Types Of Weather.docx

Types of Weather 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.

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.

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.

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

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.

Weather type 6 - Hurricane

Weather type 7 - Lightning Lightning is simply a discharge of electricity in the atmosphere

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.

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.

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.

Weather type 11 - Sun 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.

Weather type 12 - Thunderstorm Thunderstorms are cumulonimbus clouds that produce thunder and lightning.

Weather type 13 - Tornado A tornado is a violently rotating column of air usually produced by severe thunderstorms.

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 im balance 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.