Where it fails
And why the failure has a shape.
Where it fails, and why the failure has a shape
Forecast error is not random: it grows fastest where the atmosphere is least stable, which is why some situations are predictable for days and others for hours.
The butterfly, in practice
Sensitivity to initial conditions is a measured property with a timescale attached, not a metaphor.
The Grid, and What Falls Between
A model divides the atmosphere into boxes, and anything smaller than a box — a shower, a hill — has to be represented rather than resolved.
Ensembles
Running the model many times from slightly different starting points converts a single answer into a spread, which is the honest output.
Verification
A forecast is only as good as the record of how it did, and the scoring is its own small discipline.
Parameterisation
The grid stops at a certain size. Everything smaller than the grid box is represented by a formula, and those formulas — not the equations of motion — are where models diverge most from one another.
Every piece in Where it fails
The same set as a list, for reading rather than browsing.
- Where it fails, and why the failure has a shapeLongForecast error is not random: it grows fastest where the atmosphere is least stable, which is why some situations are predictable for days and others for hours.
- The butterfly, in practiceMediumSensitivity to initial conditions is a measured property with a timescale attached, not a metaphor.
- The Grid, and What Falls BetweenLongA model divides the atmosphere into boxes, and anything smaller than a box — a shower, a hill — has to be represented rather than resolved.
- EnsemblesMediumRunning the model many times from slightly different starting points converts a single answer into a spread, which is the honest output.
- VerificationShortA forecast is only as good as the record of how it did, and the scoring is its own small discipline.
- ParameterisationLongThe grid stops at a certain size. Everything smaller than the grid box is represented by a formula, and those formulas — not the equations of motion — are where models diverge most from one another.