Thunderstorms

&

Tornadoes

What are the stages of development in a Thunderstorm?What are the stages of development in a Thunderstorm?

Three stages have been identified in ordinary thunderstorms:

a) Cumulus stage: an

unstable atmosphere and vertical updrafts

b) Mature stage

c) Dissapating stage:weakening updrafts and loss of the fuel source.

Mature Stage Thunderstorm

Video: Hail.asf

Dissipating Stage of Thunderstorm

Diagram of a developing ThunderstormDiagram of a developing Thunderstorm

Trailing Stratified CloudsTrailing Stratified Clouds

Pre-Frontal Squall Line Storms on RadarPre-Frontal Squall Line Storms on Radar

What causes lightning during a thunderstorm?What causes lightning during a thunderstorm?

Charged layers in the cloud are formed by the collision of hailstones and ice with the cumulonimbus cloud.

When the negative charge near the bottom of the cloud is large enough to overcome the air's resistance a lightning bolt forms.

Video: Lightning_Strikes.asf

What causes thunder to form?What causes thunder to form?

The rapid heating of air by a lightning bolt creates an explosive shock wave called thunder, which requires approximately 3 seconds to travel about 1 mile.

What is a tornado?

A rotating column of air ranging in width from a few yards to more than a mile and whirling at destructively high speeds, usually accompanied by a funnel-shaped downward extension of a

cumulonimbus cloud.

Video: All_About_Tornadoes_and_Tornado_Alley.asf

When do tornadoes occur?

Nearly 75% of tornadoes form from March to July, and are more likely when warm humid air is overlain by cooler dryer air to cause strong vertical lift.

What scale measures tornado intensity?

Once the storm is observed, or has passed, the Fujita scale of F0 – F5 is used to classify tornadoes according to their rotational speed based on damage done by the storm.

How does a tornado begin to spin (vorticity)?

Spinning horizontal vortex tubes created by surface wind may be tilted and forced in a vertical path by updrafts. This rising, spinning, and often stretching rotating air may then turn into a tornado.

What is a “supercell”?

A thunderstorm with a persistent rotating updraft. While rare, it produces the most severe weather such as tornadoes, strong winds, and hail.

Overhead view of a Super Cell

Rotating CloudsRotating Clouds

What is a waterspout?

Warm, shallow coastal water is often home to waterspouts, which are much smaller than an average tornado, but similar in shape and appearance.

The waterspout does not draw water into its core, but is a condensed cloud of vapor.

A waterspout may, however, lift swirling spray from the water as it touches the water surface.