air, causing the fog. Often occurs over rivers and lakes, most of the time in
Autumn.
Needed Elements
High Relative Humidity
Warm Sea Surface
Cold air flowing over surface
Arctic Front Sea Smoke: Same as above, except cold air comes as a result of a passing Arctic
Front.
Pressures and Wind
Climbing
(Upper Winds)
Veers, increases in speed.
Descending
Backs, Decreases in speed.
Day Advancing
Veers, increases towards the afternoon.
Gusts: Sudden increases in wind speed lasting no longer than a few moments.
➢ Caused by:
○ Uneven surface heating
○ Mechanical turbulence
Squall: A sudden increase of wind, which maintains velocity for more than a minute.
➢ Caused by:
○ Thunderstorms
○ Rapidly Moving Cold Fronts
Pressure Gradient Force:
Steep: Isobars are close together, anticipate strong winds.
Shallow: Isobars are well spaced, anticipate shallow winds.
Sea Breeze: Surface heating creates a low pressure zone on land, wind converges onshore as
a result. Common in Daytime scenarios.
Land Breeze: The escaping terrestrial radiation at night drops its temperature to below that
of the sea. This causes a relative low pressure zone over the sea, , allowing wind to converge
back to sea.