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Weather Hazards

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Use weather radar to avoid thunderstorms ... Terminal Doppler Weather Radar provide a clearer, more detailed picture of a thunderstorm ... – PowerPoint PPT presentation

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Title: Weather Hazards


1
Weather Hazards
  • Chapter 9, Section B

2
Thunderstorms
  • Conditions
  • 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, but not
    at KSU
  • Warm crankcase breather lines since they may be
    clogged by ice from vapors that have condensed
    and subsequently frozen

27
338. I27
COM Fog produced by frontal activity is a
result of saturation due to A. evaporation of
precipitation. B. adiabatic cooling. C.
nocturnal cooling.
28
338. I27
COM Fog produced by frontal activity is a
result of saturation due to A. evaporation of
precipitation.
29
363. I31
COM A situation most conducive to the
formation of advection fog is A. a light breeze
moving colder air over a water surface. B. an
air mass moving inland from the coastline during
the winter. C. a warm, moist air mass settling
over a cool surface under no-wind conditions.
30
363. I31
COM A situation most conducive to the
formation of advection fog is B. an air mass
moving inland from the coastline during the
winter.
31
364. I31
COM Advection fog has drifted over a
coastal airport during the day. What may tend to
dissipate or lift this fog into low stratus
clouds? A. Wind 15 knots or stronger. B.
Nighttime cooling. C. Surface radiation.
32
364. I31
COM Advection fog has drifted over a
coastal airport during the day. What may tend to
dissipate or lift this fog into low stratus
clouds? A. Wind 15 knots or stronger.
33
365. I31
COM In what ways do advection fog,
radiation fog, and steam fog differ in their
formation or location? A. Steam fog forms from
moist air moving over a colder surface advection
fog requires cold air over a warmer surface
radiation fog is produced by radiational cooling
of the ground. B. Advection fog deepens as
windspeed increases up to 20 knots steam fog
requires calm or very light wind radiation fog
forms when the ground or water cools the air by
radiation. C. Radiation fog is restricted to
land areas advection fog is most common along
coastal areas steam fog forms over a water
surface.
34
365. I31
COM In what ways do advection fog,
radiation fog, and steam fog differ in their
formation or location? C. Radiation fog is
restricted to land areas advection fog is most
common along coastal areas steam fog forms over
a water surface.
35
366. I31
COM With respect to advection fog, which
statement is true? A. It can appear suddenly
during day or night, and it is more persistent
than radiation fog. B. It forms almost
exclusively at night or near daybreak. C. It is
slow to develop, and dissipates quite rapidly.
36
366. I31
COM With respect to advection fog, which
statement is true? A. It can appear suddenly
during day or night, and it is more persistent
than radiation fog.
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