People get really angry at weather forecasters when they’re wrong.
Meteorology is, by its nature, an inexact science. But when the forecast calls for snow and we don’t get it, people get pissed. They call meteorologists charlatans only concerned with ratings. They curse them out on Twitter.
If you follow meteorologists on social media at all, you probably saw a lot of back-slapping over the weekend. We heard pretty much all week that we were going to get a big snowstorm, and we did. People will probably forget this the next time a forecast hits, but the forecasters were right about the big snowstorm this time.
But it wasn’t just professional meteorologists who nailed this storm. Dr. Glenn F. Schreiber, a general dentist with a practice in the suburbs, blogs as The Weather Guy. On Friday morning he published a post: “Forecasters are underestimating the Philly snowfall.”
“I’ve been saying we would get 20-30 inches of snow for two days now, based heavily on a consistent NAM model,” Schreiber wrote. “With this morning’s GFS model output being in the same ballpark, the likelihood of getting closer to 30 inches in Philly is looking very reasonable. And if temps stay low, it could be more than 30 inches.” Earlier in the week, most forecasters were predicting just a foot of snow.
On Friday morning forecasters were still saying the city would get 12 to 18 inches of snow. We didn’t get 30 inches in Philadelphia, but Allentown did. Schreiber was right on all week: The city would get blanketed with snow. We ended up with 22.4 inches in Philadelphia, the fourth highest total ever here.
So how did Schreiber know? It’s simple: Two of the major numerical weather prediction models, the North American Mesoscale (NAM) and the Global Forecast System (GFS), are free for anyone to use. Sometimes they disagree on what’s going to happen in the next few days. But when they’re in agreement, that’s when Schreiber says he gets confident. “When the NAM has a big storm showing and the GFS has a big storm showing, it’s going to be a big storm,” he says. “There’s no magic about how the numbers play out.”
Schreiber, who grew up in Bayside, Queens, became enamored with the weather as a child. By third grade he had a section of the blackboard in his school for “Glenn’s Forecast.” He used to come up with forecasts using a homemade barometer made out of a milk bottle, a balloon and a straw. When he moved to Philadelphia to attend dental school at Penn, he drew his own weather maps, using a shortwave radio to get weather data from around the country. He established a practice after dental school in the area and has been here ever since.
In 1984 he bought his first computer and a modem so he could get weather data from the then-fledgling Internet. Weather data available on the Internet is something little Glenn with his blackboard forecast never thought possible.
“I just saw the Internet as exceeding my wildest dreams for weather data,” Schreiber says. “Everything that I look at is publicly available from the National Weather Service and wonderful university sites. … I’m fascinated by the fact that there are these numerical models created by brilliant people at the National Weather Service that have all the information anyone really needs.” (By its final Friday night forecast, the NWS was correctly predicting 18 to 24 inches of snow in Philadelphia.)
Schreiber’s been writing about the weather online since 1997 or 1998, usually doing weekend weather and storm forecasts. (He used to be the Bicycle Club of Philadelphia’s webmaster as well.) It’s a hobby: His wife does crossword puzzles, and he comes up with weather forecasts. He says he wishes TV and other mainstream weather people talked more about the confidence levels in their forecasts, something he says he always writes about and something the NWS does in its forecast discussions each day.
With the explosion of data on the Internet, any weather hobbyist online can become a forecaster. Phillywx has been posting forecasts online for more than a decade now. Schreiber cited TheWeatherPrediction.com as a good place to learn how forecasting works.
“Anyone who has a little science aptitude and likes nature can learn how to do this,” he says. “I don’t pretend to be an expert. I apparently have a very good track record, but again I’m not doing any magic.”
Follow @dhm on Twitter.