GEO 125

Physical Geography

Introduction to Atmospheric Disturbances

Major Forms of Atmospheric Disturbances

• Thunderstorms
• Cyclonic storms

Thunderstorms

• Convectional storms (summertime storms in the midlatitudes and dominant rain producing storm in the tropics)
• Thunderstorms associated with cold fronts in the midlatitudes

• Thunderstorms associated with hurricanes

Cyclonic storms

Associated with low pressure systems

• Warm, moist, rising, unstable air
• Winds converge at the earth's surface and diverge aloft

Cylconic wind circulation

• Counter clockwise in the northern hemisphere
• Clockwise in the southern hemisphere

Extratropical cyclonic storms

• Macroscale (synoptic scale) weather events caused by the collision of air masses in the midlatitudes
• Commonly called lows or depressions

Tropical cyclonic storms

• Mesoscale weather events associated with the organization of equatorial air masses
• Commonly called hurricanes, typhoons, or cyclones depending on where they occur

Tornadoes

• Microscale weather events (90% occur in the United States and Canada because of the north to south trending major mountain chains in North America)
• Commonly called twisters

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