SIOUX FALLS, S.D. (KELO) — The forecast for the Fourth of July went up in smoke as quickly as a firecracker with a short fuse. Anyone that saw the forecast expected rain in Sioux Falls and the surrounding areas Thursday morning. As we all know, that didn’t happen.
Fourth of July morning in southeastern KELOLAND was a lot more pleasant than what was in the forecast the day before. While the day did start with cloud cover, the sun eventually came out and ruled much of the day. It was the opposite of our forecast. Based on data and computer models the day before, a rainy day is what we expected. But why?
Here are three different forecast models. The European, the American, and the Canadian. Each of these models is run through computers not once – but many times with a slight variation each time intended to minimize errors.
Here is the European model from the night before the 4th. Each of the colored blocks shows when rainfall is expected. This model was run 50 times, and as you can see, all 50 variations put rain in Sioux Falls – though with different amounts.
Here is the American GFS model. All 30 variations predicted rain in Sioux Falls.
And here is the Canadian model – all 20 variations also put rain in Sioux Falls. Of course, this didn’t hold true.
So, what went wrong? Sometimes the models don’t initialize well, meaning they don’t accurately convert the atmosphere into numbers that computers can use to calculate the future. If the model can’t figure out what’s happening now, then how can they figure out what’s going to happen?
Also, the low-pressure system moved through A LOT quicker than what was expected. This helped bring in drier air via southwest winds to southeast KELOLAND… creating what we call a clear slot, allowing for dry skies during the day.
The first one to know the forecast is wrong is the person or people who put it together. At 2:30 Thursday morning when one of our meteorologists saw the rain wasn’t showing up in southeast KELOLAND, he knew something was wrong.
When we saw sunshine increase during the morning, we knew the forecast was going to be a bust. As good as all our science and technology is, occasionally we get a harsh reminder that WE are not in charge.
