Tale of two forecasts


Ash Gaston of Garden Gate Nursery covers the most tender citrus, lemon and lime trees Wednesday. Judy Brown, manager of Garden Gate, said when it is forecast for 30 degrees or below they cover the sensitive plants and trees. Brown said it is at least the sixth time they've had to use the frost cloths for their plants.

TRACY WILCOX/The Gainesville Sun
Published: Thursday, January 19, 2006 at 6:01 a.m.
Last Modified: Wednesday, January 18, 2006 at 11:14 p.m.
Winter will slog through its final days, blanketing the region with the frost Gainesville homes might see today and plaguing it with cold, wet days until March.
Or, winter will bound into spring, with above-average temperatures and below-average rainfall.
Which forecast you believe depends on which source you trust more: the Farmer's Almanac or the National Oceanic and Atmospheric Administration.
The Almanac's "Caleb Weatherbee," a forecaster who works under a pseudonym, is predicting cold and wet; NOAA's computer models are forecasting warm and dry.
The methods the two services use are as disparate as can be; their predictions often are, too. Climate experts, farmers and other weather-watchers said though the Farmer's Almanac has had its successes, it's best to trust technology.
"The Farmer's Almanac's methods, they're not, like, science methods, OK?" said James J. O'Brien, director of the Center for Ocean-Atmospheric Prediction Studies at Florida State University. "They're like homeopathic medicine - the things that have been handed down generation to generation. And some of those work, right?"
"Weatherbee" uses a formula that's been around since the Almanac was founded in 1818, said Sandi Duncan, managing editor of the Farmer's Almanac. She said the formula uses mathematical and astronomical cues like sunspots, the position of the planets and the cycles of the moon to predict the weather for a year in advance.
Duncan said readers' reports indicate that the Almanac's predictions are roughly 80 to 85 percent accurate. She said the Almanac predicted Hurricane Andrew, and came within 10 days of predicting Hurricane Katrina's landfall.
"We don't have a 100 percent accuracy rate," Duncan said. "But we often hear back from people who have used us to plan an event, and it's mostly positive feedback."
NOAA's National Weather Service offers short-term weather forecasts - the chance of specific conditions like rain, fog or clouds for a given area on a given day - by using computer simulations that include initial weather conditions, existing storms, developing storms and other factors.
For example, the Jacksonville National Weather Service office is predicting patchy frost in Gainesville this morning, with an overnight low of 29 degrees and a high of 69 degrees today.
NOAA's Climate Prediction Center predicts trends for three-month periods, issuing general statements based on historic observations and on computer models that consider the temperature of the ocean, among other factors, said Mike Halpert, head of forecast operations for NOAA's Climate Prediction Center.
Halpert said over the past 10 years, the center has been about 50 percent successful in those predictions.
"So it's definitely better than blind luck, but a long way from where we'd like to be," Halpert said.
Halpert said he doubted an independent check of the Almanac's predictions would show a much higher success rate, and said its methods were scientifically questionable.
"You mean they have methods?" Halpert said, laughing.
"I mean, (astronomical factors) are things we just don't use in forecasting. The Almanac gives you a finite window of when you'll see snowstorms or rainstorms, and we don't believe the capabilities exist to make that kind of forecast. Our seasonal outlooks aim only to provide average conditions over a three-month period, and that's hard enough for us to do as it is."
Duncan stood by the Almanac's success rate.
"We don't try to take the local meteorologist's place," Duncan said. "But even in this day and age, especially if you're planning something far in the future, it can't hurt to check in with us."
O'Brien said the Almanac's successes are lucky guesses at best.
He said the temperature of the ocean is the single most important factor in long-term forecasting, and said he's fairly certain the Almanac doesn't consider that.
"The Farmer's Almanac doesn't know anything about the ocean," O'Brien said. "Whatever methods they do use, there's no indication that they ever recognize that the state of the ocean is the most important aspect to consider in long-term forecasting."
To many farmers, accurate weather forecasting can make the difference between a profitable season and an unprofitable one.
"In Plant City, strawberry growers buy plants resistant to sunlight when we tell them to expect a drought," O'Brien said.
"In Homestead, where they grow potatoes, farmers will dig ditches so that all the extra rain from El Nio will run off. That's why some of the things we're doing are so exciting - because we can help people mitigate disasters."
Alachua farmer Lawrence Davis and nursery manager Michael Verschaeve both said they watch the weather closely, but said they put their trust in different services.
Verschaeve, manager of Blue Star Nursery near Hawthorne, said he relies mostly on the National Weather Service's daily forecasts and long-term predictions.
He's read the Farmer's Almanac before, but said he doesn't find it useful.
Davis, on the other hand, said he tries to follow the Almanac's planting instructions as carefully as possible, and pays close attention to its weather predictions.
"I don't know about the accuracy, but it gives you a longer term view of what might be coming," Davis said.
Davis said he relies mostly on local weather forecasts for short-term information, and said that even those fail to satisfy sometimes.
Last week, he said, no one predicted a hail storm that wreaked havoc on one of his fields.
"Mostly," Davis said, "You've just got to kind of go with the feeling you have at a particular time."
Amy Reinink can be reached at 374-5088 or reinina@ gvillesun.com.

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