WIND CHILL
Primary points
Wind chill is the measure of how cold the air feels on exposed skin.
In 1945, explorers Charles Passel and Paul Siple placed a cylinder of water in varying temperatures
The experiment simulated how wind and temperature affected the human body and how fast it froze
Passel and Siple established a formula that was used until 2001
In 2001 the NWS reengineered the formula to include walking against the wind and air temperature at
face level
New formula also used research data from actual skin properties
It is useful for determining how long it takes for frostbite to affect the skin
Shortcomings: Wind chill does not take into aspect cloud cover and sunlight
Shortcomings: Many people confuse the wind chill with normal temperatures
Trivia and Stories
Siple was raised in Erie, PA and attended Allegheny College
Siple was a sea scout and eagle scout
Siple the original science geek opposed using wind chill as it didn’t have good units
Only country other than America that uses the new formula is Canada
Sound Bites
Wind chill complicates the already hard task of “forecasting for the masses”
Wind chill experiments offered test subjects to “freeze their faces off for funds”
Wind chill “further complicates the fun world of forecasting”
Sources of additional info
http://www.nws.noaa.gov/om/windchill/images/wind-chill-brochure.pdf
http://www.weather.gov/os/windchill/index.shtml
Jet Stream
Primary Points
The jet stream is a narrow area of strong west to east wind aloft typically in the tropopause
The jet stream is the primary component that drives storm systems over land
It forms mainly due to the rotation of the Earth and atmospheric heating
Forms between air masses with varying temperatures because the atmosphere tries to compensate for
the gradient and the wind is propelled by the Coriolis Effect
The altitude varies with the strength of the stream, varying from 7-16 km AGL
Influences the path of storms systems so is important to weather prediction
Trivia and Stories
Travelling within the jet stream while flying can cut travel times by 1/3
Transversely travelling against the jet stream can almost double travel time
During WWII Japan used the jet stream to send cheap fire balloons as weapons from Japan to America
Scientists are attempting to harness the power of the jet stream for an alternative energy source
Sound Bites
The jet stream could get you “around the world in 5 days”
The jet stream might “drive us into a new age of alternative energy”
Sources of additional info
www.srh.noaa.gov/jetstream/
www.usatoday.com/weather/wjet.htm
Tornado
Primary Points
Tornadoes are rapidly rotating columns of air that connect from the ground to a cloud
Highly destructive their winds can reach up to 300 mph in the most extreme cases
Can vary from 30 feet up to a mile in width
Form from rotating clouds that take place in supercells known as mesocyclone
Rainfall causes a strong downdraft to form and bring the mesocyclone down to the surface
The meeting of cold and warm air causes a rotating wall cloud which is the distinctive feature of a
tornado
Form mostly east of the Rockies, but are most prevalent in the central states otherwise known as
tornado alley
Form in tornado alley because of the dry air from the Mojave meeting the moist air from the Gulf of
Mexico causes strong supercell outbreaks
Trivia and Stories
Yvette Richardson worked on an experiment similar to that of the movie Twister to learn more about
tornado prediction
A tornado recently struck Westmoreland County in Western, PA causing more than 4 million dollars in
damage
A tornado is only a tornado over land; over different terrains they have different names
Sound Bites
Although tornadoes can make you “not in Kansas anymore” it’s generally not suggested as a means of
travel
Tornadoes are the Earth’s way of “touching the skies”
Tornadoes could be said to be the result of a “storm going into a spinout”
Sources of Additional Info
http://www.nssl.noaa.gov/edu/safety/tornadoguide.html
http://www.vortex2.org/home/
Hurricanes
Primary Points
Large, well formed tropical storms that span hundreds of miles in width
Wind speed of at least 74 MPH but can reach speeds of over 170 MPH
Form over the warm tropical waters, more active when the air temperature is much different than the
sea temperature (late summer)
Required for tropical cyclogenesis: warm sea temperature, high humidity, atmospheric instability,
enough coriolis force to maintain a low pressure system, pre-existing low, and light shear
They strengthen over long stretches of warm water
Dangerous aspect of hurricanes is storm surge where the sea level increases due to winds and rains
The eye wall is the most dangerous area of the storm, it contains the heaviest rains and winds and the
ability to produce tornadoes
Forecasts of landfalls have been increasing in accuracy for years
Difficult part of landfall prediction is determining where the eyewall will hit as it ranges from 20-40 miles
in diameter and can be hard to predict the exact location of landfall
Trivia and Stories
The average death rate of hurricanes was in a decreasing trend until Hurricane Katrina in 2005
Most deadly Hurricane to hit America was the Galveston Storm of 1900, which killed at least 8,000
people
Storm names alternate between male and female each year
Hurricane hunters penetrate storms via aircraft while still at sea to gather data for better prediction and
outlooks
Sounds Bites
Hurricanes have “an eye for destruction”
Hurricanes have the ability to “take your life for a spin”
Hurricane names are like artists “they only become popular once they are dead”
Sources of Further Information
www.nhc.noaa.gov/
www.fema.gov/hazard/hurricane/index.shtm
Radar/Doppler Radar
Primary Points
Radar detects precipitation by bouncing energy off of falling precipitation that goes back to the satellite
and pinpoints where precipitation is falling
Conventional radar can only detect where precipitation is falling, Doppler can detect the motion of
precipitation, wind, and relative storm motion
Doppler radar helps to predict the possibility of a tornado by determining if a cloud has started rotating
Radar rainfall estimates are made by determining how much energy is sent back to the dish, larger
energy amount means heavier precipitation
Radar images can be misleading by incorrectly identifying obstructions as precipitation
Examples include mountain ranges, melting snow causing flares in dBz
Trivia and stories
NWS operates 159 Doppler radars across the country to keep a constant eye on the weather
State College is home to one of the 159 radars
Mobile Doppler radars used with tornado chasing to better learn to predict formation of tornadoes
Sound Bites
Radar catches a “storms energy for a better look into what makes it tick”
Radar is “only as good as the amount of energy it receives from a storm”
Without radar meteorologists would be “swinging in the dark looking for storms”
Sources of Additional Information
www.weather.gov/radar_tab.php
http://www.intellicast.com/National/Radar/Current.aspx
El Nino/La Nina
Primary Points
El Nino is a pattern where the eastern pacific waters are warmer than normal creating high pressure
over the area
La Nina is the opposite of that pattern where cold waters dominate the eastern pacific creating low
pressure
Exact causes are still being determined but trade winds carrying warm water from the equator are
thought to be one of the ingredients
Both patterns throw off normal weather patterns and cause erratic behavior from storms
El Nino winters are generally warmer and drier than normal winters in the N. America’s
La Nina winters are more intense for the eastern seaboard of America
In recent years the amount of El Nino events has increased while La Nina’s have decreased
Studies have shown that this is more than likely associated with global warming
Trivia and Stories
La Nina is thought to be the blame for Hurricane Floyd’s destruction of the American Northeast
El Nino translates into Little Boy in the Spanish language
La Nina translates into Little Girl in the Spanish language
We are currently (March 2011) in a decaying La Nina phase
Sound Bites
Although small children “El Nino and La Nina cause big changes”
El Nino can throw “weather patterns into a hot mess”
El Nino makes some global warming enthusiasts “hot under the collar”
Sources of Additional Information
www.elnino.noaa.gov/
www.pmel.noaa.gov/tao/elnino/el-nino-story.html
Long-Range Weather Prediction
Primary Points
Monthly and seasonal outlooks are put out by the climate prediction center predicting the temperature
and precipitation compared to an average
Produced using historical data when compared to the El Nino and La Nina patterns
Predictions of temperature are accurate because they are on the most basic level of being above or
below average
Predictions of precipitation are less accurate than temperatures as weather systems can easily change at
the last minute
The Farmers’ Almanac could be looked at as a long-range prediction method
The almanac has over its long length an 80-85% correct prediction rate
Trivia and Stories
The Farmers’ almanac method to weather prediction is a closely guarded secret
Predictions for CPC are made a year in advance while Farmer’s Almanac predicts up to 2 years in
advance
Thomas Jefferson was one of the first supporters of long-range forecasting in the late 18th century
Sound Bites
Long-range forecasts “provide a stepping stone for better predictions in the future”
The Farmers’ Almanac gives “guidance for a better and more productive growing season”
Although slightly archaic the Farmers’ Almanac goes with the method of “if it ain’t broke don’t fix it”
Sources of Additional Information
http://www.cpc.ncep.noaa.gov/products/forecasts/month_to_season_outlooks.shtml
http://www.almanac.com/
Thunderstorms
Primary Points
Form from rapid upward movement of warm-moist air that creates convection
Convection forms due to the moist air cool and condensing into high altitude clouds
As the clouds grow in height they eventually meet their dew point and begin precipitating
Precipitation causes downdrafts which are felt as the strong winds associated with thunderstorms
Occur in spring and summer more because of more available energy due to warmer temperatures
Strength of storm is dependent mostly on the amount of CAPE available
CAPE is a measure of the amount of energy a rising parcel of air gathers as it accelerates upward in the
atmosphere
Thunderstorms are severe because they have the potential to bring damaging winds, heavy rains,
dangerous lightning strikes, damaging hail and even the potential for tornadoes
Thunderstorms can happen at night based on two factors, lingering thermal heating from the day or a
warm front moving through that causes convection
Lightning is caused by a discharge of the energy stored in a thunderhead cloud and thunder is the result
of the air being superheated to the point of a sonic boom
Trivia and Stories
The delay between seeing lightning and hearing thunder is proportional to the distance of the stroke by
an order of 5 seconds : 1 mile.
Heat lightning is not the cause of a hot day and is actually just lightning that is too far away to hear the
thunder
The visible part of lightning is actually the return stroke of the lightning going back up to the cloud.
Sound Bites
Thunderstorms are one of “nature’s most shocking performances”
Thunderstorms are “cheaper than fireworks and double the fun”
Thunderstorms can actually “make your hair stand on end” due to electrical charges
Sources of Additional Information
http://www.lightningsafety.noaa.gov/ams_lightning_rec.htm
http://science.howstuffworks.com/nature/natural-disasters/lightning.htm
Climate Change
Primary Points
Greenhouse gases are gases in the upper atmosphere that absorb and emit radiation from the sun
Greenhouse effect is when greenhouse gases absorb radiation from the planet and emit it in all
directions, warming the air
The Earth is warming at a steady rate, but whether it can be attested to climate change or natural
occurrences is undetermined
Ozone hole is the decrease in atmospheric ozone gases over the Polar Regions.
The relationship between the ozone hole and climate change is that with a larger ozone hole the more
thermal radiation can get to the Polar Regions melting the polar caps at a quicker rate
50-100 year trends are predicted based on current trends in the depletion of ozone and average
temperature increase in past years
Trivia and Stories
Climate change is commonly referred to as global warming which is not correct due to the fact that not
all locations will get warmer
The Earth was gradually warming due to natural occurrences until a spike in the increase occurred in
1970.
Climate change has become less of a scientific fact and more political in recent years due to political
movements of recent years
Sound Bites
Climate change and severe weather are “destroying the way we live hand in hand together”
Climate change is “easily the most talked about and misunderstood aspect of weather”
Climate change can only be truly stopped by “the complete halt of all wasteful parts of society”
Sources of Additional Information
www.epa.gov/climatechange/
www.weather.gov/om/brochures/climate/Climatechange.pdf
Winter Precipitation
Primary Points
It can snow when it is above freezing because air temperature varies with height and therefore the
temperature above ground level could be below freezing and vice versa
Sleet is different from hail because sleet is mainly small and regular while hail can clump together with
other hair particles and are also irregular in shape
The different kinds of snow are determined by the amount of melting that has occurred with the snow
particles, for example wet snow has partially melted on its way down to the surface and therefore
heavier and wet
Sleet is mainly falling ice particles while freezing rain is precipitation that falls as rain and freezes as soon
as it hits the ground
Snow on the ground can disappear when temperatures are below freezing due to absorbing warming
radiation from the sun on a sunny day, or by blowing around due to high winds
Trivia and Stories
A blizzard is not determined by the amount of snowfall but instead measured by visibility and wind
speed
A blizzard in 1972 in Iran caught the country off guard and killed 4000 people, the deadliest winter
storm in history
The storm of the century, a super storm occurring in March 1993 that stretched from Canada to Central
America caused more than 6.65 billion dollars in damage
Sound Bites
Old man winter is trying to keep us warm with “a nice blanket of white snow.”
With climate change afoot “sightings of wild frosty’s may become more and more scarce.”
Winter precipitation is “a nightmare for the common public but absolute joy for weather geeks.”
Sources of Additional Information
www.weather.com/encyclopedia/winter/precip.html
http://www.cbs6albany.com/articles/snow-22087-freezing-ground.html
Folklore
Primary Points
Folklore comes from times before the use of computers was available to predict weather
Sometimes called old wives tales, knowledge has been passed down through generations
Red sky in the morning sailors take warning comes from early sailors relying on sky color to predict
weather patterns of the day.
Can work in mid-latitudes because in the morning the sun would be reflecting off of clouds to the west
which will soon hit the area where the sky is observed to be red
Red sky at night sailors delight is valid because of the exact opposite reason, the sun is reflecting off of
clouds to east which have already passed over the area
Ring around the moon means precipitation is scientifically possible because it means that cirrus clouds
are passing between the surface and the moon, and cirrus clouds usually precede precipitation
“A sunshiny shower won’t last half an hour” is an example of bad folklore as storms can continue to
propagate themselves and continue raining for long periods of time
“Rainbow at noon more rain soon” is also a bad folklore since rainbows cannot occur during the middle
of the day
Trivia and Stories
Folklore was used in the Shakespearian play Venus and Adonis
One of the earliest records of weather folklore is quoted by Jesus Christ in Matthew 16: 2-3 “When in
evening, ye say, it will be fair weather: For the sky is red. And in the morning, it will be foul weather
today; for the sky is red and lowering.”
Sound Bites
An English country saying says “April weather, rain and sunshine both together”
Comedian George Carlin may have the best and most accurate folklore “Weather forecast for tonight:
dark.”
Sources of Additional Information
http://en.wikipedia.org/wiki/Weather_lore
http://www.readwritethink.org/classroom-resources/lesson-plans/weather-detectives-questioning-fact775.html
Lake (Sea)-Effect Snow/Rain
Primary Points
Lake effect precipitation requires that the water temperature be highly contrasted to that of the air
temperature creating instability, fetch, wind shear, and upstream moisture
The amount of wind shear determines whether there will be a single band or multiple bands of
precipitation
The formation of ice on the lakes prevents the formation of lake-effect snow because the amount of
fetch that can be produced is significantly lowered
August to November is when lake-effect rain is most likely to happen
Other Lake Effect phenomena occur in Gulf Stream, Japan, the Aegean Sea in Greece; Adriatic Sea, Italy,
and the Black Sea, Turkey
Trivia and Stories
The town of Fulton, NY had 4-6 feet of snow fall over 72 hours due to Lake-Effect Snow
Houghton, MI averages around 250-300 inches of snow a season due to Lake-Effect Snow
England receives “Lake-Effect Snow” every few years when cold air moves over the warm North Sea, the
most famous of which was the occurance in 1987 which dumped over 3 feet of snow in three days
Sound Bites
A general rule is that the “thinner the band of snow, the thicker the layer will be on the ground”
Lake effect to a great lakes area resident is “just a common occurrence of annoying weather”
Although mesoscale in size “lake-effect snow can be a massive pain for commuters”
Sources of Additional Information
http://www-das.uwyo.edu/~geerts/cwx/notes/chap10/lake_effect_snow.html
http://www.weather.com/encyclopedia/winter/lake.html
Optical Phenomena
Primary Points
A rainbow forms because the sun refracts off of falling precipitation which creates a prism of light which
is visible as a rainbow
Rainbows cannot form with falling snow because light is not refracted and is instead simply reflected
Water on the road mirages are caused by the cold air being directed off of the hot pavement which
creates a concave, upward trajectory of light
Sun dogs are ice crystals that create bright spots in the sky around the sun
Halo’s form around the moon or sun by ice crystals in the upper troposphere which reflect and refract
the light to create the optical illusion
Trivia and Stories
The end of the rainbow can never be reached because the optical illusion will continue to be far away
from you due to the refraction
Rainbows that do not touch the ground and instead are stationary in the sky are called dog bows
Mirages can happen at any time of the year so long as the conditions are met, although the most
prominent times are the dead of summer
Sound Bites
The best place to hide your gold “is at the end of the rainbow as no one can reach it”
Although you won’t see a soda machine “mirages can make you see a double sun”
Using your brain, nature “creates the most realistic sleight of hand using weather”
Sources of Additional Information
http://www.islandnet.com/~see/weather/elements/mirage1.htm
http://www.weather.gov/om/educ/activit/mirages.htm
Heat Index
Primary Points
Measurement that uses temperature and humidity to estimate the feeling of heat on the human skin
Scientific basis of the heat index is the same of wind chill in that it tries to quantify the effects of
extreme temperature on the human body
Research conducted by Robert Steadman and took in account temperature, humidity, and assumptions
of human body mass, clothing, physical activity and the thickness of blood
It is useful in determining how much physical activity you can do on a hot day before having to take a
break
Shortcomings of heat index are that it doesn’t take into account that some people enjoy the heat, or
hydration, it also does not take into effect the feeling of direct sunlight onto skin
Trivia and Stories
The highest heat index recorded was Dharhan, Saudi Arabia at 172 degree Fahrenheit
Originally it was thought that the highest heat index that could be recorded on Earth would be 160
degree Fahrenheit
Sound Bites
Heat index “makes blistering heat even less bearable”
Even though “water cools you down, moisture makes the heat index rise”
Sources of Additional Information
http://www.nws.noaa.gov/om/heat/index.shtml
http://www.usatoday.com/weather/wheat3.htm
Satellite Imagery
Primary Points
Three types of radar that are available are Infrared, visible and water vapor
Satellites operate to produce these images by different ways for each image.
Visible is a visual image of the area and can only be used during hours of daylight
Infrared uses photons that bounce off of clouds and the amount of energy sent back determines how
high the clouds are and essentially what kind they are
Water vapor uses photons that measure the amount of moisture in the air
Visible satellite can most accurately verify the types of clouds but can only be used during daylight
Infrared satellites can only detect the temperature of clouds and not verify what kind they are
Water vapor can only see the amount of moisture in the air and again not perfectly verify the types of
clouds
Meteorological satellites also monitor sun spot activity, map air pollution, map ocean currents, and
energy flow
Trivia and Stories
The first weather satellite was launched by America in 1959 called “Vanguard 2”
Satellites can either be geostationary where they stay in a constant area with respect to the Earth or
they can be orbital where they spin around the Earth
Satellites produce different imagery by sending out photons of different wavelengths that correspond to
different types of cloud cover
Sound Bites
Satellites “give us an unprecedented eye in the sky”
Water Vapor imagery “shows us vast rivers of moisture in the sky”
Visible satellite “make the sunrise that much more important to forecasters”
Sources of Additional Information
http://profhorn.meteor.wisc.edu/wxwise/museum/a3/a3example1.html
http://internationalweatherarchive.org/satellite.aspx