Table of Contents.
9.1 to 9.3 Local Weather
Demonstrate a basic knowledge of local weather and describe how these phenomena may affect the safe operation of an aircraft. In particular the likely occurrence of;
- low cloud
- poor visibility
Demonstrate an understanding of weather forecasts, reports and broadcasts which are pertinent to the area of operation.
Recognise signs and describe the effect of these phenomena on flight characteristics which may indicate the presence of;
Note: “Signs” means forecast conditions and pilot observations.
- Turbulence, thermals, dust devils
- Wind gradient, wind shear
9.4 to 9.5 Composition of the Atmosphere
Know the vertical divisions of the atmosphere viz;
- Most weather effects occur below the stratosphere
In the standard atmosphere, recall;
- Sea level temperature and pressure
- Temperature and pressure lapse rates in the troposphere
9.6 to 9.9 Temperature, Pressure and Humidity
Know the means of measurement of surface air temperature, and that actual local temperatures may differ e.g. higher immediately above a runway;
Know the meaning of the terms;
- isotherm, temperature inversions
- Radiation, advection, convection, conduction
- Isobar, horizontal pressure gradient
- Saturated air, relative humidity, dew point
- Evaporation, condensation, freezing
List the effects of changes in temperature, pressure and humidity on air density.
List the factors which influence the diurnal variation of surface air temperature and explain the temperature gradient between land and sea surfaces.
9.10 to 9.11 Atmospheric Stability
Differentiate between stable, unstable and conditionally stable and unstable atmospheric conditions.
Understand the adiabatic processes and the parcel method of assessing stability.
9.12 to 9.17 Clouds and Precipitation
Identify and “classify” cloud “types”. Classifications required are;
- High, medium, low
- Cumuloform, Stratoform (Examples of cloud types are Cu, Ci etc.)
Note 1: At the PPL level a basic understanding may be necessary to meet the requirements of item 9.27(j)
Identify cloud types and know the standard abbreviation for each cloud type, where applicable;
- Lenticular and rota clouds
Know the method of reporting cloud coverage.
Describe the weather associated with each cloud type.
Differentiate between drizzle, rain, showers and virga.
(A general description will be sufficient i.e., actual droplet size is NOT required.)
Select statements which describe the conditions necessary for the formation/dispersal of various types of cloud.
9.18 to 9.21 Visibility
Know the method used in meteorological forecasts and reports to describe visibility;
Describe the term “Runway Visual Range”.
Give reasons for differences between “in-flight” and “reported” visibility.
List the meteorological factors which will reduce in-flight visibility.
9.22 to 9.25 Winds - General
Describe the relationship between pressure and wind and apply Buys Ballot’s law to assess the approximate location of high and low pressure systems.
- Squalls and gusts
- Backing and veering
Compare surface and gradient winds in terms of direction and strength.
List the “factors” which affect the diurnal variation of wind and describe typical “variations” in surface wind strength during a 24 hour period.
9.26 Airmasses and Fronts
Describe typical “flying weather” associated with;
- Cold fronts
- Warm fronts
- Wave depressions
- Occluded fronts
- Tropical cyclones
- The equatorial trough
Note: The term ‘flying weather’ embraces;
- temperature (warm/cooler)
- wind changes (back/veer, stronger/weaker)
- stability and turbulence
- cloud type(s) and approximate amount(s), precipitation.
9.27 Flight Considerations
With respect to the phenomena listed below;
- state the conditions favourable to their development and, where applicable, their dispersal
- recognise signs which may indicate their presence
- describe their affect on flight condition
- where applicable, state the pilot actions required to minimise their affect on an aircraft in flight
- Thermals, turbulence
- Dust devils and dust storms
- Wind gradient, wind shear and low level jet streams
- Anabatic and katabatic winds
- Mountain waves and fohn winds
- Land and sea breezes
- Inversions and fog
- Thunderstorms and microburst
- Downdrafts associated with terrain/cloud
- Atmospheric stability and instability
- Hoar frost, rime and clear airframe ice
9.28 to 9.29 Synoptic Meteorology
Given a Mean Sea level analysis chart, identify;
- High and low pressure systems
- A trough, a ridge, a col
- Wind gradient, wind shear and low level jet streams
- Warm, cold and occluded fronts
- A tropical cyclone
Describe typical weather characteristics associated with the items listed in sub-paras 9.28 (a) and (b);
Items (c) and (d) are covered in 9.26.
The term “weather characteristics” embraces;
- Approximate wind direction
- Moisture content (dry/humid)
- Cloud (stratoform or cumuloform)
- Clear skies
- Turbulent or smooth air
- Good or poor visibility
9.30 to 9.36 Weather Services
For given locations, extract from AIP the availability of aviation forecasts, meteorological reports and weather briefing, and state the method of obtaining this information.
State/select the conditions under which it is mandatory to obtain a forecast.
With reference to AIP extract, decode and apply information contained in;
“Decode” means ability to;
- decide whether a particular forecast is valid for a flight, and
- interpret any coded information into plain language.
Given a typical weather briefing, evaluate weather information applicable to a flight;
- Assessing likely changes in weather during the flight
- List those phenomena which could adversely affect the flight “Weather” is defined in sub-para 9.29 and includes “fine weather”
List the conditions which require a pilot to submit a short AIREP.
State the purpose of VOLMET, AERIS and ATIS broadcasts and indicate how this information is obtained.
State what is meant by a TAT or TAST service. (Meteorological Terms Discontinued)