1. Weather Hazards
Chapter 9, Section B

2. Thunderstorms Conditions Stages Unstable air Lifting action
High moisture content
Stages
Cumulus stage Mature stage
Dissipating stage

3. Hazards Embedded thunderstorms may be obscured by cloud layers
Wind shear can be found on all sides as well as directly under it
Greatest intensity during mature stage, which is signaled by precipitation at the surface

4. Types of Thunderstorms
Airmass thunderstorms are usually isolated or scattered over a large area
Frontal thunderstorms associated with frontal activity
Squall line is a narrow band of active thunderstorms normally containing severe weather

5. Hazards Lightning is always associated with thunderstorms
Hail is often associated with cumulonimbus clouds but can be found in clear area several miles from the cloud
Funnel clouds - tornado or waterspout

6. Thunderstorm Avoidance
Use weather radar to avoid thunderstorms
Avoid echoes by at least 20 miles - Do not fly between if less than 40 miles apart
Weather radar does not pick up fog or clouds

7. Turbulence Low-level Turbulence below 15,000 feet consists of
Mechanical Turbulence
Convective Turbulence
Frontal Turbulence
Wake Turbulence

8. Mechanical Turbulence
Wind forms eddies as it blows around hanger, stands of trees or other obstructions

9. Convective Turbulence
Thermal Turbulence is a daytime phenomena which occurs over land in fair weather
Capping stable layer begins at the top of the convective layer. It can be identified by a layer of cumulus clouds, haze or dust

10. Frontal Turbulence
Occurs in the narrow zone just ahead of a fast-moving cold front

11. Wake Turbulence
Wingtip vortices occurs when an airplane generates lift
They can exceed the roll rate of an aircraft
Greatest when an aircraft is heavy, slow and clean

12. Wingtip Vortices
Tend to sink below the flight path of the generating aircraft
Most hazardous during light, quartering tailwinds
Land beyond where a large aircraft has touched down

13. Wingtip Vortices
Lift off before the point a large aircraft departing in from of you lifted off climb out above his flight path or turn upwind
Helicopters in forward flight produce wingtip vortices like circulation of air

14. Clear Air Turbulence
Turbulence above 15,000 feet AGL not associated with cumuliform cloudiness is reported as CAT
CAT is common in a upper trough on the polar side of the jet stream

15. Jet Stream
A curving jet stream associated with a deep low pressure trough can be expected to cause great turbulence
Jet stream can sometime be identified by long streaks of cirrus clouds

16. Mountain Wave Turbulence
Greatest turbulence occurs approaching the lee side of a mountain range in strong headwinds
Standing lenticular and rotor clouds indicate the possibility of strong turbulence

17. Reporting Turbulence
Light - slight erratic changes in altitude or attitude
Moderate - aircraft remains in positive control
Severe - large abrupt changes in altitude and attitude and may be momentarily out of control

18. Wind Shear
Sudden, drastic shift in wind speed and/or direction over a short distance
May be associated with a strong low-level temperature inversion, a jet stream, a thunderstorm or a frontal zone

19. Microbursts
Intense, localized downdrafts seldom lasting longer than 15 minutes
Downdrafts can be as strong as 6,000 feet per minute
Performance changes drastically as an aircraft flies through a microburst

20. Low-Level Wind Shear Systems
LLWAS - system of anemometers compares wind speed at several locations around the airport
Terminal Doppler Weather Radar provide a clearer, more detailed picture of a thunderstorm
Visual - Virga

21. Restrictions to Visibility
Fog, haze, smoke, smog and dust
Fog requires moisture and condensation nuclei
Industrial areas produce much fog since they have more condensation nuclei

22. Fog
Radiation Fog - ground fog - forms over fairly flat land on clear, calm nights
Advection fog- forms near coastal areas when moist air moves over colder ground or water

23. Fog
Upslope fog forms when moist stable air is forced up a sloping land mass
Steam fog occurs as cool air moves over warmer water
Precipitation-induced fog forms when warm rain falls through a layer of cooler air near the surface

24. Fog
Ice fog occurs in cold weather when the temperature is much below freezing and water vapor sublimates directly as ice crystals

25. Icing
Freezing rain is most likely to have the highest rate of accumulation
Ice, snow or frost having the thickness and roughness of sandpaper and reduce lift by 30% and increase drag by 40%

26. Cold Weather Operations
Preheat the cabin as well as the engine
Warm crankcase breather lines since they may be clogged by ice from vapors that have condensed and subsequently frozen