Weather 101Weather 101

Or Or All the answers you need when All the answers you need when

students ask questions about the students ask questions about the WeatherWeather

Why do they call the study of Why do they call the study of weather meteorology?weather meteorology?

To the ancient Greeks a To the ancient Greeks a meteor was any object meteor was any object that appeared in the sky that appeared in the sky including rain, clouds including rain, clouds and rainbows. and rainbows.

Aristotle explained all in Aristotle explained all in his his MeteorologicaMeteorologica. . Accordingly, “hurricanes Accordingly, “hurricanes are caused by evil winds are caused by evil winds falling on good winds falling on good winds causing a moral causing a moral conflict.”conflict.”

What is the difference What is the difference between Weather and between Weather and

Climate?Climate?

You can’t weather a tree but You can’t weather a tree but you can climateyou can climate

Seriously!Seriously! ClimateClimate comes from the Greek word Klima comes from the Greek word Klima

which relates to the elevation of the sun which relates to the elevation of the sun above the horizon and refers to weather over above the horizon and refers to weather over a long period of time at one place or over a a long period of time at one place or over a region.region.

WeatherWeather is what’s happening in our is what’s happening in our atmosphere right now and includes wind, atmosphere right now and includes wind, temperature, humidity, air pressure, temperature, humidity, air pressure, precipitation and cloud cover.precipitation and cloud cover.

What is the cause of weather?What is the cause of weather?

The sun’s energy sets our atmosphere in The sun’s energy sets our atmosphere in motion.motion.

The unequal heating of the earth causes a The unequal heating of the earth causes a tremendous amount of energy to be tremendous amount of energy to be exchanged between the equator and the exchanged between the equator and the poles. poles.

The greatest exchange of energy takes The greatest exchange of energy takes place at around 45 degrees latitude. place at around 45 degrees latitude.

In the U.S., tornados, floods, hurricanes, In the U.S., tornados, floods, hurricanes, snowstorms, and hailstorms are all part of snowstorms, and hailstorms are all part of our normal weather patterns. our normal weather patterns.

Where does weather happen?Where does weather happen?

The atmosphere is made of air. The atmosphere is made of air. What is Air?What is Air?

78% Nitrogen, N278% Nitrogen, N2

21% Oxygen, O221% Oxygen, O2

~1% Water Vapor, H2O~1% Water Vapor, H2O

.03% Carbon Dioxide, CO2.03% Carbon Dioxide, CO2

What is air pressure?What is air pressure?

The pressure exerted in every direction by The pressure exerted in every direction by earth’s atmosphere.earth’s atmosphere. The volume of the troposphere, which contains The volume of the troposphere, which contains

most of the atmosphere’s mass, as well as it’s most of the atmosphere’s mass, as well as it’s weather, is about 5 trillion billion cubic yards. weather, is about 5 trillion billion cubic yards.

1 cubic yard of air at sea level weighs over 2 1 cubic yard of air at sea level weighs over 2 pounds.pounds.

The atmosphere weighs about 5.1 million billion The atmosphere weighs about 5.1 million billion tons.tons.

Why do you feel tired at the end Why do you feel tired at the end of a long day?of a long day?

There are 14.7 lbs of atmosphere pressing on There are 14.7 lbs of atmosphere pressing on every square inch of your body.every square inch of your body.

This is equal to about 1 ton of pressure on every This is equal to about 1 ton of pressure on every square foot of your body resulting in 10-20 tons of square foot of your body resulting in 10-20 tons of pressure on the average adult.pressure on the average adult.

How do we measure atmospheric How do we measure atmospheric pressure? pressure?

A mercury barometer A mercury barometer measures the pressure measures the pressure exerted by the mass of the exerted by the mass of the atmosphere.atmosphere.

Invented by Evangelista Invented by Evangelista Torricelli in 1644.Torricelli in 1644.

Mercury tube, plugged at one Mercury tube, plugged at one end, filled with mercury and end, filled with mercury and placed upright with the open placed upright with the open end in a container of more end in a container of more mercury. mercury.

At sea level the mercury will At sea level the mercury will rise to about 30 inches.rise to about 30 inches.

What is an aneroid barometer?What is an aneroid barometer? Aneroid (without air) Aneroid (without air)

barometer is a metal barometer is a metal chamber that expands chamber that expands and contracts as the and contracts as the outside pressure outside pressure fluctuates. fluctuates.

This drives a series of This drives a series of levers that produce a levers that produce a reading of pressure reading of pressure that is calibrated as if it that is calibrated as if it were reading a column were reading a column of mercury.of mercury.

What is a millibar?What is a millibar?

Bar – from the Greek Bar – from the Greek meaning weight, a unit meaning weight, a unit of pressure.of pressure.

Millibar =One Millibar =One thousandth of a bar.thousandth of a bar.

About .03 inches of About .03 inches of mercury = 1 millibarmercury = 1 millibar

Average pressure at Average pressure at sea level is 1013.25 sea level is 1013.25 millibarsmillibars

Interesting factsInteresting facts

The lowest air pressure ever measured at The lowest air pressure ever measured at sea level was 25.63 inches, in the eye of sea level was 25.63 inches, in the eye of Typhoon Tip, east of the Philippines in Typhoon Tip, east of the Philippines in October 1979.October 1979.

The highest barometer reading was 32.01 The highest barometer reading was 32.01 inches taken New Year’s Eve, 1968, in inches taken New Year’s Eve, 1968, in Siberia.Siberia.

Why is the sky blue?Why is the sky blue? As light moves through the As light moves through the

atmosphere most of the atmosphere most of the longer wavelengths (red, longer wavelengths (red, orange and yellows) pass orange and yellows) pass straight through.straight through.

The shorter blue The shorter blue wavelengths are absorbed wavelengths are absorbed by gas molecules in the air. by gas molecules in the air. Then radiated out and Then radiated out and scattered all over the sky. scattered all over the sky.

Since you see the blue light Since you see the blue light from everywhere overhead from everywhere overhead the sky looks blue.the sky looks blue.

What is humidity?What is humidity?

Absolute HumidityAbsolute Humidity – Is the mass of water – Is the mass of water in a given volume of air. in a given volume of air.

If air contains 2g/m3 H2O = 1 cubic meter of If air contains 2g/m3 H2O = 1 cubic meter of air contains 2 grams of water.air contains 2 grams of water.

Relative HumidityRelative Humidity – Is the ratio of water – Is the ratio of water vapor in the air to the total amount of water vapor in the air to the total amount of water that the air can hold.that the air can hold.

Temperature is the degree of Temperature is the degree of hotness or coldness that can hotness or coldness that can

be measured with a be measured with a thermometer.thermometer.

What instrument can What instrument can you use to measure you use to measure

temperature?temperature?

By counting the number of chirps in 15 seconds By counting the number of chirps in 15 seconds and adding 40 you can get a good estimate of the and adding 40 you can get a good estimate of the temperature in degrees Fahrenheit. temperature in degrees Fahrenheit.

Celsius & FahrenheitCelsius & Fahrenheit

Celsius – In 1948 the Celsius – In 1948 the conference of weights and conference of weights and measures decreed the measures decreed the centigrade scale would be centigrade scale would be thereafter called the thereafter called the Celsius scale after Anders Celsius scale after Anders Celsius the inventor.Celsius the inventor.

Based on the freezing and Based on the freezing and boiling point of water.boiling point of water.

Fahrenheit – Invented in Fahrenheit – Invented in 1724 by Gabriel 1724 by Gabriel Fahrenheit.Fahrenheit.

Based on a cold day in Based on a cold day in Poland and his own body Poland and his own body temperature.temperature.

Which way is the wind blowing?Which way is the wind blowing?

Wind is the movement of air and is caused by Wind is the movement of air and is caused by differences in air pressure. differences in air pressure.

When the National Weather Service reports a When the National Weather Service reports a westerly wind, that means that the air is moving westerly wind, that means that the air is moving from…from… West to East!West to East!

The arrow on a wind vane points toward the The arrow on a wind vane points toward the direction from which the wind is blowing.direction from which the wind is blowing.

Wind speed is usually measured in miles per hour Wind speed is usually measured in miles per hour unless you are in the National Weather Service unless you are in the National Weather Service where knots are used. One knot = 1.15 mph. where knots are used. One knot = 1.15 mph.

Who is Bernoulli and what is his Who is Bernoulli and what is his principle?principle?

Dutch mathematician born in 1700.Dutch mathematician born in 1700.

As the speed of a fluid (liquid or gas) As the speed of a fluid (liquid or gas) increases, the pressure within the fluid increases, the pressure within the fluid decreases.decreases.

In the study of meteorology, it is important to In the study of meteorology, it is important to understand that wind creates areas of low understand that wind creates areas of low pressure.pressure.

Is moist air heavier than dry air?Is moist air heavier than dry air?Why?Why?

Dry air is heavier.Dry air is heavier.

Because lighter HBecause lighter H22O molecules push O molecules push aside the heavier Naside the heavier N22 and O and O22 molecules molecules that comprise the major components of air.that comprise the major components of air.

Atomic weight of N=14, H=1, O=16.Atomic weight of N=14, H=1, O=16.

HH22O – 18, NO – 18, N22 – 28, O – 28, O22 – 32. – 32.

What are clouds?What are clouds?

A large collection of very tiny droplets of water or ice crystals. The A large collection of very tiny droplets of water or ice crystals. The droplets are so tiny that they can float in the air.droplets are so tiny that they can float in the air.

Clouds form at different altitudes up to about 65,000 feet.Clouds form at different altitudes up to about 65,000 feet.

Cumulonimbus are the tallest clouds and extend from a base at Cumulonimbus are the tallest clouds and extend from a base at about 3,000 feet to the stratosphere at 65,000 feet about 3,000 feet to the stratosphere at 65,000 feet

A cloud on the ground is called fog.A cloud on the ground is called fog.

What happens What happens when the fog when the fog

lifts in lifts in California?California?

How do clouds form?How do clouds form?

Air near the earth’s surface contains water in an Air near the earth’s surface contains water in an invisible form called water vapor.invisible form called water vapor.

When warm air rises it expands and cools.When warm air rises it expands and cools.

In cool air condensation exceeds evaporation In cool air condensation exceeds evaporation so that many of the water droplets condense so that many of the water droplets condense onto tiny particles of dust and salt called onto tiny particles of dust and salt called condensation nuclei.condensation nuclei.

When billions of these particles come together When billions of these particles come together they form a visible cloud. they form a visible cloud.

What is a rainbow?What is a rainbow?

The rainbow effect can be seen whenever there The rainbow effect can be seen whenever there are water drops in the air and sunlight is are water drops in the air and sunlight is shinning from behind the observer at a low shinning from behind the observer at a low elevation.elevation.

White light entering a raindrop is White light entering a raindrop is separated into different colors because separated into different colors because each color (wavelength) is refracted at a each color (wavelength) is refracted at a

different angle.different angle.

What is a storm?What is a storm?

Storms are violent disturbances in the Storms are violent disturbances in the atmosphere often accompanied by strong atmosphere often accompanied by strong winds and precipitation. winds and precipitation.

Monster storms create Monster storms create ExtremeExtreme conditions conditions of wind, and precipitation and include of wind, and precipitation and include hurricanes and tornados.hurricanes and tornados.

What is Lightning?What is Lightning?

A bright flash of electrical A bright flash of electrical energy produced by energy produced by thunderstorms.thunderstorms.

The air in a lightning bolt The air in a lightning bolt is estimated at 54,000 F, is estimated at 54,000 F, 6x hotter than the sun’s 6x hotter than the sun’s surface.surface.

A lightning bolt is only 1 A lightning bolt is only 1 inch wide and releases inch wide and releases 100 million volts of 100 million volts of electricity.electricity.

What causes lightning?What causes lightning?

Movement of Ice and Movement of Ice and rain in the cloud rain in the cloud produce separation of produce separation of positively (upper) and positively (upper) and negatively charged negatively charged particles (lower).particles (lower).

Negative charges on Negative charges on the ground are the ground are pushed away leaving pushed away leaving a positive charge on a positive charge on the ground.the ground.

Opposite charges attract so Opposite charges attract so the negative and positive the negative and positive charges are drawn to one charges are drawn to one another.another.

Since the negative charges, Since the negative charges, electrons, are thousands of electrons, are thousands of times smaller than the times smaller than the positive charges, ions or positive charges, ions or charged atoms, they move charged atoms, they move

more easily and cover more more easily and cover more distance. distance.

This first invisible stroke is This first invisible stroke is called a stepped ladder. called a stepped ladder.

As soon as the negative As soon as the negative and positive paths and positive paths connect there is a connect there is a conductive path from the conductive path from the cloud to the ground. This cloud to the ground. This is called a leader.is called a leader.

Once the path is created Once the path is created there is flash of visible there is flash of visible light as positive charges light as positive charges rush upwards. rush upwards.

This is called the return This is called the return stroke.stroke.

Does lightning ever strike twice?Does lightning ever strike twice? Nearly every bolt of lightning Nearly every bolt of lightning

strikes several times in the strikes several times in the same place.same place.

Each flash we see is really a Each flash we see is really a series of leader and return series of leader and return strokes which happens so strokes which happens so fast that it appears to flicker.fast that it appears to flicker.

The Empire State Building is The Empire State Building is struck an average of 24 struck an average of 24 times a year.times a year.

What causes thunder?What causes thunder?

Thunder is caused by Thunder is caused by lightninglightning

A result of rapidly A result of rapidly expanding gases expanding gases along the heated along the heated lightning channel.lightning channel.

How can you tell how far away a How can you tell how far away a thunderstorm is?thunderstorm is?

Count the number of seconds between when Count the number of seconds between when you see a flash of lightning and when you hear you see a flash of lightning and when you hear the thunder.the thunder.

Divide the number of seconds by 5 and this will Divide the number of seconds by 5 and this will tell you how far away the storm is in miles. tell you how far away the storm is in miles.

For example…. You see a lightning flash and For example…. You see a lightning flash and count 15 sec. before you hear the thunder. count 15 sec. before you hear the thunder. Divide 15 by 5 and the storm is approx. 3 miles Divide 15 by 5 and the storm is approx. 3 miles away.away.

Are there different types of Are there different types of lightning?lightning?

Sheet LightningSheet Lightning – cloud to cloud – cloud to cloud Heat LightningHeat Lightning – On a hot night when the sky is – On a hot night when the sky is

clear overhead a flashes of light from a distant clear overhead a flashes of light from a distant thunderstorm.thunderstorm.

Ball LightningBall Lightning – Luminous sphere that moves – Luminous sphere that moves and floats around. This type has never been and floats around. This type has never been explained.explained.

St. Elmo’s FireSt. Elmo’s Fire – Bluish glow on ship’s masts, – Bluish glow on ship’s masts, power poles, chimneys etc. Caused by build up of power poles, chimneys etc. Caused by build up of electrical charges under a thunderstorm. Named electrical charges under a thunderstorm. Named after the patron Saint of sailors.after the patron Saint of sailors.

What are Foo Fighters?What are Foo Fighters?

The name given to The name given to spherical, elliptical, or spherical, elliptical, or wedge shaped bogies wedge shaped bogies seeming to glow or shine seeming to glow or shine and witnessed mostly by and witnessed mostly by WWII pilots & flight crews.WWII pilots & flight crews.

From Smoky Stover From Smoky Stover cartoon, “where there’s foo cartoon, “where there’s foo there’s fire”.there’s fire”.

The military decided that it The military decided that it was a form of ball lightning.was a form of ball lightning.

Lightning FactsLightning Facts People don’t realize that they can be struck by lightning when People don’t realize that they can be struck by lightning when

the storm center is 10 miles away and there are blue skies the storm center is 10 miles away and there are blue skies overhead.overhead.

Lightning kills or injures more people each year than hurricanes Lightning kills or injures more people each year than hurricanes or tornadoes. Between 300-400. or tornadoes. Between 300-400.

Talking on the telephone is the leading cause of lightning injury.Talking on the telephone is the leading cause of lightning injury.

A ranger at a National Park was struck seven times by lightning.A ranger at a National Park was struck seven times by lightning.

People struck by lightning do not carry an electric charge.People struck by lightning do not carry an electric charge.

The chance of being hit by lightning is 1:28,500The chance of being hit by lightning is 1:28,500

Earth is struck by 100 lightning bolts/secondEarth is struck by 100 lightning bolts/second

What is a Blizzard?What is a Blizzard?

A snow or ice storm where the visibility is reduced A snow or ice storm where the visibility is reduced to ¼ mile or less, the wind velocity is 35mph or to ¼ mile or less, the wind velocity is 35mph or more, and it must last for more than 3 hours.more, and it must last for more than 3 hours.

What is a Tornado?What is a Tornado?

A violently spinning A violently spinning column of air extending column of air extending from a thunderstorm and from a thunderstorm and in contact with the in contact with the groundground

The most severe can The most severe can have winds up to have winds up to 300mph.300mph.

About 1,000 occur every About 1,000 occur every year in the U.S.year in the U.S.

How do tornados form?How do tornados form? Usually form inside spinning Usually form inside spinning

thunderstorms called thunderstorms called supercells.supercells.

When cold dry air meets warm When cold dry air meets warm moist air updrafts and moist air updrafts and downdrafts inside the downdrafts inside the thunderhead are formed. thunderhead are formed.

These columns of rapidly These columns of rapidly moving air interact with each moving air interact with each other and shearing winds and other and shearing winds and begin to spin.begin to spin.

The area of low pressure The area of low pressure created sucks in more wind created sucks in more wind and debris turning the funnel and debris turning the funnel blackblack

What is the Fujita Scale?What is the Fujita Scale?

Scientists Scientists classify classify tornadoes by tornadoes by wind speedwind speed and the and the damagedamage they they cause using cause using the Fujita the Fujita ScaleScale

Where is tornado alley and what is Where is tornado alley and what is a dry line?a dry line?

Warm, moist air masses moving north from the Gulf of Warm, moist air masses moving north from the Gulf of Mexico collide with dry air moving east from the Rocky Mexico collide with dry air moving east from the Rocky Mountains forming a boundary called the Mountains forming a boundary called the dry line.dry line.

Converging winds and surface heating can cause warm, Converging winds and surface heating can cause warm, moist air to rise rapidly along the dry line. Thunderstorms moist air to rise rapidly along the dry line. Thunderstorms then develop that develop into tornados.then develop that develop into tornados.

Are there ever tornadoes on Are there ever tornadoes on Long Island?Long Island?

On Aug. 12, 2005 an F1 tornado ripped On Aug. 12, 2005 an F1 tornado ripped through Glen Cove destroying four homes through Glen Cove destroying four homes and uprooting trees. Winds were clocked and uprooting trees. Winds were clocked at 112 mph and the path of damage was at 112 mph and the path of damage was about 2 miles.about 2 miles.

In 1998 a Tornado touched down in In 1998 a Tornado touched down in Lynbrook and in 1989 an F2 storm with Lynbrook and in 1989 an F2 storm with 2.5” hail stones pelted South Moriches.2.5” hail stones pelted South Moriches.

Tornado FactsTornado Facts

Most move at 12-15 mph but some have been Most move at 12-15 mph but some have been timed at 70mph.timed at 70mph.

Usually tornadoes don’t last more than an Usually tornadoes don’t last more than an hour, most are less, but some have lasted for hour, most are less, but some have lasted for several hours.several hours.

The avg. tornado carves a path of destruction The avg. tornado carves a path of destruction 1,000 ft. wide and up to 16 miles long.1,000 ft. wide and up to 16 miles long.

How do hurricanes form?How do hurricanes form? Hurricanes only form over Hurricanes only form over

very warm ocean water of 80 very warm ocean water of 80 degrees or more. degrees or more.

Warm moist air rises and Warm moist air rises and cools off quickly giving off heat cools off quickly giving off heat and lowering the pressure.and lowering the pressure.

The lower pressure forces The lower pressure forces more air to converge and rise more air to converge and rise in a growing intensity. in a growing intensity.

Winds flow outward above the Winds flow outward above the storm allowing more air to rise storm allowing more air to rise

What has an eye but cannot see?What has an eye but cannot see? TheThe eyeeye is located at is located at

the center of the the center of the hurricane and is hurricane and is characterized by few characterized by few clouds, the lowest clouds, the lowest storm pressure and storm pressure and calm weather.calm weather.

It can be 10-40 miles It can be 10-40 miles in diameter. in diameter.

The more violent the The more violent the storm, the smaller the storm, the smaller the eye.eye.

The The eyewalleyewall is a region is a region of strong winds, heavy of strong winds, heavy rain and tall clouds rain and tall clouds surrounding the eye.surrounding the eye.

Clouds in the eyewall Clouds in the eyewall can be 10 miles high.can be 10 miles high.

It is the most destructive It is the most destructive part of the Hurricane.part of the Hurricane.

Hurricane circulation Hurricane circulation covers 300 – 700 milescovers 300 – 700 miles

When is a hurricane not a When is a hurricane not a hurricane?hurricane?

What is the Saffir-Simpson Scale?What is the Saffir-Simpson Scale?

What is the difference What is the difference between a tropical depression between a tropical depression

and a tropical storm?and a tropical storm?

A tropical depression is a storm with winds A tropical depression is a storm with winds under 39 mph.under 39 mph.

A tropical storm has winds between 39 A tropical storm has winds between 39 and 73 mph. When winds reach 74 mph and 73 mph. When winds reach 74 mph the storm becomes a Hurricane.the storm becomes a Hurricane.

What is the difference between a What is the difference between a hurricane watch and a hurricane hurricane watch and a hurricane

warning?warning?

A hurricane watch is issued when A hurricane watch is issued when hurricane conditions are possible within hurricane conditions are possible within the next 36 hours.the next 36 hours.

A hurricane warning is issued when A hurricane warning is issued when hurricane conditions are expected within hurricane conditions are expected within 24 hours.24 hours.

What were the worst Hurricanes What were the worst Hurricanes to hit our area?to hit our area?

1893 – A category 2 hurricane made landfall at the 1893 – A category 2 hurricane made landfall at the marsh where JFK airport now exists. It was marsh where JFK airport now exists. It was accompanied by 30 ft storm surges that destroyed accompanied by 30 ft storm surges that destroyed everything in its path including Hog Island.everything in its path including Hog Island.

1938 – Long Island Express, 183 mph winds 1938 – Long Island Express, 183 mph winds making it a category 5 hurricane.making it a category 5 hurricane.

1954 – Hurricane Carol was a Category 3 which hit 1954 – Hurricane Carol was a Category 3 which hit the Eastern tip of L.I.the Eastern tip of L.I.

1985 – Hurricane Gloria was a category 2 storm 1985 – Hurricane Gloria was a category 2 storm that most people believed was bigger.that most people believed was bigger.

““Some people are weather Some people are weather wise and some people are wise and some people are

otherwise!”otherwise!”

• Ben FranklinBen Franklin