Ag Weather Forum

Northern Highs Are Still Around

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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Weather headlines the past couple weeks have been dominated by El Nino development in the Pacific Ocean. However, a feature which claimed center stage in much of the past two growing season--blocking high pressure in the northern latitudes--is still on the scene. And, that feature kicked in the door for attention during the past week.

The "northern block" is comprised of two high pressure centers--one on the west coast of Canada, and the second near Greenland in the North Atlantic Ocean. The influence of these two highs has affected the U.S. crop area weather pattern in these ways:

1) The western Canada high forces storm systems out of the North Pacific farther south. Those low-pressure systems cannot move eastward into the interior of Canada, so they slide south along the edge of the western Canada high.

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2) The western Canada high also allows for a warmer trend in the Canadian Rockies and the western Canadian Prairies.

3) The Greenland high prevents colder air from the far northern latitudes--yes, there is still some colder air out there--from migrating eastward and forces that cold southward through the eastern Prairies and into the northern U.S. And that cold air is--as everyone in the northern Plains knows--is mighty cold.

The colder air moving southward is one thing. But, what's another is a new wrinkle for this season in the form of El Nino-fueled southern-branch jet streams. That southern-branch jet, with its own energy (and moisture) has helped to kick in some very heavy rains in the southern Plains and western Corn Belt--with even enough moisture making its way north to bring heavy rains (and snow) to the northern Plains and the northwestern Corn Belt last week.

So yes--while we observe El Nino's influence--we also dare not disregard the continued impact of the blocking highs in the north. Combined, they have led to a volatile situation in the past couple weeks.

Bryce

Twitter @BAndersonDTN

(ES)

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