TORNADOES

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TORNADOES
Conditions for formation
Heat Moisture Conditionally unstable
environment Vertical wind shear
Wizard of OZ
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Tornadoes
Local storms with violent winds that take the
form of a rotating column of Air that extends
from a cumulonimbus cloud.

• Form in association with severe T-storms
• Interaction between strong updrafts
• And winds in the troposphere

MESOCYCLONE precondition For intense tornadoes
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Tornadoes
Inflow and Outflow convergence rapidly increases
into Updraft and Wall cloud
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The first observable step in tornado formation is
the slow, horizontal rotation (a) of a large
segment of the cloud which begins deep within
the cloud interior. The resulting large vortices
are called mesocyclones. Under the right
conditions, strong updrafts cause the horizontal
vortex of air to be tilted upward (b).
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Tornadoes
2 Ways for formation
1. Top-down process
dynamic pipe effect

• Air beneath wall cloud is
• Stretched by the updrafts
• Within Stretched column of
• Air the flow is constricted
• Leading to a tighter vortex
• Continues until tornado
• touches the ground

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Tornadoes
3 Ways for formation
2. Bottom-up process
This spinning air is tilted in the vertical As it
moves under the updrafts of the storm Near its
base
Vertical wind shear Causes a spinning effect In
the lower atmosphere
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Tornadoes
Formation in a non-supercell storm

• These are generally weaker tornadoes
• AKA landspout
• Short lived
• Occur ahead of the frontal boundary
• Occur in the NE quadrant of a hurricane
• Occur over water waterspout

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Tornadoes
STATS Diameter 500-2000ft Speed
30mph Lifetime 3mins. To 3 hours Intensity
Based on the Fujita Scale (F-Scale)
Observed in EVERY state of the US Top nine
states Texas Oklahoma Nebraska Iowa Ill
inois Missouri Indiana Mississippi Florida
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The Fujita Scale The Fujita Scale
F0gale tornado40-72 mph Some damage to chimneys breaks branches off trees pushes over shallow-rooted trees damages sign boards.
F1moderate tornado73-112 mph Lower limit is the beginning of hurricane-force winds. Peels surface off roofs mobile homes pushed over moving autos pushed off roads.
F2significant tornado113-157 mph Roofs torn off frame houses mobile homes demolished boxcars pushed over, large trees snapped or uprooted light-object missiles generated.
F3severe tornado158-206 mph Severe damage. Roofs and some walls torn off well-constructed homes trains overturned most trees in forest uprooted heavy cars lifted off the ground and thrown.
F4devastating tornado207-260 mph Well-constructed homes leveled structures with weak foundations blown off some distance cars thrown and large missiles generated.
F5incredible tornado261-318 mph Phenomenal damage. Strong frame homes disintegrate or lifted off foundations and carried considerable distance trees debarked.
Measuring A Tornado
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Tornado Watch possibility
Tornado Warning Sighting