Ag Weather Forum

I have been asked a numbers of times during the last few weeks if this cold weather pattern we have been in would give us any idea on what spring weather conditions will be like?

In general I do not believe that there is any good correlation between the seasons, so I would not want to say because we have this in winter we will have that in spring. However I do think a few comments about the character of this pattern this winter and what it would mean for spring weather if it continues are in order.

As we have said before we feel that possibly the single most important feature that drives the weather in the middle latitudes is blocking (high pressure) in the high latitudes. The lack of blocking in 2012 was one of the reasons that severe drought conditions were able to develop in the Midwest. The development of blocking during the spring of 2013 was a major reason why drought conditions eased during the 2013 growing season. And the very strong blocking across virtually all of western North America from California to Alaska is the reason what we are seeing some of the most severe cold in the Midwest and severe drought in California since 1977 this winter. Blocking in the spring and summer forces the polar jet further to the south during the growing season setting up a boundary zone between warm and cold over the Midwest allowing for mostly adequate rainfall and no persistent heat. During the winter blocking prevents the infiltration of moderate pacific air into Canada allowing very cold air to develop under winrter darkness with this cold air being transported southward into the US under the southward displaced jet stream also known as the polar vortex.

If the current pattern we are in continues into spring we would expect to see wet conditions developing over much of the Midwest and plains with the possible exception of the northwest Midwest and northern plains although those areas would likely turn wetter later in the spring. This would be a favorable situation for winter wheat in the southern plains. However it could mean some delays to planting in the Midwest.

Finally we want to say that the ability to forecast the development or dissipation of blocking in the high latitudes is not great with at best 7-10 days notice of a change. This means that a reversal in this blocking pattern could occur at any time. It basically developed out of nowhere during mid February 2013. We will be keeping a close eye on this as we head into late winter and early spring for any signs of change.

Mike

(ES/)

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