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Choosing among six deterministic forecast models

The six deterministic models publish the same windgram fields at different resolutions and lead times. Choose by lead time and required detail, then use disagreement to locate sensitivity in the day.

Choose by lead time and required terrain detail

A global model can identify a ridge or trough many days out. It cannot resolve the launch cycle on a particular mountain face. Use long-range guidance to allocate attention, not to choose an hour.

Grid resolution controls terrain and local detail

Each grid cell averages terrain and atmosphere across its footprint. A finer grid can place model terrain elevation closer to a launch and represent smaller weather features; a coarser grid describes the regional setup. Neither resolution guarantees the right answer.

Model terrain elevation changes pressure-level filtering and every height derived from the surface parcel. How a windgram is computed explains that dependency. Current grid spacing, domains, and verified model terrain elevations belong in the forecast model feed reference.

Time steps and pressure levels limit chart detail

Some windgrams contain hourly columns; others contain three-hourly columns. Their curves may look equally continuous, but the latter carry fewer observations of the model state. A narrow peak between three-hour steps is interpolation, not another forecast sample.

Vertical sampling imposes the same limit. Missing or widely spaced pressure levels reduce the detail available for lapse rate, wind shear, parcel crossings, and cloud layers. Compare the structure and sample positions behind a line before treating two smooth traces as equivalent evidence.

Use model disagreement to locate forecast sensitivity

Similar traces support the conclusion that the large-scale setup is straightforward. Separated traces identify sensitivity—to timing, moisture, initialization, terrain, or model physics—but a majority is not automatically correct. Related systems can share errors, and a coarse model can reach the right answer for the wrong local reason.

Use the comparison to locate the split:

The shaded inter-model range reports the minimum and maximum across available models. It carries no probability calibration. Return to the single-model windgrams to inspect the atmospheric structure behind it.