ADX Weather and Environmental Factors 3 — Questions and Answers
Question 1: What weather condition is indicated when a rawinsonde observation shows a sharp temperature inversion and very low dew point spread at a low altitude?
- Conditions favorable for thunderstorm development
- A stable layer that suppresses convection and may trap pollutants (Correct answer)
- Rapidly improving VFR conditions
- Upper-level jet stream activity
Correct answer: A stable layer that suppresses convection and may trap pollutants
A temperature inversion creates a stable layer where warmer air overlies cooler air, suppressing vertical mixing and convection while potentially trapping moisture and pollutants below.
Question 2: A dispatcher planning a transoceanic flight reviews a Significant Weather Prognostic Chart. Which level of chart covers flight levels from FL250 to FL630?
- Low-Level Significant Weather Prog
- Mid-Level Significant Weather Prog
- High-Level Significant Weather Prog (Correct answer)
- Surface Analysis Chart
Correct answer: High-Level Significant Weather Prog
The High-Level Significant Weather Prognostic Chart covers flight levels FL250 through FL630, the primary range for high-altitude jet operations including transoceanic routes.
Question 3: Which type of fog forms when cold air moves over a warm water surface, causing rapid evaporation and condensation?
- Radiation fog
- Advection fog
- Steam fog (Correct answer)
- Upslope fog
Correct answer: Steam fog
Steam fog (also called sea smoke or Arctic sea smoke) forms when cold air flows over much warmer water, evaporating moisture that immediately condenses into low-lying fog wisps.
Question 4: During pre-departure weather evaluation, a dispatcher finds that the destination has a METAR showing OVC003 and 1/4SM FG. The filed alternate is 85 NM away with METAR showing BKN020 and 3SM HZ. What is the dispatcher's primary concern?
- The destination weather is above minimums so no concern exists
- Whether the alternate meets the regulatory weather minimums for filing as an alternate (Correct answer)
- The hazardous inflight weather between departure and destination
- Whether fog will affect the departure airport
Correct answer: Whether the alternate meets the regulatory weather minimums for filing as an alternate
When destination weather is at or near minimums, the dispatcher must verify that the alternate airport meets the applicable alternate minimums (precision or non-precision approach) at estimated time of arrival.
Question 5: What is the significance of a 'cap' or 'capping inversion' in thunderstorm forecasting?
- It permanently prevents thunderstorm formation
- It suppresses convection until sufficient heat breaks through, often causing explosive severe storm development (Correct answer)
- It only affects thunderstorms above FL300
- It causes widespread stratiform precipitation
Correct answer: It suppresses convection until sufficient heat breaks through, often causing explosive severe storm development
A capping inversion suppresses convection and allows instability to build; when the cap erodes or is breached by intense surface heating, the stored energy releases rapidly, producing severe thunderstorms.
Question 6: Which term describes the phenomenon where an aircraft accumulates ice on its airframe from supercooled large water droplets (SLDs) that extend beyond the protected surfaces?
- Rime icing
- Glaze icing
- Freezing drizzle icing / SLD icing (Correct answer)
- Frost accumulation
Correct answer: Freezing drizzle icing / SLD icing
Supercooled Large Droplet (SLD) icing is especially hazardous because large droplets run back beyond de-iced/anti-iced surfaces, accumulating ice in unprotected areas and disrupting airfoil performance.
Question 7: A dispatcher notes a METAR reporting 'FZRA' at the destination. Which weather condition does this represent, and why is it operationally significant?
- Freezing rain — liquid rain that freezes on contact with aircraft surfaces below 0°C (Correct answer)
- Frozen rain pellets that bounce off the aircraft
- Rain that freezes only on the runway surface
- Rain forecast to freeze overnight after landing
Correct answer: Freezing rain — liquid rain that freezes on contact with aircraft surfaces below 0°C
FZRA (freezing rain) is liquid precipitation that freezes on contact with surfaces at or below 0°C, rapidly building clear (glaze) ice on airframes, wings, and runways, creating severe landing and taxiing hazards.
ADX Weather and Environmental Factors 3
What weather condition is indicated when a rawinsonde observation shows a sharp temperature inversion and very low dew point spread at a low altitude?