Winnebago Severe Watches & Warnings NOAA Weather Radio

Public Information Statement
Statement as of 9:04 PM CDT on August 27, 2015

... Most tornadoes on record in NWS Chicago forecast area in 2015...

The four tornadoes on August 18 2015 brought the total number of
confirmed tornadoes in the counties of the NWS Chicago County
Warning Area (cwa) in 2015 up to 29. This broke the previous record
of most tornadoes in the NWS Chicago cwa counties in a year set
in 2004... which had 27 tornadoes. The period of record is
1950-2015.

Note that it is likely that many of the earlier years in the
dataset had weak (f0-f1) tornadoes that went undetected. The
modern network of spotters and improved radar technology has
allowed for better detection of weak tornadoes. This includes
the introduction of current Doppler radar technology to the NWS
in 1992 and dual polarization in 2012. With that being said...
2015 has been an exceptionally active year for tornadoes in the
NWS Chicago forecast area.

Top 10 most tornadoes in NWS Chicago cwa counties in a calendar year
--------------------------------------------------------------------

Rank year number of tornadoes
---- ---- -------------------
1 2015 29
2 2004 27
3 1974 22
      2010 22
4 1965 21
5 2003 18
      2008 18
      2011 18
      2014 18* all tornadoes occurred on 6/30
10 1967 17
      1972 17
      2013 17

The average number of tornadoes per year in the counties of the
NWS Chicago cwa from 1950-2015 is 9 (8.98).

The current location of NWS Chicago and the klot WSR-88D Doppler
radar opened in 1992. This is also when the current alignment of
counties in the cwa dates back to. The average number of
tornadoes in the NWS Chicago cwa from 1992-2015 is 11 (10.8).

NWS Chicago cwa counties
------------------------
il: Boone, Cook, De Kalb, dupage, Ford, Grundy, Iroquois, Kane,
    Kankakee, Kendall, Lake, La Salle, Lee, Livingston, McHenry,
    Ogle, will, Winnebago

In: Benton, Jasper, Lake, Newton, Porter