Wind Chill PRIMARY POINTS

Transcription

1 Wind Chill - Wind Chill is not an actual measured temperature. It s calculated. - The index serves as an indicator for how dangerous the combination of winter winds and freezing temperatures can be to exposed flesh. - Developed by Paul Siple in the 1930s. - Updated index was implemented in 2001 and matched Canada s index, and produced warmer values. - It has shortcomings because it assumes no impact from the sun, humidity, and individual health. - Old scale didn t actually use humans to perform experiments and come up with values. A plastic bottle and water were put out in the wind in the Antarctic. - Canada, U.S., and U.K. all use same scale, since Wind chill factor allows meteorologists to scare people with even more biting numbers on cold nights.

2 Jet Stream - The jet stream guides our weather. - Two jet streams: mid-latitude and subtropical. - A jet stream is a fast moving tube of air at about 10km. - High and low pressure systems move with the jet stream. - The mid-latitude jet stream actually indicates where the greatest temperature variation is at the surface. - Jet pilots often travel near the jet stream when flying west to east in order to have a tail wind. - The Jet stream was discovered by pilots in WWII when flying across the Pacific. - Jet pilots actually use the jet stream for better fuel mileage. -

3 Tornadoes - Tornadoes are a vicious rotating column of air that is in contact with the ground. - If the rotating column isn t touching the ground, it is a funnel cloud. - Most tornados have wind speeds of 110mph or less. - Tornado Alley is in the Midwest, where tornadoes occur most often. - A wedge tornado is wider than it is tall. - Tornadoes often pick up debris and throw it through the air. - Fujita Scale introduced in The Enhanced Fujita (EF) Scale became operational on Feb. 1, New scale focuses on structure design and damage to estimate wind speed. - It is in the spring and early summer when tornado forecasters have the most work to do. - Tornadoes torment many people each year. -

4 Hurricanes - Hurricanes are powerful storm systems that often live longer than midlatitude storms. - They are often symmetric in nature, with calm weather in the eye. The eye averages miles across. - The highest winds are found just outside of the eye. - The right side of a hurricane is commonly the most dangerous in terms of wind, storm surge, and tornadic activity. - Herbert Saffir, a civil engineer, and Robert Simpson, then NHC Director, developed the Saffir-Simpson hurricane wind scale in Hurricanes thrive in warm water, which is often abundant in the Gulf of Mexico. -

5 Radar/Doppler Radar - Doppler radar allows meteorologists to see where it is raining, but also how fast and which way the wind is blowing. - Current Dopplers are called WSR-88D. The name means Weather Surveillance Radar, first introduced in 1988, and the D means Doppler capability. - Radars have many limitations, such as ground clutter and attenuation. - More than 100 radars are deployed across the U.S., which has the best radar-observing network in the world. - Most weather service offices have 1 Doppler, though some have more. True or false: radar can see birds and smoke from wildfires. Newly developed Dual-Pol radar data allows meteorologists to inspect the atmosphere both horizontally and vertically. -

6 La Nina/El Nino - El Nino is the anomalous warming of the eastern equatorial Pacific Ocean, while La Nina is the opposite anomalous cooling of this same region. - El Nino suppresses hurricanes near the U.S. - La Nina increases the temperature gradient in the area, thereby enhancing the jet stream. Drier conditions are experienced in the southwest, with wetter weather in the east. El Nino causes the opposite. - Neither phenomena are caused by global warming; however, both have the potential to be effecting by the warming of the earth. In recent decades, El Nino has been more prevalent. - Active winters in the northeast often occur when the ENSO cycle isn t pronounced in either direction. - The general public often finds El Nino and La Nina culpable for bad weather. -

7 Long-Range Weather Prediction - Long-range forecasting is very difficult and often inaccurate. - Monthly and seasonal forecasts are most popular. - Long-range products seek to identify whether or not precipitation and temperatures will be below normal, normal, or above normal. - The NWS operates the Climate Prediction Center (CPC) to provide official long-range forecasts. - Private companies, such as AccuWeather, also generate their own longrange forecasts. - A large amount of focus has shifted to predicting climate change. - Long-range forecasting can be compared to throwing darts. -

8 Thunderstorms - Thunderstorms form from instability in the atmosphere. - Single cell, multi-cell, and super cell thunderstorms are 3 common types. - Mesoscale convective systems are also a type of thunderstorm. - Super cell thunderstorms are most dangerous. - Three main ingredients: moisture, instability, lift trigger. - CAPE is the energy that feeds storms. Moisture is important. - Thunderstorms also need a trigger to form, such as a front. - Wind shear provides for healthier thunderstorms. - True or false: there can be lightning without thunder. - Thunderstorms often tease meteorologists and don t behave according to forecasts. -

9 Climate Change - The earth has natural cycles that occur all the time. - Climate refers to the long-term average, not the weekly weather. - Trends in multi-year data can be analyzed for a change in climate. - Climate change is occurring the data supports this conclusion. - The argument lies in whether or not humans are contributing to this change. - Global warming means the average earth temperature is going up. - Certain regions may be colder and snowier than average. - The ice age and medieval warm period represent significant differences in the earth s climate. - If the weather is like putting gas in your car, climate is like buying a new car. Temperatures in the lower 48 have been above average every year since the late 90s. -

10 Winter Precipitation Snow, sleet, freezing rain, and rain are the four main types. Freezing rain requires the warmest layer aloft in order to fully melt snow. Freezing rain is rain until it touches a surface below freezing. Sleet is basically little pellets of ice that form from refrozen rain. The pellets often bounce when they hit the ground. Snow requires a column of air that is at or below freezing. Freezing rain is most difficult to predict given stringent requirements. How much ice accretion is required for an ice storm warning?.25, but it varies by location! Hail and sleet are different in that one is made in a convective setup and the other is not! A glaze of ice looks pretty but can cause power headaches that last for weeks.

11 Folklore - Much weather folklore exists today. - Some is true while some is false. - Red sky in the morning, sailors take warning. Red sky at night, sailor s delight. - No weather is ill, if the wind be still. This is associated with high pressure. - Ring around the sun or moon indicates precipitation moving in. - Aches and pains due to decreasing pressure indicate storminess. - Groundhogs are most prominent source of false folklore. - The red sky folklore is accurate and has to do with high and low pressure. The sun rises in the east and sets in the west. Because weather moves from west to east, the heading of weather systems can be determined. Punxatawney Phil certainly deserves a jail sentence after this year s prediction. -

12 Lake(Sea)-Effect Snow/Rain - Lake effect snow occurs when very cold air moves over relatively warm lake water. - A difference in temperature of 13ºC is the common threshold for these events to occur. - The cold air over the warm water allows parcels to rise rapidly and create clouds and precipitations. - Ocean effect snow also happens when a similar pattern is in place near the ocean, such as over Cape Cod. - Wind direction is critical in determining how much an air mass is modified and thus how much precipitation falls over land. - Towns in Western New York and Northwest Pennsylvania are often buried under feet of snow from single lake effect snow storms. - The Tug Hill Plateau in New York averages more than 200 of snow per year. - Clouds often dump feet of snow in a short amount of time near the Great Lakes. -

13 Optical Phenomena - Rainbows are most common and are formed by refraction and reflection of light in raindrops. - The center of rainbows is the antisolar point, which is on the line between your eye and the sun. - Rainbows occur in falling rain. The drops are much larger than the wavelength of light, which makes for the bow shape. - Haloes are produced by the refraction of light by ice crystals high in the sky. - Coronas are produced by the diffraction of light by water drops in the clouds. - Sundogs also form from interaction of light and ice. - Aristotle, around 350 BC, was the first to was the first to seriously study rainbows. - The sun s rays can make some riveting designs when they interact with atmospheric features. -

14 Heat Index/Apparent Temperature - Heat Index is a measure of how it feels outside when humidity is factored in. - Assumes shady, light wind conditions. - The index is supposed to help people make smarter decisions about hot weather preparedness. - The NWS adopted the heat index in The index breaks down apparent temperatures into categories and identifies the potential risks. - Even at an air temperature of 84º, the heat index can be 100º with a relative humidity of 95%. - Developed in 1978 by George Winterling, who called it the humiture. The sizzling rays from the sun can t evade the heat index. -

15 Satellite Imagery/Data - Two main types of satellites: geostationary and polar orbiting. - Geostationary remain in same place with respect to earth. - Polar orbiters go around the earth, from pole to pole, once every day. - Geostationary satellites are ~22,000 miles above earth s equator. - Polar orbiters are ~550 miles above the earth s surface. - Polar orbiters offer a max resolution of 250 m. - Geostationary satellites offer a max resolution of 1km. - 3 main bands: visible, infrared, water vapor. - The first television satellite image of earth was taken in 1960 by TIROS-1. - Satellites can see forest fires and assist firefighting operations. - The visible band can see fresh snow. - Hurricane data has been greatly improved by satellites. - Satellites spy on our backyards to improve weather forecasting. - Meteorologists were up a creek without a paddle before satellites came along. -