Weather Information practice questions

Answer: A) About 2.5 miles in diameter

Per AIM 7-1-24, a microburst's downdraft is typically less than 1 mile in diameter, and its horizontal outflow near the ground can extend to about 2.5 miles.

• ACorrect. AIM 7-1-24 says the downdraft is typically less than 1 mile across, and the horizontal outflow near the ground can extend to about 2.5 miles in diameter.
• BIncorrect. That is far larger than the AIM figure. A microburst's outflow extends to about 2.5 miles.
• CIncorrect. A microburst is a small-scale event. The AIM gives an outflow of about 2.5 miles, not tens of miles.
• DIncorrect. That understates the hazard. The downdraft alone can approach 1 mile across, and the outflow can reach about 2.5 miles.

Answer: B) A weakly luminous corona discharge from sharp points and edges that looks eerie but is harmless

St. Elmo's fire is a weakly luminous corona discharge from an aircraft's sharp points and edges. It is harmless in itself, although the related precipitation static can cause radio noise.

• AIncorrect. St. Elmo's fire is a steady corona discharge from the aircraft's own surfaces. It is not the lightning channel and does not reliably warn of a strike.
• BCorrect. FAA weather guidance describes St. Elmo's fire as a weakly luminous corona discharge that looks eerie but is harmless. The AIM links corona discharge from sharp metal points and edges to precipitation static, which can cause radio noise.
• CIncorrect. Static dischargers are designed to bleed off charge at controlled points. The glow is not an electrical fire in the airframe wiring.
• DIncorrect. The glow comes from electrical discharge at the aircraft's own surfaces. It is not reflected or refracted light from lightning.

Answer: B) Precipitation is wrapping around a supercell's rotating updraft, an area where tornadoes may form

A hook echo shows precipitation wrapping around a supercell's mesocyclone. It is a radar sign that tornadoes may form in that part of the storm.

• AIncorrect. A hook echo belongs to an active, organized supercell. It does not indicate a dissipating storm.
• BCorrect. A hook echo forms as precipitation wraps around a supercell's rotating updraft (mesocyclone). It is a classic radar signature of an area where tornadoes may form.
• CIncorrect. This describes a bow echo. A hook echo is linked to rotation in a supercell.
• DIncorrect. Attenuation produces a weakened or missing return behind heavy precipitation, not a hook-shaped appendage.

Answer: A) Up to 4 hours

• ACorrect. Some hurricane and volcanic ash SIGMETs last longer.
• BIncorrect. That's too long.
• CIncorrect. That's too short.
• DIncorrect. The usual limit is 4 hours.

Answer: A) RVR on runway 27

• ACorrect. 2,400 ft visual range.
• BIncorrect. It's runway visual range.
• CIncorrect. It's runway visual range.
• DIncorrect. It's runway visual range.

Answer: A) Large drops run back before freezing and form ice aft of the boots, where the system cannot remove it

Supercooled large droplets run back past the leading edge and freeze aft of the protected surfaces. The ice protection system cannot remove ice there, so performance and controllability can degrade seriously.

• ACorrect. Large supercooled drops do not all freeze at the leading edge. They run back and freeze aft of the protected surfaces. The deicing system cannot shed that ice, and it can seriously degrade performance and controllability.
• BIncorrect. Instant freezing into rime on the leading edge is typical of small cloud droplets. Ice in that area is within the boots' coverage. The SLD hazard is ice that forms beyond the protected area.
• CIncorrect. SLD drops are larger than typical cloud droplets (over 50 micrometers in diameter). Their large size and runback are what carry ice aft of the protected surfaces.
• DIncorrect. SLD ice accumulates on the airframe, including aft of the protected areas, and can seriously degrade both performance and controllability. Its effect is not limited to visibility.

Answer: A) Rime ice

• ACorrect. Droplets freeze instantly on contact.
• BIncorrect. That's from large droplets spreading before freezing.
• CIncorrect. Frost forms by deposition, not droplets.
• DIncorrect. Small droplets form rime.

Answer: B) 7,500 ft

• AIncorrect. Recheck the lapse rate.
• BCorrect. 15 ÷ 2 × 1,000.
• CIncorrect. Recheck the lapse rate.
• DIncorrect. Recheck the lapse rate.

Answer: B) A downburst wider than 2.5 miles

• AIncorrect. That's a microburst.
• BCorrect. It can last longer than a microburst.
• CIncorrect. It's a downdraft.
• DIncorrect. It's a strong downdraft.

Answer: A) Hail may fall from the anvil and can be met in clear air several miles from the storm

FAA guidance says to expect hail beneath the anvil of a large cumulonimbus, even in clear air several miles from the storm, along with possible severe turbulence. Crews should not fly under the anvil.

• ACorrect. FAA guidance says to expect hail with any thunderstorm, especially beneath the anvil of a large cumulonimbus. Hail has been seen in clear air several miles from the parent storm, and flying under the anvil also risks severe turbulence.
• BIncorrect. Icing is a thunderstorm hazard, but anvils are made mostly of ice crystals. FAA guidance gives hail and turbulence, not structural icing, as the reason to stay out from under the anvil.
• CIncorrect. Static and electrical effects can happen near storms, but FAA guidance does not give them as the reason to avoid the area under the anvil. The hazards it names are hail and severe turbulence.
• DIncorrect. Rapid pressure changes near storms can cause altimeter errors, but lower pressure makes an altimeter read too high, not too low. This is also not the reason FAA guidance gives for avoiding the anvil; hail and turbulence are.