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April 1st, 2014 METEO 482: Weather Communications II Brad Guay Familiar Weather Topics Wind Chill Primary Points Attempts to quantify how much energy is being lost from bare human skin Originally Formulated by Antarctic researcher Paul Siple in the 1930s Siple hung plastic bags of warm water in various temperature/wind combos New wind chill values were implemented in 2001 New Formula used data from real human skin and modern heat transfer eqns. New wind chill temps are notably “warmer” than the original values Useful for general guidelines related to dangers of wind-related heat loss Shortcomings: does not account for sunshine, humidity, individual health Shortcomings: confusion with actual air temperatures Shortcomings: only applies to humans, not animals or automobiles Trivia and Stories Siple grew up in Erie, PA, was an Eagle Scout and ‘frat boy’ Siple coined the term wind chill factor Siple was opposed to wind chill temperature (wrong units) –“science geek” Canada now uses the same scale…before 2001 it was different Sound Bites New Scale required some people to “freeze their face for science” Wind chill “allows meteorologist to inflict further pain in bad weather” Wind chill “further clutters the already cluttered world of weather info” Additional Info http://www.nws.noaa.gov/om/windchill/images/wind-chill-brochure.pdf http://www.slate.com/id/2207326/ - Slate Magazine: Wind Chill Blows April 1st, 2014 METEO 482: Weather Communications II Brad Guay Familiar Weather Topics Jet Stream Primary Points “Rivers” of strong winds aloft – typically found 30-45 thousand feet off the ground Winds can flow at speeds in excess of 100 mph Two main jets – strong “polar jet,” weaker “subtropical jet” Formed by temperature gradients caused by irregular heating of the earth’s surface Weaker in the summer when temperatures are more uniform from north to south Generally a few miles thick and a few hundred miles wide Continuous around the earth, though parts are weaker and parts are stronger Flow from west to east, though they meander quite a bit Jet streams generally divide air masses, cold to the north, warm to the south They generally help to move along weather systems Trivia and Stories Pilots use the jet stream to expedite trips Jet streams exist on other plants too The strongest jet streams can reach speeds of 275+ mph Jet streams were discovered in the 1920s by Japanese meteorologist Wasaburo Oishi Sound Bites “Soaring as high as a jet plane, jet streams are fast flowing, meandering rivers of air” “Jet streams thrive when hot meets cold” “Racing jets help push weather systems down the line” Additional Sources http://www.livescience.com/27825-jet-stream.html - LiveScience: What is a Jet Stream? http://www.srh.noaa.gov/jetstream/global/jet.htm - National Weather Service: The Jet Stream April 1st, 2014 METEO 482: Weather Communications II Brad Guay Familiar Weather Topics Tornadoes Primary Points Violent, spinning columns of air that reach from clouds to the ground Most form in supercells, powerful rotating thunderstorms Ingredients: moist, unstable air at the surface, colder air aloft Ingredients: change in wind direction with height (wind shear) Ingredients: air mass boundary, front, or dry line Range from just a few feet wide to over a mile wide Most are weak (winds < 110 mph), though more powerful ones aren’t rare Tornado alley brings all of the necessary ingredients Tornado alley: hot and humid Gulf air meets cool, dry Canadian air mass Hurricanes: generally predictable, large, form over warm tropical ocean Tornadoes: small, isolated, difficult to forecast, form over land Trivia and Stories The first tornado prediction took place at Tinker Air Force Base in Oklahoma in 1948 Most powerful tornado: May 3, 1999 in Moore, OK – 317 mph winds Tornadoes can happen in all 50 states, though Kansas sees the highest concentration Sound Bites “While violent and dangerous, tornadoes are simply rapidly spinning columns of air” “Tornado alley brings together just the right mix of ingredients for a tornado recipe” “While hurricanes can be predicted days in advance, individual tornadoes strike with just a few minutes’ notice” Additional Sources http://www.spc.noaa.gov/faq/tornado/ - Storm Prediction Center: Tornado FAQ http://www.nssl.noaa.gov/education/svrwx101/tornadoes/ - NSSL: Tornadoes 101 April 1st, 2014 METEO 482: Weather Communications II Brad Guay Familiar Weather Topics Hurricanes Primary Points Powerful low pressure systems that form over tropical oceans Need warms water (>80 degrees), low amounts of wind shear, Coriolis force Develop as clusters of thunderstorms become organized Tropical Depression (<39 mph) to Tropical Storm (39-74 mph) to Hurricane (>75 mph) Storm surge: water pushed on shore by strong winds Most dangerous part is the eyewall – strong winds, driving rain Eye is an area of calm winds and clear skies Track forecast error: 50 miles (24 hours), 200 miles (5 days) NHC forecasts go out 5 days – used to be 3 days before 2001 Forecasting difficulties: intensity is more of a challenge than track Trivia and Stories Hurricane Faith in 1966 traveled 6850 miles over the course of 3.5 weeks Hurricane Wilma in 2005 went from Tropical Storm to Category 5 in 16 hours Hurricane Ivan in 2004 spawned 117 tornadoes when it made landfall 2005 was the most active hurricane season with 28 storms, 15 hurricanes Sound Bites “Hurricanes, nature’s most powerful storms, originate from lowly tropical rain showers” “Meteorologists like to talk about the wind, but a hurricane’s storm surge brings the greatest danger” “Would you believe that you can find calm winds and clear skies at the center of the most powerful storm on Earth?” Additional Sources http://www.ready.gov/hurricanes – Ready.gov: Hurricanes http://environment.nationalgeographic.com/environment/natural-disasters/hurricaneprofile/ - National Geographic: Hurricanes Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Radar/Doppler Radar Primary Points Traditional radar cannot detect rain or snow – based on surface observations Dual polarization can detect precipitation type Dual polarization radar sends out two radar waves, not just one Dual polarization allows us to see the size and shape of particles in the air Conventional radar only sees the location of precipitation Doppler radar sees the motion of raindrops/snowflakes, towards or away from the radar Most radars in the United States today are dual polarization Doppler radars Drops moving rapidly away from the radar near drops moving towards = possible tornado Rainfall estimates are made based on the reflectivity over time at a location Radar beams shoot out at a slight upward angle Low level precipitation may be missed far from the radar site where the beam is high up Precipitation that is falling but not reaching the ground may also be shown Ground clutter can be an issue Trivia and Stories World War II radar picked up echoes from rain/snow, this technology was commercialized later First Doppler radars were installed nationwide in 1988 after NSSL research Dual polarization was researched over the past 15 years – installation was completed in 2013 Sound Bites “Doppler Radar allows meteorologists to see under the hood of storms” “New Dual Polarization radar technology tells us where rain and snow are falling” “Since the 1950s, radar has been scanning the skies for dangerous weather and even tornadoes” Additional Sources https://www.nssl.noaa.gov/tools/radar/ - NSSL: Radar http://www.ig.utexas.edu/research/projects/mars/education/radar_works.htm - University of Texas: How Radar Works Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II El Nino/La Nina Primary Points El Nino: unusually warm water in the equatorial Pacific El Nino: stronger subtropical jet stream pushes moisture into the US El Nino: suppresses hurricanes in many cases El Nino: cooler, wetter southern US, especially Gulf El Nino: drier, warmer northern half of the US La Nina: unusually cool water in the equatorial Pacific La Nina: jet stream takes a more northern, variable track La Nina: cooler, wetter northern US La Nina: warmer, drier southern US La Nina: more favorable conditions for US hurricanes Not caused by global warming, though global warming could affect it Trivia and Stories El Nino may be to blame for historic famines and droughts – collapse of Columbian Incas 1998’s El Nino killed 16% of the world’s coral reefs El Nino means “the boy” in Spanish; La Nina means “the girl” Sound Bites “One of the keys to our climate lies in the waters thousands of miles offshore” “El Nino isn’t a storm – just a change in the ocean temperature” “Want to find the subtropical jet stream? Just ask El Nino” Additional Sources http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html - NOAA: El Nino http://www.fi.edu/weather/nino/nino.html - The Franklin Institute: El Nino Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Long Range Weather Prediction (Monthly/Seasonal) Primary Points Long range forecasts don’t try to be very specific – not a day-by-day prediction Forecasts involve long-range models, analogs, El Nino Predicting El Nino/La Nina holds great potential Analogs: looking at past patterns to determine what might happen Long range forecasts are most accurate late winter and late summer Forecasts least accurate during the spring and fall when weather is changing rapidly Precipitation forecasts are less accurate than temperature forecasts All long range forecasts are only marginally accurate at this point Lots of work needs to be done to improve long range prediction Farmer’s Almanac = no science involved, simply a guess Trivia and Stories Almanac forecasts have been criticized for 100+ years by meteorologists 1956: Norman Phillips developed first climate model Early 1980s: modern era of long range modeling begins at NCAR (CAM) Sound Bites “The idea of a 365-day forecast is alluring, but the reality is far less pleasant than the Old Farmer’s Almanac would have you think” “El Nino could hold the key that unlocks the secrets of long range forecasting” “Fall and spring bring changing weather which can elude the grasp of long range forecasts” Additional Sources http://www.wmo.int/pages/themes/climate/long_range_forecasting.php - WMO: Long Range Forecasting http://www.washingtonpost.com/national/health-science/long-term-weather-forecastsare-a-long-way-from-accurate/2013/04/15/1f9a2ac8-a05b-11e2-be47b44febada3a8_story.html - Washington Post: Long-term weather forecasts are a long way from accurate Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Thunderstorms Primary Points Caused by fast upward motion of unstable warm, humid air When the air cools to saturation, rain/ice form and begin to fall, creating a downdraft Best conditions: warm surface, cold aloft Generally occur in the spring/summer because these seasons are warmer and wetter Thunderstorms can occur in any season though Types: single cell, multi cell, supercell Supercell most dangerous, but least common Strength is controlled by the instability of the air and the presence of vertical shear Severe thunderstorms: 1 inch hail or 60 mph wind gusts Nighttime storms: the atmosphere can still be unstable at night Nighttime storms: warm air moving in at the surface, cold air moving in above Lightning: rain drops and ice crystals collide, building charge difference with the surface Trivia and Stories Central Florida sees the most thunderstorms in the US – averaging 90 days each year! Worldwide, approximately 1800 thunderstorms are happening at any given moment Lightning heats the air around it to nearly 50000 F Sound Bites “A sticky summer day means the air is ripe for booming storms” “Just like people, thunderstorms come in many shapes and sizes” “In a thunderstorm, moist air hurtles upward until all of its water has been wrung out” Additional Sources http://www.erh.noaa.gov/lwx/swep/Spotting.html - NWS: Thunderstorms and Severe Weather Spotting https://www.nssl.noaa.gov/education/svrwx101/thunderstorms/ - NSSL: Thunderstorms Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Climate Change Primary Points Greenhouse gases: carbon dioxide, methane, nitrous oxide, fluorinated gases Emitted by industry and agriculture, though also naturally present in the air Greenhouse effect: gases absorb radiation escaping from the earth, preventing cooling Earth wouldn’t support life without the greenhouse effect Too much of the greenhouse effect means it gets too hot on earth The earth has been shown to be warming over the past few decades Satellite observations of surface temperatures provide the best proof Ozone hole: caused by emissions of aerosols into the atmosphere Ozone hole: becoming less of a concern with harmful emissions on the decline Climate predictions: generally made using models Climate models: take into account emissions, snow melt, etc. Trivia and Stories Since 1971, 90% of warming has occurred in the ocean If warming projections pan out, sea levels could rise by 1-2 feet by 2100 Warming has been observed to be the fastest near the poles Sound Bites “The greenhouse effect may sound evil, but it keeps us all alive” “The best climate observations come from high above the earth” “Greenhouse gases may be creating too much of a good thing” Additional Sources http://news.nationalgeographic.com/news/2004/12/1206_041206_global_warming.html National Geographic: Global Warming http://www.epa.gov/climatechange/ - EPA: Climate Change Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Winter Precipitation Primary Points Precipitation type depends greatly on the temperatures across the column Cold air near the surface, warm air aloft: freezing rain Cold air near the surface, small layer of warm air above: sleet Cold air throughout: snow Sleet: snow that melted, re-froze on the way down Hail: produced in thunderstorms by rain drops clumping together in updrafts When the air is dry, snow can stay solid in above freezing temperatures Powdery snow falls at lower temperatures Fluffier snow generally falls when it is quite cold Snow disappears by sublimation Snow lifts into dry air, the sun plays a role Trivia and Stories A 15” snowflake was observed in Fort Keogh, MT in January of 1887 Snow has been observed as far south as Homestead, FL in the US in 1977 Silver Lake, CO recorded nearly 76 inches of snow in 24 hours in 1921 Sound Bites “Don’t you dare call it hail – sleet is very different from its summer cousin” “Believe it or not – it can rain when it’s below freezing – the secret lies just above the ground.” “Depending on the temperature, snow can be as light as cotton or as heavy as fresh cement” Additional Sources https://nsidc.org/cryosphere/snow/index.html - National Snow and Ice Data Center: All About Snow http://geonews.tamu.edu/weather-whys/718-sleet-vs-freezing-rain.html - Texas A&M: Sleet vs. Freezing Rain April 1st, 2014 METEO 482: Weather Communications II Brad Guay Familiar Weather Topics Folklore Primary Points Red sky caused by particles in the air diffracting the light – indicative of low pressure Red sky in the east at sunrise: sun shining on approaching clouds to the west Red sky in the west at sunset: sun shining on departing clouds to the east Storms may fizzle before they reach you after a red sky in the morning Ring around the sun/moon: caused by ice crystals in high altitude cirrus clouds Cirrus clouds are usually the first layer of clouds seen from an approaching storm Cirrus clouds aren’t always with a storm, so this isn’t always true “March comes in like a lion, goes out like a lamb” – not scientifically supported “No weather is ill, if the wind be still” – clear, calm conditions mean high pressure Groundhog Day – no better than flipping a coin Trivia and Stories “Red sky by morning” dates back hundreds of years and is found in many languages Some weather lore must be reversed in the southern hemisphere – rotation is opposite Most weather lore is designed to apply to the mid-latitudes Sound Bites “Red sky by morning? Check your local meteorologist – a storm may be approaching.” “When it comes to weather forecasting, Punxsutawney Phil is just a glorified rat.” “Remember, weather lore is just that: lore. Storms may fizzle before you even see drizzle” Additional Sources http://www.cmos.ca/weatherlore.html - Environment Canada: Weather Lore and Proverbs http://www.bbc.com/news/magazine-14087734 - BBC News - Weather lore: What’s the Science? Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Lake (Sea)-Effect Snow/Rain Primary Points Lake effect snow is caused by the temperature difference between the wind and water Water must be at least 20 F warmer than the air in the lowest mile of the atmosphere When cold air moves over warm water, the air becomes unstable Upward motion then ensues and clouds form and begin to drop snow The size and shape of the lake determines the size and shape of bands Larger lakes create more intense snow because more moisture is involved When the lake freezes, the lake effect snow stops Frozen lakes mean that the temperature difference between ground and air is gone Lake effect rain happens in the fall when the lake is warm but the air is cooling This also happens in the Great Salt Lake in Utah and Lake Tahoe Ocean effect snow is common in Massachusetts Bay and Chesapeake Bay International: Sea of Japan, Canadian Maritimes, Caspian Sea Trivia and Stories Buffalo, NY received 82 inches of snow in 5 days in December 2001 Lake effect snow was observed from the Atlantic off Cape Canaveral in 2003 Michigan’s Mt. Bohemia relies on lake effect snow, averaging 250-300” each year Sound Bites “What do you get when you combine wind, water, and winter? A whole lot of snow.” “When the lake freezes, the snow pauses.” “Just ask any resident of Buffalo: the Great Lakes can bring some great snows.” Additional Sources http://www.noaa.gov/features/02_monitoring/lakesnow.html – NOAA: Lake Effect Snow http://www-das.uwyo.edu/~geerts/cwx/notes/chap10/lake_effect_snow.html - University of Wyoming: Lake-effect snow Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Optical Phenomena Primary Points Rainbows: caused by the reflection and refraction of light through water droplets Rainbows: appear in the part of the sky opposite the sun Rainbows: caused by the different wavelengths contained within light Rainbows: can’t happen during snow – shape of flakes scatters light too much Mirages: caused by the bending of light across a temperature gradient Mirages: cold air is denser than warm air – light rays bend away from warm ground Mirages: bending is most likely to happen with extreme heating at ground level Mirages: instead of water, what you’re really seeing is the bluish sky Sun Dogs: bright spots of light on either side of the sun Sun Dogs: caused by the refraction of light through ice crystals in high clouds Sun Dogs: much like rainbows, but constant Halos: essentially like sun dogs, but a full circle Stories and Trivia The end of a rainbow is impossible to reach – it will always move away as you approach Under the right circumstances, triple and quadruple rainbows can be seen Besides sun dogs and halos, there are dozens of other arcs/halos that can be found Sound Bites “Sun dogs aren’t a type of hot dog– rather; they just mean there are cold clouds aloft” “When you see water in the distance on a flat road on a hot day, you’re actually just looking at the sky” “A ‘snowbow’ would be beautiful, but the irregular shape of the snowflakes makes them impossible” Additional Sources http://science.howstuffworks.com/nature/climate-weather/storms/rainbow.htm - How Stuff Works: Rainbows https://nsidc.org/cryosphere/arctic-meteorology/phenomena.html - National Snow & Ice Data Center: Arctic Phenomena Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Heat Index/Apparent Temperature Primary Points Heat index: based on temperature and dewpoint Dewpoint: saturation temperature of the air Measure of how hot it “feels” as opposed to the actual temperature Relates temperature at high humidity to another one at low humidity Base for the heat index: a dewpoint of 57 F Humans cool by sweating – sweat evaporates less when it is humid Limitations: the heat index makes many assumptions Limitations: feeling may vary from person to person Limitations: different people will suffer differently Limitations: the heat index is useless outside of a certain range Trivia and Stories The Canadian heat index is called “humidex” and it uses a base of 45 F dewpoint The highest heat index recorded was 176 F in Saudi Arabia in 2003 (108/95) Appleton, WI recorded a heat index of 148 F on July 13, 1999 (101/90) Sound Bites “The saying goes: ‘it’s not the heat, it’s the humidity,’ and that’s exactly what the heat index is designed to measure” “The heat index makes many assumptions – if you were to wear a wool suit out on a summer day, the heat index would fall short for you” “When we sweat on a scorching summer day, we cool off. Humidity slows that process, and that’s where the heat index comes into play” Additional Sources http://nws.noaa.gov/os/heat/index.shtml – NWS: Heat: A Major Killer http://www.weather.com/encyclopedia/charts/heat_index.html - The Weather Channel: Heat Index Brad Guay Familiar Weather Topics April 1st, 2014 METEO 482: Weather Communications II Satellite Imagery Primary Points Three types of imagery: visible, infrared, water vapor Visible: photographs taken from the sky Visible: higher resolution, detects all clouds visible from above Visible: only works during the day, not at night Infrared: works based on radiation being sent up from the earth Infrared: cold things made to appear bright (clouds), warm things appear dark (ground) Infrared: lower resolution, may miss some low clouds and fog Infrared: works at all times of the day and night Water Vapor: used to identify areas of moisture in the mid-levels Water Vapor: detects energy at wavelengths emitted by water vapor Water Vapor: brighter colors mean more moisture in the mid-levels Water Vapor: works both day and night Satellites can also be used to determine temperature profiles and ozone concentration Trivia and Stories The first weather satellite was launched in 1959 (vanguard 2) The first satellite image from space came from TIROS-1 in 1960 Temperature information from satellites has been available since Nimbus 3 in 1969 Sound Bites “Miles above us, a fleet of satellites is charged with tracking storms around the world” “Infrared sensors allow us to track clouds based on their temperature, even in the dead of night” “A satellite’s sounder allows us to peel back the layers of the atmosphere and see the temperature at each place along the way” Additional Sources http://noaasis.noaa.gov/NOAASIS/ml/genlsatl.html - NOAA: NOAA’s Weather Satellites http://www.accuweather.com/en/features/trend/evolution-of-weather-satellite/1184427 AccuWeather: Evolution of Weather Satellites
