by David Murphy
Yes. Air Mass Thunderstorms are small, weak, short-lived and usually occur during sultry summer afternoons and evenings. The storm is triggered by a small disturbance or ripple moving through an otherwise stagnant but humid atmosphere. The storms blossom, producing lightning and heavy rain over a relatively small area before dying out, usually within 30 minutes. They do not produce much wind. Aside from lightning, the biggest threat is flash flooding, mainly because the storm moves so slowly and has a chance to drench the areas it passes over.
A General Thunderstorm, or Garden Variety Thunderstorm is the most common. It forms in the general way, usually sparked by a cold front moving into a warm, humid air mass, along with any of several other forcing mechanisms (See What causes thunderstorms? and How do thunderstorms form? for more on forcing mechanisms). General thunderstorms can produce downpours, lightning, some degree of gusty winds and occasional hail. But the hail and winds do not approach the levels that usually cause much property damage. In our region, these storms generally have a life span of less than one hour.
A Severe Thunderstorm is the same as a General Thunderstorm, except that's it larger, stronger and produces winds and/or hail that are capable of doing damage. The hail is three-quarters of an inch in diameter or larger. The wind gusts are in the 50-to-60 mile-per-hour range or greater. Tornadoes sometimes occur within Severe Thunderstorms. These storms can last more than an hour.
A Supercell Thunderstorm is an especially large Severe Thunderstorm that takes on a very well defined kidney shape on radar screens. It's the most powerful type of thunderstorm---basically a storm engine---with a potential life span of many hours. The largest tornadoes on earth are spawned by Supercells---some with bases more than a mile wide.
