- 注册
- 2002-10-07
- 消息
- 402,583
- 荣誉分数
- 76
- 声望点数
- 228
A map from the U.S. National Weather Service shows the big snowstorms coming Saturday may clobber one spot but leave a only light dusting a few kilometres away.
The map shows probabilities, not the amount of snow.
Here’s how it works:
This map illustrates the likelihood of getting at least six inches (15 centimetres) of snow by the end of Saturday, and you can pick different time periods on the U.S. National Weather Service winter precipitation page.
The brown strip around the edge of the storm’s expected path shows areas that have a chance of five per cent or less of getting that much snow. Yellow represents a chance of up to 10 per cent, and it grows up into blue, representing up to a 70-per-cent chance. Yet these areas are only a short distance apart.
It all adds up to a forecast that Ottawa will miss the worst of the storm, though there’s a chance we could get a significant snowfall. But areas along Lake Ontario and into Montreal have a far snowier forecast.
And the map illustrates a perennial problem with weather forecasting: Meteorologists are pretty successful at forecasting temperature, but they often miss with precipitation. All it takes is for the storm’s “track,” or main direction of travel, to shift a small amount.
Environment Canada says the current storm still may have some surprises.
“At this point there is still uncertainty. We have seen the models bouncing around,” said meteorologist Geoff Coulson. “There is still a chance of Ottawa itself could be getting 15 to 25 centimetres out of this thing by mid-Saturday… and bigger amounts along the St. Lawrence.”
Friday afternoon is expected to bring a sudden drop in temperature with some freezing rain and possibly a “flash-freeze warning” if Environment Canada thinks there is danger that moisture already on the ground will turn to ice.
tspears@postmedia.com
twitter.com/TomSpears1
查看原文...
The map shows probabilities, not the amount of snow.
Here’s how it works:
This map illustrates the likelihood of getting at least six inches (15 centimetres) of snow by the end of Saturday, and you can pick different time periods on the U.S. National Weather Service winter precipitation page.
The brown strip around the edge of the storm’s expected path shows areas that have a chance of five per cent or less of getting that much snow. Yellow represents a chance of up to 10 per cent, and it grows up into blue, representing up to a 70-per-cent chance. Yet these areas are only a short distance apart.
It all adds up to a forecast that Ottawa will miss the worst of the storm, though there’s a chance we could get a significant snowfall. But areas along Lake Ontario and into Montreal have a far snowier forecast.
And the map illustrates a perennial problem with weather forecasting: Meteorologists are pretty successful at forecasting temperature, but they often miss with precipitation. All it takes is for the storm’s “track,” or main direction of travel, to shift a small amount.
Environment Canada says the current storm still may have some surprises.
“At this point there is still uncertainty. We have seen the models bouncing around,” said meteorologist Geoff Coulson. “There is still a chance of Ottawa itself could be getting 15 to 25 centimetres out of this thing by mid-Saturday… and bigger amounts along the St. Lawrence.”
Friday afternoon is expected to bring a sudden drop in temperature with some freezing rain and possibly a “flash-freeze warning” if Environment Canada thinks there is danger that moisture already on the ground will turn to ice.
tspears@postmedia.com
twitter.com/TomSpears1
查看原文...
