Earth Science

Storms Unit 5

Severe Weather Safety

• Watches- conditions are favorable • Warnings- conditions already exist• Examples- Tornadoes, Flooding,

Thunderstorms, Blizzards, Winter Mixes and Hurricanes

How Thunderstorms Form

• For a thunderstorm to form, three conditions must exist.

• Thunder, Lightning, Rain, High Winds• Possibly Hail, Tornadoes

1. There must be an abundant source of moisture in the lower levels of the atmosphere.

2. Some mechanism must lift the air so that the moisture can condense.

3. The portion of the atmosphere through which the cloud grows must be unstable.

Earth Science

Thunderstorms

Earth ScienceMr. Ertl

Lightning and Thunder• Lightning – discharge of electricity

from a t-cloud to ground, to another cloud, or from the ground to a cloud

• Extremely high temp., air expands explosively – causes thunder

• Light travels faster than sound – causes delay between lightning and thunder

• Thunder can be heard up to 16 km

Lightning

Lightning

Earth ScienceMr. Ertl

Tornadoes

• Narrow, funnel shaped-column of spiral winds that extends downward from cloud

• Occur more frequent in US than anywhere else

• Mississippi River Valley and Great Plains• Grow out of T-Storms, produced when

cold, dry air meets warm, moist air• Winds between 360-500 km/hour• Usually travel SW to NE

Earth ScienceMr. Ertl

• Intensity measure on Fujita Scale– The scale ranges from F0, which is

characterized by winds of up to 118 km/h, to the violent F5, which can pack winds of more than 500 km/h.

Earth Science

Tornadoes

Storm Surges

Formation of Hurricanes

• Hurricane seasons starts June 1 – November 30

• A tropical disturbance forms.– Has to form near the equator over

water.– The warm air rises and cool to form clouds.– Forms large intense low pressure system.

• Winds reach 23 mph tropical depression• Winds reach 39 mph tropical storm

– Receives a name• Winds reach 74 mph hurricane

How to Name a Hurricane

• Each time a storm reaches tropical storm status it receives a name. – Name are picking from a list in

alphabetical order.

Classifying a Hurricane

• Use the Saffir- Simpson Scale– Based on a 1-5 scale.

• 1 being the least amount of damage.• 5 the most amount of damage.

Saffir- Simpson Scale

Hurricane Hazards

Hurricane Advisories

Mr. Ertl Science 8

Then came Katrina…

…a strong category 3 hurricane when it struck New Orleans.

Compare satellite images before and during the flood. (Dark blue is water.)