MANKATO, Minn. (KEYC) - Hurricane Dorian wrecked havoc across parts of the Bahamas this past weekend and continued producing hurricane force winds as it moved along the coast of the Carolina’s. As Minnesotans we are lucky, we don’t have to deal with these massive and destructive beast. Hurricanes don’t like land even though they tend to impact coastal regions. So why don’t hurricanes form over land and how do they differ from our most powerful thunderstorm, the supercell
How Do Hurricanes Develop?
Hurricanes generate energy from the warm waters near the tropics. Ideal water temperature to fuel a hurricane is roughly 80 degrees Fahrenheit. Hurricanes first start out as a disturbance (general thunderstorm) that moves across warm water sucking up more moisture. An area of low pressure develops under the single or cluster of storm(s). This area of low pressure starts to pull in more water vapor from the surrounding area. Rising water vapor produces more clouds and thunderstorms. When water vapor condenses to produce cloud droplets it releases latent heat, fueling further development of the storm. Once the rotating cluster of storms has reached sustained wind speeds of 74 mph it is now considered a hurricane.
What’s The Difference Between Hurricanes And Thunderstorms?
Hurricanes use warm water to continue to strengthen and rely on an environment that has little to no shear. Hurricanes die off when they travel over land and/or run into areas with high amounts of shear. Landmass not only lacks in the warm moist water that fuels the hurricane, but also produces friction near the surface that slows down the rotation within the tropical cyclone. Shear is a change in winds, both speed and direction with height. Hurricanes develop and strengthen vertically, keeping it a perfectly contain heat engine. Shear tilts the thunderstorms, disrupting the perfect heat cycle, causing the storm to weaken and eventually die.
Supercells are thunderstorms with deep rotating updrafts (mesocyclone) and are most likely to have all forms of severe weather including violent tornadoes. Supercells develop in an environment with high moisture, strong lift, large instability, and substantial shear. High amounts of moisture (dew points), especially in the lowest levels, makes it easier for thunderstorms to develop. Lift allows air in the lowest levels to overcome the environments Convective Inhibition (CIN). Instability, without it the atmosphere would not support deep convection. Shear, if you recall, causes for hurricanes to weaken but is a key factor in supercell development of supercells. Shear is what causes supercells to take on its rotational shape and also tilts the thunderstorms updraft, allowing for continued development of the strong updraft. Without this tilting mechanism, storms would simply explode up and then die off as cool rain would cut off further development.
Hurricanes don’t form over land because the main fuel system is warm moist water. Also, land will produce friction causing the hurricanes rotation to lose strength. Hurricanes also don’t thrive in areas with strong deep level shear. Shear disrupts the perfect heat engine, causing weakening and death to hurricanes.
Supercells and hurricanes differ in how they form, and how they respond to deep level shear. Hurricanes can’t thrive in environments with deep level shear were supercells rely on shear to help produce a strong updrafts and give them there rotation. Supercells require lift, instability, moisture and shear to generate when hurricanes just really need a disturbance and warm water to kick start there development.