Weather Theory

Question 1

What is an Air Mass?

Answer 1

Large bodies of air in which the temperature and humidity are fairly uniform.
Air masses are created whenever a large body of air approaches and remains at a source

Question 2

What are the best source regions?

Answer 2

Large snow and ice covered Polar Regions
Cold northern oceans
Tropical oceans
Large desert areas.

Question 3

What is a Front?

Answer 3

The zone between contrasting air masses is called a front.

Font is a zone of change

Question 4

What happens when you cross over a front ?

Answer 4

When moving across a front, the change of temperature, wind, and humidity may be quite abrupt or very gradual depending on the properties of each air mass.

Question 5

What is front length?

Answer 5

A frontal slope can be as steep as 1 to 50 and as shallow as 1 to 300.

Question 6

What happens to winds when you cross over a front?

Answer 6

Winds always change direction when you cross a front.

Question 7

How does wind is deflected in the northern hemisphere?

Answer 7

to the right in the northern hemisphere. Around a low, the flow is counter clockwise or cyclonic.
Flow around a high is clockwise or anticyclonic.

Question 8

How does the fronts are classified?

Answer 8

Fronts can be classified as cold, warm, stationary, and occluded.

Question 9

What is a cold front?

Answer 9

When cold air advances and replaces warmer air the leading edge of the cold air is called a cold front.
The chart symbol for the cold front is a line with triangles pointing in the direction of movement.

Question 10

What is a squall line?

Answer 10

Squall lines are lines of thunderstorms that form along lines of instability.
While not directly associated with fronts, squall lines tend to form 50 to 100 miles ahead of and parallel to a cold front.
Squall lines are indicated on a weather map by a line drawn with two dots alternating with a long dash.

Question 11

What is a stationary front?

Answer 11

If a front is not moving it’s called a stationary front.

The cold and warm front symbols are alternated to indicate a stationary front – pointing in opposite directions.

Question 12

What is Occluded Front?

Answer 12

is symbolized by warm and cold front symbols on the same side of the line indicating the direction of movement.
It’s long lived and can cause violent weather.
The warm front moving northward is followed by a cold front which moves faster catching up with the warm front – pushing air upward which tends to build towering cumulus clouds.
Weather associated with the occluded front is a combination of warm and cold front weather.
The worst weather associated with an occlusion is normally in the northeast portion of the occlusion.
It colored as purple or red

Question 13

What are the features of warm fronts?

Answer 13

• Because warm fronts have a shallower slope, warm frontal weather is usually found over a much wider band than cold front weather.
• If the warm air is unstable there may be thunderstorms embedded in the massive layers of stratus clouds.

Question 14

What are the four panels on the Prog Chart?

Answer 14

The top panels forecast the weather conditions between the surface and approximately 24,000 feet.
Weather conditions at the surface are forecast by the bottom charts.
The left-hand panels are 12 hour progs
the right hand panels are 24 hour progs.

Question 15

What are the features of warm fronts?

Answer 15

Because warm fronts have a shallower slope, warm frontal weather is usually found over a much wider band than cold front weather.
If the warm air is unstable there may be thunderstorms embedded in the massive layers of stratus clouds.

Question 16

Steady precipitation preceding a front is an indication of

Answer 16

Precipitation from stratiform clouds is usually steady and there is little or no turbulence.

Question 17

What is the connection between cumuliform clouds with precipitation?

Answer 17

Steady precipitation is not associated with cumuliform clouds. Cumuliform clouds have showery precipitation.

Question 18

What is the connection between startiform clouds with turbulence?

Answer 18

Stratiform clouds usually have little or no turbulence.

Question 19

Which atmospheric layer is typified by a relatively small change in temperature?

Answer 19

Above the troposphere is the stratosphere typified by relatively small changes in temperature with height except for a warming trend near the top.

Question 20

What feature is associated with a temperature inversion?

Answer 20

If the temperature increases with altitude through a layer, an inversion, the layer is stable and convection is suppressed.

Question 21

An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 knots or more, is referred to as

Answer 21

a lenticular cloud.

Question 22

The suffix ‘nimbus,’ used in naming clouds, means

Answer 22

a rain cloud.

Question 23

There are three conditions necessary to create thunderstorms. They are:

Answer 23

Unstable air, high moisture content, and a source of lift.

Question 24

What would decrease the stability of an air mass?

Answer 24

Warming from below.Cooling from below tends to stabilize an air mass.

Question 25

What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 feet MSL is 70 °F and the dewpoint is 48 °F?

Answer 25

As a rule of thumb, divide the difference between the temperature and dew point by 4.4 to determine the height of the cloud base. 70° F - 48° F = 22. 22 / 4.4 = 5 (in thousands of feet). Add the field elevation of 1,000’ to the 5,000’ to find 6,000’.

Question 26

Moist, stable air flowing upslope can be expected to

Answer 26

When stable air is forced upward, the air tends to retain horizontal flow, and any cloudiness is flat and stratified thus stratus type clouds.

Question 27

After takeoff you encounter a temperature inversion. You should expect:

Answer 27

Inversions commonly occur within the lowest few thousand feet above ground. Strong wind shears often occur across temperature inversion layers, which can generate turbulence.

Question 28

Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?

Answer 28

A ground based inversion favors poor visibility by trapping fog, smoke, and other restrictions into low levels of the atmosphere. An inversion is a stable air mass and would have smooth air.

Question 29

Crests of standing mountain waves may be marked by stationary, lens-shaped clouds known as

Answer 29

Standing lenticular altocumulus clouds are formed on the crests of waves created by barriers in the wind flow - can be caused by mountain waves. They are an indication of very strong turbulence.

Question 30

Which conditions result in the formation of frost?

Answer 30

Frost forms in much the same way as dew. The difference is that the collecting surface must be colder than the dew point of the surrounding air and the dew point must be colder than freezing

Question 31

Clouds are divided into four families according to their

Answer 31

The four basic cloud types are divided into four families, high, middle, low, and clouds with extensive vertical development.

Question 32

Clouds, fog, or dew will always form when

Answer 32

Clouds, fog, and dew are all forms of visible moisture which occur when invisible water vapor condenses into its liquid form.

Question 33

The most frequent type of ground or surface-based temperature inversion is that which is produced by

Answer 33

warm air being lifted rapidly aloft in the vicinity of mountainous terrain.

Question 34

What are the processes by which moisture is added to unsaturated air?

Answer 34

Evaporation is the changing of liquid water to invisible water vapor. Sublimation is the changing of ice directly to water vapor bypassing the liquid state. Both processes add water to unsaturated air.