Ernesto is now a hurricane with sustained winds of 75 mph. It's expected to become a hurricane later this morning and a Category 3 storm by Friday.

Tropical Storm Francine strengthened into a Category 1 hurricane Tuesday night in the Gulf Coast as it continued to churn toward Louisiana with maximum sustained winds of 75 miles per hour. Francine becomes the fourth hurricane this Atlantic hurricane season,

Warm ocean water is essential for forming and strengthening hurricanes. Heat helps the water evaporate faster, fueling the storm and producing more rainfall. Mid-September is typically the peak of hurricane season and Francine moved through a part of the ocean that held an exceptional amount of energy.