PUBLISHED: 3:53 PM on Wednesday, January 16, 2008
Inside the weather factory
Winter is the toughest season to forecast in Southeast Alaska
"In the spring I have counted one hundred and thirty-six different kinds of weather inside of four and twenty hours," Mark Twain observed about New England weather about 130 years ago. Tom Ainsworth may count just as many kinds of weather over a short period of time in Juneau. Ainsworth is meteorologist in charge of the National Weather Service Juneau office. He says in Juneau alone there are five different microclimates. "Ten miles can make a huge difference. Downtown Juneau gets 50 percent more rainfall than the airport and it gets 50 percent less snowfall than airport," he says.

Weather in the region can be freakish. In early December, waterspouts, which

the weather service defines as a tornado occurring over water, were reported in Lynn Canal. Usually they emerge in tropical or subtropical regions. Last winter, it was record snow-200 inches in the capital city. In 2004, rarely-heard thunder shook Juneau buildings and sparked mud slides. In an hour about 1.85 inches of rain fell north of downtown, and forecasters, at the time, said the downpour might make a statewide record.

In 2000, freezing drizzle blanketed the capital city for 52 hours. The precipitation created hazardous flying, driving, even walking conditions.

"In the summer we have jökullaups. A glacier dam breaks and suddenly you have a whole lake added to the Taku River," says Ainsworth. Even though jökullaups may sound freakish, they actually occur with regularity in two areas of Southeast: the Tulsequah Glacier near Juneau and the Salmon Glacier near Hyder.

Unfortunately, meteorologists don't always see unusual weather before it becomes a hazard. But they use powerful computers and crunch millions of data points 24/7 in an effort to stay in front of storms.

The Juneau office of the National Weather Service employs a staff of 20. Nearly all are trained as meteorologists, but not all work in that capacity. The office is responsible for a huge area-from the Dixon Entrance south of Ketchikan to the Eastern half of the Gulf of Alaska. The office, nestled off Back Loop Road in the Mendenhall Valley, handles the third largest geographic area of responsibility in the National Weather Service.

In the office, forecasters click on computers that display graphics in magenta, scarlet and neon yellow. Each color tells trained professionals about different elements that make up the weather forecast including temperature, barometric pressure, wind speed and humidity. To create the graphics the weather service pulls from thousands of weather stations, including readings taken high in the atmosphere by weather balloons.

The balloons are all launched at the same time in a 24-hour period from points around the world. They feed data back to government weather services around the globe including the Juneau station. That data is plugged into modeling software.

"The amount of data we use is unbelievable. We have access to Japanese weather satellites, European, Canadian and U.S. satellites. We can composite these things, and compare historic and current data," says Ainsworth. After the computer spits out a model, forecasters compare it to conditions from observers around the region.

Ainsworth says sometimes disagreements erupt over what way a storm front will go.

"We have accountant types, Wall Streeters, every combination," and they get excited about what's shaping the weather, he says.

A shift supervisor, known as the lead forecaster, settles differences in opinion over forecasts. Ainsworth says the deliberative process generates the most reliable results. "It's a consensus forecast, which is always the best one." The office issues forecasts at 5am and 4pm daily.

Ainsworth believes winter is the toughest season to forecast accurately.

"Snow is one of those variables that's inconsistent from day to day. Everybody wants to know how much we're going to get and that's probably the most difficult thing to convey," he says. The long term forecast calls for a colder and less snowy winter in 2008 than last year.

Historians now know Mark Twain did not say, "Everybody talks about the weather but nobody does anything about it" even though it's been widely attributed to him. Charles Dudley Warner, a friend of Twain's came up with the words more than a century ago.

Today people probably talk about the weather as much as they did in Twain's time and Ainsworth, for one, is trying to do something about it.