Private Pilot License

Air Pressure

Air pressure is a very important part of flying. In general, a pilot will want to fly in ‘stable’ air conditions which often occur in cooler temperatures of high pressure such as cumulus clouds and avoid low pressure areas of higher temperatures and instability. Of course, these temperatures are relative. For example, if an area of 90° F is surrounded by a cooler belt of 85° F, you will want to fly in the cooler belt of 85° F.

Fronts and Air Masses

There are two kinds of air masses, tropical and polar air masses, depending upon their location. When the air mass moves over water, it is deemed maritime and when it moves over land, it is called continental. The last part of naming air

masses is cold or warm depending on the air current temperature. For example, you may encounter a “polar maritime cold air mass” or a “tropical continental warm air mass.”

The route that an air mass travels is very important because it will affect the air mass. An air mass that travels over water picks up more moisture than one going over land.

When an air mass is traveling, it encounters other air in its line of travel. The boundary line between both is called a front. A cold front is the boundary line between the cooler air mass and the warmer air that it is overtaking. Fastmoving, a cold front is generally smooth, clean, heavy, and stable, creating good visibility and clear flight conditions. As they move quickly, they can cause violent weather. Squall lines are long lines of thunderstorms created along the frontal zone.

A warm front is the boundary line between the warmer air mass and the cool air that it is overtaking. Slow-moving, warm fronts are more spread out and harder to see. They generally result in slow worsening of good weather conditions, including poor visibility and precipitation.

A stationery front occurs when a warm front really slows down and stops. This causes misty weather, poor flight visibility. The weather is not violent and rarely turbulent.

The Weather Decision

Now that you know all the various factors that will affect your weather, you will be better prepared to handle your flight weather. Weather hazards are primarily winds and turbulence, reduced ceilings and poor visibility, and airframe icing.

Avoid these conditions and you will fly safely. Every pilot must accurately learn how to gauge these conditions.

Some things about weather still cannot be predicted. They are:

Time that freezing rain occurs

Location and occurrence of severe turbulence

Location and occurrence of icing

Ceiling of 100 feet or less before that they occur

Thunderstorms before they

start to form

Fog

Hurricane movement more

than 24 hours in advance

Realizing that even the best weather  forecaster cannot accurately predict these above conditions, it is good to be cautious when flying. Here are some general rules of thumb to follow:

• A forecast of good flying weather is generally applicable for 24 hours (this means a ceiling of 3,000 feet or more and visibility of 5 miles or more)

• A forecast of poor flying weather is generally applicable for 3-4 hours (this means a ceiling of 1,500 feet or less and visibility of 3 miles or less)

• Ceiling and visibility forecasts are suspect after the first 2-3 hour forecast, especially if changes are indicated during the forecast.