Unit 5 Test Severe Weather

Which agency issues watches and which agency issues warnings?

Watches are possibilities of storms! They are issued by the storm prediction center

Warnings mean it’s time to take action! They are issued by local National Weather Service office.

What is the direction of winds in the warm sector?

Southerly winds

What are the differences between ordinary storms, multicell storms, and supercell storms?

• Ordinary thunderstorms have isolated updrafts and downdrafts; they are short and weak storms. They have minimal wind shear and severe weather is rare.

• If relatively isolated thunderstorms develop when vertical wind shear becomes more "moderate," they tend to become multicells. Multicell thunderstorms are a "group" or "family" of single cells at various stages of their life cycles. They can last for several hours and they have moderate wind shear.

• Supercell storms are strong, mesocyclone (rotating), and they last several hours. They have strong wind shear and are almost guaranteed to have severe weather and chance of tornadoes.

In lightning, what connects the leader/cloud and the ground?

Stepped leader

Identify in general where charges are in a thundercloud. (Positive/negative)

Negative charges are located near the bottom/middle of a cloud

Positive charges are located near the top of the cloud 

lower clouds have a weak positive charge

Where would one find the greatest frequency of thunderstorms, severe thunderstorms?

The greatest frequency of thunderstorms in the US is along the Gulf of Mexico, especially in Florida. (unstable atmosphere)

The greatest frequency of severe thunderstorms in the US is in the Great Plains. (warm unstable air is dry and shallow)

What are the common triggers for thunderstorm development?

Sufficient moisture

Rising air/unstable atmosphere

Strong convection

The buoyant force causes the updraft to grow stronger

Frontal boundary

Unequal surface heating

Surface convergence and divergence aloft

Topographic barriers

Arrival of cold air aloft

In a thunderstorm life cycle (which phases), when are you most likely to have updrafts, downdrafts, and/or both?

Updrafts are only entity present during the CUMULUS stage

Updrafts and downdrafts are present during the MATURE (most intense) stage

Downdrafts are most prevalent during the DISSIPATING stage, because the updraft begins to collapse and the storm follows.

What is the criteria for a severe thunderstorm warning?

• large hail

• winds gusting above 50 kts

• development of a tornado

What caused many plane crashes in the 70s?

Microbursts/downbursts

What is the primary difference between an ordinary cell and supercell?

The updraft in an ordinary cell is non-rotating, and the updraft and downdraft interfere with each other.

The updraft in a super cell is rotating, causing the updraft and downdraft to be separated.

Where would one find the greatest frequency of hailstorms?

In the central us, in the great plains

What is the minimum size of hail that makes it a severe hailstorm? 

One inch diameter, about the size of a quarter.

How long does it take sound to travel one mile after a lightning strike?

It takes sound 5 seconds to travel one mile after a lightning strike.

Divide seconds by 5 for miles or by 3 for km.

If a storm is 5 miles away how long would it take to hear the thunder

25 seconds

What are the different types of lightning? 

• Forked lightning

• Ribbon lightning

• Bead lightning

• Ball

• Sheet

• Dry

• Heat

Where would one find squall line thunderstorms?

Squall line thunderstorms show up as a line along or in front of an advancing cold front.

What are 3 of ted Fujita’s contributions to the science?

• The Fujita (F) scale measures tornado intensity based on the severity of the damage

• Microbursts/downdrafts and the danger that they caused in aviation

• Identification of suction vortices, smaller vortices within tornadoes

What are two examples that distinctly categorize a negative cg strike and a positive cg strike?

Negative CG strike

• originates from the base of the cloud

• flickers multiple times because it is composed of multiple rapid electrical strokes.

Positive CG strike

• originates from top of the cloud

• one solid electrical strike does not flicker

How does a thunderstorm training event occur and what is the usual impact?

Thunderstorm training occurs when new storms repeatedly from on the gust front of previous storms, moving over the same location.

Flash floods can occur, excessive rainfall, prolonged severe weather.

Briefly explain why thunderstorms create a green, bluish sky

Hail is present in the storm,

Explain the formation process of a hailstorm (3 sentences)

when strong updrafts carry raindrops high into freezing altitudes, where they freeze and grow by collecting more supercooled water, forming layers, until they become too heavy for the updraft and fall as ice