Thunderstorms Form along low-pressure fronts Lightning - discharge of electricity from a

thundercloud Positive charge on top and bottom, negative in

the middle

THUNDERSTORMS AND LIGHTNING

They appear at the back of a thunderstorm For a tornado to form there must be a

rotating updraft called a mesocyclone. Mesocyclone is an updraft that occurs

when low winds are blowing at a different speed/direction than the winds higher up.

http://www.youtube.com/watch?v=I7MXHw_R4ps

TORNADOES

extends from Texas northward to North Dakota

Warm, moist air blows in from the Gulf of Mexico while cool, dry air blows in from the west higher up in the atmosphere, setting conditions for tornadoes to form.

Tornado Alley

Fujita Scale

how we measure tornadoes. It tells us wind speed and damage

STORM WATCHES AND WARNINGS

Storm Watch: If conditions are favorable for a severe storm or tornado to form a WATCH is issued.

Storm Warning: If a severe storm or tornado has been seen and is approaching a WARNING is issued.

HURRICANES Hundreds of kilometers wide. Have at least 119 km/h wind

Extreme low pressure center, gets energy from warm water between 5o and 20o of latitude

usually June through November. The strongest winds and rain occur in the

eye wall.

Hurricanes weaken as soon as they make land fall or move over cold ocean water.

Hurricanes that occur in the Atlantic Ocean north of the equator initially move to the west/northwest

Hurricanes

Hurricanes can cause tremendous amount of damage along the coast and inland. Storm surge results from the strong winds

of the eye wall which blows water into a broad dome.

Storm surge is what cause the massive destruction and deaths in New Orleans from Hurricane Katrina.

Hurricanes

Hurricanes Hurricanes are classified using the Saffir-Simpson

Hurricane Scale. All hurricanes start as tropical depression then become

tropical storms and eventually can become a hurricane. A hurricane can change categories many times during its

lifecycle depending on wind speeds. Hurricane Watches and Warnings

Watches are issued to communities that could see the hurricane arrive in the next 24-36 hours.

Warnings are issued to communities that could see the hurricane in less than 24 hours.