Weather

Question 2

What atmospheric factor causes rapid movement of surface fronts?

Answer 2

Upper winds blowing across the front

Question 3

What weather difference is found on each side of a dry line?

Answer 3

Dew point difference, a dew point front or dry line is formed when two air masses of similar density and temperature meet

Question 4

What term describes an elongated area of low pressure?

Answer 4

A trough is an elongated area of low flow pressure

Question 5

Where is the normal location of the jet stream relative to surface lows and fronts?

Answer 5

The jet stream is normally located north of the surface systems

Question 6

What type of icing is associated with the smallest size of water droplet similar to that found in low level stratus clouds?

Answer 6

Rime ice forms when drops are small such as those in level stratus clouds

Question 7

What condition is necessary for the formations of structural icing in flight?

Answer 7

Flying thru visible moisture and the temperature where the water strikes the aircraft must be freezing

Question 8

What condition is indicated when ice pellets are encountered during flight?

Answer 8

Freezing rain at higher levels

Question 9

When will frost most likely form on aircraft surfaces?

Answer 9

When both the temperature and dew point are below freezing. Occurs on clear nights with little or no winds

Question 10

What type of precipitation is an indication that super cooled water is present?

Answer 10

Freezing rain at flight level

Question 11

Radiation fog occurs when there is a surface based temperature inversion, what characterizes a ground based inversion?

Answer 11

Poor visibility

Question 12

What condition produces the most frequent type of ground or surface based temperature inversion?

Answer 12

Terrestrial radiation on a clear, calm night

Question 13

What causes advection fog to form?

Answer 13

Warm moist air flowing over colder surfaces

Question 14

What causes upslope fog to form?

Answer 14

Moist, stable air moving over higher ground, cooling adiabatically

Question 15

What minimum thickness of cloud layer is indicated if precipitation is reported as light or greater intensity?

Answer 15

More than 4000ft thick

Question 16

Which weather phenomenon signals the beginning of the mature stage of a thunderstorm?

Answer 16

Rain begins to fall

Question 17

What is and where do squall lines most often develop?

Answer 17

A narrow band of active thunderstorms, develops ahead of a cold front in moist unstable air

Question 18

Which types storms are most likely to produce funnel clouds or tornadoes?

Answer 18

Steady state (frontal) thunderstorms

Question 19

You are observing cumulonimbus mamma clouds. What inference can be made to this sighting?

Answer 19

Violent thunderstorms and tornadoes, turbulence.

Question 20

Where is the greatest area of thunderstorm turbulence?

Answer 20

Under the anvil

Question 21

What is the recommended flight separation from thunderstorms?

Answer 21

20 miles

Question 22

What is a definition of a wind shear?

Answer 22

A change in wind speed and/or direction over a short distance.
It can occur either horizontally or vertically and is most often associated with strong temperature inversions or density gradients.
Wind shear can occur at high or low altitude.
Four common sources of low-level wind shear are—
1. Frontal activity.
2. Thunderstorms.
3. Temperature inversions.
4. Surface obstructions.

Question 23

Which wind shear condition results in an increase in airspeed?

Answer 23

Tailwind shearing to a headwind

Question 24

Where can the maximum hazard zone caused by wind shear associated with a thunderstorm be found?

Answer 24

All sides and directly under the center

Question 25

What is a necessary condition for the occurrence of a low-level temperature inversion wind shear?

Answer 25

A calm or light wind near the surface and a stronger wind above the inversion, 2000 to 4000ft winds 25kts or more

Question 26

Where are the jet streams located?

Answer 26

Near the altitude of the tropopause.
The jet streams form near breaks in the tropopause, at the transitions between the Polar & Ferrel and Ferrel & Hadley circulation cells.

Question 27

At what altitude of cloud tops should a thunderstorm be considered extremely hazardous?

Answer 27

Tops above 35,000ft

Question 28

What separation is recommended from any thunderstorm?

Answer 28

20 miles

Question 29

CAT associated with mountain waves may extend how far vertically and laterally from mountains?

Answer 29

5000ft above the tropopause and 100 miles downwind

Question 30

What is the difference between occasional, intermittent and continuous chop?

Answer 30

1/3, 1/3 to 2/3, and more than 2/3

Question 31

What are the different types of frontal systems? Define.

Answer 31

Cold Front:

A cold front occurs when a mass of cold, dense, and stable air advances and replaces a body of warmer air. Cold fronts move more rapidly than warm fronts, progressing at a rate of 25 to 30 m.p.h. However, extreme cold fronts have been recorded moving at speeds of up to 60 m.p.h. A typical cold front moves in a manner opposite that of a warm front; because it is so dense, it stays close to the ground and acts like a snowplow, sliding under the warmer air and forcing the less dense air aloft. The rapidly ascending air causes the temperature to decrease suddenly, forcing the creation of clouds. The type of clouds that form depends on the stability of the warmer air mass. A cold front in the Northern Hemisphere is normally oriented in a northeast to southwest manner and can be several hundred miles long, encompassing a large area of land. Prior to the passage of a typical cold front, cirriform or towering cumulus clouds are present, and cumulonimbus clouds are possible. Rain showers and hazes are possible due to the rapid development of clouds. The wind from the south-southwest helps to replace the warm temperatures with the relative colder air. A high dewpoint and falling barometric pressure are indicative of imminent cold front passage.

As the cold front passes, towering cumulus or cumulonimbus clouds continue to dominate the sky.

Depending on the intensity of the cold front, heavy rain showers form and might be accompanied by lightning, thunder, and/or hail. More severe cold fronts can also produce tornadoes. During cold front passage, the visibility will be poor, with winds variable and gusty, and the temperature and dewpoint drop rapidly. A quickly falling barometric pressure bottoms out during frontal passage, then begins a gradual increase.

After frontal passage, the towering cumulus and cumulonimbus clouds begin to dissipate to cumulus clouds with a corresponding decrease in the precipitation. Good visibility eventually prevails with the winds from the west-northwest. Temperatures remain cooler and the barometric pressure continues to rise.

Warm Front

A warm front occurs when a warm mass of air advances and replaces a body of colder air. Warm fronts move slowly, typically 10 to 25 miles per hour (m.p.h.).The slope of the advancing front slides over the top of the cooler air and gradually pushes it out of the area.

Warm fronts contain warm air that often has very high humidity. As the warm air is lifted, the temperature drops and condensation occurs.

Generally, prior to the passage of a warm front, cirriform or stratiform clouds, along with fog, can be expected to form along the frontal boundary. In the summer months, cumulonimbus clouds (thunderstorms) are likely to develop. Light to moderate precipitation is probable, usually in the form of rain, sleet, snow, or drizzle, punctuated by poor visibility. The wind blows from the south-southeast, and the outside temperature is cool or cold, with increasing dewpoint. Finally, as the warm front approaches, the barometric pressure continues to fall until the front passes completely.

During the passage of a warm front, stratiform clouds are visible and drizzle may be falling. The visibility is generally poor, but improves with variable winds. The temperature rises steadily from the inflow of relatively warmer air. For the most part, the dewpoint remains steady and the pressure levels off. After the passage of a warm front, stratocumulus clouds predominate and rain showers are possible. The visibility eventually improves, but hazy conditions may exist for a short period after passage. The wind blows from the south-southwest. With warming temperatures, the dewpoint rises and then levels off. There is generally a slight rise in barometric pressure, followed by a decrease of barometric pressure.

Stationary Front

Neither air mass is replacing / displacing the other

When the forces of two air masses are relatively equal, the boundary or front that separates them remains stationary and influences the local weather for days. This front is called a stationary front. The weather associated with a stationary front is typically a mixture that can be found in both warm and cold fronts.

Occluded

Cold air mass catches up to warm air mass and displaces it from underneath. An occluded front occurs when a fast-moving cold front catches up with a slow-moving warm front. As the occluded front approaches, warm front weather prevails, but is immediately followed by cold front weather. There are two types of occluded fronts that can occur, and the temperatures of the colliding frontal systems play a large part in defining the type of front and the resulting weather. A cold front occlusion occurs when a fast-moving cold front is colder than the air ahead of the slow-moving warm front. When this occurs, the cold air replaces the cool air and forces the warm front aloft into the atmosphere. Typically, the cold front occlusion creates a mixture of weather found in both warm and cold fronts, providing the air is relatively stable. A warm front occlusion occurs when the air ahead of the warm front is colder than the air of the cold front. When this is the case, the cold front rides up and over the warm front. If the air forced aloft by the warm front occlusion is unstable, the weather will be more severe than the weather found in a cold front occlusion. Embedded thunderstorms, rain, and fog are likely to occur. The warm front slopes over the prevailing cooler air and produces the warm front type weather. Prior to the passage of the typical occluded front, cirriform and stratiform clouds prevail, light to heavy precipitation is falling, visibility is poor, dewpoint is steady, and barometric pressure is falling. During the passage of the front, nimbostratus and cumulonimbus clouds predominate, and towering cumulus may also be possible. Light to heavy precipitation is falling, visibility is poor, winds are variable, and the barometric pressure is leveling off. After the passage of the front, nimbostratus and altostratus clouds are visible, precipitation is decreasing and clearing, and visibility is improving.

Question 32

What changes will you notice after crossing a front?

Answer 32

Temperature, wind speed and direction, and humidity will change rapidly over a short distance

Question 33

What are the three stages of a thunderstorm?

Answer 33

1. Cumulus - updrafts
2. Mature - rain starts, updrafts and downdrafts,
3. Dissipating - downdrafts

Question 34

What in-flight hazards are associated with thunderstorms?

Answer 34

1. Turbulence
2. Lightning
3. Icing
4. Hail
5. Low ceiling, low visibility
6. Wind shear
7. Microbursts

Question 35

What is wind shear?

Answer 35

A difference in wind speed and direction over a relatively short distance in the atmosphere.

Question 36

What are the types of icing?

Answer 36

1. Clear - hard and glossy
2. Rime - Brittle and frost-like
3. Mixed - mixture of Clear and Rime - hard and rough

Question 37

What are the types of fog?

Answer 37

1. Ground (radiation) - cool humid air over cool ground (no wind)
2. Steam - cold dry air passes over warm ocean water

Moisture evaporates from water surface

Happens just above water surface

3. Advection - moist air moves over colder ground or water (winds)
4. Upslope fog - moist stable air cooled as it moves up sloping terrain
5. Precipitation induced fog - warm rain falling through cool air. Evaporation from rain saturates cool air and forms fog
6. Ice fog - occurs in cold weather when the temperature is much below freezing andwater vapor freezes directly as ice crystals.

Question 38

How would you recognize wind shear?

Answer 38

• Rapid decrease in airspeed
• Rapid decrease in climb rate
• Rapid increase in sink rate
• Increase in AOA above normal range

Question 39

How would you recognize a thunderstorm?

Answer 39

Look for “anvil”, cumulus “boiling up”effect, lightning

Question 40

How would you escape wind shear problems?

Answer 40

1. Listen to PIREPS and avoid that area
2. If encountering wind shear, report as PIREP

Question 41

What are some do’s and don’ts of thunderstorm flying?

Answer 41

DON’T

Don’t land or take off in the face of a thunderstorm

Don’t attempt to fly under a thunderstorm

DO

Do avoid large thunderstorms by 20 miles

Do remember that vivid and frequent lightning indicates a severe thunderstorm

Question 42

What would you do if you entered a thunderstorm?

Answer 42

1. Tighten safety belt and harness
2. Plan course to take you through the storm in a minimum amount of time (and hold that course)
3. Turn on pitot heat
4. Use power settings for reduced turbulence airspeed recommended in aircraft manual.
5. Turn up cockpit lights to lessen temporary blindness caused by lightning
6. Keep eyes on instruments
7. Don’t change power settings
8. Maintain constant attitude
9. Don’t turn back once in the thunderstorm (NOTE: In Rotorcraft, consider possibility of slowing to best manuver speed and reverse course to exit ASAP. Consider which way the storm is moving)