January 27, 2010 - Silly Models, Tricks Are For Kids!

By: Mallory Brooke
By: Mallory Brooke

Why do computer models change so much, so fast? And what can we expect this weekend? Read all about it in today's blog.

Sometimes we have too much faith in our technology. For 4 days straight, computer models were indicating that a significant snowstorm would impact the Valley Friday and Saturday. This storm was on the level of the Blizzard of 2009. By the time we reached Tuesday, 3 days out, things started unraveling. Some models were indicating that the heaviest precipitation would be suppressed to the south. Others still cranked out a huge storm. By Wednesday, most models indicated that our ‘would be’ snowstorm may be a few inches of snow – and that’s the high end of the spectrum.

Why do computer models do this? It’s not just to get our hopes up (if you wanted a big snow) or because you wished enough (if you didn’t). It’s not really a lack of technology, but rather a lack of observations.

Think about it. When we receive huge storms, where does the energy originate from? We can track it back to the southeast, through the southwest, and out to the Pacific Ocean. Are there many observing stations out in the Pacific Ocean?

Exactly. Until the energy reaches the United States, the models have little to no information about what’s going on in the atmosphere with that piece of energy. Therefore it makes sense that 2-3 days out, when the energy is over land, everything changes.

The same thing happened with the Blizzard of 2009. On the Monday before the Blizzard, December 14, 95% of the models took the energy to our south and off the coast. By Tuesday, about 90% still did the same thing. By Wednesday morning, 60% of the models had a massive east coast snowstorm. By Thursday morning, it wasn’t a question of if the storm will happen, but how many feet of snow we would receive.

When it’s 5 days out, the best we can do is to let you know that there are indications of a significant storm in the future. However, there will likely be major changes to the forecast. That’s the time when I’ll be updating my blog and the First Alert Storm Team will constantly update our web channel so you can get up to the minute updates.

Getting back to this weekend, I’m going to run through a few of the models so you can get a feel of what they’re saying. Snow to liquid ratios are going to be higher than normal, closer to 15:1. That means every inch of liquid is 15” of snow. The GFS model gives us 0.1”-0.25” of liquid out of this storm. Therefore we’d still see a couple of inches, based on the GFS. The WRF model gives us 0.25”-0.50” liquid. The Canadian model has about 0.20”-0.40” liquid for the Valley. Remember, if the moisture is being suppressed to the south, the southern Valley will likely see more snow than the northern Valley. All models have the snow starting mid morning Saturday and lasting through Saturday evening.

While it may not be another storm of the century, a few inches are not out of the realm of possibility.  Of course, stay tuned to WHSV on-air and online for the latest!

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