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Science Sundays: Predicting the Weather

Science Sundays, Seven Day Forecast Accuracy
Posted at 6:00 AM, May 29, 2022
and last updated 2022-05-29 09:00:37-04

BAKERSFIELD, Calif. (KERO) — Any meteorologist will tell you that they're not always right. Predicting the future can be challenging, and there are a lot of limits on forecast accuracy. But how far out can we really forecast? To answer that question, let's look at what goes into a forecast. Generally a meteorologist will use three things:

  1. Real-time Observations: These are things like temperatures readings, satellite, and radar that are used to determine what the weather currently is.
  2. Conceptual Knowledge: This is knowledge of how the weather works, and how forecasting works.
  3. Numerical Models: These are models that take the equations that govern how the atmosphere moves and processes them into data we can use to make a forecast.

Forecast models are arguably our most important tool used to forecast the weather. There are dozens of models available for use, and they all have two things in common: they're not perfect, and they get less accurate with time. That means as we forecast further out in time, our predictions get less accurate.

Our best forecast will almost always be for the next 24 hours. This is when models are in best agreement, and even fine details of the forecast are usually clear. Even out to three days we usually know what is going to happen, but may need to make small changes to the forecast details. Forecast confidence continues to decline in days four through seven, and past seven days we're looking mostly at trends, and the forecast details are likely to change significantly.

There are methods that can be used to forecast the weather well beyond 7 days, but they're subject to even more limitations. We'll go over those in another edition of Science Sundays!