Thunderstorm Types
Air-Mass Thunderstorms (Single Cell)
Tend to develop in warm, humid, almost tropical air masses away from a front.
Usually single celled or a weak multi-cell cluster (A cell is one particular updraft and downdraft)
Rarely severe
Scattered variety
The precipitation that creates the downdraft tends to cut off the warm, humid updraft and then the storm collapses on itself.
Cold gust front usually kicks up more warm, humid air and it creates a new thunderstorm cell. Usually creates a weak multi-cell cluster or a weak multi-cell line.
Rarely last longer than an hour. Usually last about 30 minutes.
Usually 2/3 of the way through the life cycle it will release rain and small hail.
Multi-Cell Cluster Thunderstorms
Most common type of thunderstorm
A group of cells moving as one unit
New cells form upwind or usually south, southwest, or west edge of storm.
Each cell lasts about 20 minutes.
Whole cluster may last for several hours.
Stronger than air-mass thunderstorms
Can produce heavy rainfall, downbursts, moderate-size hail, and occasional weak tornadoes.
Multi-Cell Line Thunderstorms
Commonly called squall line
A long line of thunderstorm cells with a continuous, well-developed gust front.
The cold gust front forces warm air into the updraft. Once the line gets to a dry or cold point it will die out.
Can produce golfball size hail, heavy rain, and maybe a weak tornado.
Prolific downburst producers
- A downburst may accelerate a portion of the storm ahead of the rest producing a bow echo or a large bow echo called a derecho.
Supercell Thunderstorms
Highly organized thunderstorm
Rare
One main updraft that is estimated at 150-175mph.
One characteristic is the element of rotation, which produces mesocyclones.
The mesocyclone helps produce extreme severe weather: giant hail (sometimes more than 2 inches in diameter), strong downbursts, torrential rain, and strong to violent tornadoes.
Conditions needed are high instability, strong mid and upper level winds, and veering or helical flow.
Microbursts
Just as damaging as tornadoes
A downburst less than 2.5 miles across
Capable of blowing down trees and inflicting heavy damage on structures
Produce high gusts up to 100mph.