Tornadoes

A violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud. Tornado definition: from the AMS Glossary

Classic funnel with debris sheath.

A large “wedge” tornado. It might be a mile wide at the ground.

general/

A classic funnel. If it’s in contact with the ground, it’s a tornado. If not, it’s a funnel cloud.

Tornadoes never occur without a parent thunderstorm. There are over 1000 tornadoes in the U.S. most years.

Miami, Florida tornado

Remarkable image of four tornadoes on the ground at the same time. (Multiple tornadoes over Albania in Photographed by Roberto Giudici. )

Sometimes all you see is the dust or debris sheath. The funnel is invisible since no water vapor is condensing.

Blue dots are high winds, Green dots are large hail, Red dots are tornadoes The most severe year on record

The number of tornadoes observed in the U.S. appears to be increasing. Or are we just getting better at finding them?

This is just tornadoes in There were 1894

2011 severe statistics

In 2011, U.S. winds, hail, and tornadoes began in late winter and continued through early Fall but some events happened in every month. Tornadoes spiked in April and May:

On average …

On radar, often big tornadoes are seen with a “hook echo” Oklahoma City May 3, 1999

This is what you saw in that hook

Doppler Radar image The radar is located at KTLX Green is toward KTLX, Red is away from KTLX The general wind flow is from east to west, EXCEPT in the mesocyclone

A simplified view of a supercell thunderstorm with a strong updraft and downdraft, forming in a region of strong wind speed shear. Regions beneath the supercell receiving precipitation are shown in color: green for light rain, yellow for heavier rain, and red for very heavy rain and hail.

Greensburg, KS tornado hook echo May 5, 2007 in western Kansas

Greensburg, KS tornado Doppler velocity

It was a large wedge tornado, the strongest type known

This is what Greensburg looked like after the tornado (

Greensburg High School (

The most famous single tornado in history is the Tri-State Tornado of 1925

695 people died from this one storm

Modern watches and warnings help to keep death tolls down

Tornadoes form with specific conditions. When these conditions occur, the NWS issues Watches and Warnings.

In 1973, Prof. T. Fujita devised his famous F-scale.

How would Fujita have classified the Tri-State Tornado?

Damage from the May 31, 1998 tornadoes in Albany, NY.

Just a few of the tornado tracks from May 31, 1998

In 2006, the NWS introduced the Enhanced Fujita Scale, a more realistic tool for putting tornadoes into categories.

House damaged House untouched Houses demolished Houses untouched Tornadoes do damage on a very small scale

A typical damage path

Where don’t you want to be when a tornado strikes?

Opening windows during a tornado will help balance the pressure between the inside and outside of the house and may prevent destruction of the structure One should seek shelter in the southwest corner of a house or basement. Tornadoes avoid large cities. A highway overpass is a safe place to take shelter under during a tornado Tornado Myths

Show UnderPassTornado.flv

Tornado Look-alikes Waterspout

Dust Devil

Shelf Cloud (

Tornado Outbreaks

Xenia, OH

After damage surveys, the final tally was 87 tornadoes

It looks like it used to be a mobile home

Even solidly built structures were heavily damaged

Many supercells at 5 p.m. CDT

Almost everything you see is a supercell. Many have tornadoes at this time. Show videos

Hook Echo with Birmingham tornado

Doppler velocity of Birmingham tornado

What do we take from all this? 1. Tornadoes occur more often in the U.S. than anywhere else in the world! 2. Tornadoes are often spectacular whirlwinds but they are extremely dangerous. 3. The NWS has a system for alerting the general public. The Tornado Watch is issued when conditions are favorable for thunderstorms to form tornadoes. When tornadoes exist or are imminent, the Tornado Warning is issued. Doppler Radar is a key tool for early detection. Fatalities have been reduced from the days of the Tri-State tornado in Take Watches and Warnings seriously. Even EF0 and EF1 tornadoes can be killers.