Thursday, February 26, 2015

Forecasting In My CSA Home - And It's Not The Confederate States Of America

With a life-long interest in weather, it's no wonder more than a few of my classmates referred to me as "WiHi's weatherman." when I attended my 50th high school reunion last year. It all began six decades ago in the western Maryland mountains in a population measured in the tens of thousands. In the same manner that weather and climate change, my location over those decades has changed. The huge difference today is both the size and geography of "home." To call Atlanta "home" means looking at what the Bureau of the Census calls a Combined Statistical Area (CSA) of almost 7 million people living in more than forty counties covering almost 11,000 square miles. Add to that a physical geography ranging from the coastal plain at an elevation of 300 feet to the Appalachian Mountains approaching 4000 feet.

I can only imagine the difficulty of forecasting a winter weather event for this area sixty years ago. There's no question weather forecasting improved significantly over those decades, but the CSA's size and variation still makes forecasting for Atlanta a serious challenge. Our National Weather Service (NWS) does well in what I would call a macro-forecast two to three days out. By the sixth day accuracy begins to drop at an accelerating rate. That's why you see seven day forecasts these days, something the NWS has done since 2000. Looking in the other direction we can see some remarkably accurate spot forecasts measured in hours. It gets complicated when you have a lot of spots.

That brings me to the big snow non-event here at "home" over the last two days. Readers may recall that Atlanta was pilloried in the national media last year over "Snowmageddon," an ice and snow event in late January that paralyzed north Georgia. Those who were not here to experience it should be aware that the media chose to ignore reporting that snow concealed a nice blanket of freezing rain on virtually every paved surface. In addition, limited storm preparation at all levels worsened the situation.

This time, they took every precaution from multiple coats of brine sprayed on major roads a day in advance to distributing the usual tons of road salt to preparing scores of emergency shelters. They said "Snowmageddon" wouldn't happen again. And this time for the most part they were correct. The freezing line snaked across the middle of the CSA rather as expected. Yes, there was snow and ice yesterday followed by "black ice" on the roads this morning around "home," but for millions it was a best case scenario. As for our spot on the Atlanta matrix it was a rainy non-event. I'd like to think these non-events will continue for many weeks in this aging winter.  In the spirit of the transition there is much to enjoy wherever we live. If you don't believe me look out the nearest window and listen to this:

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