FAA Aircraft Dispatcher (ADX)MeteorologyMedium
A dispatcher is briefing a crew on thunderstorm hazards along the route. What is the primary factor that determines the ultimate size of hailstones produced within a thunderstorm?
- AThe distance of the storm from the nearest mountain range
- BThe surface dew point temperature at the storm's location
- CThe amount of lightning activity within the storm cell
- DThe strength and duration of the updraft suspending the hailstone in the supercooled region
Show answer & explanationAnswer & explanation
Correct answer: D. The strength and duration of the updraft suspending the hailstone in the supercooled region
Hailstones grow by accumulating successive layers of ice as they are carried repeatedly through supercooled liquid water regions of a thunderstorm. A stronger, more sustained updraft keeps the hailstone suspended longer, allowing more layers to accrete before it becomes too heavy to be supported and falls.
Why the other options are wrong
- A. Terrain proximity does not directly determine hailstone size.
- B. Surface dew point affects moisture supply but not directly the hail growth mechanism.
- C. Lightning is a byproduct of charge separation, unrelated to hail growth.
Hail Formation
Hail forms when strong updrafts repeatedly carry ice particles through supercooled water regions of a cumulonimbus cloud, adding layers of ice until the stone is too heavy to remain aloft.
- Requires strong, sustained updrafts
- Grows via repeated cycling through supercooled water
- Falls when weight exceeds updraft's lifting capability
Memory trick: Bigger elevator (updraft) rides longer, bigger hailstone builds.