Jet streams are currents of fast moving air found in the upper levels of the atmosphere

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Daniel Pettite

Meteo 482

Primary Points:

  • Jet streams are currents of fast moving air found in the upper levels of the atmosphere.

  • Jet streams have two important roles. The first is they separate cold and warm air masses. For the U.S. the two Jet Streams that affect us are the Polar Jet Stream and the Subtropical Jet Stream. The Polar Jet separates the cold Arctic air from warmer air and the Subtropical Jet separates tropical air from the Equator from cooler air. The second role is that they transport weather systems eastward.

  • Jet streams form when there is a large, but tight gradient of pressure between cold and warm air masses that cause strong winds within that gradient.

  • They can reach thousands of miles around the world, a few hundred miles wide, and three miles thick.

  • Jet streams have a meandering shape and can stop, start, split up into two, or combine into one jet stream.

  • Meteorologists talk about the jet stream for it influences the motion of air masses and as a result, the motion of weather systems.


  • The Jet Stream was discovered in World War II by aviators flying across the Pacific.

  • Japan used the Jet Stream to carry balloons with bombs attached to them to bomb the U.S near the end of WWII.

  • The African Easterly Jet above West Africa helps in the formation of tropical cyclones in the Atlantic and eastern Pacific in the summer months.

  • Aviation uses the Jet Stream to cut travel time from west to east shorter.

Sound Bites:

  • Jet streams bring the bone chilling cold and the tropical warmth.

  • Jet streams are as windy as riverbeds.

  • Ride the jet stream, and you’ll go faster than anywhere else in the lower atmosphere.

Additional Links:

Primary Points:

  • Tornados are violently rotating columns of air that connects to the ground and a cumulonimbus cloud.

  • In order for tornadoes to form, you need warm moist air from the Gulf of Mexico and cold, dry air coming down from Canada. When these air masses meet, they form instability in the atmosphere.

  • Tornadoes can appear in many shapes and sizes. They start out as narrow funnels before growing in size to become wedge tornadoes. Their size can also determine their strength. Narrow, funnel tornadoes tend to be relatively weak and have a narrow path of destruction. On the other hand, wedge tornadoes can be strong tornadoes and as wide as a mile long.

  • In the early 1970’s, the Fujita Scale, or F-Scale, was developed by Dr. T. Theodore Fujita to estimate the wind speed of a tornado. Ranging from F0 the weakest to F5 the strongest, he connected damage done by a tornado to its wind speed. The scale would later be revised in the mid 2000’s with revised wind speeds and is now known as the Enhanced Fujita Scale.

  • As mentioned before, tornadoes form when moist air from the Gulf of Mexico and cold, dry air from Canada and the Rockies meet. The meeting place occurs in tornado alley far more than anywhere else on the planet. Now, that doesn’t mean that tornadoes solely exist in tornado alley as they can happen anywhere else in the United States and overseas if these kind of conditions are met.

  • Tornadoes and hurricanes are two completely different weather phenomena. Tornadoes can become the strongest weather on the planet but they are smaller and have a shorter life compared to hurricanes which are entire weather systems that can stretch for hundreds of miles and last far longer than tornadoes.

Trivia and Stories:

  • From the late 1800’s to the early 1900’s, the word “tornado” was banned from the U.S Army Signal Corps forecasts due to limitations of the observing network and fears of mass panic.

  • The widest tornado ever record was in El Rino, Oklahoma in May 31, 2013 where the tornado was a record 2.6 miles wide.

  • Tornadoes have other forms such as waterspouts, tornadoes that form over water, and gustnadoes which are rotating columns of air, but do not extend from cloud to ground.

Sound Bites:

  • Tornadoes can be as thin as ropes, or as wide as giant wedges.

  • The strength of a tornado can suck everything it destroys and turns debris into missiles. Basic
Primary Points:

  • Hurricanes are strong tropical cyclones. Tropical cyclones are non-frontal large scale low-pressure systems over tropical and sub-tropical systems with organized convection and definite cyclonic surface wind circulation.

  • Hurricanes begin their life as a tropical wave which are small disturbances in the tropical ocean. The tropical wave would then intensify, especially if it is over warm waters and grow into a tropical storm and further into a hurricane.

  • Storm surge is an abnormal rise of water that is generated by a storm and above astronomical tides.

  • Storm surge forms when strong winds from the hurricane push the water onto shore.

  • The most dangerous part of hurricanes is the storm surge and strong winds.

  • While hurricane accuracy for landfalls has greatly increased over the past fifty years, there is still a relatively large error.

  • On top of accuracy, the other challenges are time and intensity. While at times it is straight forward in predicting the intensity of a storm, there can be unforeseen factors such as intensity either increasing or decreasing in strength. In time, there is no certainty in the position a hurricane will take until it is too late. It will not be certain if a hurricane will make landfall until just a few hours before it does, or if it will even make landfall at all.

Trivia and Stories:

  • September is the most active month in the Atlantic Hurricane season.

  • Every second, a hurricane releases as much energy that is equivalent to the atomic explosion at Hiroshima.

  • The right side of a hurricane is where the strongest winds take place.

  • Hurricanes can spawn tornadoes.

  • While hurricane season officially starts from June 1st to November 31st in the Atlantic, tropical storms and hurricanes can occur at any time.

  • In 2005, tropical storm Zeta was the latest tropical storm to ever develop, forming on December 29th before dissipating in early January.

Sound Bites:

  • Hurricanes are cyclonic systems that form in a large pool of warm waters in the Atlantic basin.

  • You have to keep a constant eye on hurricanes for they can grow in a feeding pool of warm water.

Additional Links:

Radar/Doppler Radar

Primary Points:

  • Radar sends out a burst of energy and when it strikes something like a rain drop or snowflake, that energy is scattered in all directions. Some of that energy is directed back towards the radar.

  • Conventional radars measure precipitation through echoes and reflectivity.

  • Doppler Radars do what conventional radars do, but also detect wind speed and wind direction.

  • There are several ways to see a tornado is forming on radar. If rain or hail is tilting, radar can see the movement and structure of a storm in detail.

  • Since Doppler radar also detects the wind speed and direction, they look for any rotation inside of a thunderstorm.

  • Also, if debris is being lifted into the air by a tornado, the radar will detect it when the energy it sends out is reflected back.

  • When radar sends out its beam of energy towards precipitation and that energy is reflected back, it also measures the intensity of that reflected energy and estimate the projected rainfall.

  • Radar beams cannot be placed horizontally. They must be at an angle. If the beam is somehow deflected, it’ll end up reaching the ground and the radar would think that there is precipitation all around the radar dish. In reality, it is called ground clutter.

  • The difference between ground clutter and precipitation is that ground clutter doesn’t move and it is almost circular in shape.

  • If a cloud is too shallow, or in other words below the radar beam, then the radar might not detect it. This is true with lake effect snow events.


  • Radar was first used by the Air Force in World War II to detect fighters and bombers. When it was found out it could be used to detect weather systems, weather stations began using it for their forecasts.

  • There is a fleet of mobile radar dishes called Doppler on Wheels to examine tornadoes.

Sound Bites:

  • The radar sends energy out to tell if we have rain or snow and we are about to get dumped on.

  • If radar isn’t tilted at an angle above the horizon, people would mistaken mountains and buildings for rain.

Additional Links:

El Nino/La Nina

Primary Points:

  • An El Nino/La Nina is when there is a fluctuation of temperatures between ocean and atmosphere in the east-central Pacific, near the equator. El Nino is when the waters are above average and La Nina is when they are below average.

  • In the U.S, El Nino’s usually mean flooding rains in Peru and California, warmer than normal temperatures in western and northern U.S, and drier than normal conditions in the Ohio Valley and Pacific Northwest. They also cause fewer hurricanes than normal in the Atlantic and caused drought in places such as Africa and Australia.

  • In La Nina’s, they can cause above normal hurricanes, wetter than normal conditions in the Pacific Northwest, Australia, and Indonesia, drier than normal conditions in the southeast in the winter and the central plains in the fall.

  • No. El Nino and La Nina are not tied to global warming as it is an oceanic event and not atmospheric.


  • El Nino means little boy in Spanish and La Nina means little girl in Spanish.

  • El Nino’s and La Nina’s are irregular and they can occur every 2-7 years depending.

  • Since the 1970’s, there have been more El Nino’s than La Nina’s in the eastern Pacific.

Sound Bites:

  • El Nino keeps hurricanes away while La Nina develops hurricanes in droves.

  • El Nino is nothing more than a big puddle of warm water in the equatorial Pacific.

Additional Links:

Long Range Weather Prediction
Primary Points:

  • Long-range forecast models are done through numerical equations using computers. They compare normal conditions of the past to current weather events and conditions and make a prediction of the future.

  • Weather forecasts beyond eight days are not accurate in terms of precipitation and temperature and are more considered as outlooks and how they may compare in the future to normal conditions.

  • The earth’s atmosphere is complex and in better terms chaotic. There are many factors and it reacts in different ways. So while long-term forecasts in temperature and precipitation may seem like there is something to look forward to, it is far from perfect and the patterns can change on a weekly, or even daily basis.

  • Accuracy does depend on season as warmer temperatures in the summer are easier to predict that colder temperatures in the fall and winter months.

  • The Old Farmer’s Almanac predicts weather trends and events by comparing solar patterns and historical weather conditions with current solar activity. They emphasize temperature and precipitation deviations from average. But like long-range weather prediction, this Almanac also suffers from inaccuracy when making long-term forecasts.


  • The Old Farmer’s almanac first started back in 1792 with the “Farmer’s Almanac” started in 1818.

  • In 1922, Lewis Fry Richardson was the first meteorologist to create a long-range forecast using differential equations. It took him six weeks to complete.

Sound Bites:

  • Meteorologists may try and predict the future, but Mother Nature has other plans and cannot be predicted.

  • Long-range forecasts are crystal balls of what might happen, instead of what will happen.

Additional Links:

Meteorology Today, 8th Edition, Ahrens, Donald C.


Primary Points:

  • Thunderstorms need three things in order to create it: moisture, rising unstable air, and something to nudge that unstable air up.

  • If the air is forced upward due to mountains, or warm/cold and wet/dry air collide to cause rising motion, it will continue as long as the air weighs less than the air around it.

  • Thunderstorms form more in the spring/summer than in the fall/winter due to the land and air is being heated and warm/cold and wet/dry air masses colliding more frequently.

  • A severe thunderstorm is classified if it contains one of the following things: hail one inch or greater, winds gusting nearly 60 miles per hour, and/or a tornado.

  • Some occur at night due the heat rising from the ground and meeting up with cooler, condensing air once the sun goes down, causing instability.

  • Lightning starts as static charges in a rain cloud. It occurs when you have a negatively charged bottom and a positively charged top and when the strength is overcharged, lightning happens. This also happens on the ground as if you have a positively charged bottom and negatively charge cloud, you get cloud-to-ground lightning.

  • Lightning heats the atmosphere around it and it expands explosively, creating a shockwave as the air around is rapidly compressed.


  • Lightning has a temperature of over 50,000 degrees F, five times hotter than the surface of the sun.

  • There are 100 lightning strikes on the Earth per second.

  • Central Florida is considered to be Lightning Alley, as more lightning strikes happen here than anywhere else in the world.

  • Without thunderstorms, Earth would lose its electrical charge in less than one hour.

  • Cumulonimbus clouds are the tallest clouds in the atmosphere, with some of them reaching thousands of feet high in the atmosphere.

Sound Bites:

  • If your hair stands up during a thunderstorm, then lightning will zap you where you stand.

  • In the spring and summer, when cold and warm air met, thunderstorms will be brewing.

Additional Links:

Climate Change

Primary Points:

  • Greenhouse gases are gases that can absorb heat. Some of the more common greenhouse gases are carbon dioxide, water vapor, and methane.

  • The greenhouse effect is when infrared radiation that would have escaped into space is instead absorbed by greenhouse gases and as a result, heats up the planet.

  • What happens is infrared radiation emitted by the sun enters our planets atmosphere and some of that radiation is absorbed by the surface. The radiation that is not absorbed is either reflected by the ground or clouds back into space. However, some of that reflected radiation is absorbed by greenhouse gases.

  • Yes, the earth is warming. Since 1970, the earth has warmed by 0.5 degrees Celsius.

  • The evidence is the result of greenhouse emissions dating back since the time of the Industrial Revolution. As a result of the burning of fossil fuels (coal, oil, and natural gas), there are more carbon dioxide and methane in the atmosphere and with more of the greenhouse gases, the more heat that can be absorbed and heat the planet.

  • The ozone layer protects the planet from harmful ultraviolet radiation. When gases/chemicals such as Chlorofluorocarbons from aerosols are released into the atmosphere, they break down ozone and caused the ozone hole. Climate change may also contribute to the thinning of the ozone layer.

  • Climate predictions are simulations of future greenhouse emissions and temperature based on the current and past knowledge of the climate system.


  • The planet Venus is an example of a runaway greenhouse effect.

  • Since the late 1800’s, sea levels have risen by eight inches.

  • There is more carbon dioxide in the atmosphere than at any point in the last 800,000 years.

Sound Bites:

  • If Global warming heats the planet, then the sea will be in your backyard.

  • Fossil fuels add in more fuel to the engine that is the greenhouse effect.

Additional Links:

Winter Precipitation

Primary Points:

  • Snow forms up in clouds where the temperature is below freezing. The air near the surface may be 36 degrees F but if that layer of warmer air is not that deep, the snow will not have time to melt and will remain as snow.

  • With rain, if the air in the clouds is warmer and the air near the surface is cold at 26 degrees F but not that deep, then it’ll remain as rain or more likely be freezing rain.

  • Sleet and hail can easily be differentiated. Though they are both the same, small around balls of ice, sleet only occurs in the winter and at temperatures near freezing. Hail can come in an array of sizes from pea size to grapefruit size and occurs during thunderstorms.

  • Powdery snow is when snow falls but is typically not moist.

  • Sticky snow is when snow falls at temperatures at or just below freezing and contain lots of moisture in them.

  • Sleet is when snow melts into water droplets in the air when it descends due to a warm pocket of air but then, it reaches a pocket of cold air at or below freezing before reaching the ground and freezes into a small ice ball.

  • Freezing rain is the same when it either falls as snow that melts due to a warm pocket or rain and falls into a cold pocket of air before reaching the surface. However, in the case of freezing rain, the cold pocket of air is not as thick as it was as sleet and doesn’t turn into ice. Instead, when the droplet hits the ground, it freezes on contact.

  • If snow is near dark material surfaces such as asphalt and absorbs solar radiation from the sun, the dark materials will heat up, causing snow to melt nearby.


  • There are over 35 different types of snowflakes as they arrange in various sizes and forms.

  • The discovery of the one who found out that no two snowflakes were alike was Wilson Bentley in the late 1800’s in a small town in Vermont. He was not a meteorologist but a farmer.

  • About 10 inches of snow melts to about one inch of liquid water.

Sound Bites:

  • The temperature of the air can make wintery precipitation either a snowy wonderland or an icy glaze.

  • Sleet is nothing but pebbles while the size of hail will make you run for cover.

Additional Links:


Primary Points:

  • Folklore is based on observation and evidence. Some of it has merit.

  • The red sky in the morning saying is when lows and highs move around and the colors in sunlight are scattered due to dirty and clean air.

  • Low pressure is associated with bad weather hence sailor’s take warning and high pressure is associated with god weather, sailor’s delight.

  • A ring around the sun or moon means there are ice crystals in the high atmosphere and is a sign that moisture is descending to the lower levels of the atmosphere and produce precipitation. It is more reliable in the summer months than the winter months.

  • An example of bad folklore is tornadoes never happen in the mountains. Tornadoes can happen anywhere, including mountains and cities.

  • The saying March comes in like a lion and out like a lamb means that when March begins, it is winter and at the end of March, it is spring. The saying lion and lamb refers to the constellations Leo, the lion, and Aires, the lamb. Leo dominates the night sky during the beginning of March and Aires dominates at the end.


  • The rumor that lightning never strikes the same place twice is a false one as lightning can strike multiple times per second.

  • Groundhog Day, another folklore used to predict the remainder of the winter, started back in full swing on 1886 in Punxsutawney, Pennsylvania. Since then, it has been a tradition whether the groundhog will see his shadow and if we will have six more weeks of winter or not.

Sound Bites:

  • Phil the Groundhog can’t compete with today’s forecasts predictions.

  • Weather folklore are sayings that are grandmother’s would use to say.

Additional Links:

Lake Effect Snow/Rain

Primary Points:

  • Lake effect snow occurs when cold air meets a warm body of water below. The warm waters rises air up into the sky, condenses, and forms clouds and precipitation.

  • Lake effect rain occurs in a similar fashion only it is still warm enough to be rain rather than snow.

  • Single and multiple bands depend on the amount of body of water it travels over. Single bands form when they are over the center of a lake and tend to have more precipitation.

  • Multiple bands are when the distance from water to land is shorter. They tend to be bigger and wider but they have less energy and thus less precipitation.

  • If there is ice on the lake, the process to produce lake effect snow is disrupted. If the lake is frozen over, there is no warm water and the air cannot rise, resulting in no lake-effect snow.

  • Lake-effect rain is at its greatest chance in the autumn months when the air is beginning to cool and the lakes are warm, but the air is still warm enough to produce rain instead of snow.

  • Outside of the Great Lakes, lake-effect snow occurs at the Great Salt Lake in Utah, the North Sea to the United Kingdom, as well as the seas of the Baltic, Black, and Adriatic Seas in Europe and the Sea of Japan to Japan and Korea.


  • Since Lake Ontario is a deep lake, it takes the lake longer to freeze than the others and causes the New York area around Lake Ontario to get blasted with snow longer than anyone else along the Great Lakes.

  • Syracuse, New York is considered one of America’s snowiest cities as it is south of the Tug Hill Plateau, an area that sets daily records of snowfall in the United States.

  • Lake effect snow is greatest in areas east to southeast of the Great Lakes.

Sound Bites:

  • Lake effect snow likes to bury entire houses eighty to a hundred feet under.

  • The less of a lake or sea cold air uses to produce lake-effect, the less heartache people have to dig themselves out.

Additional Links:

Optical Phenomena
Primary Points:

  • Rainbow’s form when rain and sunlight combine. The sunlight enters the drops and separates into the colors we see in a rainbow.

  • Snow cannot produce a rainbow because snowflakes are ice crystals and lack the curved surfaces that are needed for refracting light that drops do.

  • Water on the road mirages occur when convection causes the temperature of the air to vary. The difference between the hot surfaces of the road to cooler, denser air above causes a gradient that creates a blurring, shimmering effect like water.

  • Mirages in general form when light rays from the sun causes a displaced image of distant objects.

  • Sun dogs, or phantom suns, are an atmospheric phenomenon that consists of a pair of bright spots on either side of the sun that concur with a large halo. They appear as suns to the left and right of the actual sun and are best scene and created when the sun is close to the horizon.

  • Halos are formed when sun or moonlight reflects and refracts through ice crystals high in the atmosphere.


  • The story “Ring around the son or moon means rain soon” is a true fact of science. The ice crystals that cause halos are usually from high cirrus clouds and cirrus clouds are usually in front of rain systems that are about to move through.

  • There are times when double rainbows occur, but when they do, the colors of the second rainbow are inverted with red at the bottom and purple on top. It also appears fainted than the other due to more light escaping and a larger rainbow area. .

Sound Bites:

  • When light refracts through droplets, it creates a dazzling display of colors in the sky.

  • The heat and sunlight that make mirages can make your eyes play tricks on you

Additional Links:

Heat Index/Apparent Temperature

Primary Points:

  • A heat index is simply put the discomfort felt as a result of the temperature and humidity.

  • Heat index is how the combination of heat and humidity affect the human body. A person that begins to sweat cannot have the sweat evaporate if humidity is high Evaporation is a cooling process and if sweat doesn’t evaporate, the body’s temperature will continue to rise and so will the discomfort.

  • The heat index is created as a precaution and/or warning to people exposed during hot days. There is a chart listing ranges for the heat index to warn people the possibility of what could happen at certain heat index temperatures of what could happen to their bodies. For instance, a heat index between 80 to 90 degrees F will cause fatigue with prolonged exposure and/or physical activity.

  • The heat index only focuses on temperature and humidity and does not incorporate other variables such as wind speed, cloud cover, and solar radiation.


  • The heat index values are meant for shady areas outside, not in direct sunlight.

  • The creator of the heat index was George Winterling who is considered one of the pioneers of television weather forecasting.

Sound Bites:

  • The heat index will make you feel as if your face is melting off.

  • The heat index will make you sweat buckets.

Additional Links:

Satellite Imagery
Primary Points:

  • The three basic types of satellite imagery are visible, infrared, and water vapor.

  • Weather satellites are installed with instruments to help create the images we see in forecasts. To do so, they either orbit the earth or are parked at a certain distance away and take images of the earth as a selected area of a whole section of the planet.

  • Visible imagery is created when solar radiation is reflected back by an object. It can also show if there is a pack of snow on the ground.

  • The shortcoming of visible imagery is that it can be used during the day as it needs solar radiation to paint the picture.

  • Infrared imagery is used to detect infrared radiation inside of clouds. Higher cloud tops means that it is colder and less radiation. White represents cold cloud tops, usually thunderstorms.

  • Infrared’s shortcoming is it has a hard time detecting low clouds as they and the ground are nearly the same temperature.

  • Water vapor is a special kind of infrared imagery to detect radiation coming off from moisture. Like infrared, the whiter it is, the more moisture it holds.

  • Water vapor imagery can only detect moisture up in the mid to upper altitudes. It cannot detect moisture lower near the surface.

  • Besides producing images, weather satellites have equipment that can determine vertical profiles of temperature and moisture. In other words, figuring out the temperature and moisture content is at certain levels at the atmosphere. While it is helpful to places that don’t send up weather balloons, it is not as accurate as weather balloons.


  • Standard infrared imagery is different from meteorological imagery. White is hot and black is cold in standard. In meteorology, white is cold and black is warm.

  • Verner Suomi is considered the father of satellite meteorology.

  • There are two kinds of metrological satellites, polar-orbiting and geostationary. Polar-orbiting satellites are 850 km away from the earth with geostationary satellites 36,000 km away from the planet.

  • The first weather satellite image was produced back in 1960.

Sound Bites:

  • With all three satellite imagery, the growing monstrous thunderstorms cannot hide.

  • By day, the world of weather is visible to us with the visible satellites imagery.

Additional Links:

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