Weather Blog

Friday's snow was big victory for weather model developers

Friday's snow was big victory for weather model developers
Snow sits at the Seattle Center, Dec. 20, 2013.

Chalk up a point to humanity in the everlasting battle to solve Mother Nature's meteorological whims. Predicting snowfall is the most daunting challenge weather forecasters face, because there are so many factors working against it -- namely we're flanked by a 50 degree ocean that's always ready to warm us up above freezing -- plus we have quite a bit of varied terrain and inland water bodies that are always eager to toss us a curve.

But Friday's snow event went perfectly to the script. Forecasts were for snow from about 4-9 a.m. in Seattle, peaking in the 6-8 a.m. time frame and that was the case -- nearly to the minute. (The snow did end around 8, but pretty close).

Models had predicted snowfall totals would be in the 0-1" range in the South Sound, about 2-3" in the Seattle-Bellevue area and 2-4" in the North Sound. Most areas ended up in the 1-2" range -- with some spots in the far north and east in the 3-4 inch range -- about an inch or so under the predictions for some areas, but all things considered, a pretty decent snowfall forecast.

And as promised, the snow turned to rain in the mid morning hours and the eventual high in Seattle was 47 degrees.

Here is a good illustration-- the photo on the left is the radar from just after 7 a.m. around the peak of the storm and the image on the right is the forecast model's calculated snowfall accumulations. Note it even had the snow band would set up just east of Puget Sound!

So I wanted to give a shout out to those who developed the computer forecast models and all of the researchers who study atmospheric dynamics to create these critical products.

The way the models work now is we put in all of the current weather observations across the globe and then the magic begins -- it's been decades of research to create and tinker with the incredibly complex mathematical equations needed to simulate the dynamics of the atmosphere.

When you think about just how much air is on the planet -- the surface area of Earth is roughly 15.7 million miles and the troposphere, which is basically where our weather occurs, extends from the ground to roughly 40,000 feet (or roughly 7 1/2 miles) high. That's an incredible playground for weather to be created and move around.

To have a perfect computer model, we would need to know what is going on at every parcel of air at a given moment, have a perfect terrain map of every inch of the globe, and then have the perfect mathematical equations to calculate that data, and account for every nook and cranny on the planet that could affect the data.

We don't have enough computer power to simulate every parcel of air, plus it's impossible to know the exact meteorological makeup of every single molecule of air on the planet, so we have to improvise a bit. Thus, forecast models aren't perfect -- as we've seen times before -- and likely never will be (at least in our lifetimes) but the fact that we can get pretty close, considering the challenge, is quite a testament to human ingenuity. We were essentially able to predict the future a few days in advance. Try doing that with other parts of our lives.

Major storms never really sneak up on anyone anymore -- think of Superstorm Sandy and how unusual that storm was, yet was nailed nearly perfect by the models -- and while there will inevitably be days when the models and forecasters are wrong, there will rarely be days when big weather events will be a surprise.

So when you're in school and you might think math doesn't really matter, here is one instance where math very much does matter, and it helped let everyone around Seattle know that it was likely going to snow Friday morning. How cool is that?