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 lasts for 15min
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 (supercooled droplets)

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

Rime Ice

Formed by small water droplets that freeze quickly to an aircraft

Milky, rough appearance

Avoid stratiform clouds

Mixed Ice

Possess negative quality of rime and clear

Combination of liquid water, snow and ice results in mixed ice

Ice particles become imbedded in what wouldve become clear ice that results in a rough accumulation of ice

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

Report icing to ATC with the following levels of intensity

Trace - Not a whole lot of ice

Light - Could create a problem for you if it accumulated for more than 1 hour

Moderate - Short encounters could create a problem in just a little bit of time (boot usage, immediate diversion)

Severe - Anti ice or de-ice cannot keep up with the rate of accumulation and you need to take immediate action

How should you fly in icing conditions differently

Turn around

Climb above/below clouds

• Rapidly to limit build up of ice

• Find temps above freezing or below -10C because at these temps air can’t hold liquid water

Fly faster (5-10kts on appch)

Don’t change configuration

What are the different kinds of deicing system

Anti icing - Prevents ice accumulation (pitot heat, hot props, and wings that “weep” anti ice fluid TKS. Essentially there is a reservoir of glycol and microdrilled holes in the wing that allow it to weep)

Deicing  - Removes accumulated ice by inflating rubber boots that have tubes in them (pneumatic boots)

What are the icing regulations

FIKI regulation
IFR cant fly into known or forecast - light or moderate icing conditions
VFR cant fly into known - light or moderate icing conditions

By regulation no person may takeoff in an aircraft when frost, ice or snow adheres to the wing, control surfaces, propellers, engine inlets or other critical surfaces of an aircraft

ICTS

Tailplane will collect ice the fastest due to its thin size relative to the wing

Ice contaminated tailplane stalls occur when a tailplane accumulated with ice is put at a significant negative AOA that causes it to stall

To recover

• Recover in the reverse that you would of a normal stall meaning pull back which increases the camber of the wing

• Retract flaps to previous setting

• Nose up elevator trim

• Make nose down changes slowly

• No autopilot

What are the different flight categories

LIFR - <500, <1SM
IFR - 500-1000, 1-3SM
MVFR - 1000-3000 - 3-5SM
VFR - >3000 - >5SM

Why should you be alert for turbulence?

Turbulence can lead to spatial disorientation in IMC if it is light or moderate