Hurricanes that affect the US usually form in the Northern Atlantic Ocean. As solar radiation warms the ocean surface evaporation increases. The warmer the temperatures, the greater the rate of evaporation. As you may recall, warm, moist air rises, expands and cools to the dew point and clouds form. Energy and water vapor continue to be added to the atmosphere. This creates a low pressure area, known as a tropical depression. If winds are sustained above 39 miles per hour it is considered a tropical storm. If the winds are over 74 miles per hour it becomes a hurricane. Most hurricanes occur in late summer early autumn because this is when the ocean surface is warmest. They are the most destructive storms. High winds, storm surges (ocean water pushed onto the coast) and major flooding occur. One more thing that adds to the hurricane Category Winds 1 74-95 mph 2 96-110 mph 3 111-130 mph 4 131-155 mph 5 > 155 mph disaster is that tornados can form. A hurricane is sometimes referred to as a cyclone because it is such a large area of low pressure. A typhoon is the same as a hurricane, however forms over the Northwest Pacific Ocean. Hurricanes are fairly easy to predict because advancements in weather radar and satellite technology allows meteorologists to watch them develop and keep track of their path. Where exactly they hit land is not full proof. If a hurricane appears to pose a threat to your area within 48 hours, a hurricane watch is issued. A warning is issued if conditions are expected within 36 hours. When you are ordered to evacuate LEAVE THE AREA. Need to know: 1. Where do hurricanes form? 2. How do clouds form in a hurricane? 3. What is added to the atmosphere to fuel the development of a hurricane? 4. What is a tropical depression? 5. What is the difference between a tropical storm and a hurricane? 6. What is the difference between a sustained wind and a wind gust? 7. How fast are sustained winds in a category 5 hurricane?