The Effects of the Weather on Aviation
Except perhaps for local or very short flights, a pilot, before taking off, obtains a weather forecast giving him the weather conditions which are expected along the route of his flight and at his destination. Because weather conditions affect aircraft in flight, to a considerable extent, special aviation forecasts are provided by meteorologists at weather offices all over the world.
The meteorologist, or forecaster, prepares a weather chart which shows the current weather conditions over the whole country. The current weather chart is called a synoptic chart. This synoptic chart shows the areas of low pressure, the areas of high pressure, where precipitation is falling, and all other weather conditions across the country.
From this weather map, the forecaster can advise pilots of the weather conditions they can expect to encounter during their flights. A high pressure area, for instance usually means good weather while a low pressure area usually involves one or more fronts producing clouds and precipitation over many hundreds of miles.
Pilots will pay particular attention to a low pressure area which lies en route, and the weather conditions associated with that low pressure area. The associated cold or warm fronts could involve clouds, thunderstorm, snow, rain, and turbulence. From his charts, the meteorologist can forecast where this weather will be at a certain time in the future, and with the help of these predictions, the pilot will decide which route to fly and when and he will know what weather conditions to expect. Should the forecast be very bad, for example, dense fog or poor visibility due to snow, the pilot may decide to postpone his flight. A pilot flying VFR would also cancel his flight because of low ceiling or low overcast conditions en route.
A pilot needs to know the wind direction and speed. A headwind will obviously delay the arrival of flights and is to be avoided if at all possible. A tailwind on the other hand, can be of great advantage as it increases the ground speed and results in a reduction in fuel consumption. Winds vary with altitude, and also from one place to another, so information on winds is very important.
Wind blowing between areas of different air pressure, has an important influence on aircraft operations. A pilot needs to know how the wind will affect his aircraft. He needs to know things about the wind: its direction and its speed. The wind direction is where it is blowing from and the wind speed is how fast the wind is blowing. ATC gives to a pilot information about the surface wind, that is the wind at ground level, in the following way: surface wind is 180/20. This means the wind is blowing from the south at a speed of 20 knots.
The words used to describe how strong the wind is are: calm, breeze, strong, gale (very strong), storm.
Calm means that there is no wind; storm means that the wind is very strong. A sudden increase in wind speed lasting only a few seconds is called a gust and the wind is described as gusting.
A squall is similar to a gust but lasts longer. ATC might pass the following information to a pilot: surface wind is 280/15 gusting 25.
Wind shear is the word used by ATC to warn pilots of a sudden change in wind direction or speed. Wind shear is a rapid change in wind speed or direction over a short distance horizontally or vertically. It can occur at any height, but is far more dangerous when encountered close the ground.
When wind shear is forecast or is reported by aircraft, ATC will warn other aircraft until such time as aircraft report the phenomenon no longer exists.
e.g. G-GD at 0745 a departing B-757 reported wind shear at 800 feet airspeed loss 20 kts.
Jet streams are high level winds which are very important for navigation because they blow very fast. They can blow faster than 200 knots.
Visibility is how far you can see in the weather conditions when you are flying. Visibility can affect flight operations.
Turbulence happens when the smooth flow of air is disturbed by something in its path on the ground or by rising or descending air.
Turbulence can be light, moderate and severe. In severe turbulence an aircraft can lose or gain a lot of height.
Clear air turbulence, or CAT, occurs at high altitudes away from clouds. It is normally associated with jet streams.
Information about significant changes in metconditions in the take-off or climb area is transmitted without delay, e.g. changes in surface wind direction and speed, visibility, RVR, air temperature, thunderstorm, moderate or severe turbulence, wind shear, hail, moderate or severe icing, severe line squall, freezing rain, sand storm, dust storm, blowing snow, tornado, waterspout.
Answer the question.
1 Is the weather forecast important to the pilot?
2 What can a meteorologist do?
3 Why is the pilot more interested in the weather forecast than in the present weather?
4 What chart does a meteorologist prepare?
5 What sort of weather does a low pressure area bring? Cana meteorologist show a low pressure area on his chart? Why is a pilot interested in a low pressure area?
6 Does a high pressure area bring fair weather? Sunny skies? Clear days? Does a meteorologist show a high pressure area on a synoptic chart?
7 Is rain precipitation? Snow? Hail? Turbulence? Wind? Name the kinds of precipitation.
8 Does a plane consume more or less fuel with a headwind? Does a plane go faster or slower with a headwind?
9 Are tailwinds good for fuel consumption? What type of wind affects aircraft ground speed?
10 How many types of fronts are there?
11 Who prepares a weather map showing the cold fronts?
12 Can pilots recognize a warm front on a weather map?
13 What do you consider is a low ceiling of clouds? What effect can a low ceiling have on flying?
14 With a low ceiling are there many clouds in the sky? Are there more clouds in the sky when the sky is overcast? Can you see any blue sky when the sky is overcast?