Ag Weather Forum

El Nino Effect On Prairies

Doug Webster
By  Doug Webster , DTN Senior Ag Meteorologist

After a few bumps in the road earlier in September, Canadian Prairies weather conditions, possibly helped along by El Nino, have helped bring harvest progress along at a decent pace during the past week, despite some shower activity here and there. The good news is that more good harvest weather is likely during the next week or more, allowing many areas to begin to finish harvest for 2015.

El Nino is more than likely going to be in the news during the coming months since there is currently a strong one in place across the tropical Pacific. While nearly a world away from western Canada, the zone of warmer than average ocean waters extending westward from the South American coast into the central Pacific can have a significant impact on the Prairies.

During the summer El Nino probably has minimal effect on the Prairies weather pattern. But, as the fall chill begins, some of El Nino's impacts begin to become more noticeable. El Nino tends to deflect the polar jet stream north and east of western Canada during the winter season, and allows more Pacific air into the Prairies than during a non-El Nino winter. That is a major difference between El Nino and La Nina. La Nina brings cooler waters to the tropical Pacific, and tends to make western Canada quite cold on average.

During the recent week, we have seen more signs of El Nino-type weather across North America, including some heavy rain across far southern California and Arizona where cooler weather has also developed. Warmth has become widespread across a large portion of the remainder of the U.S. and Canada, and the lack of a widespread frost and freeze across the Prairies to date is a result of the polar jet being kept further north and east than average.

The recent downturn in wet weather is also probably a result of the increasing effects of El Nino across western Canada and will help farmers get crops into the bin quite easily before time runs out. A mostly dry weather pattern is on the horizon for the Prairies into next week, with only a few spotty showers expected. Temperatures will remain mild into the weekend, but some chill may invade eastern areas early next week before warming returns.

Harvest progress continues to run ahead of average, and sowing of fall crops has also been doing well for most areas. Soil moisture levels saw a rebound during the second half of summer and with the milder than average start to fall we are seeing fall crops emerge without any major issues.

El Nino is expected to build during the next couple of months and probably will peak very early in the winter before weakening later in the winter and spring. This El Nino is forecast to be one of the strongest we've seen and should bring western Canada a milder and drier than normal winter. The threat for any crops that require snow cover for protection is that diminished snow cover this winter could leave open the door for some winter kill during any cold air outbreaks that can still happen, even during an El Nino.

It's important to remember that even though El Nino may be in place, it will not completely shut down cold weather threats. El Nino will help reduce the number of cold air outbreaks from what we might see during a normal winter. As the months pass we will have to see how much precipitation falls between now and spring. El Nino usually brings drier than normal conditions and if so we could see some reduced soil moisture levels next spring, which could affect spring planting.

Doug Webster can be reached at doug.webster@dtn.com

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