© 2019 Terry Swails

A PREVIEW OF WINTER?

August 3, 2019

This past 5 days were amazing weatherwise. For the period Monday through Friday in Cedar Rapids. the average high was 81, the low 58, and the mid-day dew point 56. Precipitation was zero. Two of those days highs stayed in the 70s. You can't beat that at this time of the year!

 

What I'm wondering is whether or not this cooler pattern is the beginning of a trend that might give us some insight into the coming winter. Let me show you the sea surface temperature departures in the Pacific Ocean as I think this could be a big player in the months to come.

What's quite obvious is the fact that water temperatures are abnormally warm in the Gulf of Alaska and the Bering Sea. This set-up is prime for a winter ridge to set-up over the Pacific Northwest which forces an amplified jet stream pattern that makes the eastern 2/3rd of the nation vulnerable to cold air outbreaks. Something like you see below.

The sea surface departures in 2013-14 are similar to this year and should be a strong analog for this winter. That year was cold and snowy over the Midwest and Great Lakes.

 

It's also likely that the warm waters in the Pacific are driving the current round of below normal temperatures over the central U.S. Next week the jet is expected to buckle again bringing a reinforcing punch of cool air. The EURO ensembles 500 mb forecast next Wednesday depicts the ridge (in red) associated with the warm water surrounding Alaska. Downstream the heights are much lower where the jet has buckled around the ridge, delivering cool air to the Midwest. It's what we call northwest flow.

The GFS has an even colder look based on the same idea.

 

It's my belief that this could very well be a preview of the upper air pattern what we might see plenty of during winter. There are a number of other factors that will come into play including the waters of the south Pacific where most models are indicating the lack of an El Nino or La Nina. The La Nada  signal or (neutral phase) of the southern Oscillation means this key teleconnection won't have the power to alter the strength of the Alaskan ridge. 

 

We are also at a solar minimum which means that bursts of energy from sun spots should be limited in scope and power. That would promote a more stable pattern that locks in for significant periods of time. 

 

Of course there are other factors to consider but those will remain hidden for a few more weeks, maybe as much as a couple of months. For that reason I'm still in the formative stages of my winter outlook but leaning towards one with the potential to at least be cold. Roll weather and have a great weekend...TS

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