Winter is Coming
(and I’m not talking about Game of Thrones!)
It’s time to dig out the heavy coats, thick gloves, and cloud microphysics analyses—the winter season is already arriving in full force. A large chunk of North America has already received the first snows of the season—and quite a bit of it, in some instances. This is just the beginning, as we have a long winter ahead. The winter outlook from NOAA’s Climate Prediction Center, shown here, suggests a good chance of wetter-than-average conditions across the northern U.S. thanks to La Nina, which is expected to stick around well into 2018.
With every new winter season comes new models and tools to help with forecasting and weather communication, and this year is no different. At the forefront is GOES-16* and its myriad of revolutionary products, including the snow/ice near-infrared band.
An example of this imagery from May 2017 is shown here, along with the red visible band (images courtesy of CIMSS). The snow/ice band helps to discern snowpack from cloud cover, as the highly-reflective clouds show up as bright white while the snowpack shows up as dark areas (snow strongly absorbs radiation at this wavelength). Other useful GOES-16 imagery includes the layer water vapor products, which will allow us to better identify jet streaks and other weather features, thereby improving our model diagnostics and short-term forecasts. You can find some great GOES-16 imagery from CIRA, the College of DuPage, and the GOES-R program office.
It goes without saying that we operational forecasters always try to get our warnings and forecasts 100% correct. But even if we can accomplish that, our jobs are still not done. My theme for this year, “Putting Science into Service,” is a reflection of the process by which we use our knowledge and understanding of the science of weather, climate, and related fields in service to a wide variety of partners and users to help them make decisions in support of their safety and livelihoods. So what does this mean for us? In addition to creating forecasts, we also must understand what our partners and customers need and how they interpret and use our products. That is a tall order for many of us who were trained in meteorology but who now must also have a firm handle on the social sciences and the application of warnings and forecasts by our partners and customers. Fortunately, fantastic social science research has been conducted in recent years (and is ongoing) by some very smart folks, with the goal of gaining a better understanding of how people view, interpret, and react to weather information.
For me, the importance of understanding the consequences of our forecasts really hits home during the winter months. The difference between how people deal with an inch of snow versus an inch of sleet, or a mix of sleet and freezing rain is staggering—and it varies tremendously among different areas of the country. Even small amounts can have an enormous impact. One particular event sticks in my head as a prime example. During the midday hours of January 19, 2005, an upper level wave embedded in northwest flow crossed the Appalachain mountains—a regime typically not known for producing significant precipitation east of the mountain chain. The preceding air mass was quite cold through a significant depth, ensuring that whatever fell would be just snow. This chilly air also resulted in very cold pavement temperatures—a crucial factor in what was to come. My forecast that morning was for only small amounts of snow, generating just a dusting to an inch at most in the metro area. But the snow-liquid ratios ended up being higher than expected—as much as 20:1. While the snow was mostly light and only lasted a little over 2 hours, it was efficient in quickly coating the roads and causing mass panic around the metro area (recall people in the south typically react spontaneously to whitening pavement as it is an unusual sight down here). Area schools and many businesses abruptly closed in response, forcing all of those people on the roads at once and causing a “rush hour on steroids” as the highways suddenly became jammed. As the glut of vehicles hit the unusually cold pavement, rapid melting of the dusting of snow (induced by vehicle exhaust and compression) and immediate refreezing turned all roads into sheets of thin ice. Countless accidents and traffic jams brought the area to a complete standstill for many hours. Some people were trapped on the roads well into the night, as were many children who had to stay at school with their parents unable to pick them up. (A similar scene played out in Atlanta, Georgia, in January 2014, in which a light snowfall shut down the city with gridlock, making national headlines). This event became cemented in my office folklore as the “Snow Dusting Disaster”, and it has informed my winter forecasting ever since. Not only do I think about precipitation amounts, types, and timing, but I also think about all of those factors that are not as directly weather-related, including the preparation timeline of our users and the variety of reactions of the general public to winter weather.
The winter of 2017–18 is certain to bring some surprises, some successes, and likely a few failures as well. But all of these will help us learn and grow as forecasters, making us more ready for the next big event.
-Gail Hartfield, NWA President, November 2017
* this article was written before GOES-16 became operational as GOES-East on December 18, 2017