Thunderstorms are common storms that produce lightning and thunder through heating of the air. They form in three stages - air rises to form clouds, moisture falls as rain or hail when clouds can no longer hold it, and static electricity builds from air moving in opposite directions causing lightning. Thunderstorms usually form ahead of cold fronts in warm air and can sometimes spawn tornadoes in areas where warm, moist air meets cold, dry air masses like the Great Plains and Mississippi Valley.

1. Meteorology Severe Storms

2. What are thunderstorms? Very common storms that cause electric sparks called lightening that heat the air and cause the noise called thunder. They usually have heavy rains and strong winds and sometimes hail. They often happen when the weather is hot and a cold front is approaching. They are formed in 3 stages…

3. Stage 1 Intense heating causes air to rise quickly and form a cloud. More and more moist air is carried up and the cloud grows larger. When the clouds can’t support the moisture anymore it falls as heavy rain or hail.

5. Stage 2 Once the rain falls the air in the cloud moves downward. When the air going up rubs the air going down it causes static electricity. When enough of this builds up there is lightening. Lightening slams into the air around it with such force that it makes thunder.

7. Stage 3 A thunderstorm ends when the air moving down becomes stronger than the air moving up. Heavy rain lightens and stops.

8. Where do thunderstorms usually form? In the warm air just ahead of a cold front.

9. How and where do tornadoes happen? The most violent thunderstorms can turn into tornadoes. They form where dry, cold air masses mix with warm, moist air masses. In the U.S. this is most likely to happen in the Great Plains region and the Mississippi Valley and also in Florida. They happen most often in early spring and summer.

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11. Hurricanes 7. Hurricanes are very large, swirling storms with very low pressure at their center. They form over tropical oceans near the equator. See p. D70-D71.

12. Hurricane Ivan

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