THE SKY IS THE LIMIT...
It was another banner day around the region with highs cracking the 40s in most areas. even touching 50 in spots south of HWY 34. This welcome change began slowly but has really blossomed the past few days. In the Cedar Rapids meteogram below, you can see that after a high of 6 below the 14th, highs have increased every day for 9 consecutive days reaching today's peak of 42.
The warming trend ended a 12 day stretch from February 6-17th where highs remained below 15 degrees. That 12 day string is the 4th longest for that benchmark. The 3 streaks that are longer all occurred at least 85 years ago. 1936, as we've mentioned numerous times, was really nasty with 19 consecutive days of highs below 15!
So why the big change? It's all in the position of the jet stream my friends. Back on February 7 when we were headed into the teeth of the cold, the 500mb jet looked like this. The source region for our air was the Arctic with an extension of the Polar Vortex situated over the NC United States.
Now the stratospheric warming that drove the bitter cold has reversed and the Arctic Oscillation which was strongly negative has flipped to positive. This is the current 500mb pattern which has turned upper level winds zonal (west to east) over the Midwest. That cuts the tie to the worst of the cold and brings more of a Pacific influence to out air masses.
A very important teleconnection had been a major driver during the month long siege of cold. It's known as the A0 (Arctic Oscillation). Here you can witness how deeply negative the AO was back on February 7th when it was nearly off the scale. When you see it in a negative phase, especially one as deep as this, you know the door to cold is wide open. That was a big tip-off as to what was ahead of us.
Now the AO has evolved to this which has a healthy positive phase indicated all the way out to March 10th on the EURO ensemble. That should highly restrict our chances of another surge if severe cold through that period.
Additionally, once you get to March 10th you can see that average highs range from 41 in Dubuque to 46 in the Quad Cities and 48 in Burlington. If a similar situation developed as we saw a month ago, the air mass would not be nearly as vicious thanks to the longer days, stronger sun, and mostly likely far less snow cover. There is light at the end of the tunnel.
Taking this a step further, assuming the AO remains positive, the next couple of weeks should be tolerable and many of those days should be near to above normal. Here is the 15 day temperature departures on the GFS broken down into 5 day increments. These would be even warmer were it not for the existing snow cover.
Days 0-5
Days 5-10
Days 10-15
So with that good news. and not much else to talk about the rest of the week, I'll sign off. The sky is the limit! Until next time, roll weather...TS
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BOOK ENDORSEMENTS.
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*Hi Terry and Carolyn!
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