How forecasters develop hurricanes' 'cone of uncertainty'
This is the National Hurricane Center's forecast track for Hurricane Irene, released at 5 p.m. Wednesday.
August 24th, 2011
10:05 PM ET

How forecasters develop hurricanes' 'cone of uncertainty'

It sounds like something out of the Austin Power movies or Robert DeNiro’s “circle of trust” in the Focker movies, but in the world of hurricanes the “Cone of Uncertainty” is just that; as the forecast goes out in time, the exact location of the hurricane becomes less certain.  Therefore the official forecast from the National Hurricane Center paints an area around the expected track to reflect the average error of the forecast.

You'll see the cone in the image above. The image shows the National Hurricane Center's prediction, as of 5 p.m. Wednesday, of where the hurricane could go over the next three days. The "cone of uncertainty," representing a range where forecasters think the hurricane's center could go, is in white.

The hurricane center, located near Miami, is tasked by the National Weather Service and the National Oceanic and Atmospheric Administration to constantly watch the tropics and warn when tropical waves and disturbances grow into organized low-pressure areas known as tropical depressions. When tropical depressions develop, the hurricane center starts issuing advisories on the system.

Sophisticated models running on some of the fastest computers in the world ingest data from satellites, ship reports, radar (if it is available), and data from weather balloons, airplanes and weather stations. Literally billions of calculations are done with very complex equations to help model the atmosphere into the future. More than 20 different kinds of models are run some being more reliable and complex than others to help forecast the track and intensity of the storm. You may have seen one of our meteorologists show the "spaghetti" maps on television depicting a storm's possible paths, or seen the plot maps on cnn.com/hurricane.

Example of plots:

Forecasters use this model data along with real-time information obtained by satellite, radar, observation and hurricane hunter planes that fly right into the center of the storm to help the hurricane center issue an official forecast track. That forecast track, issued every six hours, shows where the storm is expected to go over the next five days and how strong the storm may be.

Even I, as a meteorologist, know that weather forecasts are far from perfect. The hurricane center, which keeps records of every track it issues, is aware of that fact as well. The hurricane center figures out what its average error is at various forecast horizons - 12 hours, 24 hours, 48 hours, etc. - to help it generate the “cone of uncertainty” on its forecast track (the white area on the map).

The cone basically shows that the center's 12-hour forecast position is, on average, 36 miles off. At 48 hours, it is around 100 miles off.

So, let's say that I live in City X, and the storm is forecast to pass 100 miles to the south of me two days from now. I have nothing to worry about, right? Wrong. Because the average error at 48 hours is 100 miles, the storm could be right over me in two days.

This is why meteorologists and emergency managers will constantly preach not to look at the line on the forecast track, but to look at the "cone." If you are inside that area, you could end up in the direct path of the storm.

Because the atmosphere is so complex, errors from a particular forecast become larger over time. So the cone is much smaller at 12 hours than at five days out, because we know that on average, our short-term forecasts are much better.

So as Hurricane Irene approaches, remember not to focus on that line you see on the forecast track maps. Instead, look at the “cone of uncertainty." In the end, the storm may go anywhere in that area.

soundoff (59 Responses)
  1. raven

    Cone of Uncertainty.. just makes me miss Mystery Science Theater..

    August 24, 2011 at 10:18 pm | Report abuse |
    • bailoutsos

      They forgot the "cone of silence." Get Smart

      August 25, 2011 at 5:32 pm | Report abuse |
  2. Cesar

    I find tornadoes much much more dangerous and scarier than hurricanes. @raven: Hi. Look out raven, hurricane Irene may hit you in Alaska. Hope you have flood and wind insurance.

    August 24, 2011 at 10:31 pm | Report abuse |
  3. raven

    Hi cesar!!Actually Im not even IN Ak.now..sshh..dont tell..

    August 24, 2011 at 10:34 pm | Report abuse |
  4. Jeff Frank ( R - Ohio ) "NOAA Coneheads"

    Imagine that. Cones of uncertainy. Predicted by a conehead. Doesn't matter where the cone is...you run anyways.

    August 24, 2011 at 10:39 pm | Report abuse |
  5. Robbie

    The cone of uncertainty is NOT "the area where the serious winds, storm surge and all the other things that come along with a hurricane are possible," as is stated in the article. It only describes where the center of the storm may go. The winds, storm surge, rainfall, and tornadoes are very likely to fall outside of the cone, especially since the cone shrinks a little bit each year!

    August 24, 2011 at 10:56 pm | Report abuse |
    • Anonymous

      As a meteorologist, I concur. You are correct. This is the first thing I thought upon reading this article.

      August 24, 2011 at 11:57 pm | Report abuse |
    • Rick

      hahaha...and what is that you do for a living Robbie?

      August 25, 2011 at 2:15 am | Report abuse |
  6. Cesar

    To the world Web; the entire world population: raven is in .....(I'm not telling)

    August 24, 2011 at 10:59 pm | Report abuse |
  7. jeff77101

    dont worry everyone this is gonna be nothin.... hopefully not another katrina haha

    August 24, 2011 at 11:15 pm | Report abuse |
  8. Jeff Frank ( R - Ohio ) "NOAA Coneheads"

    Thank you Dave Hennen. An outstanding graphic depiction. In all seriousness, I pray it stays away from our friends in the east coast.

    August 25, 2011 at 12:11 am | Report abuse |
  9. 4F

    Remember the "cone of silence" on that TV show with Maxwell Smart? Now we have the "cone of uncertainty".
    In addition to the hurricane cone of uncertainty we have the Obama cone of uncertainty. Unfortunately this cone will not pass soon enough; its effects are wide-spread; and it defies all logic. 2012 – the year of the no-cone zone.

    August 25, 2011 at 12:44 am | Report abuse |
    • magellanous

      Way to work Obama into something completely unrelated. There could be an article on grass growing and someone would figure out a way to connect it to Obama. Maybe we should just make the hurricane a person, just like a corporation, and then we create a loophole for it and allow it to wreck the middle class...just like a corporation.

      August 25, 2011 at 2:19 am | Report abuse |
  10. Goodspeed

    Florida learned this lesson with Hurricane Charley in 2004.

    August 25, 2011 at 1:13 am | Report abuse |
  11. bubba

    Obama will you part the waves lol

    August 25, 2011 at 1:47 am | Report abuse |
    • Angel

      He tries but the evil tea Party will vote against it and then blame the President made them do it.

      August 25, 2011 at 6:22 am | Report abuse |
  12. magellanous

    Shouldn't CNN just look to twitter for its weather updates? CNN goes there for everything else.

    August 25, 2011 at 2:16 am | Report abuse |
  13. gung hoe

    You have the weathermans attempts
    at forcasting the weather let alone major storms Huh ya right they are unable to tell What the weather is going to be

    August 25, 2011 at 2:23 am | Report abuse |
    • Angel

      Hi Gung, yeah I usually walk outside and see if I need an umbrella.

      August 25, 2011 at 6:24 am | Report abuse |
  14. eg

    the Cone Of Uncertainty.. sounds liike a place to visit in a Carnival ride

    August 25, 2011 at 3:22 am | Report abuse |
  15. Cone of uncertainty

    There is an 'cone of uncertainty' for terror attacks too. One man's terrorist is another mans freedom fighter. One mans thief is another mans provider. One man's God is another mans executioner. One man's wife is another mans hoe. One boy's priest is another boys lover. It all depends on your personal point of view.

    August 25, 2011 at 4:24 am | Report abuse |
    • Nikolas

      Point of view differs significantly from cone of uncertainty. POV describes differing bias in observing fixed events. Cone of uncertainty describes a statistical distribution of possible outcomes in a chaotic system. Think of it like darts, where the path of the darts as a system will be into the target area, but most of the darts will actually miss the bulls eye, and occasionally one misses the board entirely.

      August 25, 2011 at 10:47 am | Report abuse |
1 2 3