What an EF4 tornado is
A tornado touchdown early Wednesday left devastation behind in the Harrisburg, Illinois, area.
February 29th, 2012
06:57 PM ET

What an EF4 tornado is

A tornado that hit an Illinois city during a storm that killed at least six people there Wednesday has preliminarily been given a rating of EF4 – the second-most powerful on the Enhanced Fujita Scale, according to the National Weather Service.

A report indicated the tornado in Harrisburg, Illinois, had winds estimated at 170 mph. EF4 tornadoes have wind speeds between 166 mph and 200 mph.

The Enhanced Fujita Scale rates tornadoes by estimated wind speed, which is determined not by measurements, but by observations of the damage left behind, according to the National Weather Service’s Storm Prediction Center.

To get the wind speed, the weather service goes to “damage indicator” tables that describe the wind speeds that would be required to do certain types of damage to certain structures. For example, if the exterior walls of one- and two-family homes collapsed, but not the interior walls, the service would consult the one- and two-family home table and find that wind speeds of about 132 mph were needed to do that.

A tornado of 132 mph would have an EF2 rating, which encompasses tornadoes between 111 mph and 135 mph.

EF0 is the weakest Enhanced Fujita rating, and EF5 is the strongest. Below is a description of the categories, with the general kinds of damage that may be associated with them.

EF0: 65-85 mph. Light damage. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; signboards damaged.

EF1: 86-110 mph. Moderate damage. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.

EF2: 111-135 mph. Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

EF3: 136-165 mph. Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.

EF4: 166-200 mph. Devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated.

EF5: 200 mph. Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yds); trees debarked; incredible phenomena will occur.

Post by:
Filed under: Illinois • Tornadoes • Weather
soundoff (56 Responses)
  1. banasy©

    An F-4.
    This early.
    We're screwed.

    February 29, 2012 at 7:26 pm | Report abuse |
    • rtbrno65

      It might be really bad because all the cold air that has stayed north all winter is going to start coming down and running into all the warm air from the south. We might see quite a few big storms. Bottom line is, if you live in the south and the midwest and the weather report says severe weather might be coming, you had better take it seriously.

      February 29, 2012 at 8:03 pm | Report abuse |
    • loliwinyoulose

      gonna be just like last season. La Nina two years in a row. Not "man made" global warming. It's actually a natural cycle.

      February 29, 2012 at 10:43 pm | Report abuse |
    • leeintulsa

      global warming is a natural cycle, too

      March 1, 2012 at 7:45 am | Report abuse |
    • Joe T.

      Tornadoes occur all throughout the year. To think there can't be strong storms in February is showing ignorance. They can happen at any time.

      March 1, 2012 at 8:50 am | Report abuse |
    • Nunya

      Warming can come from natural sources and it can come from man-made sources. Dismissing either as a possibility without looking at the data is just plain ignorant. Try looking at actual data instead of just listening to predigested opinions about the subject, so that you can see for yourself whether we're seeing it come from one or the other.

      March 1, 2012 at 9:31 am | Report abuse |
    • banasy©

      It is not typical, though it can happen.
      The operative words being not typical.

      March 1, 2012 at 9:33 am | Report abuse |
    • djmuth

      Wow, deniers out in force without even the suggestion of global warming. Enjoy the paycheck.

      March 1, 2012 at 10:52 am | Report abuse |
    • weatherhead

      You folks making all the commentary about peculiar weather patterns, and the connections (or not) to anthropogenic climate change, *do* understand the difference between climate and weather, right?

      Good grief.

      March 1, 2012 at 11:00 am | Report abuse |
    • Sara Bean

      EF-4 is JUST about wind speed, it's also about the amount of damage it does. This is the case that is often overlooked. Structural engineers are brought in to devastated areas to look at damage and even the manipulation/twisting of tree branches to help decipher just where on the Enhanced Fujita Scale the tornado in question should be identified with.

      March 1, 2012 at 11:41 am | Report abuse |
    • banasy©

      The Midwest does"t usually get them this early, Joe T.
      I sincerely hope that this isn't the start of our tornado season, rather, a freak storm.
      It is not showing ignorance to state something that doesn't normally happen this early.
      It's an observation that I know well; I live here.

      March 1, 2012 at 12:36 pm | Report abuse |
  2. no apology

    Looks like it's going to be a BAD tornado year!!??

    February 29, 2012 at 7:30 pm | Report abuse |
    • loliwinyoulose

      Will be very similar to last year. Expect the outbreaks to be closer to the midwest instead of the southeast this go around.

      February 29, 2012 at 10:46 pm | Report abuse |
  3. banasy©

    Hey, no apology.

    Not looking to good right now....hope this trend changes!

    February 29, 2012 at 7:36 pm | Report abuse |
  4. no apology

    We've had a very mild winter, therefore probably going to have a nasty spring & summer, need to strap the house & pets down!

    February 29, 2012 at 7:39 pm | Report abuse |
    • loliwinyoulose

      We actually had a very active winter. Our precipitation was above last year's, the exception was that it was rain instead of snow, but in liquid water measurements we had a very active winter. Lanina dipped further than expected then reverberated preventing a lot of necessary air moisture for snow temperatures in the midwest and south this year.

      February 29, 2012 at 10:48 pm | Report abuse |
    • banasy©

      Active ≠ mild.

      March 1, 2012 at 9:40 am | Report abuse |

    OOPS !!! ;( Sorry ( crouching over ... tiptoeing away)

    February 29, 2012 at 8:08 pm | Report abuse |
  6. Hadenuffyet

    Dig a hole folks...

    February 29, 2012 at 8:18 pm | Report abuse |
  7. Joenado

    And every year these storms are going to become more powerful as well as more frequent.

    February 29, 2012 at 8:38 pm | Report abuse |
    • loliwinyoulose

      Nope. La Nina wont have as much of an effect next year. storms will decrease.

      February 29, 2012 at 10:44 pm | Report abuse |
  8. R.J.

    I have that feeling to that it's going to be a bad storm season. I just had a weather spotting class the other night and the lady from the National Weather Service says that they can't even forecast the weather because they haven't seen anything quite like this before. I'm sorry to hear about all the damage it has done especially in Harrisburg, IL. since I am from IL. and only 100 miles away from Harrisburg. I knew something was up when the noaa weather radio went of for a Tornado Watch at 1:00 A.M. in the morning. Pretty rough stuff moving though Illinois last night.

    February 29, 2012 at 8:42 pm | Report abuse |
    • Ally

      I'm not sure how experienced your storm spotter person was, R.J. We're forecasting things just fine here. This has been a very warm winter, but it's also been seen before during La Nina patterns. So it's not any more difficult to forecast than any other day.

      March 1, 2012 at 12:58 pm | Report abuse |
  9. no apology

    It's not going to be a pretty year. We don't usually get a ton of tornadoes up here, but this might just be the year! Probably a good idea to start watching Doomsday Preppers!!!!

    February 29, 2012 at 8:54 pm | Report abuse |
  10. joo

    God bless our country

    February 29, 2012 at 9:12 pm | Report abuse |
    • JayJ7

      Just going by the evidence, God doesn't seem to like the Midwest.

      February 29, 2012 at 10:42 pm | Report abuse |
    • Walker

      You'll be waiting an eternity for that, joo.

      March 1, 2012 at 8:36 am | Report abuse |
  11. Lilyrosalie

    Still don't believe in global warming??

    February 29, 2012 at 10:41 pm | Report abuse |
    • loliwinyoulose

      According to my field, Meteorology, this is a natural cycle called La Nina, it is not man made.

      February 29, 2012 at 10:45 pm | Report abuse |
    • losethefear

      To bad there are no climatologists or fluid dynamics engineers posting some expertise...

      February 29, 2012 at 11:32 pm | Report abuse |
    • Bob

      Why do you allow yourself to say stupid things like this? Seriously, one bad storm pointing to global warming? How do you make that connection? I would love to know the process your brain goes through in deciding that global warming is responsible for this.

      February 29, 2012 at 11:49 pm | Report abuse |
    • djmuth

      It's not one bad storm. It is the continuation of a clear trend in more violent storm activity that has been ramping up for the last few decades, exactly as climate models predict.

      March 1, 2012 at 10:55 am | Report abuse |
    • Ally

      djmuth, I look at climate models every day. And there are just as many solutions that point to global cooling as there are that point to warming. Therein lies the debate.

      March 1, 2012 at 1:12 pm | Report abuse |
  12. Robert

    I just love how people see one or two bad years, or a few bad events and start to point toward global warming as the cause. They obviously do not understand meteorological science, and just want to drive some policial agenda. If they would look at past history, they would see there have always been nasty storms. I wonder how they would explain the drought of the 30's and 50's away....was THAT due to global warming too?

    March 1, 2012 at 1:21 am | Report abuse |
    • Common sense over fear.

      @ Robert
      Global warming (climate change) is a natural event genius. The Earth goes through stages of warming and cooling. The ‘agenda’ is over man-made contribution accelerating the process. That said yes, people need to get a “longer view’ of the situation. You know like the scientists have brought our attention to the issue.

      March 1, 2012 at 9:03 am | Report abuse |
    • Nunya

      The drought in the 30s was in part natural, but was made much worse by farming practices of the time. Simply saying 'it is a natural cycle' is a bogus argument. We work at countering the effects of our environment in many ways. Even if it were 100% verifiably natural, that doesn't mean we shouldn't be trying to do what we can to minimize it or not make it worse through our actions.

      March 1, 2012 at 9:37 am | Report abuse |
  13. Mark

    Meteorological science???!!! Please, You guys are right 1/2 the time and you call that science? My grandma's knees are more accurate then these meteorologist!

    March 1, 2012 at 1:59 am | Report abuse |
    • Ally

      Mark, we (meteorologists) go through the same curriculum as an engineer. It's a course load that many people can't finish. Please stop perpaturating the tired old saying of "half right...blah, blah.

      March 1, 2012 at 1:04 pm | Report abuse |
    • Mark

      Right......and your rebuttle? blah blah blah, I rest my case

      March 1, 2012 at 10:38 pm | Report abuse |
  14. UCFknightman

    The author's use of the word "Missile" is a little funny. Missiles are actually guided, and I don't believe tornadoes to be sentient beings nor controlled by a pilot as some sort of weather weapon. They aren't that fast either. It would be more apt to call them "Rockets"...

    March 1, 2012 at 9:04 am | Report abuse |
    • Jason

      Missile: noun. An object thrown or projected.

      Rocket: noun. An object propelled through the air by the rearward discharge of the gases liberated by combustion.

      March 1, 2012 at 11:17 am | Report abuse |
    • andy


      March 1, 2012 at 12:03 pm | Report abuse |
  15. belladonna

    Thoughts and prayers for the folks in the midwest! We've had a very mild winter here in Florida; the old saying has always been "mild winter, wild summer." Florida's tornado season is all year round, but we seem to get our worst ones between November and February (when cold fronts are strong enough to actually push their way this far south); with this year's quiet winter, I'm expecting a rather busy "storm season" (not to be confused with hurricane season), which is usually May to September, when we get thunderstorms almost every afternoon – many times, if the winter's been mild, the summer storm season tends to be on the bad side. And then there's hurricane season...if it's not one thing, it's another. You folks take care. we're thinking of you, and several places are already asking for donations of clothing, food and such and volunteers to take it up to you.

    March 1, 2012 at 9:09 am | Report abuse |
1 2