What causes hurricanes to decay and dissipate? Hurricanes can become very powerful, but they're not immortal. Tropical cyclones such as tropical storms and hurricanes have a finite life span and their share of enemies such as cooler sea surface temperatures, hostile upper level winds, land, and sinking air that all inhibit further strengthening, or even dissipate them altogether.
- Colder sea surface temperatures--Warm water is the engine of all tropical cyclones. Sea surface temperatures must be at or above 80 degrees Fahrenheit in order for a tropical storm or hurricane to flourish. Anything colder than that will cause the storm to weaken or even dissipate.
- Shearing winds aloft--Tropical storms and hurricanes are "vertically stacked systems." That means that clouds in the hurricane engine build vertically to great heights in the troposphere and lower stratosphere. In order for this to happen, these storms must have light winds aloft. Hostile upper level wind conditions produce shearing, which blow off the high cloud tops of these storms, and causes them to become disorganized.
- Sinking air--Sinking air, or subsidence from high pressure such as the subtropical ridge can also inhibit development. Again, hurricanes are vertically stacked systems so they need to have air rise from the surface to the upper levels. Sinking air from high pressure hinders thunderstorm development, which is a critical element in hurricane strengthening.
- Land, of course--The ultimate hindering factor to hurricanes is of course land. When hurricanes or tropical storms make landfall, the friction caused by a large land mass, and their terrain cuts off the hurricane's circulation, and squeezes out the storm's moisture. In some cases rugged terrain such as mountains can squeeze out tons of moisture, which in turn produces heavy rainfall and flooding.