DOUBLING DOWN ON MORE RAIN...
UGA CHUGGA....UGA CHUGGA
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SUDDEN STRATOSPHERIC WARMING ROUND 2...
Well, this is quite interesting. As you know if you've been following the site recently, a sudden stratospheric warming has been underway for about 3 weeks. In a nutshell, at very high latitudes near the North Pole, temperatures have been rapidly warming. This is the region where the polar vortex and high pressure resides. A strong Polar Vortex is typically surrounded by a powerful westerly circulation. This tends to lock the cold air into the Polar regions limiting cold air intrusions over most of the United States. When temperatures rapidly warm in the stratosphere, the Polar Vortex collapses, the circulation around it weakens and the higher pressure comes crashing down, pushing the cold air out of the polar regions, into the United States. It's a timely process and it usually takes 30 to 40 days before the colder air makes it into the Midwest.
All SSW's are not created equal and their impacts vary depending on the intensity of each event. What's unusual about this initial event is that's its early, rarely due we see one take place in October, In fact, the majority usually form during the later half of winter. What's even more fascinating is that hot on the heels of the first SSW, a second one seems to be developing. You can see the two distinct warmings at 10mb on the EURO out 10 days.
From all the data I can dig up, the only time I can find back to back stratwarms this early in the year is 1989. That year one occurred in October, the other followed in December. You see where I'm going with this? Here's more on the historic December deep freeze associated with the SSW of 1989.
That December went on to feature several surges of Arctic air into the central and eastern United States beginning around mid month and lasting until Christmas. The Arctic outbreak was a historic event, with many locations establishing monthly or all-time record lows. Sub-freezing temperatures extended across much of the southeast U.S. with considerable damage to citrus crops in Florida and south Texas (newspaper reports indicated "nearly total destruction" of the citrus industry across the north half of Florida). Dallas had $25 million damage caused by broken water pipes that froze in the cold, along with subsequent production losses due to failures at manufacturing plants.(shades of last February). Many other locations across the southeast U.S. had damage from frozen pipes as well. The cold weather resulted in snow and sleet falling as far south as central Florida just before Christmas, and parts of northern Florida had its first White Christmas on record. As an area of low pressure moved northeast across Florida, the cold weather resulted in the largest snowstorm in history on the southeast U.S. coast, with totals in excess of a foot along the Atlantic coast of North and South Carolina.
Some of the coldest weather occurred from the 21st through the 23rd. The image below shows the surface map from the morning of the 22nd. A massive high pressure area (central pressure of 1055 millibars or 31.15 inches) had settled into the central Plains, where temperatures in Nebraska were as low as -42F at Scottsbluff and -39F at Valentine. By the next morning, temperatures were in the single digits as far south as Houston. Freezing temperatures occurred as far south as Miami on Christmas Eve and Christmas Day (even Key West, Florida, tied its December record low of 44 degrees).
Across my region many areas saw temperatures bottom out colder than 20 below zero on the 23rd. Wind chills in parts of the region reached 40 below. Here's temperature and precipitation data for that December in the Quad Cities. From the 12th-23rd, 10 days experienced below zero readings. Highs on the 21st and 22nd were -4 and -5 respectively The departures during that period were consistently 20-35 degrees below average.
Record lows were established on the 16th and 23rd. The 24 below in the Quad Cities is the coldest temperature ever recorded in December. Also notice record lows were also established in 1985 (in yellow). Guess what, three was an early stratwarm that December but not one October.
These are the monthly temperature departures for December, 1989
I'm not saying this December will be anything like that. In fact, it's unlikely. Really, who knows? What I am saying is that the double stratwarms make 1989 an weighty analog for what could happen this year. Knowing the past can help you see the future and I do think this lends credence to my belief that December will be colder than the one's we've seen recently.
THE NEXT RAIN EVENT
Our next weather maker is rounding the bend and getting set to descend on the Midwest within 24 hours. You can see the moisture feed extending north/south out ahead of the system on the satellite.
