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Posts Tagged ‘tornado’

Classic Plains Tornado Outbreak Ingredients

May 24th, 2011 No comments

There was a recent article at weather.com called Classic Plains Tornado Outbreak Ingredients. It gives an excellent overview, along with weather map examples, of what it takes to generate a tornado. This is absolutely worth a read for any chaser.

Tornado Infographic

April 26th, 2011 1 comment

The tornado season this year has been absolutely HUGE so far! So, here’s an infographic dedicated to teaching you more about this amazingly powerful weather phenomenon!

Arizona Tornado

October 6th, 2010 No comments

It’s not often we get a tornado in Arizona, but today we got TWO of them, within minutes of each other! Thanks to a low pressure system in California creating some serious storms in Arizona, the conditions were just perfect for this type of activity. Unfortunately, 7 people were injured, and lots of property destroyed. Check out the video capture of this event.

Severe Weather Sign

June 19th, 2010 No comments

Severe weather shelter sign in Columbus, OH airport.

Categories: Tornadoes Tags: , ,

Hook Echo

May 12th, 2010 No comments

I’ve been doing some reading lately on mesocyclones and tornado development, and one of the hallmark signs of a potential tornado forming is a “hook echo” being seen on the weather radar. A hook echo is produced by rain, hail or even debris being wrapped around a supercell, giving the impression of a hook on the radar. Meteorologists consider the presence of a hook echo enough justification to issue a tornado warning for an area. The hook echo has been recognized as a sign of tornado development for most of the history of weather radar. The first hook echo was detected in 1953 by the Illinois State Water Survey during their test to use radar to measure precipitation rates. In the southern US states, hook echos are not always obvious due to the heavier rainfall from the supercell. Instead, the echo will take on a more kidney shape. Here is an example of a classic hook echo – if you see this while checking out the radar, either seek shelter, or head out with your camera!

Classic Hook Echo

Tornado Alley Actually Four Regions?

April 28th, 2010 No comments

When people hear the term “Tornado Alley,” they tend to think of the area from mid-Texas up through the heartland that spawns a greater number of tornadoes annually than any other area of the country. However, recent research by Michael Frates of the University of Akron, reported on MSNBC, suggests that there are actually four regions of active tornado development in the US, and the original Tornado Alley is not the most active!

Michael Frates, a graduate assistant at the University of Akron in Ohio, devised the new boundaries and a more nuanced set of “Tornado Alleys” by analyzing the spatial distribution of F3 to F5 tornadoes with tracks greater than 20 miles in the Central and Eastern U.S. from 1950 to 2006. The output of that work is spread across a grid of more than 3,000 cells across the region.

Each cell was then given a different “frequency value” depending on the frequency of tornadoes with intersected the unit, and out of this process came “major spatial patterns, which served as the basis for delineating new tornado alleys,” as shown on his map, above.

“Results from this analysis indicate that Dixie Alley has the highest frequency of long-track F3 to F5 tornadoes, making it the most active region in the United States,” Frates concluded. Dixie Alley had a frequency value of 2.92, followed by Tornado Alley (2.59), Hoosier Alley (2.37) and Carolina Alley (2.00).

When Frates’ data is presented on a map, it gives the regions indicated below as the four Tornado Alley regions:

Four Tornado Alley Regions

Four Tornado Alley Regions

This new data should help the National Weather Service understand better where to focus tornado predicting technologies, and where to concentrate research efforts. This years spring tornado season, while delayed likely due to the El Nino effect, has been particularly active.

How Are Tornadoes Rated?

April 27th, 2010 No comments

Given that tornado season appears to be in full swing now (a recent tornado killed 11 in Mississippi), I thought it would be a good time to describe how tornadoes are rated. From time to time you might hear the weather reporter talk about an “F0″ or “F3″ tornado, and you might not know what they mean. I’m hear to set you straight!

Tornadoes are measured using the Fujita Scale, which was developed by Ted Fujita of the University of Chicago back in 1971. The scale Fujita developed is used to determine the intensity of a tornado after it has passed through an area and done its damage on human-based structures and vegetation. After a tornado has gone through an area, meteorologists and engineers will do a ground and/or aerial damage survey. If possible, they will also take into account things like eyewitness accounts, ground-swirl patterns, radar tracking and media reports and imagery. After everything has been considered, a rating of F0 to F5 is assigned to the tornado. Here is the criteria that they use to determine the rating:

Scale

Wind Estimate (MPH) Typical Damage

F0

<73

Light damage. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.

F1

73-112

Moderate damage. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.

F2

113-157

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.

F3

158-206

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.

F4

207-260

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

F5

261-318

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.

Keep in mind that the rating cannot be applied until after the tornado has gone through and done its damage…the rating depends entirely on a guess of wind speed, and a measure of the damage done to structures and vegetation.

All of the world uses the Fujita Scale except the United States, which moved to the Enhanced Fujita Scale in 2007. It was revised to reflect better examinations of tornado damage surveys, so as to align wind speeds more closely with associated storm damage. Better standardizing and elucidating what was previously subjective and ambiguous, it also adds more types of structures, vegetation, expands degrees of damage, and better accounts for variables such as differences in construction quality.

The Fujita/Enhanced Fujita Scales are good ways to gauge just how bad a tornado was…not that you have to tell the people who were in them!

Does El Niño Mean More Active Tornado Season?

March 12th, 2010 No comments

USA Today had a brief article earlier this week regarding the question of whether the strong El Niño this week will cause a more active tornado season than in past years. The article quotes Greg Forbes, a severe weather expert at The Weather Channel, as saying in past winters with similar El Nino strengths, “the average was 9% more tornadoes than a typical year.”

El Niño is a seasonal weather pattern in which warm equatorial winds that periodically push toward the West Coast send moist air to the nation’s interior.

While tornadoes can happen anytime of the year, in the USA, they are most common in the first half of the year. The 2010 tornado season has had a slow start, with 44 tornadoes reported through Monday, according to the National Weather Service. The average number for this time is 162, according to the weather service. Although data are not yet final, The Weather Channel counted 1,145 tornadoes last year, compared with 1,272 in an average year. The federal Storm Prediction Center counted 1,156 tornadoes last year, which killed 21 people.

Personally, I’m hoping for an active tornado season, but not a destructive one. I’m hoping to get out and do some storm chasing this season, but I would hate for a tornado to injure anybody or cause mass destruction. I’m looking forward to getting some awesome pictures!

National Weather Service (NWS)

February 22nd, 2010 3 comments

If you plan on following the weather seriously, you should bookmark the National Weather Service. Operated by the National Oceanic and Atmospheric Association (NOAA), the NWS web site provides you with detailed weather information for all of the United States. Of particular interest to those who love to track the weather are:

  • Detailed warning information
  • Forecast discussions
  • Graphical forecasts
  • Forecast discussions with a glossary to help you understand terms
  • Radar
  • Satellite
  • Severe weather

There is tons more there, and it’s all worth a look. You can get local forecasts, with great discussions about them, for your local area. You can also monitor severe weather in the event that you’re looking to do some storm chasing. And, you can watch the satellite to see when that next rain or snowstorm will hit your area. The NWS site is a treasure trove of information for people like me who love the weather. Check it out, and I’m sure you’ll find it interesting as well!