Lightning, Thunder, and Tornadoes Study Guide: Part 1

False: lightning

True or False: Storms produce lightening.

80%

What percent of lightning is cloud to cloud?

occurs when negative charges build up in the lower part of the cloud, positive charges are attracted to an area beneath the cloud, remaining 20% of lightning bolts are between the sky and the ground

Describe how lightning forms and discharges from cloud to ground.

an initial separation of positive and negative charges

What appears to be necessary for lightning to form in a cloud?

False

True or False: Lightning is a giant spark?

x-rays

What are emitted with lightning?

have been accelerated to near the speed of light

Lightning results from electrons that?

the rapid and staggered advance of negatively charged air

What is a stepped leader?

once the charge difference between the cloud and the ground is large enough, the electric field overcomes the airs resistance and a stepped leader (a channel of negative charge), starts to move downwards from the cloud, stepped leader searches for the most conductive path towards the ground

How does the stepped leader work towards the surface?

20,000

Up to how many amps can be found in lightning?

54,000 degrees

How hot can lightning be?

due to a large discharge between opposite charges in a thunderstorm cloud

Why does lightning flash?

positive charged

Which type of lightning is more power, positive or negative charged?

it carries a much larger charge, potentially up to 10 times greater and its longer duration and stronger current lead to a higher fatality rate

What are some of the dangers of positively charged lightning?

Roy Sullivan

Who was struck by lightning 7 times?

sprites

Lightning that occurs about 1% of the time?

blue jets

Lightning that extends up to 30 miles from the cloud?

tremendous increase in temperature caused by lightning, both in amount and speed, causes air to explode explosively, the sound produced is thunder

How does thunder form?

0.2mps

What speed does sound move?

5

To determine distance from the lightning you should divide the number of seconds by what?

12 miles

Sound typically doesn’t travel further than how many miles?

69

How many people die each year from lightning?

air mass

Which thunderstorms extinguish themselves with downdrafts?

severe

If downdrafts intensify the storm they are often classified as what?

cumulus stage begins with rising unstable air, often localized convection caused by uneven evaporation, Mature stage begins with precipitation, as heavy rain and/or graupel begins to fall, downdrafts form, strongest part of the storm, entrainment causes droplets to shrink, dissipative stage-downdrafts dominate/precipitation diminishes

Explain the formation, life and death of an airmass thunderstorm?

3

How many stages of airmass thunderstorms are there?

as the sun sets, the Earth’s surface cools and the source of heating is diminished

Why does the Sun setting kill air mass thunderstorms?

it evaporates

What happens to the majority of the moisture in an air mass thunderstorm?

storms with wind speeds in excess of 58 mph, hailstones larger than 1 inch in diameter or are producing a tornado

By definition, what is the severe thunderstorm?

size of a nickel

Approximately how big is 1 inch in diameter hail?

Mesoscale Convective System

What does MCS stand form?

Squall lines - long linear bands, Mesoscale Convective Complexes (MCC’s) - roughly oval clusters

What are the two examples of MCS?

False

True or False: MCS do not create severe weather?

intense and powerful storms that contain a single updraft zone, they can occur in isolation and as part of an MCS

What is a supercell storm?

MCC’s (Mesoscale Convective Complexes)

Which MCS type is more likely to create severe weather?

South

MCC’s tend to grow in a North or South direction?

along the leading edge

Where are the strong to severe thunderstorms in a squall line typically found?

False

True or False: Squall lines only last a couple of hours?

the wedge of cold dense air that acts like a mini cold front, as downdrafts reach the ground they surge ahead as a wedge of cold air, displaces warm air upwards and are often seen with a dust cloud, appear very dark and foreboding

What is a gust front, how does it appear and how does it form?

consists of a single extremely powerful cell rather than a number of individual cells, remarkably complex with updraft and downdrafts bending and wrapping around each other due to the strong windshear aloft

How doe supercell thunderstorms form and function?

yes

Are shelf clouds dangerous?

smaller

Supercell storms are larger or smaller than an MCC?

the presence of a tornado

What does a hook and echo indicate?

forms when precipitation from a supercell thunderstorm wraps around the storm’s rotating updraft, which creates a hook-shaped echo

How/why does a hook echo form on radar?

1957

When was the weather service radar invented?

early 1990s

When was Doppler radar released by the NWS?

a boundary between moist (mT) and dry (cT) air masses, most likely to form over Texas and Oklahoma, meeting point of two different air masses which can be unstable

What is a dry line? Why does it generate severe weather?