Weather Hazards

Document Sample
Weather Hazards Powered By Docstoc
					Weather Hazards


Chapter 9, Section B
           Thunderstorms

• Conditions
  – Unstable air
  – Lifting action
  – High moisture content
• Stages
  – Cumulus stage       Mature stage
  – Dissipating stage
              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
      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
               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
    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
            Turbulence

• Low-level Turbulence below
  15,000 feet consists of
  – Mechanical Turbulence
  – Convective Turbulence
  – Frontal Turbulence
  – Wake Turbulence
     Mechanical Turbulence

• Wind forms eddies as it blows
  around hanger, stands of trees or
  other obstructions
     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
        Frontal Turbulence

• Occurs in the narrow zone just
  ahead of a fast-moving cold front
        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
        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
         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
      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
             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
   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
      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
             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
            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
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
    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
                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
               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
                 Fog

• Ice fog occurs in cold weather
  when the temperature is much
  below freezing and water vapor
  sublimates directly as ice crystals
                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%
    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
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.
338.                I27                COM
Fog produced by frontal activity is a result
of saturation due to
A. evaporation of precipitation.
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.
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.
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.
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.
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.
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.
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.
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.

				
DOCUMENT INFO