It has been a very warm spring & early summer so far. In fact, Spring 2021 is the 4th warmest on record at Purdue since 1879.
, but amidst all of the heat, we have seen some extremes with chill. For example, after temperatures as high as 87 in early April, we had the historic snow of up to 5" in the viewing area on April 20 & highly-damaging freeze in our eastern counties with lows to 21 (clouds kept us at 32-33 at Greater Lafayette area, resulting in lack of damage).
After 89 in late April, we saw up to 7 days of patch to areas of frost in the first 14 days of May. After 93 in late May, we saw lows to the upper 30s in part of the area on the morning of May 30.
We saw the warmest early, mid & late spring weather since 2010 to 2012 with vegetation up to 2 weeks ahead of schedule in April.
May 6-12 was one of the coolest periods for early May since 2005.
You would think with these extremes that you would have A LOT of severe weather here, but that is not the case. In fact, it is not the cast for much of the Great Lakes & Corn Belt.
This lack of any severe weather despite upwards of 10 days of SPC MARGINAL RISKS for severe weather in 2021.
Overall, severe weather has trended downward since a very robust start this spring with two HIGH RISK days (first back to back HIGH RISKS since the violent tornado outbreaks in the Plains in April 1991) with strong to violent tornadoes, billion dollar hail disasters in Oklahoma & Texas & even unusually early-season tornado & damaging wind events in the Northeast.
Nationally, large hail reports are the lowest in at least 16 years:
Severe wind reports are extremely low (near lowest since 2005):
Tornado counts are below normal, but not to the extremes of severe wind & hail:
Nationally, tornado counts are below normal with the epicenter of the high tornado counties in the South & the southern High Plains.
As if June 7, we have not had a single Severe T'Storm Watch for any part of the viewing area (core of the Severe T'Storm Watch issuance has been west Texas):
As of June 7, we have not had a single Tornado Watch issued for the viewing area (core of the Tornado Watch issuance has been central Alabama):
As for any convective watch, Tornado or Severe T'Storm, we have not seen a "0" up to June 7 since 1992.
Our first Tornado Watch was June 17 & it was a significant severe weather outbreak.
We average 13-15 Severe T'Storm Watches per year:
We average 3-5 Tornado Watches per year:
When I analogged this year in my Spring forecast, there was a strong match to 2010, 2011 & 2012, but severe weather-wise 2010 & 2011 were the best matches; both big severe weather springs &/or early summers in our area. This was followed by intense heat & even droughts in our region & over large parts of the Plains, Midwest in the summer.
In 2010, we saw the core of the greatest number of Severe T'Storm Watches across the Corn Belt!
Most of these occurred in early June with a 21-day stretch of highly-frequent severe weather events & outbreaks.
In 2010, the greatest number of Tornado Watches were in east-central Mississippi.
In 2011, the greatest number of Severe T'Storm Watches were in the eastern Corn Belt & then Missouri to Nebraska.
Greatest Tornado Watch occurrence was across southern Mississippi & southwestern Alabama.
As for 2012, even in a big hot, dry drought year, the two areas with the greatest number of Severe T'Storm Watches were southwest Ohio to southern Indiana & over western Oklahoma & northwestern Texas.
In 2012, the Tornado Watch frequency was greatest in southern Mississippi & far southwestern Alabama.
We tend to have 17-22 "severe weather days" per year with at least one severe weather report within 25 miles in the viewing area. We have not had a severe weather day yet this year. The last severe weather day or event day was back in August 2020 with the Progressive Derecho.
Really, the South has tends to have more severe weather days per year than any other location in the U.S. Data below is from 2003-2012 average, but when you start digging into 2000-2021, it is central Mississippi to central Alabama that tends to have more severe weather event days in a given year than anywhere.
It has also been a long time since a Tornado Warning was issued by any NWS weather forecast office (WFO). 300 days for the Northern Indiana office, 226 for Indianapolis & 208 for Chicago. However, the Lincoln office did have Tornado Warnings issued back in early May in central Illinois.
We have had a few Severe T'Storm Warnings in April & May for Benton, southern Newton & Jasper, as well as Montgomery counties.
So, what is behind the lack of severe weather?
Much of it is tied to a semi-permanent upper ridge that developed in the Arctic in late winter, was enhanced by intensifying West & Plains to western Corn Belt drought, & worked to cap things off, make for LOW dew points & either shifts the main upper jet well north of the region or displace unusual cold into the area as it moved back into Canada.
We have see in these sudden freak cool snaps, it actually heat up in the Arctic & across Canada in a massive way, displacing the cold south.
So, either the strong mid & upper winds are too far north & displaced away from moisture & storm systems or the colder, stable air is too far south to make for much severe weather. Again, all tied to position upper ridge.
The jet was just right back in March to early April, leading to a very robust start to severe weather season in the South, but it has not gained tremendous momentum elsewhere. Severe weather has been episodic, sub-normal & not concentrated as typical in spring to the start of summer.
Note the precipitation anomalies for March 1-May 31, 2021.
The horseshoe-shaped dome mimicking the current upper ridge showing the lack of water for a good part of the country except the Deep South & parts of the Plains. A strip of overall above normal rainfall even sneaks into Illinois & the viewing area, though our far southern & northern counties ended up with below normal rainfall.
It was the 3rd driest spring on record since 1871 at Chicago & parts of the West have seen very little precipitation since late winter. Even northern North Dakota saw 10-15% of their normal precipitation & large areas of the Carolinas & the Northeast to Great Lakes saw just 40-50% of their normal precipitation.
As expected, mean temperatures ran above normal from the Northern Plains & Great Lakes through New England.
Amazingly, this, even with the freaks of cold that blasted in about three times. In early May, record cold occurred in the Great Lakes & even in late May, a record-breaking bout of cold near Memorial Day dropped temperatures to the lower 20s in northern Minnesota & Wisconsin, leading to extensive damage to crops.
The temperature anomalies show up even more when it is focused on the daily highs. Northeast half of the U.S. (including our area) was all warmer than normal, while the Far West & Southwest was warmer than normal.
The Highs Plains, Rockies to Texas were all cooler than normal.