Name:
Per.
Hazardous Weather and Indiana Weather
Hazardous Weather
• Thunderstorms
• Tornadoes
• Blizzards
• Flooding
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•
•
Hurricanes
Drought
Lake Effect Snow
Thunderstorms
The 3 Key Ingredients of a Thunderstorm
• MOISTURE
▫ Large bodies of water (warmer temperatures = good)
• INSTABILITY
▫ Warm moist air underneath colder dense air
▫ As the warm air rises it will cool and form the CUMULONIMBUS clouds
• A LIFTING MECHANISM
▫ Differential heating (Water vs. land), Fronts, Terrain
The 3 Stages of a Thunderstorm
• TOWERING STAGE
▫ The warm air is forced upwards making the tall fluffy cumulonimbus clouds.
• MATURE STAGE
▫ The air that has raised higher cools and the precipitation begins to fall.
• DISSIPATION STAGE
▫ The storm runs out of the warm moist air that fuels it.
Types of Thunderstorms
• Ordinary Cell - One cycle through the previous phases
• Multi-cell - The storm builds and cycles through several of the phases
• Squall Line - The thunderstorm forms a horizontal line that spreads several miles.
• SUPERCELL - Last for several hours traveling over long distances. Produce almost all of the significant
tornadoes
Name:
Per.
Hazards of Thunderstorms
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Hail
Damaging Winds
Tornadoes
Flooding
Tornadoes - A violently rotating column of air descending from a thunderstorm and touching the ground.
EF Scale
Class
EFO
EF1
EF2
EF3
EF4
EF5
Weak
Weak
Strong
Strong
Violent
Violent
Enhanced Fujita Scale
Wind Speed
mph
km/h
65-85
105-137
86-110
138-177
111-135
178-217
136-165
218-266
166-200
267-322
> 200
> 322
Description
Gale
Moderate
Significant
Severe
Devastating
Incredible
Flooding
What is the cause of flooding?
• Basics – Too much water in, not enough water out.
• Water “Out” sources – rivers, lakes, INFILTRATION, CSO’s.
Dangers of flooding
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People underestimate how powerful moving water can be.
Even at low levels moving water is strong.
Lake Effect Snow
• is produced during cooler atmospheric conditions when COLD winds move across long expanses of
WARMER LAKE WATER, providing energy and picking up water vapor which freezes and is deposited
on the opposite shores.