What causes the most powerful mid-latitude extratropical storms?
Extratropical storms storms that form outside the tropics are caused by the uneven heating of the Earth, with areas near the equator receiving much more solar energy than spots near the poles. Extratropical cyclones serve to diminish this imbalance by transporting heat and moisture toward the poles. The larger the contrast in temperature and moisture between the air masses, the more vigorous the resulting storm. Extratropical storms are the low-pressure systems typically depicted on daily weather maps. These differ from tropical cyclones, such as typhoons and hurricanes, in that they form away from the tropics. The center of the storm is colder than surrounding air, the storm has attendant warm and cold fronts and surface winds are typically less than winds higher in the atmosphere. For more about extratropical cyclones, check out this USA TODAY resource page.
