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In this short presentation, we're going to take a look at the tornado outbreak
that occurred on May 13, 1995.
This will be a little different than what we would normally look at,
as this is a comparison between the old-style weather radars, and the new style radars.
Here's a bit of an overview of the event that particular day.
Nine tornadoes touched down across central Illinois.
Two of them were violent, F4-strength tornadoes.
Both of them occurred in the general vicinity of Macomb.
One was off to the northwest and north of Macomb,
while the other one was to the southeast.
The one that was off to the north and northwest
went through Hancock, Henderson, and Warren Counties.
It was on the ground for 50 miles,
touching down shortly after the storm crossed the Mississippi River
2 miles south of Niota, and it finally lifted
6 miles southwest of Abingdon.
Seven people were injured from this particular tornado.
A little further to the east, in Fulton County,
a separate tornado was on the ground for 7 miles.
It touched down 1 mile northeast of Ipava,
and it finally lifted 2 miles northeast of Lewistown.
This particular tornado injured 45 people.
At the time of this event, our Doppler radar here in Lincoln was brand new, and it was
and it was still undergoing some testing,
so it was not able to be used for this particular event.
The Springfield weather office continued to operate
its 1974-model radar from Capital Airport.
This particular radar did not have the capability to have
pictures saved of its data.
That type of capability was reserved to network radars.
The Springfield radar was what was referred to as a local warning radar,
primarily used for issuing severe weather warnings.
In order to create any kind of an archive for this,
a grease pencil would be used to trace the radar echoes onto the display,
and then a map was overlaid on top to trace the outlines onto the map.
Here in the lower right corner,
we have an example of what this looks like.
However, this usually was not done,
unless a specific radar observation was being coded.
This is a, for lack of a better term,
a "radar loop" of what was observed on the Springfield weather radar that day.
These pictures were taken about every half an hour,
from 4:25 pm to 7 pm.
Again, because there was no formal "picture" that was able to be taken,
this is essentially what the radar's operator drew onto the screen,
at each half hour interval.
There are a couple storms that we are going to be focusing on,
as we go through the following slides.
One is the primary storm
that produced the F4-strength tornado, further to the north,
and one that will produce one further to the south.
Breaking this down, this is what the Springfield weather radar looked like at 4:25 pm.
Although the Lincoln and the Quad Cities Doppler radars were not in operation at this time,
the one in St. Louis had been in operation for a couple of years,
so we have radar data available from it to look at.
However, the radar beam from St. Louis all the way up to Burlington, Iowa,
is pretty far off the ground, approximately 14,000 feet off the ground,
so we are unable to see any sort of low-level rotation
that was caused by this particular storm.
We're keying in on this storm that's just southeast of Burlington.
It produced a tornado shortly after it crossed
the Mississippi River at 4:18 pm,
so at this point, it had been on the ground for 7 minutes.
At 4:25 pm, the storm was near F3 strength,
and it would go on to become an F4 strength tornado.
We'll also be keying in on this particular storm,
just northwest of Quincy, in later slides.
Moving on about 40 minutes later, at 5:05 pm,
our tornado is still on the ground north of Macomb.
The southern storm, that had been northwest of Quincy,
was now northeast of Quincy,
and was strengthening quite a bit, however it was not producing a tornado yet.
Moving on to 5:25 pm,
the storm across the north, which had produced the F4 strength damage,
had lifted. However, a new tornado has touched down since then,
across southern Knox County,
and has been on the ground for about 7 minutes at this point.
Our southern storm is showing signs of a hook echo.
It's not producing a tornado at this point;
however, it has produced softball size hail.
Moving on to 6:00,
the tornado that had been moving across southern Knox County has dissipated.
However, the southern storm has finally produced a tornado.
This is the F4 strength tornado that moved across portions of Fulton County.
At this point, the tornado had been on the ground for about 5 minutes.
Moving on to 6:25 pm,
another tornado has touched down north of Peoria
in the general vicinity of Princeville.
The storm across Fulton County, the tornado has lifted.
However, a new tornado did touched down at 6:15 pm,
and had been on the ground for about 10 minutes at this point.
Moving on to 7:00, the storm has gotten too far away from the St. Louis radar
to do much good, so we switched to using the Chicago Doppler radar.
However, it also was quite a distance away from the storm,
so we're unable to see the really low-level features with it.
As of this particular time, we are still showing signs of a hook echo with the storm.
No tornadoes are on the ground at this point,
but two will touch down in a little while,
at 7:10 pm and 7:15 pm in McLean County.