Weather by Numbers
Judging the talent of a forecaster isn't easy. According to the National Weather Service's Eric Thaler, it would require about a year's worth of data to scientifically rate a predictor's accuracy. As such, tests of broadcast meteorologists are usually conducted by amateurs. Channel 9's Mike Nelson says the viewers who most frequently grade him are elementary school students working on class assignments.
Just over a decade ago, on April 15, 1992, Westword followed in this proud fourth-grade tradition with "Storm Warnings," an article that offered a snapshot of the skills exhibited by the weather personalities at the city's three network affiliates: Channel 4, Channel 7 and Channel 9. From March 17 until April 2 of that year, their forecasts were tracked using temperatures as a guideline. If the extremes on a given day were within a cumulative ten degrees (for instance, a high off by seven degrees and a low wrong by just three), the prediction was judged correct -- or at least correct enough. Anything further awry received a thumbs-down rating.
Back then, all three stations did fairly well one or two days in advance: Channel 4 passed 73 percent of the time; Channel 7 scored with 79 percent; and Channel 9 trailed the field with a still respectable 64 percent. But things went south more often in the three- to five-day range, with Channel 4 ringing the bell for just 38 percent of its guesses and channels 7 and 9 tying at 48 percent. Simply put, forecasts more than two days in advance were considerably wide of the mark over half the time.
In the decade since then, the tools used by weather pros have reportedly improved tremendously. But has this gear translated to better forecasts? To find out, the "Storm Warnings" experiment was repeated over a very similar span, from March 19 to April 3 this year. This time, though, all five major Denver stations were critiqued under two separate criteria. The first duplicates the cumulative ten-degree benchmark used in the original article, and the second employs a slightly different, and more difficult, yardstick. Channel 7's Marty Coniglio says the human body can't feel temperature variations unless the swing is over five degrees. So Westword counted the number of times the high or the low was off by more than that, rendering a negative verdict if either or both failed to meet the standard. (Using this procedure, the example above of a predicted high off-base by seven degrees and a low incorrect by three degrees would be wrong, because the high was askew enough to feel the difference.) Unsurprisingly, this tally wound up lower than the other measure in every case.
Overall, the picture today is very much like the one taken in 1992, despite the fact that the sixteen days analyzed below were fairly uneventful for springtime in Colorado. The outlets were reasonably good at anticipating how things would turn out 48 hours or less in advance, but they proved to be considerably weaker with each succeeding day.
Dave Fraser and Casey Curry helmed Channel 2's weather segments during the assessment period, and they had a bit of a rough go. Predictions two days or less in advance were within ten degrees 69 percent of the time, and the three- to five-day forecasts wound up at 38 percent. Things got even uglier when the station was judged by the five-degree rule. The one- and two-day forecasts landed within range just 41 percent of the time, and only 17 percent of the three- to five-day hypotheses were in this ballpark by both measures.
Still, Channel 2, which wasn't rated a decade ago (to the profound displeasure of then-chief meteorologist Al Fogelman), had relatively few catastrophic busts, usually missing by less than twenty degrees, especially as the actual dates grew closer. (Its worst moment was April 2, when a prediction two days earlier stumbled by a collective 31 degrees.)
Fraser, who's predicted the weather at assorted stations since the 1980s but has been in the Denver market for less than a year, feels he's improving each day. "Everything comes with experience," he says.
Larry Green is one of just three weather forecasters who have managed to survive in Denver TV long enough to have been part of Westword's initial trial; the others are Channel 7's Coniglio, who worked weekends at Channel 4 in 1992, and Channel 9's Nelson. But this time around, Green was on vacation for thirteen of the sixteen test-period days, leaving the job of monitoring the skies mainly to Jennifer Zeppelin and Dave Aguilera. Their efforts led to a mixed result.
One- to two-day predictions were within ten degrees on 70 percent of their tries, as opposed to 73 percent in 1992, but three- to five-day assumptions scored 48 percent, a ten-degree upgrade. Channel 4 also scored well in the five-degree challenge, predicting the high and low on that scale 62 percent of the time one or two days ahead, and registering 36 percent three to five days in advance. The latter may not seem terrific, but none of its competitors even came close.
Perhaps one of the reasons for Channel 4's triumph is its decision to make individual predictions for Denver and DIA -- the only local station to routinely do so. In Green's view, this approach makes the predictions more useful to viewers. "It's the old George Carlin joke: 'Why are they telling us what temperature it is at the airport when nobody lives there?'" Green says, adding, "We want to be where the people are, and we try to be as site-specific as we possibly can."
Unlike the weather crew at Channel 4, Channel 7's Coniglio focuses on DIA's numbers, since they're recognized as official. But in his predictions, he tries to pick a digit that splits the difference between what it will probably be like at the airport and the conditions for the metro area in general. "If my forecasts are being verified with DIA," he says, "then I'm in deep doodoo."
Actually, Coniglio, assisted by Pam Daale, didn't do too poorly in comparison with his peers, especially when it came to fresher predictions; calculations one or two days in advance were within ten degrees on 73 percent of his attempts. But the longer-range numbers were troublesome -- and because Channel 7 predicts seven days into the future instead of five, Coniglio and Daale had more chances to stray. For days three through five, they scored 33 percent; on days six and seven, they racked up just 21 percent. The station predicted the high and low within five degrees 62 percent of the time, tying Channel 4 for the highest average by the tougher criterion. But it managed only 16 percent for days three to five, and the same for days six and seven. The fifth day in advance was its Achilles' heel: Neither Coniglio nor Daale got both the high and low within five degrees a single time in sixteen stabs. As for their prediction seven days before April 2, it was high by a record-setting 49 degrees. The forecast: 66 and 36. The reality: 32 and 21. Brrrrr.
Mike Nelson, Nick Carter and Kathy Sabine combined forces for Channel 9 during the test period, and they ended up with much the same level of success as their rivals. They were within ten degrees of the official figures 75 percent of the time from one to two days, dropping to 39 percent over three to five days. Getting the high and low within five degrees was trickier; the outlet scored a 41 percent over the first two days, and 25 percent from three to five.
No doubt Nelson will be disappointed by this performance, since he's kept records of his efforts on a daily basis for over fifteen years; he says his average is within two and a half degrees during warm-weather months, and three and a half degrees in the winter. Even so, he believes that the typical viewer doesn't choose a particular newscast because of how well the men and women in question read crystal balls.
"Ultimately, people tune in to the weathercasters they feel comfortable with, and that will always be the case," he says. Nelson must do pretty well in this respect: Channel 9 has been the top-rated late newscast for practically his entire tenure at the station.
Bob Goosmann may be one of the newer kids in town, but with the help of Karen Eden and Craig Herrera, he and Channel 31 bested the Denver veterans by a key measure: One- to two-day predictions were within ten degrees 80 percent of the time. Three- to five-day predictions weren't bad, either; the station's 41 percent was second only to Channel 4 in this bracket. But the outlet's team was less accomplished at predicting both the high and the low within five degrees. The one- to two-day score: 55 percent. The three- to five-day score: 11 percent. Ooof.
Given his druthers, Goosmann probably wouldn't pick a single number to represent temperature predictions. He's the only local chief TV meteorologist who offers forecasts over a five-degree range -- say, a high of 71 to 76 and a low of 38 to 43. This not only echoes the way the National Weather Service does business, but it acknowledges the disparity of temperatures that are common in a place as large and geographically diverse as the Denver metro area. Yet because Fox's five-day forecast graphic has room for just one number, he has to narrow things down. He generally goes with the one smack in the middle of his preferred span.
For all the idiosyncrasies of individual forecasters, however, they're in lockstep more often than not: When they're right, they're usually all right, and when they're wrong, they've got plenty of company. Reps at all five stations knew that March 23 was going to be lovely four days earlier, but no one was ready for the cold snap that hit on March 21, when the mercury bottomed out at 10 degrees and peaked at 23. The predictions two days before were off from between 23 and 35 degrees.
Why? Detective work can offer hints in specific cases, but much about forecasting remains mysterious even to those who make a living at it.
"A few years ago, there was a car commercial that gave people an idea of what predicting weather is like," says Channel 2's Fraser. "A butterfly is sitting on the back end of a frog, and when the butterfly flutters, the frog is scared and jumps. The frog splashes and scares a wildebeest, which causes an entire herd of wildebeests to run. That stirs up a dust storm, which causes a thunderstorm -- and then you see a guy washing his car, and it starts raining.
"Everything really is that interconnected," he notes. "So why do we miss a storm? Maybe it's a butterfly on a frog."
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