Can typhoons impact the weather in Canada?
Friday, October 18, 2013, 9:14 -
Computer-generated forecast models are a valuable tool for predicting the weather, but long range forecast models are notorious for flip-flopping their forecasts.
So, how can one determine whether a long range forecast model has a good chance of being accurate?
One of the tools that meteorologists can use to assess their confidence in a long range forecast is the track of typhoons in the western Pacific and eastern Asia.
Typhoons release a tremendous amount of heat into the atmosphere which will often influence the weather pattern over North America in a predicable way, but in a way that is often not well handled by the models.
For much of the autumn season this year we have seen tropical cyclones and typhoons track primarily from west to east into southeast Asia. One such storm was Typhoon Usagi.
Typically when this happens, we see a strengthening of the subtropical ridge (often referred to as the Bermuda High) over eastern North America, which results in warmer than seasonal temperatures over the eastern half of Canada.
However, last week we saw a change in the pattern over eastern Asia which resulted in Typhoon Danas tracking between South Korea and Japan.
When typhoons turn north with a track near Japan, we often see an upper level trough develop over central or eastern North America six to 10 days later. This dip in the jet stream will typically bring colder temperatures to the region. We have actually seen this change in the weather pattern over Canada during the week as cooler temperatures have moved into the Prairies and Ontario.
Earlier this week we saw Typhoon Wipha track to the east of Japan.
Confidence is typically low for forecasts that extend beyond a week, but the forecast track for typhoon Francisco (along with several other factors) gives us confidence that we can forecast the overall pattern all the way through the final days of October.
Typhoon satellite thumbnail image courtesy of NOAA.