THE BOTTOM FELL OUT...
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THE BOTTOM FELL OUT...
When the hammer came down for winter a few days ago, it wasn't a little one. It was the long-handled sledgehammer that the boys bang. When it hits, people listen. So it was with our weather this past week. Temperatures were going along slightly above normal in the 30s and then Shazam, down goes Frazier! Readings went below zero the 13th, and we haven't been above since. For many of us, we'll have been below zero for at least 66 hours come 6:00am Tuesday. In some spots, the streak could reach 84 hours before we end it Wednesday. What an eye-opener!
The coldest "cold" has been quite impressive. While sub-zero lows are not unusual in January, not every winter sees 18-20 below, which was the case Monday. Iowa City and Fairfield bottomed out at 20 below and were the coldest.
You can see the sub-zero temperature isotherm Monday morning extending through most of Missouri, Illinois and Indiana.
While these frigid temperatures will be with us through the weekend, the pattern shows a significant tendency to moderate around the 21st. Before that happens, one more surge of Arctic air is on the way. It shows up nicely at 500mb Friday the 19th.
Here's the big 1048mb high that delivers the Arctic reinforcements Friday.
It produces lows like this Saturday morning.
Temperatures of that magnitude are 33 to 37 degrees below normal.
Ahead of the cold shot, we will see highs get back into the low to mid-teens Wednesday and Thursday. (I like that party). As for snow, I don't see much of that in our future, perhaps a dusting Thursday night.
ANOTHER PATTERN CHANGE AHEAD
Just when it appears winter has locked in, the snap back to a more tolerable brand of weather is on the table (within a week). It's well teleconnected, so my confidence is high we will get highs back above freezing and melt some snow. However, that deep snow will be a detriment, keeping the warm-up at least 10 degrees cooler than if we didn't have the impressive snow cover.
Evidence for the that starts with the MJO (Madden Julien Oscillation). Note how it's shown cycling into phases 5 and 6. It will take some time to do its dirty work, but as you can see in the phase diagram to the right, those correlate to mild temperature anomalies in January. It then heads for 7 in February, which is still relatively mild. I personally think we will make another run at phases 8, 1, and 2 towards mid-February, which should bring another round of wintry weather mid-February through early March.
In support of the MJO is the AO (Arctic Oscillation). During the last two weeks, it's been strongly negative. Below you can see it going positive, which means a stronger Polar Vortex for a time that will limit Arctic intrusions.
The EPO (Eastern Pacific Oscillation) is doing a similar reversal. That indicates the big ridge over Alaska that's currently providing Arctic air is breaking down.
The NAO which was in a stormy negative phase is headed positive. That makes it hard to get the big storms and cold. The pattern should be relatively quiet for a time, and what precipitation falls next week could very well be light rain. That pains me.
This is all tied to a snap back theory that essentially says after such an energetic and impactful period, the atmosphere needs to recharge and reload. It basically wore itself out. Kind of like a rubber band, it gets stretched until it snaps back into a more normal state. Honestly, I think this winter is far from over, but we are going to have to face the reality that the 500mb jet is reverting to this next week. That has an El Nino look with split flow and air masses coming off the Pacific instead of Canada. It looks mild!
Note the resulting temperature departure January 23rd.
Quite the change from where we are currently.
Well, that will do it for now. One of the greatest 10-day winter periods is slowly coming to an end in this region. All I can say is man, that was something. Glad I was here to be a part of it! P.S. If you can swing a donation to the site, anything would be immensely appreciated. Roll weather...TS CLICK HERE TO CONTRIBUTE
