Objective: s.w.b.a.t. • Explain the steps in formation of a thunderstorm • Define: lighting and thunder & explain how the two

are connected and created. • Understand how to protect themselves from

lightning and what to avoid during thunderstorms • Observe a video connect to static electricity and

lightning • Complete by reading a worksheet with question

about lightning.

Activities • Warm-up

• Notes/discussion

• Video - question/discussion

• Worksheet Lightning 1-4

Weather 21-2 cont.

Severe Weather

Severe Weather Severe Weather – violent circulation (storms) A thunderstorm is usually a brief, heavy storm that consists of rain, strong winds, lightning, and thunder. - - Produced cumulonimbus clouds - - usually occur along cold fronts - - strong updrafts and down drafts - - occur in 3 stages

Severe Weather Stage 1- Strong updrafts from rapidly rising warm air

In the cumulus stage, warm, moist air rises, and the water vapor within the air condenses to form a cumulus cloud.

Severe Weather Stage 2 – heavy rain begins creating up and downdrafts.

In the mature stage, the cloud rises and becomes a dark, cumulonimbus cloud from which heavy, torrential rain and hailstones may fall.

Particles moving and sliding past each other lose electrons building up static charges – generating - lightning

Severe Weather Stage 3 – light rains and calm down drafts only

During the dissipating stage, the strong downdrafts stop air currents from rising. The thunderstorm dissipates as the supply of water vapor decreases.

Severe Weather During a thunderstorm, clouds discharge electricity in the form of lightning.

Severe Weather Lightning is a large electric spark caused by the static electricity of particles moving in a storm

- Lightning is a form of plasma – charged particles

- When the area in a cloud becomes overcharged lightning occurs

- As the thunderstorm cloud develops it has +(positive charge at top) & -(negative charge) at bottom

Severe Weather - Ground (Earth’s surface has a positive charge)

Electricity flows from negative to positive charge

-Lightning is occurs when these areas become overcharged – and the unlike charges attract each other.

Severe Weather The released of lightning electricity heats the air, which rapidly expands and produces a loud noise known as thunder.

Severe Weather Lightning heats the air to 30,000

C or hotter which causes the air to expand violently causing a shock wave of thunder

- Timing between lightning flash and thunder – one can calculate distance to lightning

- For every second = 1000 feet, 5 seconds = 1 mile

Objectives: S.W.B.A.T. • Define Hurricane and its parts

• Explain where hurricanes form an why and what causes most damage and deaths related to hurricanes

• Define tornado and how most damage and deaths are caused by them

• Plot tornado alley and answer questions related to this area and tornado development

Activities: • Warm-ups & quiz

• Collect any outstanding work

• Complete video from prior day

• Notes/discussion

• Tornado alley – plot & questions

Severe Weather Hurricanes – are powerful cyclones (low pressure storms) that form over tropical air near the equator.

Other names for hurricanes: Typhoons – in North Pacific

Willy-Willies – in Australia

Tropical cyclones in other areas

Severe Weather A hurricane is a severe storm that develops over

tropical oceans. Its strong winds spiral in toward the intensely low-pressure storm center.

To be a

hurricane, a storm’s winds must be 75 miles per hour or greater.

Severe Weather A fully developed hurricane has of a series of thick cumulonimbus low pressure cloud bands that spirals counterclockwise upward around the center of the storm.

Severe Weather Hurricanes start out as tropical depressions winds at 38 mph

Then they become tropical storms winds 39-73 mph

Then hurricane when winds reach 74 mph

Severe Weather Eye of a hurricane is a calm many times cloudless low pressure center – it is surrounded by the most powerful winds and storm region.

Severe Weather • Winds range from 75 to 155+

• Diameter can be 300-400 miles

• Hurricane Season: June 1 – November 30

Severe Weather

The most dangerous aspect of a hurricane is a rising sea level and large waves, called a storm surge. (large dome or tide of seawater) covers 50-100 miles, 10-20 ft. above normal high tide

Severe Weather Tornadoes are the smallest, most violent, and shortest-lived severe storm. Tornadoes that forms over water are called a waterspout

Severe Weather • Tornadoes – is a small destructive storm having a rapidly spinning

funnel shape cloud (also a low pressure area)

• Caused by warm air being trapped below cold air and the warm air rises rapidly

• Tornado watch means: conditions are favorable

• Tornado Warning means: one has been sighted in local area

• Time of April to June are best conditions for tornadoes

• The zones/region is USA where hurricanes form is know as tornado alley

Severe Weather A tornado forms when a thunderstorm meets high-altitude horizontal winds. These winds cause the rising air in the thunderstorm to rotate.

Severe Weather If the funnel does touch the ground, it generally moves in a wandering, haphazard path.

Last week of April, 2011

Severe Weather The destructive power of a tornado is mainly due to the speed of the winds, which may reach speeds of more than 250+ mph.