I made mention in yesterday’s European posts about the continuation of a pattern which started back at the beginning of last winter and has continued right through till now. By that I mean the chilly US pattern and warm Europe. We here in the UK, like most of our neighbouring continent have been warm throughout while it’s been near opposite over particularly the Midwest US. The only reason the East is warm is because of that anomalous warm water off the coast.

What’s brewing up in Canada and comes down over the upcoming 96 hours will rival most major mid summer cold shots of the last 50 years. A summertime version of the, dare I say it, polar vortex!

With a real, anomalous mid-July cold shot, comes a lot of rainfall!

Here’s the QPF rainfall chart for the upcoming 7 days.

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While the very upper low currently over N Manitoba (due W of Hudson Bay) is not polar, energy seen in the upper air charts that will help force that low into the US, is, born over the tundralands of the Northwest Territories. We’ve seen a lot of troughs drop south in the last 7 months.

Meteorologically speaking, the early and midweek upper pattern is strikingly similar to what we saw back in January. Only real difference is, it’s summer, not winter and obviously the atmosphere is different and behaves different but strip away the difference in time of year, there has been no real change in pattern overall.

Look at the global sea surface temps from back on January 1 and now. Still have that warm water over the Gulf of Alaska which is helping pump a West Coast to Alaska ridge and in turn a trough further east.

Jan 2

Jul 10

Only big difference in the two charts is that the warm waters of the North Pacific and Atlantic have heated further and we have the warming off South America reflective of the El Nino coming on. The overall setup and positioning of warm and cold remains the same, therefore the same hemispheric pattern remains the same despite a completely different time of year.

Check out the similarity with global SST’s at this time back in 2009 to now. Warm GOA, North Atlantic with big cold pool in the middle as well as the El Nino coming on. Summer of 2009 was a benchmark for cold summers in recent times. In fact it was 34th coldest!

NOAA: Summer 2009 was 34th coolest on record; thousands of low temp records set

Let’s take a look at the ECMWF upper pattern through the next few days and see the southward progression of the trough. To see 546 surface heights and 552 at 500mb over Lake Superior at this time of year, is very significant!

Upper at 48 hrs

Surface at 48 hrs

Anomaly at 48 hrs

North America wide view at 500mb chart through the next few days.

Let’s take a look at the ECMWF surface charts to see the amount of rain falling as the strong front drills into the Lower 48.

Regarding temperatures, this air mass is sure to break record cold maximum and minimum temperatures on the Plains into the Ohio Valley Monday through Wednesday.

GFS 5 day mean 2-metre temperature departures.

Expect widespread 60s over the N Plains and Upper Midwest, 70s reaching all the way into the Lower Mississippi, possibly Tennessee Valleys with impressive cooling by night. It wouldn’t surprise me if we see 40s reaching all the way to rural Missouri and widely (outside of towns and cities) across the Upper Midwest. 30s for N Minnesota and inland areas away from the Great Lakes.

The cool theme continues in August as well as September according to the CFSv2, fits nicely with my late summer idea.

See today’s video for the discussion!

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Tags: polar vortex, US long range pattern, US Summer forecast