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Canadian weather

Possible Clues Into the Summer

3/17/2014, 11:23:11 AM

As I mentioned in the previous blog, I wanted to show you what the general long-range computer model forecast consensus indicates in terms of weather patterns each month through August. A few things to keep in mind.....

1. My interpretation is strictly based on the latest combined multi-model ensemble forecast system (National/International), which is still experimental but has shown increased skill over individual models. These are not AccuWeather. com forecasts.

2. Model skill declines steadily beyond April, so do not take these as gospel. Model skill is usually higher with temperature compared to precipitation.

3. Due to a lack of signal (neutral ENSO for instance), these forecasts are heavily influenced by current conditions such as ocean water temperatures and ice coverage. The forecast for cooler temperatures around the Great Lakes in May is likely a reflection of the much higher-than-normal ice cover, which may lead to colder-than-normal waters in April/May, which has a localized cooling influence.

3b. Also, when there is a lack of signal I have noticed that the model ensemble tends to lean much more toward warmer anomalies versus cooler anomalies. Part of this may be due to the fact that the Canadian normals are still too low and need to be adjusted upward due to longer term climate change.

4. There continue to be growing signs that we are headed for overdue El Nino conditions in the equatorial Pacific, perhaps as early as the summer, though I lean more toward the early fall. If El Nino does return, we could start to see some impacts perhaps as early as this winter in the northern U.S. and Canada. With an El Nino, the good news is that the extended long-range models will have a stronger climate signal to latch onto, which could lead to improved forecast skill next winter and the following spring.

5. There appears to be solid consensus for a stronger-than-normal monsoon in the southern U.S. Rockies this summer.

6. Models are also projecting drier-than-normal conditions (less tropical storms/hurricanes) in the tropical breeding grounds of the Atlantic late this summer and into the fall, which may be a reflection of cooler waters, dry air and the start of El Nino.

7. Areas that are not shaded in the maps below either indicate near-normal temperatures/precipitation or are an indication of high uncertainty.

Projected average pattern for April

590x458_03171843_april14


May

590x458_03171843_may14


June

590x458_03171846_jul14


July

590x458_03171847_july14


August

590x458_03171847_aug

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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Canadian weather