Forecast Models
Weather Model Run Explained: What 00z, 06z, 12z, and 18z Mean
A guide to weather model run times, forecast hours, and why new model data does not instantly mean the forecast has changed.
Quick answer: A weather model run is one cycle of model calculations that starts from observed atmospheric conditions and projects the future.
Run times
Model cycles are commonly labeled by UTC time, such as 00z, 06z, 12z, and 18z.
Those times do not mean the model output is available everywhere instantly.
Forecast hours
A model map labeled hour 48 shows what that run predicts 48 hours after its starting time.
Comparing the same forecast hour across runs helps reveal trends.
Smart use
One model run can be noisy.
Forecasters look for consistency, model agreement, observations, and whether the atmosphere supports the scenario.