Hurricanes form only over the warm tropical oceans near but not at the equator. Several form in the Atlantic each year and either curve away from the coastline, hit the United States or continue into Central America. Even more form in the Eastern Pacific because huge stretches of warm Pacific water allow numerous storms to form. A few of these strike the Mexican coast, but most move away from the shore.
Fewer than 10 percent of tropical weather disturbances grow into tropical storms because the right ingredients are relatively rare.
1) Ocean water above 80 degrees F is needed for the proper amount of water to evaporate. Warm water must be about 200 feet deep because storms stir up the ocean, bringing up cold water from below.
2) Winds need to be coming together-converging near the surface.
3) The air needs to be unstable so it will continue rising
4) Air up to about 18,000 feet needs to be humid as it’s pulled into the storm. The extra water vapor supplies more latent heat energy.
5) Pre-existing winds –-- those not created by the storm – should be coming from nearly the same direction and at close to the same speeds at all altitudes to avoid ripping the storm apart.
6) The upper atmosphere high pressure area helps pump away air rising in the storm. |
Hurricane Allen in the Gulf, 1980
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