CBM Numerical Weather Prediction and Forecast Models 1 — Questions and Answers
Question 1: What does the acronym GFS stand for in operational weather forecasting?
- Global Forecast System (Correct answer)
- General Frontal Scheme
- Gridded Forecast Summary
- Geophysical Flux Simulation
Correct answer: Global Forecast System
GFS stands for Global Forecast System, the primary global NWP model run by NOAA/NCEP four times daily.
Question 2: Which numerical weather prediction model is known for consistently high skill in medium-range forecasting and is operated by a European consortium?
- NAM
- GFS
- ECMWF (Correct answer)
- RAP
Correct answer: ECMWF
The ECMWF (European Centre for Medium-Range Weather Forecasts) model is widely regarded as the world leader in medium-range forecast accuracy.
Question 3: The North American Mesoscale (NAM) model is best suited for which forecast time range?
- 0–84 hours (Correct answer)
- 84–240 hours
- 240–384 hours
- 10–30 days
Correct answer: 0–84 hours
The NAM is a regional model designed for short- to medium-range forecasts up to 84 hours, with higher resolution over North America than global models.
Question 4: What is 'data assimilation' in the context of numerical weather prediction?
- The process of combining observations with a prior model state to create an optimal initial analysis (Correct answer)
- Converting model output into broadcast graphics
- Downloading model data from NCEP servers
- Applying statistical corrections to model temperature forecasts
Correct answer: The process of combining observations with a prior model state to create an optimal initial analysis
Data assimilation merges real-world observations (radiosondes, satellite, surface stations) with the model's background field to produce the best possible initial conditions for a forecast run.
Question 5: In ensemble forecasting, what does a large spread among ensemble members generally indicate?
- High forecast confidence
- Low forecast confidence and greater atmospheric uncertainty (Correct answer)
- A deterministic outcome
- Model initialization errors only
Correct answer: Low forecast confidence and greater atmospheric uncertainty
A large ensemble spread signals greater uncertainty in the forecast, meaning the atmosphere is in a less predictable state and meteorologists should communicate lower confidence.
Question 6: Which of the following best describes 'model grid spacing' and its effect on forecast quality?
- Finer grid spacing generally resolves smaller-scale features more accurately but requires more computing power (Correct answer)
- Coarser grid spacing improves short-range accuracy by averaging noise
- Grid spacing only affects precipitation forecasts, not temperature
- All operational models use the same standard grid spacing
Correct answer: Finer grid spacing generally resolves smaller-scale features more accurately but requires more computing power
Finer (smaller) grid spacing allows a model to explicitly resolve smaller meteorological features like terrain effects and convective cells, improving detail at the cost of greater computational demand.
Question 7: How many times per day does NCEP operationally run the GFS model?
- Two times (00Z and 12Z)
- Four times (00Z, 06Z, 12Z, and 18Z) (Correct answer)
- Once per day at 00Z
- Six times per day every four hours
Correct answer: Four times (00Z, 06Z, 12Z, and 18Z)
The GFS is run four times daily at 00Z, 06Z, 12Z, and 18Z, providing fresh global forecast data every six hours.
CBM Numerical Weather Prediction and Forecast Models 1
What does the acronym GFS stand for in operational weather forecasting?