Storms

Storm Types There are 5 types of storm: Thunderstorm Tornado Blizzard Snow/Ice Storm Hurricane (cyclone, typhoon)

Thunderstorm Thunderstorms form when warm, moist air rises into cold air. The warm air becomes cooler, which causes water vapor, to form small water droplets - a process called condensation. The cooled air drops lower in the atmosphere, warms and rises again. This circuit of rising and falling air is called a convection cell. If this happens a small amount, a cloud will form. If this happens with large amounts of air and moisture, a thunderstorm can form.

Thunderstorm Thunderstorms created by just one convection cell in the atmosphere are called single-cell storms. Most of these are small, lasting only about an hour, and are also called ordinary thunderstorms. These storms often form during summer and include towering cumulonimbus clouds that can grow 12 kilometers high in the atmosphere. Rain and lightning are common. Sometimes hail falls.

Thunderstorm Other severe thunderstorms are made from many convection cells. These are called multi-cell thunderstorms. Often the cells form a line called a squall line up to 600 miles (1000 km) long at a cold or warm front where warm air is pushed above cold air, higher in the atmosphere. Strong wind gusts often blow just ahead of the storm.

Tornadoes Tornadoes are violent storms that strike as a powerful rotating mixture of wind and thunderstorm clouds, extending from the cloud to the ground in a funnel shape. They are one of the most powerful and destructive atmospherically generated storms, and  are very common in the plain states and the south east Tornadoes occur most frequently in the spring, and are born out of supercell thunderstorms. A supercell storm is a thunderstorm characterized by powerful updrafts. Tornadoes can form over land or over water, sometimes they will form over land and move over a body of water. Tornadoes spinning over water are called waterspouts. Tornado Alley= Kansas and the Great Plains

Tornadoes: Fujita Scale

Blizzards Blizzards occur in very Low temperatures ( usually below 20˚F) 35mph winds with zero visibility These conditions go on for 3 hours or more Deadliest Blizzard - The 1972 blizzard in Iran lasted from February 3rd to 9th and killed approximately 4000 people. In southern Iran, there was as much as 28 feet of snow. There were no survivors from the towns of Kakkan, Kumar or Sheklab.

Snow/Ice Storm For a snowstorm to form, warm air must rise over cold air. It might seem illogical that warm air would have anything to do with making a snowstorm, but it does. When warm air and cold air are brought together, a front is formed and precipitation occurs. Winds pull cold air toward the equator from the poles and bring warm air toward the poles from the equator. Warm air can also rise to form clouds and blizzard snows as it flows up a mountainside. Snowstorms are one type of winter storm. Icy winter storms bring freezing rain or sleet as well as snow.

Hurricane/Cyclones Closed, circular motion system rotating in same direction as Earth Spiraling winds, rotate CCW (N. Hemi) and CW (S. Hemi) Occur in areas of low pressure

Cyclones: Three Types Extratropical: occur in mid latitudes; occur everyday and are the cyclones that drive most weather patterns that occur on Earth Subtropical: broad wind patterns; no weather fronts connected to center; lower temps for formation; form from extratropical cyclones Tropical Cyclones: associated with numerous thunderstorms, strong winds, heavy rain; center warmer than surroundings at any height in atmosphere

Hurricane Hurricanes form from disturbances in the atmosphere over warm, tropical ocean water. They die down when they move over land or if they move out of the tropics and into cooler latitudes. These storms are called hurricanes in the Atlantic and typhoons or tropical cyclones in other areas of the world. Because of the Coriolis effect, the storms rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. At the center of the rotating storm is a small area of calm weather and clear skies called the eye of the storm. Surrounding the calm of the eye are the most intense winds of the storm and thick clouds of the eyewall.

Hurricane Hurricanes grow when the storms travel over areas with warm ocean water, low winds outside the storm, and high levels of moisture in the atmosphere.

Hurricane Not all storms are the same. Large and strong storms cause much more damage than small storms. In the Atlantic and Eastern Pacific, the Saffir-Simpson Hurricane Scale is used to describe hurricanes by their wind speed. Storms with winds less than 74 m/hr. are known as tropical storms. And if the wind speeds are less than 40 m/hr, the storm is called a tropical depression.