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

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.

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.


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).


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.

0833 AM CDT FRI APR 04 2014

                                  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




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.



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



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.


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.

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


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.
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.