LONG RANGE: The first post tonight is regarding weather prediction and accuracy. I am using the graphics below, which are long term outlooks to this Christmas, as an example. This post is mainly for those of you who enjoy the Weather 101 segments on WSBT 22 First at 4 and have a thirst for knowledge when it comes to science. :) Everyone reading this knows the weather is unpredictable. The model guidance we use to make a forecast is, literally, hundreds and hundreds of complex math equations that are attempting to calculate different parameters in the atmosphere at different times (moisture, lift, temperatures at different levels, winds, etc). Because there is no one specific answer for these complex equations, there are many different solutions (aka forecasts) that exist. For me, this means great job security! While computers certainly can compute math faster than humans, they have a very tough time learning from previous forecasts mistakes. Plus, most of you just want the forecast! You dont care about the math equations and models. Great news for my job in the future... ha! :) Below are spaghetti plots (thats really what we call them -- because it looks like spaghetti!) of 500mb geopotential heights at different times in the coming two weeks. We use geopotential heights to approximate how cold (lower) and warm (higher) airmasses will be. Notice how in the first two pictures, the lines are fairly close to each other. This means there is fantastic agreement upon the 50+ different sets of models, thus increasing our confidence in this particular solution. Since the red lines are closer to us, we can be confident this weekend will be mild in the 40s and 50s. Thats why we have had it in the forecast for over a week now! But, as we go through time, the lines get farther and farther apart. These are the different mathematical solutions to those complex equations. By the time we make it to Christmas, literally, the lines are everywhere. This means confidence in an exact forecast is LOW, but, notice that many of the blue lines are farther south than the first picture. Despite the lines not being close, we can be confident that by Christmas, the overall temperature will be cooler because nearly all of the lines are farther south. So, I cant be exact (because look how many different solutions there are!), but 20s and 30s seem fair for afternoon temperatures. Hopefully that gives you a little idea of how meteorology works. Simply put, if you see a specific forecast that is farther than 7 days out (for example, if you see a forecast that says 40° and sunshine for Christmas day), you know its, literally, a shot in the dark and likely will be wrong. But, if you see a forecast that is speaking about a general trend (for example, Christmas looks cooler than the past several days with highs in the 20s and possibly 30s), you can likely take that to heart a bit more. #science :)
Posted on: Fri, 12 Dec 2014 02:44:38 +0000
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