The difficulty of forecasting ‘disrupted’ weather
Sometimes, the National Weather Service gets it wrong.
Even in the best of circumstances, attempting to predict something with so many variables and data points is a daunting process. Meteorologists at the Grand Junction office have the additional challenge of overseeing wide stretches of land in western Colorado and eastern Utah, where the rugged landscape and weather interact in unpredictable ways.
“Topography has a huge effect on the type of weather that occurs in the mountains,” said meteorologist Jim Daniels. “Most of our storm comes from the west. We don’t have clean fronts coming through here. Our weather is very disrupted.”
According to Daniels, the station tempers the national forecasts with local readings and topographical eccentricities.
“We as the human forecaster come in and try to fine tune the forecast for areas of interest due to recreation or areas of population,” Daniels said. “What happens at Aspen is not necessarily the same thing that happens at Vail or Glenwood Springs, even though it may be the same weather system.”
That means that once in a while, your phone will inform you that it’s sunny outside during a downpour or a blizzard.
“We can’t get every little nook and cranny in the mountains, but I think overall we do fairly well.” Daniels said. “Sometimes we lean on the forecast models, especially as we get out farther into the future, and weather being fluid as it is, things change.”
Here’s the good news — you can help. The NWS has a network of volunteer storm spotters and cooperative observers, and is looking for more of them in Garfield County.
“We depend heavily on eyewitness reports, which help us to verify things,” said Jim Pringle, warning coordination meteorologist. “There’s a lot of holes in that network. We can’t have too many storm spotters.”
The NWS uses the data gathered to double check remote readings, verify the accuracy of warnings and advisories, and keep a climatological record.
Gabe Chenoweth of KMTS has run across his own handwriting in records from 1988, when the station took over the Glenwood cooperative observer gig from KGLN.
“At the end of the day, it’s one of those reminders that certain things will always change and some things will always remain the same,” he observed. “How many people can say that they’ve been doing essentially the same thing at least five days a week for more than 20 years?”
Besides being a spotter, you can also volunteer with the Colorado Collaborative Rain, Hail, and Snow Network (CoCoRaHS), which is overseen by the Colorado Climate Center. CoCoRaHS volunteers keep a detailed daily precipitation record at sites throughout the state, which can be freely perused at cocorahs.org.
The figures give some interesting insight into the eccentric weather in Garfield County. On July 16, 2014, an observer in Rifle reported .72 inches of rain and marble-sized hail. In Glenwood, only .11 inches were measured, while Carbondale had next to nothing. A couple weeks later on July 29, Glenwood received .73 inches of rain in one hour, while Rifle and Carbondale saw almost none at all.
In the end, Daniels observed, experience goes a long way toward predicting the weather. That old timer who can predict a storm might have learned to recognize the change in barometric pressure or a shift in the wind.
“There’s nothing like living in the place you’re forecasting for,” Daniels said. “You just get used to what happens and if you’re observant you can tell.”
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