Why the Wretched Wet Weather?

Have you ever heard of a "Polar Vortex"? Well, that's what the weather experts tell us we are experiencing in southern Ontario this spring. The definition of a Polar Vortex, as described by the National Snow and Ice Data Centre, is "a large-scale cyclonic circulation in the middle and upper troposphere centered generally in the polar regions".

Essentially, what happens is that a strong disturbance in the jet stream is created by a very high circular rotation of cold air in the high arctic. This is fine during winter when we expect poor weather. However, this spring the traditional movement of the vortex to the east has been stalled and has resulted in much of the weather we are experiencing. The good news is that the experts anticipate that it should start to move towards Greenland shortly.

The polar vortex sets up a counter clockwise rotation of air movement. This draws cold air out of the high arctic and sends it down into the central plains states. As it moves eastward, it warms slightly and then crashes against warm moist air that the vortex has drawn up from the Gulf of Mexico. Unfortunately, this spring these two systems of contrasting air masses are meeting over a trough that extends north-south from the east end of Lake Superior down through the Mississippi valley. The result is unstable or turbulent air that releases rain, and maintains cool temperatures. Does this sound like what we are getting?

Source: Frank Giannasca, Weather Services Corp.

So what has this meant for rainfalls and Crop Heat Unit (CHU) accumulations in Ontario? Table 1 shows the accumulated precipitation and CHU's for the period May 1 to June 2 each year. It is obvious that some parts of the province have been harder hit that others. The implications of this weather pattern have been delayed planting (especially corn) and possibly replanting of significant acres where the seed drowned or the soil crusted and prevented emergence.

Hopefully the remainder of the growing season will be more favorable.

Data compiled from information provided from the Ontario Weather Network and Farmzone.com. Some information was not available.