1. Weather Systems Vocabulary
Air mass – huge body of air with the same temperature and moisture characteristics
Front – a boundary between two air masses
Hurricane – a tropical cyclone of low pressure and very strong winds
Thunderstorm – Cumulonimbus cloud possessing thunder and lightning, usually accompanied by strong winds, rain and sometimes hail
Tornado _ whirling funnel of air of very low pressure and very strong winds; must touch the ground to be called a tornado

2. Air Masses Usually 1,000 miles across or more
Has the same temperature and moisture characteristics
When it travels out of its area it carries the characteristics (front from Alaska will be cold and dry)
Usually from a Tropical or polar region
They are classified by their source region, such as (P) Polar, (A) artic, (T) tropical and (E) equatorial

3. FRONTS They are classified as warm, cold, stationary or occluded.
When warm air moves in this is a warm front
When cooler (cold) air moves in this is a cold front
When two air masses bump into each other and neither moves it is called stationary.
An occluded front is when three air masses meet.
Cold fronts are indicated in blue, warm fronts in red

4. Severe weather There are three main weather phenomena
Thunderstorms
Tornadoes
hurricanes
All three are associated with cumulonimbus clouds
All three are potentially deadly

5. Thunderstorms
Come from cumulonimbus clouds and always have thunder and lightning
Lightning is a flash of light produced by electrical discharges in a thunderstorm. It discharges millions of volts and heats the air to 60,000 degrees F.
Thunder is the sound sent out by rapidly expanding gases along the lightning's trail
They usually contain heavy rain, strong winds and sometimes hail
Hail is small balls of ice

6. Thunderstorm stages
They have three stages: building, mature, and dissipating
Building stage has updrafts as the storm builds and grows vertically.
Mature stage the moisture that is carried up gets heavier and starts to fall, this creates downdrafts… there are still updrafts so the moisture moves up and down several times
Dissipating, contains only downdrafts (the storm is blowing itself out)
In the US alone 200 people are killed by lightning each year and are injured.

7. Safety rules for thunder and lightening
Stay away from windows and doors
Don’t use electrical appliances
Don’t use the phone or take a shower or bath
If outside, go inside if possible
Move away from water such as pools, lakes and the ocean
If you are in a boat, go ashore
Stay away from metal objects like gold clubs, fishing poles, bicycles, farm equipment or motorcycles
Don’t stand in an open field, a hilltop or golf course, stay low by sitting.
Don’t stand under a single tree (if you must be under a tree, look for a group of trees of similar height)
If in a group of people, stay low and spread out
If in a car, stay there.

8. How do thunderstorms affect aviation?
Cumulonimbus clouds mean the air is unstable
Thunderstorms have violent up and down drafts
Unstable air causes turbulence which raises havoc with planes
Hail can do serious damage to airplanes
Lightning can cause electrical devices on the plane to go out or even shut down engines
Pilots usually fly above or around thunderstorms

9. Tornadoes

10. Tornadoes Destructive and devastating to life, property and nature
Occur in every month of the year
About 700 annually in the US
Unstable air of low pressure
Most are counter-clockwise
Air is sucked into the center (vortex) of the storm
The funnel of a tornado appears dark because of the dirt and debris it picks up

11. Tornado winds They can be stronger than 261 mph
They can be as big as 500 yards (5 football fields) across
They are measured on the Fujita wind damage scale
F-0 light up to 72 mph
F-1 moderate 72 to 112mph
F-2 considerable 113 to 157 mph
F-3 severe 158 to 206 mph
F-4 devastating 207 to 260 mph
F-5 incredible above 261mph

12. HURRICANES Produce many thunderstorms and tornadoes within them
Their winds are not as strong as tornadoes usually but still devastating
Affect hundred of miles wide
Flood coastal cities and dump many inches of rain
The eye of the hurricane can be 15 miles wide!
Before storms become hurricanes they are first tropical depressions then tropical storms
Judged on the saffir-simpson scale
Cat 1
Cat 2
Cat 3
Cat 4
Cat 5