Warm, Wet, and Active Spring

March was warmer and wetter than average across the state, continuing the pattern from winter. The preliminary statewide average March temperature was 43.5 degrees, 2.20 degrees above the 30-year normal and the 28th warmest on record going back to 1895. Preliminary statewide average total March precipitation was 3.96 inches, 1 inch wetter than the 30-year normal and tied for the 34th wettest on record.

Data are provisional and may change slightly over time

Persistent Warmth in March

Much like the first two months of 2020, March temperatures were consistently above the long-term average.

The first two months of the climatological winter season were much warmer than average, with very few cold air incursions. The plot below shows the March daily average temperature as a departure from average in Rockford. Since the start of 2020, over 70 percent of days in Rockford have been warmer than the long-term average. This has caused 2-inch and 4-inch soil temperatures to generally remain above freezing over this time, according to observations from the Illinois Climate Network (https://www.isws.illinois.edu/warm/soil/).

Average temperatures in March ranged from the high 30s in northern Illinois to the low 50s in southern Illinois. Temperatures ranged between 1 and 5 degrees above the long-term average. The statewide average March temperature was 43.5 degrees, which is 2.20 degrees above the 30-year normal and tied for the 28th warmest on record. March marked the fourth consecutive month with statewide average temperatures above the 30-year normal. By comparison, the first three months of 2019 were all 1 to 3 degrees below the 30-year normal, considerably cooler than 2020 so far.

The warm weather in March resulted in three daily high maximum temperature records and seven daily high minimum temperature records being broken across the state. The few cold, cloudy days we had in March also resulted in six daily low maximum temperature records and one daily low minimum temperature record being broken across the state. The long-running station in Carbondale was only 1 degree away from its all-time March high minimum temperature record on March 28, thanks to a strong mid-latitude warm sector bringing warm air from the south. Multiple stations in southern Illinois recorded daily maximum temperatures at or over 80 degrees during the last week in March. At one of these stations, Fairfield in Wayne County, this was two weeks before the average first 80-degree day based on the long-term record.

The highest temperature recorded in the state in March was 81 degrees in Alexander, Pope, and Hardin Counties, while the lowest temperature was 8 degrees in Jo Daviess, Knox, and Whiteside Counties.

Storms Bring Heavy Rain to Northern and Southern Illinois

Frequent precipitation persisted from February into March for the southern part of the state. Most areas south of Interstate 64 received over 6 inches of total precipitation in March, and some areas received over 8 inches. This represents between 150 percent and 200 percent of normal March precipitation in southern Illinois (see map below). Most stations in southern Illinois received 50 percent or more of their total March precipitation in one 24-hour period between March 20 and 21, thanks to a series of storms that tracked across the region.

One-day precipitation totals reached 4.50 inches in Clay County, which set the all-time March one-day precipitation record at the station in Clay City and broke the previous record by over three-quarters of an inch. Other large one-day totals from the March 20 storms included 3.85 inches in Mt. Vernon in Jefferson County and 3.55 inches in Olney in Richland County. With these one-day totals subtracted, March 2020 was very close to March 2019 total precipitation in southern Illinois; however, because of this event, most areas in southeast Illinois received between 1.5 and 2.5 times the amount of March 2019 precipitation this month.

Although March precipitation totals in northern Illinois were not as generous as those in the south, northern Illinois was not averse to very large one-day precipitation totals. A series of storms that moved through on March 28 generated between 3 and 4 inches of precipitation in a less than 24-hour period for a stretch of Illinois between the Quad Cities and the western suburbs. One CoCoRaHS observer in Prophetstown in Whiteside County recorded 5.34 inches on this day. Unfortunately, the heaviest precipitation missed the longer-term COOP stations in the region, but the storm did manage to break the all-time March one-day precipitation total in DeKalb.

Total March precipitation ranged from over 8 inches in far southern and southeast Illinois to just over 2 inches in central Illinois. These totals ranged from over 200 percent of average March precipitation in southeastern and northern Illinois to just over 75 percent of average March precipitation in western Illinois. Most of central Illinois received between 75 percent and 125 percent of average March precipitation. This combined with above average temperatures allowed soils to dry a bit across central and western Illinois.

Last month was the wettest March on record at Rock Island Lock & Dam 15, with 6.17 inches recorded. The wettest place in the state last month was Clay City with 8.31 inches.

Overall, the preliminary statewide average total March precipitation was 3.96 inches, exactly 1 inch more than the 30-year normal and the 34th wettest on record. Although the March average does not reflect the 5- to 6-inch differences in precipitation between central and northern/southern Illinois.

Most of the northern half of the state experienced measurable snowfall last month. March totals ranged from around 6 inches in northeast Illinois to just over one-tenth of an inch along the Interstate 70 corridor. A winter storm on March 22 and 23 accounted for the vast majority of snowfall in the northern part of the state, with one-day totals exceeding 6 inches in Grundy County. Morris in Grundy County was the snowiest point in the state in March, with just over 7 inches of total snowfall.

March total snowfall departures mimic the spatial patterns for the entire winter season. Most areas of western, northwest, and west-central Illinois had totals within 5 inches of the long-term average, whereas most counties south of Interstate 70 as well as counties in the Chicagoland metro area have experienced 5 to 10 inches below average snowfall since the first snow of the season.

Severe Weather

Illinois experiences severe weather and storms in all calendar months, but March often begins the unofficial severe weather season. This last month we had numerous severe weather and storm reports, ranging from snowstorms to large hail and a few tornadoes. Trained spotters reported 2-inch hail in both Williamson and Vermilion Counties last month, with many more reports of 1.5- to 1.75-inch hail across southern and central Illinois. The AWOS station in Hyde Park in Cook County recorded a 61 mph non-thunderstorm wind gust on March 29. Finally, multiple tornadoes were reported in Illinois last month in southern and west-central Illinois, including three tornadoes between Peoria and the Quad Cities on March 28. One of these, an EF-1 tornado, developed just a quarter mile east of the Peoria International Airport, according to the Lincoln National Weather Service https://www.weather.gov/ilx/032820Tornadoes).

 Outlooks

Short-term 8-14-day outlooks from the NOAA Climate Prediction Center show strongly elevated odds of both above normal precipitation and above normal temperatures across the state.

Longer-term 30-day outlooks are similar to the 8-14 day outlooks, with continued elevated chances of warmer and wetter conditions across the state for April.

Heavy precipitation in northwest and southern Illinois, combined with continual snowmelt in the Upper Midwest has continued the threat of flooding along most major rivers in Illinois. Currently, gauges along the Mississippi, Ohio, Illinois, and Wabash Rivers are at or above minor flood stage, with nine gauges in moderate flooding, according to the National Weather Service River Forecast Center.

Widespread, heavy rains possible over next week in Illinois

As of April 25, the statewide average precipitation for Illinois is 2.8 inches, which is 94% of normal. However, we have several opportunities for widespread rains this week and into the weekend, according to the NWS precipitation forecast.
The first round of rain on Wednesday and Thursday has potential rainfall amounts of 1 to 2 inches across most of Illinois, along with the chance for severe weather. Continue reading “Widespread, heavy rains possible over next week in Illinois”

New Tornado Tracking Tool

The Midwestern Regional Climate Center, located at the Illinois State Water Survey, recently released a new tornado tracking tool. You can choose the range of years, and the tornado intensity (EF scale), as well as zoom in for more details (screen shot below). BTW, the tool covers the entire US, not just the Midwest. It is another great tool developed by our talented GIS expert Zoe.

tmap1
Screen shot of tornado track tool. Click to enlarge. Better yet, try out the tool at http://mrcc.isws.illinois.edu/gismaps/cntytorn.htm

Speaking of tornadoes, here is the monthly tally of tornadoes in Illinois for 2014. Half of our tornadoes this year occurred in February while March through July have been very quiet.

  • January: 0
  • February: 14
  • March: 0
  • April: 5
  • May: 2
  • June: 2
  • July: 0

That is about the opposite of the tornado climatology for Illinois, which shows that winter months are typically much quieter than the spring and early summer months.

tornado-month

Tracking Tornado Statistics in the US (Part II)

Yesterday I mentioned the national archive as a source for reports on tornadoes and other forms of severe weather. Today I wanted to mention the NOAA Storm Prediction Center and the many statistical products they have available on their website. Of course, their primary mission is to provide forecasts but they have accumulated an impressive collection of other products as well.

Local Storm Reports

While these are preliminary and subject to change later, one of the best and longest-lived product the SPC provides are the daily storm reports. These are dot maps showing tornadoes, wind and hail damage, with a detailed list below the map showing dates, times, cities, counties, type of damage. You can see “today” and “yesterday” or pick your own date. See example below (click to enlarge).

example1

Monthly and Annual Tornado Summary

This page starts by giving you a table of running totals of tornadoes and tornado deaths for this year, and the last 3 years, plus the 3-year average. So as of April 3, we have 81 tornadoes reported across the US with zero deaths.

TORNADO TOTALS AND RELATED DEATHS...THROUGH THU APR 3 2014
NWS STORM PREDICTION CENTER NORMAN OK
0833 AM CDT FRI APR 04 2014

       ...NUMBER OF TORNADOES...  NUMBER OF          KILLER
                                  TORNADO DEATHS     TORNADOES
    ..2014.. 2013 2012 2011 3YR                 3YR             3YR
    PREL ACT  ACT  ACT  ACT  AV   14  13  12 11  AV  14 13 12 11 AV
---  --   -- ---  ---- ---- ----  --  -- --- -- ---  -- -- -- -- --
JAN   4   --   75   79  16   57    0   1   2  0   1   0  1  2  0  1
FEB  41   --   39   57  63   53    0   1  15  1   6   0  1  7  1  3
MAR  25   --   18  154  75   82    0   0  43  1  15   0  0 10  1  4
APR  11   --   86  206 758  350    0   1  6 363 123   0  1  1 43 15
MAY  --   --  268  121 326  238   --  41  0 178  73  --  5  0  9  5
JUN  --   --  125  111 160  132   --   1   4  3   3  --  1  2  1  1
JUL  --   --   72   37 103   71   --   0   0  0   0  --  0  0  0  0
AUG  --   --   46   38  57   47   --   0   0  2   1  --  0  0  2  1
SEP  --   --   21   39  51   37   --   0   0  0   0  --  0  0  0  0
OCT  --   --   61   37  23   40   --   0   0  0   0  --  0  0  0  0
NOV  --   --   79    7  44   43   --   8   0  5   4  --  3  0  2  2
DEC  --   --   18   53  15   29   --   2   0  0   1  --  2  0  0  1
---  --   --  ---  ---- ---- ----  --  -- --- -- ---  -- -- -- -- --
SUM  81   --  908 939 1691 1179    0  55  70 553 227  0  14 22 59 33

PREL = 2014 PRELIMINARY COUNT FROM ALL NWS LOCAL STORM REPORTS.
ACT  = ACTUAL TORNADO COUNT BASED ON NWS STORM DATA SUBMISSIONS.

COMPARISONS BETWEEN PRELIMINARY AND ACTUAL COUNTS SHOULD BE AVOIDED.

..CARBIN..04/04/2014

And if you look beyond the table you can get a year by year summary for the US. For example, here is the summary for 2014 so far.

example3

 

I like to check the Illinois statistics periodically so I choose the year and then the state and look at reports like this one …

example2

 

Annual Fatal Tornado Summary

This is a nice, modern interface for mapping fatal tornadoes across the US.

Annual Fatal Tornado Summaries

Warning Coordination Meteorologist page

Because this page is geared towards NWS meteorologists, it has more extensive and technical information than the other pages. However, it has lots of information of general information. You can find maps of tornadoes by year, basic tornado climatology, number of watches issued by year, severe weather databases, and GIS support. For example, you can find the map of the number of tornadoes by county across the US.

tornadoes-by-county

Winter and Spring Collide in Illinois

Thursday was an interesting weather day in Illinois. Many areas experienced a rapid melt of the snowpack as warm, humid air moved into Illinois. The by-products of this included heavy fog, rain, severe weather, and localized flooding. I was driving back from a meeting in Pittsfield and was chased by severe thunderstorms and tornado warnings all the way back to Champaign. As I approached Champaign, the visibility on Interstate 72 dropped to 20-40 feet as the warm, moist air blowing over the cold, snowy fields produced heavy fog.

Below is a map of the preliminary storm reports for Thursday, including several possible tornadoes in Illinois. Click on the map to link to the reports from the NOAA Storm Prediction Center.

February tornadoes are relatively rare but they do happen. The second graph is from a study of 2,239 tornado reports in Illinois (link to more plots). Of those, just 1.3 percent occurred in February. However, one event that occurred after that study was the deadly Harrisburg tornado that killed 8 people on February 29, 2012.

yesterday_filtered
NOAA Storm Prediction Center. Click to go to the reports for that day.

tornado-month

All Quiet on the Severe Weather Front

As of May 8, 2013, the severe weather statistics for Illinois this year are relatively low (see first map). There have been 2 tornado reports (red dots), 25 hail reports (green dots), and 62 wind damage reports (blue dots). By this point last year, we had 22 tornadoes including the deadly February 29 tornado at Harrisburg, IL, that killed 8 people.
Harold Brooks of the NWS has an interesting post on the current “tornado drought” in the US for the period from May 2012 to April 2013. He says,

The 12-month period from May 2012 to April 2013 was remarkable for the absence of tornado activity and tornado impacts in the United States.

The number of tornadoes in the US was the lowest on record (197) and the number of deaths (7) was the second lowest during this 12-month period. Brooks’ looked at tornadoes that were rated EF-1 or greater. Those tornadoes tend to be better documented over time than the relatively weak EF-0 events. Those records go back to 1954. The number of tornado deaths were based on records going back to 1875.
A possible explanation for the low numbers during this May 2012 to April 2013 period was that much of the central US was in drought in 2012 (see second map). This was followed by a late, cold spring in 2013 (see third map). Both of these conditions seem to produce fewer severe thunderstorms, at least in Illinois.
There has been lots of discussion about whether the low numbers this year or the high numbers in 2011 either prove or disprove climate change. It is hard to track historical climate changes in the tornado reports in Illinois and the US because of major changes in how the data were collected over time. Furthermore, climate models used for understanding future climate change are not designed to simulate severe weather at such a small scale. As a result, the Intergovernmental Panel on Climate Change last year stated there was “low confidence” in finding historical trends or making projections of possible future tornado activity (IPCC, 2012 pdf). You can find a short discussion on historical tornado trends in Illinois on my website.
While these are interesting statistics, it’s important to keep in mind that things can change in a hurry. All it takes is one day with the right conditions, especially now that we are finally getting warmer, and Illinois could be faced with another tornado outbreak. Stay alert!

Severe weather reports for 2013 through May 8, 2013. Figure courtesy of the NOAA Storm Prediction Center.
Severe weather reports for 2013 through May 8, 2013. Figure courtesy of the NOAA Storm Prediction Center. Red dots are tornadoes, green dots are hail, and blue dotes are wind damage.

MJJ12PNormUS
Map of percent of average precipitation for May, June, and July of 2012. Areas in yellow or red are drier than average.

Map of temperature departures from average for February, March, and April. Areas in green are below average and areas in blue are much below average.
Map of temperature departures from average for February, March, and April. Areas in green are below average and areas in blue are much below average.

Tornado Drought

Tornado Drought in Illinois

One of the side effects of drought is that usually reduces the amount of severe weather we experience in Illinois. This year was a good example of this. After the deadly Harrisburg tornado on February 29, things have been relatively quiet. Here is the monthly breakdown of tornado reports in Illinois, as reported by the NOAA Storm Prediction Center:

  • 2 in January
  • 4 in February
  • 8 in March
  • 0 in April
  • 8 in May
  • 0 in June
  • 1 in July
  • 23 total by the end of July
Severe weather reports in Illinois for 2012 through the end of July. Figure courtesy of NOAA’s Storm Prediction Center.

Tornado Drought in the US

Harold Brooks of NOAA wrote about the US tornado drought on his blog. Here is the figure he used in his post for the US.

The number of tornadoes reported across the US from April 15 to July 31, for 2012 (red line at the bottom) as well for the most active year (2003) and the last widespread tornado-land drought (1988). Figure courtesy of NOAA.

Severe Weather in January

It was somewhat strange seeing lightning and hearing thunder yesterday evening, considering that it was January. The NOAA Storm Prediction Center listed two reports of 1 to 1.5 inch hail around Mt. Vernon. There were other reports of high winds and wind damage such as trees down. Meanwhile, tornadoes were reported in Arkansas, Tennessee, Mississippi, and Alabama. You can see the preliminary report at http://www.spc.noaa.gov/climo/reports/120122_rpts.html
While tornadoes are rare in Illinois in January and the other winter months, they do occur. Here are the number of tornadoes by month for Illinois (first figure) and their distribution around the state (second figure). You can see more figures like these here and here.

Click to enlarge.

And here is their distribution across the state for January:
Click to enlarge.

Severe Weather in Illinois for 2011

According to statistics compiled by NOAA’s Storm Prediction Center, so far in 2011 Illinois has had 58 reports of tornadoes, 298 reports of significant hail (1 inch or more), and 674 reports of wind damage. That’s about average for us. Fortunately, we escaped the worst of the 2011 season that centered on the southeastern U.S. and Joplin, MO.
See the first figure below for the distribution of events. In some cases, we may have multiple tornado reports from the same tornado as it travels along.
The second figure shows the distribution of severe weather reports by month for Illinois. After a quiet start to 2011, severe weather activity picked up in April and continued through July before tapering off in August and September. You can see the monthly raw data and chart in Google Docs.

Severe weather reports for 2011. Red dots are tornadoes, green dots are hail, and blue dots are wind damage. Click to enlarge.

Wild Weather in Chicago Area

The severe thunderstorms that swept though Chicago on July 11, 2011, caused widespread damage. Here are the maps and initial reports of damages from the NOAA Storm Prediction Center. The wind damage was common throughout Chicago, as well as parts of southeastern Wisconsin, Indiana, and Michigan.
Some parts of the Chicago area received up to 0.75 inches of rain from this event, according to the reports from the Community Collaborative Rain, Hail, and Snow  network (CoCoRaHS). See last map below.

Summary of Damage Reports (PDF)

Storm Reports for July 11
Storm Reports for July 11, 2011, for the Midwest. Click to enlarge.

Storm Reports for July 11
Storm Reports for July 11, 2011, for the Chicago area. Click to enlarge.

July 11 rainfall
July 11, 2011, rainfall from the CoCoRaHS network (cocorahs.org). Click to enlarge.