Tornadoes

Tornado Formation
In tornado alley, twisters are normally caused when warm, humid winds from the Gulf of Mexico move north and collide with cool, dry air from the west


















As the warm air and colder winds collide, they begin an invisible horizontal rotation.
Energy from the sun warms the ground, which in turn warms the air near it. This warm air then rises even further.
This warm air pushes itself upwards through the colder air and starts to form a vortex.
This then forms into the fully-fledged funnel of a tornado.


















Elie, MAnitoba tornado, June 22, 2007

Tropical Storms and Hurricanes

Extremely strong tropical storms go by a number of different names, depending on
where they occur. Over the Atlantic and the eastern Pacific they are known as hurricanes.
Those over the extreme western Pacific are called typhoons; those over the
Indian Ocean and Australia are cyclones.

Hurricanes obtain most of their energy from the latent heat released by condensation and are most
common where a deep layer of warm water fuels them. August and September are the prime hurricane months
in the Northern Hemisphere, while January to March is the main season in the Southern Hemisphere.


The hurricane eye is a region of relatively clear skies, slowly descending air, and light winds.
Along the margin of the eye lies the eye wall, the zone of most intense storm activity with
the strongest winds, thickest cloud cover, and most intense precipitation of the entire hurricane.
























Hurricanes form only where the ocean has a deep
surface layer with temperatures above 27 °C (81 °F).
The need for warm water precludes hurricane formation
poleward of about 20 degrees because
sea surface temperatures are usually too low there.

Storm surge is a rise in water level induced by the hurricane.
Strong winds blowing toward a coast force surface waters
landward and thereby elevate sea level. Low atmospheric
pressure in a hurricane also contributes to the storm surge.
For every millibar of pressure decrease,
the water level rises 1 cm.

Three's Activity

Three's Activity for Friday December 5, 2008
Tosan - Internet
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Fronts

A cold front occurs when a wedge of cold air advances toward the warm air ahead of it.
A warm front represents the boundary of a warm air mass moving toward a cold one.
A stationary front differs in that neither air mass has recently undergone substantial movement.
Occluded fronts appear at the surface as the boundary between two polar air masses, with a colder polar air mass usually advancing on a slightly warmer air mass.

Mid-Latitude Storms

Mid-Latitude storms are weather systems that:
- Bring rain to Canadian regions.
- Extend from 25º to 50º latitude.
- Form the area where cold A air masses meet moist, warm m air masses.
- When two masses collide, storms are born.

Air Masses
Air masses are bodies of air that develop over large areas of the earth’s surface
Two conditions are necessary for formation:
Source region – air must stay over an region for long period of time
The air must be stable
Air masses take on characteristics of the region
Warm maritime air masses – formed over water
Cold continental air masses – formed over land

The five types of North American air masses are:
Continental Tropical (cT)
Maritime Tropical (mT)
Maritime Polar (mP)
Continental Polar (cP)
Arctic (A)

Question 5 Page 282

Additional Questions:

1. What patterns exist in Figure 16.2?
2. Why are there no air masses in equatorial zones?
3. Using a map outline of North America draw in the air masses and indicate regions where the storms would likely occur.

Three's Activity

Three's Activity for Monday, December1, 2008
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