Earth Science Ch 13 Tornadoes
What are the steps of a formation of a tornado?
1. A change in wind direction and speed creates a horizontal rotation in the lower atmosphere. 2. Strong updrafts tilt the rotating air from a horizontal to a vertical position. 3. A tornado forms within the rotating winds that could be 2-6 miles wide. Most strong and violent tornadoes form within this area of strong rotation.
What is the average speed of a tornado?
30 mph, but may vary from nearly stationary to 70 mph
On the average, how many deaths and injuries are reported nationwide?
80 deaths and over 1,500 injuries
On the average, how many tornadoes are reported nationwide?
800
tornado
A violently rotating column of air extending from a thunderstorm to the ground. It is associated with changes in wind speed and direction.
Tornado warning
Actually been sighted by spotters or indicated on radar and is occurring or imminent in the warning area. It will include where the tornado is and what towns will be in its path. Take cover...only minutes until its arrival.
When can tornadoes occur?
Any time of year
When do tornadoes form?
Any time of year, but mostly in May
Why do scientists think that the Corolis effect does not cause the rotations in a tornado?
Because there are records of anticyclonic tornadoes.
funnel cloud
Before a tornado reaches the ground
What time of day do tornadoes usually occur?
Between 3 and 9 pm
Tornado watch
Conditions are favorable for the development of tornadoes in and close to the watch area. Usually in effect for several hours, with 6 hours being the most common.
Category F3
Considerable damage (113-157 mph) Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.
Category F5
Devastating Damage (207-260 mph) Wellk-constructed houses leveled; structure with weak foundations blown off some distance; cars thrown and large missiles generated.
Where are tornadoes mostly found in the US?
East of the Rocky Mountains
When do secondary tornadoes occur in some states?
Fall
What is the name of the scale that ranks tornadoes according to the path of destruction?
Fujita tornado intensity scale
When do tornadoes mostly happen?
In the spring and summer months
Category F6
Incredible Damage (261-318 mph) Strong frame houses lifted off foundations and swept away; automobiles sized missilies fly through the air in excess of 100 meters (109 yards);trees debarked.
Category F1
Light damage (less than 73 miles per hour) Some damage to chimneys; branches broken off trees, shallow-rooted trees pushed over; sign boards damaged
When is peak tornado season in the southern states?
March through May
Category F2
Moderate damage (73-112 mph) Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off road.
Category F4
Severe Damage (158-206 mph) Roofs and some walls torn off well-constructed houses, trains overturned;most trees in forest uprooted; heavy cars lifted off ground and thrown.
Why are tornadoes probably higher in the western states?
Sparse population reduces the number reported.
What frontal systems are associated with tornadoes that form in the winter and early spring?
Strong frontal systems that form in the Central States and move east.
When is peak tornado season in the northern states?
Summer
Tornado Alley
The most common place in the US where tornadoes ocur.
When does the most damage occur with tornadoes?
The most severe tornadoes occur in April where the most damage occurs.
What happens to the frequency of tornadoes the farther north you go?
The peak tornado season is later because it takes longer to warm the northern part of the plains.
Where is the path of a tornado with a storm center?
To the right and ahead of the path of the storm center as it comes onshore.
What thunderstorms often produce tornadoes?
Where cool, dry polar air meets warm, moist tropical air.
How can you see a tornado?
You can see swirling debris at the base of the funnel.
How do most tornadoes spin?
cyclonically
Where does the average tornado move?
from southwest to northeast, but tornadoes have been known to move in any direction.
Where does a tornado begin to form?
in a severe thunderstorm called a supercell. The wind soming into the storm starts to swirl and form a funnel. The air in the funnel spins faster and faster and creates a very low pressure area which sucks more air (and objects) into it.
What are tornadoes often associated with?
tropical storms and hurricanes
What is the atmosphere like for a tornado?
unstable
