CTO Weather Observation & Reporting 5 — Questions and Answers
Question 1: A controller notices the barometric pressure has dropped below 28.00 inches Hg. What action is required?
- Issue a low altimeter setting alert to all aircraft (Correct answer)
- Immediately close the airport
- Contact the National Weather Service only
- Restrict IFR operations until pressure recovers
Correct answer: Issue a low altimeter setting alert to all aircraft
Controllers must alert pilots when the altimeter setting drops below 29.00 inches Hg, and especially note extremely low settings such as below 28.00 in Hg.
Question 2: What does a microburst wind shear alert from LLWAS typically include when transmitted to pilots?
- Location, wind gain or loss, and recommended action (Correct answer)
- Only the runway affected
- Microburst intensity on a scale of 1-5
- Duration forecast for the microburst
Correct answer: Location, wind gain or loss, and recommended action
A microburst alert includes the location relative to the runway, wind gain or loss value in knots, and controller-issued advisory.
Question 3: Which type of fog forms when moist air moves over a surface that is colder than the air's dew point?
- Advection fog (Correct answer)
- Radiation fog
- Steam fog
- Upslope fog
Correct answer: Advection fog
Advection fog forms when warm, moist air moves horizontally over a cooler surface, causing condensation near the ground.
Question 4: An aircraft reports moderate icing in cloud. Which ASOS sensor measures this condition?
- ASOS does not measure icing; PIREPs are the primary source (Correct answer)
- Icing detector on the anemometer mast
- Freezing rain sensor integrated with the ASOS
- Precipitation identifier with ice mode
Correct answer: ASOS does not measure icing; PIREPs are the primary source
ASOS cannot detect airframe icing; pilot reports (PIREPs) are the primary means of identifying icing conditions in flight.
Question 5: How is blowing snow (BLSN) differentiated from drifting snow (DRSN) in a METAR?
- Blowing snow reduces visibility and rises above 6 feet; drifting snow stays below 6 feet (Correct answer)
- Blowing snow is reported only at night; drifting snow during daylight
- Blowing snow requires wind above 30 knots; drifting snow below 30 knots
- They are interchangeable terms in METAR reporting
Correct answer: Blowing snow reduces visibility and rises above 6 feet; drifting snow stays below 6 feet
BLSN is reported when wind-driven snow reduces visibility and rises to 6 feet or more AGL, while DRSN stays below 6 feet.
Question 6: What visibility criterion triggers a mandatory SPECI when conditions improve after having been below minimums?
- Visibility rises to 3 SM or more after having been below 3 SM (Correct answer)
- Visibility rises to VFR minimums (5 SM)
- Visibility rises above 1/4 SM
- Any improvement in visibility over 10 minutes
Correct answer: Visibility rises to 3 SM or more after having been below 3 SM
A SPECI is required when visibility rises to 3 SM or above after having been reported below that threshold.
Question 7: A controller receives a SIGMET for severe icing. According to ATC procedures, what must the controller do?
- Issue the SIGMET information to affected aircraft in a timely manner (Correct answer)
- Ground all aircraft until the SIGMET expires
- Relay the SIGMET only to IFR aircraft
- Notify only the ARTCC; local towers have no responsibility
Correct answer: Issue the SIGMET information to affected aircraft in a timely manner
Controllers are required to promptly relay SIGMET information to potentially affected aircraft, regardless of flight rules.
CTO Weather Observation & Reporting 5
A controller notices the barometric pressure has dropped below 28.00 inches Hg.
What action is required?