Summer Flying—Thunderstorm Quiz 1.
For a thunderstorm to form the atmosphere must having certain characteristics. These factors include:
A. B. C. D.
Air temperature greater than 30° C, dew point greater than 10°C and cumulus clouds. Daylight to heat the earth’s surface, an on shore flow of tropical moist air and a temperature inversion aloft. Sufficient water vapor, an unstable lapse rate and an initial upward boost. The tropopause must be lower that about 25,000 feet, rapidly building cumulus clouds and a moist air mass.
2. A thunderstorm cell during its life cycle progresses through three stages, which are defined as: A. B. C. D.
Cumulus, mature and dissipating. There are distinct transitions from one stage to the next which helps pilots decide when it’s safe to fly under the thunderstorm. Updraft, mature and downdraft. It is virtually impossible to visually detect the transition from one stage to the next. Cumulus, mature and microburst. Cumulus, mature and dissipating.
3. Although most cumulus clouds do not grow into thunderstorms, every thunderstorm begins with the cumulus stage. What is the key feature of the cumulus stage? A. B. C. D.
An updraft. Downdrafts striking the earth’s surface. A cold downdraft coexisting inside a cumulus cloud along with an updraft. Precipitation beginning to fall from the cloud base
4. What event normally signals that a thunderstorm has entered the mature stage? A. B. C. D.
An updraft. Downdrafts striking the earth’s surface. A cold downdraft coexisting inside a cumulus cloud along with an updraft. Precipitation beginning to fall from the cloud base
5.
What event normally signals that a thunderstorm has reached the dissipating stage?
A. B. C. D.
An updraft. Downdrafts striking the earth’s surface. A cold downdraft coexisting inside a cumulus cloud along with an updraft. Precipitation beginning to fall from the cloud base
6. Which of the following lists contains hazards associated with thunderstorms? A. B. C. D.
Tornados, turbulence, icing, hail, lightening Stratus clouds, turbulence, icing, hail, lightening Lenticular clouds, tornados, hail, lightening Fog, precipitation static, squall lines, microbursts
7.
Which of the following items is not a correct thunderstorm avoidance tactic?
A. B. C. D.
Don’t land or takeoff in the face of an approaching thunderstorm. Fly under the thunderstorm only when you can clearly see the ground on the other side of the storm. Avoid flying within 20 miles of any severe thunderstorm Clear the top of a known or suspected severe thunderstorm by at least 1,000 feet altitude for each 10 knots of wind speed at the cloud top.
8. You cannot avoid penetrating a thunderstorm. Which of the following tactics is recommended to help you survive your encounter with the storm? A. B. C. D.
Plan your course to take you through the storm in minimum time. Make a 180° turn if you’re in the storm for more than 5 minutes. To avoid the most critical icing, establish a penetration altitude below the freezing level or above the level of -15° C. Adjust power to fly at maximum endurance airspeed. Adjust power as needed to maintain this speed and to hold altitude as precisely as possible while you’re in the storm. If your aircraft is equipped with an autopilot, engage heading and altitude hold to minimize your flight time through the storm.
9. Microbursts can be found almost anywhere that there is convective activity. What are the typical characteristics of a microburst? A. B. C. D.
Less than 1 mile in diameter as it descends from the cloud base to about 1000 – 3000 feet AGL. In the transition zone near the ground the downdraft changes to a horizontal outflow that can extend to approximately 2 ½ miles in diameter. Downdrafts can be as strong as 6,000 feet per minute. Horizontal winds near the surface can be as strong as 45 knots resulting in a 90 knot shear (headwind to tailwind change for a traversing aircraft) across the microburst. All of the above.
10. There are several types of inflight aviation weather advisories including AIRMET’s and SIGMETs. A SIGMET advises of weather that is potentially hazardous to all aircraft. In the conterminous U.S., a SIGMET will be issued for tornadoes, lines of thunderstorms, embedded thunderstorms and hail greater than or equal to ¾ inch in diameter. A. B.
True False
Answers will be posted on the NEHC Website on May 1, 2009. Please visit www.nehc.org. 11