Interesting weather news looking to affect the late season of the melt season what do Ya'll think?
An amplified jet stream pattern will set-up next week and this will bring a sharp contrast in temperatures across North America. Summer-like heat could become the story in the Great Lakes, but parts of the West will be feeling a wintery chill with more snow in the Rockies and possibly into the Foothills of Alberta.
The pattern change will start to develop during the weekend and early next week as a deep trough digs into southwestern Canada and the western U.S. This will send temperatures tumbling, first in BC and then spreading east across the Prairies. As the pattern becomes more amplified, a ridge will build into the Great Lakes, allowing unseasonal warmth to surge north. The warmest and coldest areas will see temperatures that are at least 5 to 10 degrees above or below seasonal. Parts of Southern Ontario, including Toronto may see one more 30 degree day at the end of next week.
Amplified flow – deep troughs and strong ridges – is common enough in the transitional autumn season, but this particular pattern change has an interesting connection to ongoing active weather in a region far removed from Canada: the western Pacific basin.
A pair of intense typhoons, Meranti and Malakas, have made their impacts felt across the western Pacific in recent days. And though these powerful storms are thousands of miles away from Canada, they will have an impact on weather patterns across the Northern Hemisphere, including our upcoming pattern change.Meteorologists use the term “teleconnection” for an atmospheric or oceanic feature in one part of the globe that have an effect somewhere else far away. A classic example of a teleconnection is the El Nino Southern Oscillation. This pattern, which relates to water temperatures and air pressure patterns in the equatorial Pacific, has a major and well-documented effect on North American weather. If you enjoyed last year’s mild winter in Canada, you have a teleconnection to thank.
The tracks of western Pacific typhoons are a different type of teleconnection, and they can give us important clues about how weather patterns will change over North America in the following 7-10 days. Specifically, a recurving typhoon like Malakas is often a sure sign of a deep trough developing over North America the next week.
This is not a direct cause-and-effect relationship – the typhoon doesn’t cause the North American trough, but there is a linkage. The typhoon pumps heat into the ridge commonly found to the east of Japan. This in turn causes a trough to dig in over the Bering Sea, which builds a ridge over the Gulf of Alaska. Finally, a trough begins to dig in over British Columbia, which builds a ridge into the Great Lakes.You can think of it as a domino effect, or perhaps more precisely, like kids on a playground making waves in a jump rope. Although in this case the jump rope is the jet stream, and the kid tugging on the end is the typhoon.
This image shows the forecast jet stream pattern over the North Pacific for next week. As you can see, the jump rope is making some wild swings, just as you would expect in the wake of a typhoon. A strong jet max is located northeast of Japan, and a powerful ridge over the Gulf of Alaska is bookended by deep troughs on either side. The trough impacting British Columbia will be the driver for next week’s pattern change.
What makes this relationship particularly useful for forecasters, is that the track the typhoon takes can help us forecast the position of the trough 7-10 days later. It tells us not only that there will be a trough, but where it is likely to be. If the typhoon tracks east of Japan, the trough is often found in eastern North America. A typhoon recurving further west, off Taiwan (as is the case with Malakas) suggests a trough over western and central North America, with ridging and warm weather developing near the Great Lakes.
Each weather pattern is different, and the relationship between typhoons and troughs isn’t always perfect. But teleconnections are a valuable tool that forecasters use in long range and seasonal forecasts. They can help us make sense of model madness, and lend confidence to our ideas about upcoming pattern changes.