Hurricane Lili is a powerful hurricane that is threatening the coast of Louisiana today (Oct. 3, 2002). This JavaScript movie shows Lili approaching the southern coast of Louisiana.

Two weeks ago e-ReefNews Vol.4 No.2 reported that Hurricane Isidore had crossed the western tip of Cuba and also was threatening the coast of Louisiana. But Hurricane Isidore went west instead of north, and wound up over land at the northern tip of Mexico's Yucutan Peninsula. Hurricane Isidore lost a lot of strength while it was over land. Why did this happen?

Hurricanes form when warm air rises above a warm ocean in the summertime. Sunlight heats the surface of the ocean, and this warm water heats the air above it. Then the warm air rises through the colder air above it. Some of the water from the ocean evaporates, and the rising air carries this steam high into the atmosphere. This rising steam then cools in the colder air high in the atmosphere, turning into clouds. If the conditions are right, the clouds will form a thunderhead and it will rain. But if the conditions are just right, the rising steam will form a hurricane.

Hurricanes depend on this source of energy from the warm ocean. As soon as the hurricane goes over land, it "runs out of steam," and the winds begin to slow down.

Just like Hurricane Isidore, Hurricane Lili passed over the western tip of Cuba. But it wasn't over land long enough to lose much steam. But, unlike Isidore, Hurricane Lili then went north across the warm Gulf of Mexico. Now Lili has built into a powerful storm with winds as high as 100 m.p.h. This storm may cause a lot of damage when it comes ashore in the United States.