Weather Theory

Cloud Types (Cirroform and cumuliform)

Cirriform - Thin wispy clouds of ice crystals. No sig weather comes from this type of cloud

Cumuliform - Puffy fair weather type clouds. Indicates unstable air and can develop into towering cumulus

Cloud Types (Nimbus clouds and lenticular)

Nimbus - Shallow and broad (nimbostratus) or tall/powerful (cumulionimbus)

Lenticular - Lens shape and indicates severe turb, common in mountainous areas

How does cloud formation occur?

Air is forced aloft and it cools to its saturation point. Water vapor condenses or sublimates creating clouds

What are some obstructions to visibility caused by clouds?

Rain
Sleet
Snow
Hail
Freezing Rain

Smoke

Caused by the suspension of combustible particles

Creates the illusion of being at greater distance than actual from runway resulting in lower approach

Haze

Caused by fine dry particles from fire

Creates the illusion of being at greater distance than actual from runway resulting in lower approach

Radiation fog

Forms over land on calm clear cool humid nights

Produced by condensation of water vapor due to condensation cooling. Dissipates in the morning quickly unless cloud layers form above

Advection fog

Forms when a low layer of warm moist air moves over a cooler surface

Most common under clouds skies along coastlines

Intensified by winds up to 15knots anything greater will dissipate it

Upslope fog

Moist stable air is forced up a slope

Similar to advection fog

Precipitation induced fog

Formed when warm rain/drizzle falls through a layer of cooler air near surface

Associated with warm fronts but can occur with slow moving cold/stationary

Ice fog

Formed in cold WX when temp is much below freezing

Caused by sublimation of water vapor directly into ice

Steam fog

Caused by cool air moving over warmer water

What is needed for the formation of a thunderstorm?

Unstable air

High moisture content of the air

Lifting action

Cumulus stage of TS

Lifting action indicating the vertical movement of air

Water vapor condenses as it rises releasing energy for further vertical growth

Mostly strong updrafts result no precip

Towering cumulus clouds form rapidly and reach mature stage in about 15minutes

Mature stage of TS

Starts when precip begins to fall at the surface

Precip becomes too heavy to support triggering downdrafts

Updrafts will still dominate in this stage

Lightning occurs here

Dissipating stage of TS

Downdrafts begin to disspiate the updrafts

Entire storm weakends

Storm is considered dead when rain is no longer produced

What are some of the hazards of TS?

Severe turb/wind shear - microbursts, downdrafts exceed 6000fpm
Icing - Severe or greater
Hail - occurs in mature dissipating stage
Low visibility - Caused by hail and precip

Formation of hail

Hail is formed by precipitation carried above and below the freezing layer by up and down drafts
Water than refreezes as the droplet is carried above the freezing level
Hail occurs in mature/disspiating stage

What are the types of icing

Clear
Mixed
Rime

Clear Ice

Formed by large water droplets that freeze slowly after striking the airframe forming a blanket

Accumulates quickly, adheres strong and difficult to remove

Avoid cumulus clouds, freezing rain, especially if below temp.

Rime Ice

Formed by small water droplets that freeze quickly to an aircraft

Rough, opaque cloudy appearance form on leading edge

Avoid stratiform clouds

Mixed Ice

Possess negative quality of rime and clear

What conditions are needed to cause icing

Contact surface temp below freezing
Moisture

Will snow cause icing?

Snow will not cause icing because its not liquid it has to be liquid and not already frozen

Icing reports

Trace - Only hazardous if experienced for over an hour
Light - Rate of accumulation may prevent a problem, use of de ice prevents it, doesn’t prevent a problem if de ice used
Moderate
Severe - Requires immediate altitude or route change

How should you fly in icing conditions differently

Turn around

Climb above/below clouds

Fly faster (5-10kts on appch)

Don’t change configuration