CCM Forecasting and Operational Meteorology 2 — Questions and Answers
Question 1: Which numerical weather prediction technique uses an ensemble of model runs with slightly perturbed initial conditions to estimate forecast uncertainty?
- Ensemble forecasting (Correct answer)
- Deterministic forecasting
- Analog forecasting
- Statistical post-processing
Correct answer: Ensemble forecasting
Ensemble forecasting runs multiple simulations with perturbed initial conditions to sample the range of possible outcomes and quantify forecast uncertainty.
Question 2: A mesoscale convective system (MCS) is most likely to develop when which of the following conditions are present?
- Strong wind shear and abundant low-level moisture with an initiating trigger (Correct answer)
- Weak wind shear, dry mid-levels, and stable surface layer
- Strong high pressure aloft and dry low-level air
- Isothermal lapse rates throughout the troposphere
Correct answer: Strong wind shear and abundant low-level moisture with an initiating trigger
MCS development requires strong wind shear for organization, ample low-level moisture for fuel, and a triggering mechanism such as a boundary or front.
Question 3: When issuing a forecast for a client requiring aviation weather information, which ceiling and visibility threshold defines IFR conditions?
- Ceiling below 1,000 ft AGL and/or visibility less than 3 SM (Correct answer)
- Ceiling below 3,000 ft AGL and/or visibility less than 5 SM
- Ceiling below 500 ft AGL and/or visibility less than 1 SM
- Ceiling below 10,000 ft AGL and/or visibility less than 10 SM
Correct answer: Ceiling below 1,000 ft AGL and/or visibility less than 3 SM
IFR (Instrument Flight Rules) conditions are defined as ceiling below 1,000 feet AGL and/or visibility less than 3 statute miles.
Question 4: The Q-G omega equation relates vertical motion to which two primary forcing terms?
- Differential vorticity advection and temperature advection (Correct answer)
- Surface pressure tendency and geopotential height
- Moisture flux convergence and precipitation rate
- Boundary layer height and turbulent kinetic energy
Correct answer: Differential vorticity advection and temperature advection
The QG omega equation shows that upward vertical motion is forced by positive differential vorticity advection increasing with height and warm air advection.
Question 5: Which phenomenon describes the deepening of a low-pressure system by 24 hPa or more within 24 hours, commonly called 'bombogenesis'?
- Explosive cyclogenesis (Correct answer)
- Thermal wind adjustment
- Frontolysis
- Orographic enhancement
Correct answer: Explosive cyclogenesis
Explosive cyclogenesis (bombogenesis) occurs when a low-pressure system deepens by 24 hPa or more in 24 hours, producing rapidly intensifying storm conditions.
Question 6: A forecaster notes a strong temperature inversion at 850 hPa. What type of precipitation is most likely at the surface if temperatures below the inversion are below freezing?
- Freezing rain or ice pellets depending on the depth of the sub-freezing layer (Correct answer)
- Heavy snow
- Ordinary rain
- Hail
Correct answer: Freezing rain or ice pellets depending on the depth of the sub-freezing layer
A warm layer aloft melts precipitation to rain, which then refreezes—as freezing rain if the sub-freezing layer is shallow, or as ice pellets if it is deep enough for re-freezing in the air.
Question 7: In probabilistic forecast verification, the Brier Score measures the accuracy of which type of forecast?
- Probability forecasts for binary events (Correct answer)
- Categorical yes/no deterministic forecasts
- Continuous variable forecasts such as temperature
- Wind direction forecasts only
Correct answer: Probability forecasts for binary events
The Brier Score is the mean squared error of probability forecasts for binary (yes/no) events, where a perfect score is 0.
CCM Forecasting and Operational Meteorology 2
Which numerical weather prediction technique uses an ensemble of model runs with slightly perturbed initial conditions to estimate forecast uncertainty?