Weather apps are a common method used to view forecasts: they’re easy to use, full of information, and require little time to fully review. If such a powerful tool is always available essentially free of charge, why should we continue to read human-written forecasts?
To approach this, consider what information we receive from an app and how it is produced. Each app is unique, but generally, most provide output from one or more weather models.
While models are powerful tools that do a good job at simulating the atmosphere, two key limiting factors to address here are:
1. Limits in spatial granularity – Ever noticed that
sometimes an app tells you it’s raining in your city, but there’s not a drop of
rain around you? Perhaps you’re even seeing sunlight. Models are limited in how
small an area they can analyze (called a “grid cell”), and thereby generalize
the outputs to broad areas, often on the scale of kilometers. Place a grid cell
on a mountain range: several peaks, valleys, and other features are likely to
fit into a single cell. The model needs to collectively represent these
features in the cell, thus smoothing out and possibly eliminating the
microclimates.
2. One single model run is only one representation of how the atmosphere may behave in the coming hours and days. Modern models have become highly skilled a short-term weather prediction, but some situations remain complicated and details are not accurately forecast. Apps may use a combination of models or an ensemble (multiple runs of the same model), but nonetheless, it is only a sampling of how the atmosphere may behave.
A screenshot of the weather forecast for Braemar from msn.com
A meteorologist can review these results and “fill in the gaps” with knowledge of microclimatology and model performance. Unlike a model, a meteorologist can think through the minor differences one may expect between, for example, the shores of Loch Tay, southern slopes of Ben Lawers, and the various surrounding glens and corries. Furthermore, with several models at hand to review, the meteorologist can make choices about which data makes the most sense, and therefore what the most likely outcome is. All that information comes together in the written forecast.
Models provide valuable data, but the meteorologist’s ability to think about the output is key to a written forecast of quality above and beyond what an app can offer.
That's the story for now, thank you for reading!
-Dan