may i join your party?
ahaahah作者: shutterbug 時間: 2009-1-10 13:48
dry snow over here...even worse...aren't we supposed to have rain warning???作者: tiffiant 時間: 2009-1-10 13:53
ya, we only have rain warning
we don't have snow warning
and i check weather website
none mentions about snow, but rain作者: low_B 時間: 2009-1-10 14:18
wet snow here ...作者: bluemoon 時間: 2009-1-10 14:19
forecast of snow for today was on theweathernetwork since a few days ago..作者: tiffiant 時間: 2009-1-10 14:29
what's wrong with weather.....
do we need to shovel snow like last 2 or 3 weeks?作者: bluemoon 時間: 2009-1-10 14:51
i remember... on the forecast.. it only snow a bit today... then will turn into rain.作者: tiffiant 時間: 2009-1-10 14:53
forecast is not always right作者: bluemoon 時間: 2009-1-10 15:33
forecast is mean "fore"-casting.. just a prediction.. =) anything can change with time in life..
hope the snow stop soon lar..作者: tiffiant 時間: 2009-1-10 15:38
ya, a week of forecast does not match with our weather in a week
i want snow also stopped作者: songor 時間: 2009-1-10 15:46
I am at Broadway looking out the window from work it is WET snow alright!
Sigh need to go home in Burnaby!!! SCARED!作者: Purpleheart 時間: 2009-1-10 15:52
Don’t blame your local weather forecaster for getting it wrong every now and then, especially in this province.
Blame the ‘data void’ — a big gap in information from over the Pacific Ocean — plus the region’s complex geography for making it tougher to predict the weather in B.C. than elsewhere else in the country.
Roland Stull compares the situation to bowling: When someone throws a bowling ball, the initial speed, direction and spin on the ball determine where it will go and how fast.
Getting an accurate read of initial conditions at a given location is vital to the accuracy of a forecast, said Stull, an earth and ocean sciences professor at the University of B.C.
Weather systems in Canada mostly move from west to east, so to predict what’s in store for B.C., local forecasters look to current conditions over the Pacific Ocean, explained Global BC senior meteorologist Mark Madryga.
The data collection points in the Pacific are limited to commercial aircraft, satellites, ships and weather buoys. Those in the business call the area a “data void.”
If there is a storm in the Pacific, satellites will pick it up, but these images provide an incomplete picture, Madryga said.
“We don’t have enough data to understand exactly what’s in those storms. It’s a very sparse data network.” This makes it hard to accurately predict things like rainfall once the storm hits land, Madryga said.
Forecasters in Toronto, by contrast, will be looking to Manitoba weather for their cues and the data network is much more extensive over land, Madryga said.
The other factor that tends to make a B.C. forecaster’s life difficult is geography. East of the Rockies, things tend to be fairly level. But this province is full of mountains, inlets and valleys that produce dramatic differences in weather within the same region.
It’s not unusual for Tsawwassen to get three centimetres of snow while Coquitlam gets 20. Madryga said accurately forecasting for each region in Metro Vancouver — how much rain will fall on the North Shore as opposed to White Rock, for example — is his biggest challenge.
Meteorologist David Jones of Environment Canada’s Vancouver office is responsible for giving forecast information to local media as well as to provincial emergency preparedness officials. He said it would have been almost impossible to predict that 25 millimetres of rain would fall at the Victoria airport between Tuesday and Thursday, while nearby Esquimalt would get drenched by nearly 100 mm over the same period.
“In a very short distance, because of the terrain, because of the geography, the amount of rain varies widely,” he said. “But when that variation — that gradient that goes from light rain to heavy rain — goes across a populated area, and when it’s snow, you can understand how people basically can’t understand why the forecast is so wrong. We know that there’s a fine line in there somewhere, but we can’t resolve exactly where it is.”
Jones said his major challenge is predicting when and where severe weather is going to hit given the complex terrain of B.C.
“Where is it going to be 100 mm? Where is it going to be 30? Where is it going to be snow?” he asked. “Our question is, what’s going to fall where, because it’s going to vary like crazy.”
How accurate are B.C. weather forecasts? Most meteorologists will say that depends how you define accuracy, and its subjective nature makes it difficult to compare B.C. forecasters’ accuracy with those elsewhere.
UBC’s Stull said B.C. forecasts tend to be quite accurate a half day into the future, while those in central and eastern Canada are fairly accurate three days in advance.
Madryga said temperature forecasts for the next day are about 80- to 85-per-cent accurate. By the fourth or fifth day, accuracy drops off to about 50 per cent. After day five “you’re better off flipping a coin, almost,” he said.
Chris Burke, with the U.S. National Weather Service in Seattle, said that agency only tracks accuracy with regard to extreme weather warnings.
As if B.C. weather forecasters don’t have enough problems, they are also at considerable risk of being replaced by machines.
A computer may not be able to stand in front of a TV weather map and point out where the next cold front is headed — yet — but they may be well on their way to sending your local weather personality the way of the dodo. Not only can Environment Canada computers do complex forecasting equations and projections into the future, they can also take that data and produce written weather reports — in English and French.
But don’t mention this to Global’s Madryga. It’s a touchy subject.
“I'm very disappointed that we’re letting computers write forecasts for us,” he said, the tension clearly audible in his voice. “The final thought process has to go through a human brain. I’m a fighter against automation.”
But automation is the way of the future, Jones said, though emphasizing there will always be a role for humans.
There used to be forecasting stations in Whitehorse and Kelowna; now, many of the weather stations in the province are unmanned and all the forecasting is done out of the downtown Vancouver office, where the ratio of computers to humans is about five to one.
Any forecast longer than two days in advance is entirely computer generated. Meteorologists are mainly focused on short-term, localized weather patterns, something the computer doesn’t do as well, Jones said, predicting this trend will continue.
The problem with the computer-generated forecasts is that they don’t tell a story and don’t identify what’s important to people, Jones said.
He offered the example of a meteorologist looking at a long-range forecast that predicts a temperature drop.
“We’re restricted in what we can say,” he said. “[The computer] spits out a forecast, it spits out ‘cloudy’ and it might show the temperature on day four and five dropping five or six degrees. It won’t say ‘turning cooler,’ which is the story or anything like that. It’ll have a smoothed-out temperature forecast and it’ll have a very generic expression of the weather.
“A lot of the story behind the weather is lost because there are stock phrases that are used. If you look at our forecasts 15 years ago and look at them now, there’s much more of a story apparent in the weather.”
