Weather - easttennesseewildflowers.com...Hurricanes ¾Hurricanes form only over warm ocean water, usually between June and October. These monster storms can last 2 -3 weeks and grow

WeatherWeatherAll photos, graphics, and text copyright 2007All photos, graphics, and text copyright 2007

Kris LightKris Lighthttp://http://www.easttennesseewildflowers.comwww.easttennesseewildflowers.com//

Weather is a Weather is a ““Child of the Sun, Child of the Sun, Atmosphere, and WaterAtmosphere, and Water””

The 3 elements necessary to have weather on The 3 elements necessary to have weather on earth are:earth are:1. The warmth from the 1. The warmth from the sunsun to evaporate the to evaporate the waterwater2. The 2. The atmosphereatmosphere (the blanket of air around the (the blanket of air around the earth), where weather takes place (up to 9 miles earth), where weather takes place (up to 9 miles high)high)3. The 3. The waterwater in the lakes, oceans, and ice capsin the lakes, oceans, and ice capsAll of the planets in our solar system have All of the planets in our solar system have weather except Mercury (it doesnweather except Mercury (it doesn’’t have an t have an atmosphere). atmosphere).

The Water CycleThe Water CycleWhen the sun shines on the Earth it causes the water to When the sun shines on the Earth it causes the water to eevaporvaporateate (note the word "vapor") and go into the air. If (note the word "vapor") and go into the air. If the vapor rises high into the atmosphere, gets cold and the vapor rises high into the atmosphere, gets cold and then the molecules begin to stick together, then the molecules begin to stick together, condensationcondensationoccurs and clouds form. If the clouds become saturated occurs and clouds form. If the clouds become saturated and can no longer hold the moisture, and can no longer hold the moisture, precipitationprecipitation occurs occurs in the form of rain, snow, sleet, freezing rain, or hail. in the form of rain, snow, sleet, freezing rain, or hail. Condensation and precipitation occur on a glass with a Condensation and precipitation occur on a glass with a cold drink on a humid day, resulting in a water ring on cold drink on a humid day, resulting in a water ring on the table. There is a common misconception that the the table. There is a common misconception that the water gets on the side of the glass when the glass water gets on the side of the glass when the glass "sweats". I explain to my students that in order to sweat, "sweats". I explain to my students that in order to sweat, water has to come out of something, (like their armpits!) water has to come out of something, (like their armpits!) water water doesn'tdoesn't come out of the glass!come out of the glass!See diagram on following pageSee diagram on following page

The Water CycleThe Water Cycle

Surface water

Water MoleculesEvaporation

Condensation

Precipitation

CloudSun

Basic Cloud TypesBasic Cloud TypesCirrus

Cumulonimbus

CumulusCumulus

Stratus

Fog

Above 20,000 feet

6,500 – 23,000 Feet

Below 6,500 feet

Ground

Tornado

Cirrus CloudsCirrus CloudsCirrus Cirrus means means ““hair curlhair curl””, , these are also called these are also called ““maremare’’s tailss tails”” because of because of their long wispy their long wispy appearance. appearance. Cirrus clouds form in the Cirrus clouds form in the high atmosphere high atmosphere (>20,000 feet) where the (>20,000 feet) where the temperatures can be temperatures can be less thanless than--5050ººF, they are made up F, they are made up of tiny ice crystals. of tiny ice crystals. These clouds do not These clouds do not make rain or snow. They make rain or snow. They are often the precursors are often the precursors of approaching rain of approaching rain systems.systems. K. Light

What is a What is a ““SundogSundog””??

A A SundogSundog is an is an ““icebowicebow””, formed , formed when sunlight is when sunlight is refracted into the refracted into the spectrum by the spectrum by the ice crystals of ice crystals of cirrus clouds. cirrus clouds.

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Cumulus CloudsCumulus Clouds

Cumulus means means ““piled uppiled up””, these , these are midare mid--level level clouds (6,500 clouds (6,500 ––20,000 feet) made 20,000 feet) made up of water up of water droplets. There is droplets. There is not enough water not enough water in these clouds to in these clouds to make rain or make rain or snow.snow.

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Stratus CloudsStratus CloudsStratusStratus means means ““sheetsheet--likelike””. These clouds . These clouds are low, flat and are low, flat and widespread like the widespread like the sheets on a bed. sheets on a bed. These clouds can These clouds can cover entire states cover entire states and even regions of and even regions of the country! They are the country! They are between 50 between 50 –– 6,500 6,500 feet in altitude.feet in altitude.These clouds can These clouds can produce rain or snow. produce rain or snow.

Stratus clouds as seen from aboveK. Light

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FogFog FogFog is a groundis a ground--level level cloud (below 50 feet cloud (below 50 feet in altitude). It often in altitude). It often settles in low areas settles in low areas near water. Fog is near water. Fog is common near the common near the ocean.ocean.The small water The small water droplets can droplets can sometimes be seen sometimes be seen on a foggy night if on a foggy night if they are lit by a porch they are lit by a porch light. light.

Fog in the Grand Canyon

Fog on a mountain top

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Cumulonimbus CloudCumulonimbus Cloud

These These ““piledpiled--up rain cloudsup rain clouds”” can can tower to 60,000 feet. Cumulonimbus tower to 60,000 feet. Cumulonimbus clouds can produce thunderstorms clouds can produce thunderstorms with torrential rain, downburst winds, with torrential rain, downburst winds, lightning, hail, and even tornadoes. lightning, hail, and even tornadoes.

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Cumulonimbus cloudCumulonimbus cloudThunderstorms Thunderstorms are formed by are formed by cumulonimbus cumulonimbus clouds. It is often clouds. It is often possible to watch possible to watch these clouds these clouds billow and grow as billow and grow as the warm air rises the warm air rises within them. within them. These clouds can These clouds can be sheared off at be sheared off at the top by strong the top by strong upperupper--level winds, level winds, producing the producing the anvilanvil--head shape. head shape. Warm, humid air

Cold, dry air

Hailgrowsas it rises

UprisingWarm Air

SinkingCool Air

Tornadoes can form if the airbecomes unstableenough and beginsto spin within the cloud.

Up to 60,000 feet

“Anvil-head”-- NegativeCharges - -

+ Positive Charges ++

- NegativeCharges - -

+ Positive Charges ++

LightningLightning

Lightning is a powerful bolt of Lightning is a powerful bolt of static electricity. It is produced static electricity. It is produced within a cumulonimbus cloud within a cumulonimbus cloud when the electrons are stripped when the electrons are stripped from the water molecules as from the water molecules as they are buffeted around by they are buffeted around by rising and sinking air. The rising and sinking air. The negative and positive charges negative and positive charges attract each other, resulting in a attract each other, resulting in a visible flash. At 56,000visible flash. At 56,000ººF,F,Lightning is 5x hotter than the Lightning is 5x hotter than the surface of the sun. Seek shelter surface of the sun. Seek shelter in a car or sturdy building if you in a car or sturdy building if you see lightning or hear thunder, see lightning or hear thunder, never stand under a tree or in never stand under a tree or in an open field during a storm. an open field during a storm. Thunder occurs due to the Thunder occurs due to the sudden expansion of air when sudden expansion of air when the temperature changes the temperature changes immediately after a lightning immediately after a lightning strike.strike.

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This is why you should not stand This is why you should not stand under a tree during a thunderstorm!under a tree during a thunderstorm!

This oak tree was struck by lightning in September 1999.

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RedRed Skies Skies and and

HalosHalos

There is truth in the old weather poem,There is truth in the old weather poem,““Red sky at morning,Red sky at morning,Sailors take warning. Sailors take warning. Red sky at night, Red sky at night, Sailors delight.Sailors delight.””The red color comes from the low angle of the sunThe red color comes from the low angle of the sun’’s s

light and water vapor in the atmosphere from light and water vapor in the atmosphere from advancing or retreating weather systems. Red advancing or retreating weather systems. Red sunrises indicate coming rain or snow; red sunrises indicate coming rain or snow; red sunsets indicate the passing of a weather sunsets indicate the passing of a weather system. system.

A halo around the moon indicates an approaching A halo around the moon indicates an approaching rain or snow system.rain or snow system.

Red Sky at Morning

Red Sky at Night

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When a rain system When a rain system passes sometimes the passes sometimes the sun shines behind it. sun shines behind it. Sunlight passing Sunlight passing through raindrops can through raindrops can be refracted into the be refracted into the colors of the spectrum: colors of the spectrum: redred, , orangeorange, , yellowyellow, , greengreen, , blueblue, indigo and , indigo and violetviolet. An easy way to . An easy way to remember the order is: remember the order is: ROY G BIVROY G BIV sunlight

Raindrop

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Types of PrecipitationTypes of Precipitation

Rain Rain –– above 32above 32ººFFSnow Snow –– below below 3232ººFFSleet (Frozen raindrops) Sleet (Frozen raindrops) –– Starts out as rain in Starts out as rain in warmer air, then freezes in colder air layer warmer air, then freezes in colder air layer Freezing Rain (Ice Storm) Freezing Rain (Ice Storm) -- Starts out as rain in Starts out as rain in warmer air, then freezes in colder air layer near warmer air, then freezes in colder air layer near the groundthe groundHail Hail –– Forms only in thunderstorms, the stronger Forms only in thunderstorms, the stronger the storm, the larger the hailstonesthe storm, the larger the hailstones

Precipitation Precipitation DiagramDiagramWarm airWarm air >32ººFFCold airCold air < < 32ººFF

SnowflakesSnowflakes

Snowflakes always have Snowflakes always have 6 sides or points. 6 sides or points. Different kinds of Different kinds of snowflakes form in snowflakes form in different temperatures. different temperatures. These snowflakes are the These snowflakes are the dendritedendrite type, they form type, they form when the temperature in when the temperature in the clouds is between 3 the clouds is between 3 degrees and 10 degrees. degrees and 10 degrees. There are also There are also columnscolumns, , needlesneedles and and platesplates. .

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LL Air Pressure Systems Air Pressure Systems HHLow Pressure systems Low Pressure systems are made up of warm, are made up of warm, moist, rising air. moist, rising air.

They move in a counterThey move in a counter-- clockwise direction. clockwise direction. They are signified by aThey are signified by a ““LL”” on a weather map. on a weather map. Low pressure systems Low pressure systems can bring rain or snow. can bring rain or snow. The lower the pressure The lower the pressure reading, the stronger the reading, the stronger the storm system.storm system.

High Pressure systems are High Pressure systems are made up of cold, dry, made up of cold, dry, sinking air. sinking air.

They move in a clockwise They move in a clockwise direction. They are signified direction. They are signified on a weather map by a on a weather map by a ““HH””. . High pressure systems High pressure systems bring cooler, but dry bring cooler, but dry weather. Think: weather. Think: ““High, Dry High, Dry and Blue Skyand Blue Sky””..

WindWind

Wind is moving air Wind is moving air produced by produced by change in air change in air pressure, often pressure, often preceding a preceding a dramatic change in dramatic change in weather. weather.

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Storm SafetyStorm SafetyWhen a When a ““Storm / Tornado Storm / Tornado WatchWatch”” has been issued it has been issued it means the weather means the weather conditions are suitable for conditions are suitable for a severe storm or tornado a severe storm or tornado to occur. People should to occur. People should listen to the weather listen to the weather radio, TV or watch the radio, TV or watch the sky and be prepared to sky and be prepared to take cover. take cover.

When a When a ““Storm / Tornado Storm / Tornado WarningWarning”” has been issued by has been issued by the National Weather the National Weather Service, it means the storm Service, it means the storm or tornado is or tornado is occuringoccuring. . People in the affected area People in the affected area should take cover should take cover immediately in the lowest immediately in the lowest part of their building, part of their building, preferably away from preferably away from windows, crouching low next windows, crouching low next to an inside wall, covering to an inside wall, covering the neck and ears. the neck and ears.

TornadoesTornadoes

Tornadoes are shortTornadoes are short--lived, but lived, but violent cyclonic winds. These violent cyclonic winds. These storms can occur at any time of storms can occur at any time of the year, but usually in the spring, the year, but usually in the spring, summer and fall. Tornadoes summer and fall. Tornadoes almost always form over land, last almost always form over land, last less than 30 minutes, and are less than 30 minutes, and are usually not much larger than a usually not much larger than a mile wide at the base. Tornado mile wide at the base. Tornado winds are measured by the winds are measured by the Fujita Fujita ScaleScale from Ffrom F--1 to a devastating F1 to a devastating F--5. 5. Dust devilsDust devils are a type of are a type of ““minimini--tornadotornado””, the winds in one can , the winds in one can reach speeds up to 60 miles per reach speeds up to 60 miles per hour.hour.

A “dust devil” on a soda lake in southern California K. Light

HurricanesHurricanes

Hurricanes form only over warm Hurricanes form only over warm ocean water, usually between June ocean water, usually between June and October. These monster storms and October. These monster storms can last 2 can last 2 --3 weeks and grow to over 3 weeks and grow to over 300 miles across. When wind speed 300 miles across. When wind speed reaches 74 miles per hour, the storm reaches 74 miles per hour, the storm is considered a hurricane. The air is considered a hurricane. The air pressure drops dramatically during a pressure drops dramatically during a hurricane. hurricane. Much of the damage from a Much of the damage from a hurricane is not done by the wind, hurricane is not done by the wind, but the storm surge, a wall of sea but the storm surge, a wall of sea water pushed ahead of the storm. It water pushed ahead of the storm. It floods lowfloods low--lying areas of the coast, lying areas of the coast, washing away buildings and eroding washing away buildings and eroding shorelines. More people die from shorelines. More people die from flooding than being injured by flying flooding than being injured by flying debris or falling buildings. debris or falling buildings. The winds in a hurricane can reach The winds in a hurricane can reach over 160 miles per hour. Hurricanes over 160 miles per hour. Hurricanes are measured by the are measured by the SaffirSaffir--Simpson Simpson scale from Category 1 to a scale from Category 1 to a catastrophic Category 5. catastrophic Category 5.

Damage in Florida from Hurricane Ivan - 2005

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FollowFollow--up Questionsup Questions1. Name the three parts of the water cycle.1. Name the three parts of the water cycle.2. Name the basic cloud types. Which ones 2. Name the basic cloud types. Which ones produce rain or snow?produce rain or snow?3. How does freezing rain occur?3. How does freezing rain occur?4. What is the difference between a Low 4. What is the difference between a Low pressure system and a High system?pressure system and a High system?5. What is the difference between a 5. What is the difference between a ““watchwatch”” and and a a ““warningwarning”” in weather reporting?in weather reporting?6. Tell the differences between a tornado and a 6. Tell the differences between a tornado and a hurricane. hurricane.

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