This one will be a long one....
The previous posting was on the 25th of November (you can read that one here) and I waited to update with a purpose. As many readers are aware, the repeating or cycling of the "new" weather pattern that develops in the fall and the periodicity of that repeating is not known until the first cycle has ended. Looking closely at the northern hemispheric upper pattern, I believe pretty strongly that the second cycle has begun and has a relatively short cycle length. So, now there should be slightly higher confidence of what is possible going forward. However, there is still a small chance that the cycle time may be up to 12 days longer which completely screws up the timing of forecasting certain high impact events. I'm going forward right now based on the shorter time scale.
In that previous post, I ended with: "Looking ahead I suspect that mid-December ought to get really interesting based on a hunch, thinking the wavelength is around 55 days give or take." I now believe the wavelength (cycle) is on a shorter time scale; perhaps as short as 48 days, but that would have still led to an active mid-December for at least southwest Kansas and into western Oklahoma. As most of you are aware, unless you've been in a coma, it has been pretty active this December. Now, I do see a problem at the moment. The geographical region targeted by these storms has been relatively small in areal extent. Not all locations of the drought area has benefited which continues to be a concern.
For December, there has been what would now be considered a near record amount of snow at some locations. Look at the closeup of how much snow has fallen in the 3 storms for December!
The 3 storms have targeted basically the same area but with a tight gradient (especially to the north) of very little to a whole bunch!
The drought map shows improvement where it snowed significantly. Here is the latest map ...
After this last storm on the 15th, the snow field was pretty impressive viewing from satellite....
Back to the earlier storms, here is a map of snowfall from December 3rd and the view from satellite from that particular storm (sorry I changed the color scale)...
And here is the snowfall map from the storm on the 12th/13th and notice the target area is basically the same....
Imagine trying to forecast for a particular county. On the 12th/13th event, the snow amounts across Ford County (Dodge City) were from around 2 inches to over 12 inches!
So, now what?
One key element through the end of December will be the Arctic Oscillation. It has gone strongly negative (very cold air building up in the high northern hemispheric latitude region). It is also projected to go even more negative by the end of the month. I haven't seen it projected to be this negative in a long time. But, we'll see if it actually does go that negative.
Essentially this cold air buildup which is reflected in the negative index will help to energize the polar jetstream even more than it has been. I expect that there will be rapid and significant changes upcoming. The first impact is what produced the snow across the area a few days ago on the 15th and eventually the mega ice and snow storm across the eastern part of the U.S. (several reports of 4 feet of snow) yesterday and today. The next two systems impacting the central U.S. will be fast moving with little or no moisture to work with so I don't believe we'll see much precipitation, if any, and only a glancing blow of cold air.
So with a pretty good idea of the cycle length, if I'm right about the time period, then here is what I expect...
1) There should be a pretty good warmup leading up to Christmas. Now, the snowpack will definitely impact (or mitigate) the amount of warming. Those areas of the high plains without snow cover will see a few days next week that should be pretty mild!. Timing of particular fronts will always be a challenge across the high plains, regardless of weather patterns in place.
2) The next chance for a significant storm will be a day or two centered on the 27th (Dec). However, if that storm does occur, it is impossible to predict if it will be the southern, central, or northern high plains. Based on what has been going on this month and with the projected phase of the Arctic Oscillation, I would favor the odds to be closer to southwest Kansas. The balance of December after the 27th and into the first few days could be pretty cold!
3) Mid-January could be pretty active (8th-20th) but confidence of that period is still very low.
4) I would put high odds of several more BIG storms this winter, including storms in February AND March.
BTW, in the numerous presentations I've done the past few years (and also mentioned in this blog), at Dodge City there had never been more than 3 years in a row with annual above normal precipitation (based on the current 30 year average). Last year (2019) ended as the 6th year in a row with above normal precipitation. Just based on laws of averages, that seemed highly unlikely to occur. So what about making it 7 in a row? Believe it or not, 2020 will end up with above normal precipitation once again (even if no more falls)! Absolutely incredible! Seven years in a row! If there had been just a bit more precipitation in 2013, then this would be the 8th year in a row! Records began in October 1874 at Dodge City. The closest I could find that had this many years in a row of above normal precipitation was from 1922 through 1928 when 5 of 7 were above normal (3 in a row) with the other 2 pretty close to normal. You know what followed? The next 11 years (in a row) were below normal on precipitation. Laws of averages...it's real.
More statistics....
This current weather pattern cycle began around Oct 7. The amount of precipitation that has fallen in Dodge City from the 7th up through yesterday, the 16th, is the 19th wettest on record (147 years of records). Of the top 20 wettest periods (10/7 thru 12/16), here is what occurred the following spring and summer...
Out of those 20 years, the following spring (Mar-Apr-May) was drier than normal 9 times. Of those 9 years the spring was drier than normal, the following summer (Jun-Jul-Aug) was wetter than normal 6 times and the other 3 were not too much drier than normal! If the following spring was wet, the majority of the summers afterwards were dry.
So, to recap. I think there will be plenty of opportunities for more moisture going into spring. But my concern is that those areas largely missing out may continue to miss the majority of those chances. Typically though, as the jetstream reaches it's maximum intensity (on average) storms become larger in areal extent and intensity. At least there are chances going forward.
Later this winter I'll jump forward with an outlook for the spring and summer. I would like to see another cycle of this weather pattern and nail down the actual periodicity.
I'll try to get an update done right before Christmas to update the thoughts of that late December opportunity of a storm, if it occurs.
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