4 ms·

> I use the forecast put out by weather.gov that's supposedly tailored to the square mile because it gets the 12 hour forecast right about 40% of the time. U

> I use the forecast put out by weather.gov that's supposedly tailored to the square mile because it gets the 12 hour forecast right about 40% of the time. Unfortunately, this is an example of false precision. The highest resolution numerical forecasts run by NOAA have a grid of about 3km, already coarser than your one-square-mile "tailored" output. The effective resolution of numerical weather models is also 2-3 times coarser than their grid spacing (because of numerical diffusivity and similar effects). What you're seeing isn't a "tailored" output, but instead an interpolated result from a coarser grid. Forecasting of very high-resolution effects is the subject of active and ongoing research, but unfortunately popular meteorology does not do a good job of discussing current limitations. Look at the confusion in this set of comments, for example, about what degree of forecast error is normal/acceptable.

voyager2 8y ago
If I move my forecast location a few hundred yards, my elevation changes rather drastically, changing the forecast. Elevation isn't a factor most forecasts even consider. Is it false precision to use elevation to tailor the forecast?
- Majromax 8y ago
  In that case, the interpolation includes a vertical component as well. You'll see the effects of the lapse rate (change in temperature with height). That's great for you, but it means that your forecast (of [my elevation, my coordinates]) is not much more accurate than one for ([my elevation, my coordinates plus a few hundred yards]). More technically: "surface" isn't a smooth variable when elevation changes quickly, but interpolation like that performed by weather.gov necessarily works on smooth fields. Applying post-facto elevation is great and worthwhile, but it doesn't improve the accuracy in a technical sense.

voyager2 8y ago

If I move my forecast location a few hundred yards, my elevation changes rather drastically, changing the forecast. Elevation isn't a factor most forecasts even consider. Is it false precision to use elevation to tailor the forecast?

Majromax 8y ago
In that case, the interpolation includes a vertical component as well. You'll see the effects of the lapse rate (change in temperature with height). That's great for you, but it means that your forecast (of [my elevation, my coordinates]) is not much more accurate than one for ([my elevation, my coordinates plus a few hundred yards]). More technically: "surface" isn't a smooth variable when elevation changes quickly, but interpolation like that performed by weather.gov necessarily works on smooth fields. Applying post-facto elevation is great and worthwhile, but it doesn't improve the accuracy in a technical sense.