Flooding Lake Allatoona, Georgia
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Weather


Clouds

Clouds - Marietta, GA - photo by Rich Johnson     Clouds, mesocyclone - Marietta, GA - photo Rich Johnson

Weather type 1 - Clouds

There are four basic types of clouds. High clouds, middle clouds, low clouds, and clouds with vertical developement. There are also clouds that don't fall into any of these groups. Low clouds are from the surface to about 6,500 feet and are usually composed of water droplets unless temperatures are several degrees below freezing. Clouds on the ground are called fog. Middle clouds range from about 6,500 feet to about 20,0000 feet. They are also mostly composted of water droplets unless temperatures are cold. High clouds are above 20,000 feet and are composed of ice crystals.

Click the link to get the whole story on clouds.



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Dust

Dust storm - courtesy of NOAA, George E. Marsh    Duststorm, KS - courtesy of NOAA

Weather type 2 - Dust Storm

Dust storms are created by winds moving across an arid region. Many times a strong dry cold front is the mechanism that creates the dust or sand storm. As strong winds move across an arid landscape, sand or dirt is picked up from the ground. Sometimes the lighter dust particles can be lifted up to 20,000 feet high into the atmosphere. A classic example of this is a sand and dust storm that develops over the Sahara desert. Easterly winds may carry the dust particles across the Atlantic ocean to the Caribbean Islands or Florida. Severe sand and dust storms can obscure visibility to zero and last for days. Picture courtesy of NOAA, George E. Marsh.


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Fog

Fog - Marietta, GA - photo - Rich Johnson    Fog - Golden  Gate Bridge, CA courtesy of NOAA

Weather type 3 - Fog

Fog is a stratus cloud on the ground. There are several types of fog. Advection fog is produced by a hortizontal motion of warm moist air over colder ground. An example of this would be a warm front moving across land with a recent snow or cold weather. Radiation fog is produced as heat from the earth surface is radiated back to space at night. A moist layer and nearly calm winds need to be present. Wind can mix in dryer air aloft, keeping the air below the saturation point. Steam fog forms when cold air moves over relatively warm water. This can be observed as wisps of "steam" rising from lakes, rivers or oceans when a cold air mass moves in. Upslope fog occurs as air is pushed up a mountainside and becomes saturated so that condensation occurs. Fog photographs courtesy of Rich Johnson and NOAA


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Freezing Rain / Ice

Freezing Rain - High Point, NJ Courtesy of Nick Stefano    Freezing Rain - High Point, NJ courtesy of Nick Stefano

Weather type 4 - Freezing Rain / Ice

Freezing rain - known as "ice" occurs when a thin layer of freezing or below freezing air exists near the earth's surface. Typically this occurs when snow falls into warmer air changing the precipitation into rain. If a very thin layer of freezing air is present near the ground the rain will freeze on objects such as power lines, trees, and cars. Ice accumulations begin to cause serious problems when the ice is 1/2" or greater on objects. Freezing rain pictures courtesy of Nick Stefano.


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Hail

Hail - Picture courtesy of NOAA / NSSL    Hail - Picture courtesy of Jim Reed

Weather type 5 - Hail

The exact processes that creates hail are still being studied. Traditionally, textbooks showed hailstones being formed as a water droplet was carried aloft with an updaft into subfreezing air and freezing. As the ice moved into a downdraft, more water coated the hailstone. The cycle continued with the hailstone continuing to grow with each ride up and down the updraft and downdraft.

More recent studies suggest that super cooled water droplets are carried aloft by strong updrafts in thunderstorms. A small ice particle forms and grows as "waves" of supercooled water droplets continue to bump into the ice particle. A new coat of ice grows with each cycle. The hailstone is kept aloft by the strong updraft. The stronger the updraft the greater the force to keep the heavier hailstones aloft. The hailstone eventually falls to the grown when the the weight is too great for it to remain aloft or when it gets pushed out of the updraft. Sometimes hailstones bump into each other while being bombarded with supercooler water droplets and stick together giving the hailstone a spiked appearance.

The largest known hailstone fell on June 23, 2003 in Aurora, Nebraska and had a diameter of seven inches and weighed almost one pound. The heaviest hailstone fell in Coffeeville, Kansas on September 3, 1970 and weighed 1.7 pounds. Hail is considered severe when the diameter reaches one inch or quarter size.

Hail photographs courtesy of NOAA and Jim Reed. jimreedphoto.com


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Hurricanes

Hurricane Ida - Picture courtesy of NOAA    Hail - Picture courtesy of NOAA

Weather type 6 - Hurricane

Check out our complete library on hurricanes on our hurricane school page. We also have hurricane tracking charts so that you can follow the path of hurricanes. Check out just about anything you want to know about hurricanes on the hurricane library tab at the top menu. Hurricane pictures courtesy of NOAA.




Lightning

Lightning - Picture courtesy of Jim Reed     Lightning - Norman, OK - Picture courtesy of NOAA

Weather type 7 - Lightning

Lightning is simply a discharge of electricity in the atmosphere. For a complete look at this interesting phenomenon check the facts about lightning page. Lightning photographs courtesy of Jim Reed jimreedphoto.com and NOAA.


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Rain

Rain - Venice Beach, Florida - photo Rich Johnson     Rainbow - Orlando, Florida - Picture Rich Johnson

Weather type 8 - Rain

Rain is precipitation in liquid form. Liquid precipitation can occur as mist, drizzle, or rain. Droplet size differentiates the type that it is classified. Mist is generally 50-500 microns in size. Drizzle is .5 to 2 millimeters in size and rain is 2 millimeters to 1 centimenter in size. Rain is formed when condensation of water vapor occurs condenses into water droplets.

Precipitation in the form of rain can be created in a number of different ways. First, two types of processes cause minute droplets to form rain drops. Collision coalescence is a process where tiny droplets gradually grow in size by bumping into each other and growing. This is mostly a warm cloud process where temperatures are above freezing. The second process is a cold cloud process where super cooled water droplets freeze on ice nuclei. These ice nuclei grow into ice crystals. The snowflakes fall and turn into rain drops as the temperatures go above freezing closet to the ground. This is the primary process that produces rainfall.

Lifting to produce rainfall occurs in a number of differnt ways. 1. A low pressure system and associated fronts 2. Mountains or higher terrain 3. Atmospheric convection


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Sleet

Sleet     Sleet -   Picture courtesy of NOAA

Weather type 9 - Sleet

Sleet is transparent frozen raindrops. Sleet or ice pellets are created when snow falls into air above freezing and melts into rain drops. If another below freezing layer below the warm air is of sufficient depth, the rain drops freeze into balls of ice or ice pellets. Any significant amount of sleet is farily rare. This is due to the fact that there needs to be just the right conditons to get a perfect layer of warm air in between the layers of cold air. There have been cases of storms producing several inches of sleet. A mix of snow and sleet and sleet and rain is more common. Sleet pictures courtesy of NOAA.


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Snow

Snow - Washington, D.C 2/2010. courtesy of Paul Kocin      Snow - Washington, D.C. 2/2010. courtesy of Paul Kocin

Weather type 10 - Snow

Snow is the accumulation of crystal snowflakes. Snowflakes are made as water ice crystalizes. The crystals may form in many different shapes dictated by the water content and temperature in the cloud as the snowflakes are forming. Snowflakes can take the shape of columns, dendrites, plates, needles and other six sided shapes. It is possible for it to snow several degrees above freezing if the air aloft is very cold and the above freezing layer is shallow near the ground.

The greatest 24 hour snowfall in North America was 76" Silver Lake, Colo. April 1415, 1921. The greatest amount of snow for one storm in North America was 189" at Mt. Shasta Ski Bowl, California, Feb. 1319, 1959. The one season snowfall record for North America was 1,140" at Mount Baker, Wash. 19981999. Snow pictures courtesy of winter weather expert Paul Kocin.


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Sun

Sunny skies - Hollywood, California - Photo Rich Johnson     Sunny skies - Hollywood, California - Photo Rich Johnson

Weather type 11 - Sunny


Sunny weather or clear skies is defined as less than 1/8 sky cloud cover. Mostly sunny skies is characterized by 1/8 - 2/8 sky cloud cover. Sunny skies many times are observed when a high pressure area is dominating the weather pattern. High pressure signifies a region of sinking air which tends to dry out the atmosphere resulting in less mositure to form clouds. Deserts are locations with sunny or mostly sunny skies due to high pressure systems influencing the weather pattern much of the year.


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Thunderstorms

Thunderstorm - Picture courtesy of Rich Johnson    Thunderstorm - Courtey of NOAA / NSSL

Weather type 12 - Thunderstorms

Thunderstorms are cumulonimbus clouds that produce thunder and lightning. Discover more about thunderstorms here. Thunderstorm photographs courtesy of NOAA / NSSL and Rich Johnson.


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Tornado

Tornado - Picture courtesy of Jim Reed    Tornado - Picture courtesy of Jim Reed

Weather type 13 - Tornado

A tornado is a violently rotating column of air usually produced by severe thunderstorms. For much more about tornadoes, check out our tornadoes page. Tornado photographs courtesy of Jim Reed. jimreedphoto.com


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Wind

Windy weather, Atlantic Beach, N.C.  photo Rich Johnson    Windy weather, Kingston, Jamaica - Picture courtesy Smh.com.au

Weather type 14 - Wind

Wind is air in motion in the atmosphere. Windy weather is caused by an imbalance of heating in the atmosphere. It can be caused from an imbalance from solar heating or a difference over a boundary such as a front. The uneven heating generates an unbalanced pressure field. Air from a high pressure area flows toward a region of low pressure to balance the pressure field. A wind vane points to the direction from where the wind is blowing from and an anemometer measures how fast the wind is blowing. The strongest surface wind gust was 253 mph on Australia's Barrow Island during Cyclone Olivia in 1996. The previous wind record was 231 mph set on top of Mount Washington, New Hampshire on April 12, 1934. Photographs courtesy of Rich Johnson and the Sydney Morning Herald.


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Tropical Weather / Hurricane Forecasts / Travel


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