- Our Weather City Pages give you today's and tomorrow's weather, an hour-by-hour forecast, a 14-day forecast, searchable past weather, and climate information for a location. Go to the weather pages for your city. Are 14-Day Forecasts Accurate? Modern weather predictions are a combination of computer-based models and human experience.
- Be prepared with the most accurate 10-day forecast for Eugene, OR with highs, lows, chance of precipitation from The Weather Channel and Weather.com.
- Forecasts are all about accuracy, right? So why settle for less when you can have the wisdom of a master? Weather Guru Pro will tell you all you need to know, with inspirational quotes, a 7 day animated forecast and with an outstanding accuracy thanks to Windguru and their own forecast stations.
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- Weather Guru 2 1 – Accurate Weather Forecasts Today Forecast
- Weather Guru 2 1 – Accurate Weather Forecasts Today Tomorrow
The warmest day over the next 25 days weather in Guru is forecast to be Tuesday 8th September 2020 at 17°C (63°F) and the warmest night on Wednesday 16th September 2020 at 11°C (52°F). Easyping 2 3 – ping client to determine host accessibility. The average temperature over the next 25 days in Guru from this forecast is 14°C (57°F) and there will be 1 day of sunshine.
By Anne Buckle . Published 1-Oct-2009
We provide weather forecasts for millions of locations around the world. How reliable are they?
Our Weather City Pages give you today's and tomorrow's weather, an hour-by-hour forecast, a 14-day forecast, searchable past weather, and climate information for a location.
Are 14-Day Forecasts Accurate?
Modern weather predictions are a combination of computer-based models and human experience. As a rule of thumb, the closer a weather forecast is in time, the more accurate it is. Long-term predictions have a larger margin of error because there are more unknown variables.
This means that our short- and medium-range forecasts are the most accurate. Long-range forecasts predicting the weather for more than 7 days in advance should be seen as a rough guide, as the accuracy of weather predictions falls considerably around the one-week mark.
If you notice a weather forecast that is repeatedly incorrect, please let us know.
Weather Station Limitations
Past, current, or predicted temperature values displayed in a weather report may not always represent the warmest or coldest temperature for a location on a particular day.
This is due to practical limitations:
- Time: If the temperature is recorded at 13:00 (1:00 pm) and again at 14:00 (2:00 pm) but the temperature peaks at 13:30 (1:30 pm), the readings for the maximum temperature will be a little too low.
- Frequency: Some weather stations do not report as frequently as others. Some stations transmit their readings every 30 minutes or every hour while others may do so every 2 or 3 hours. Also, some stations are not consistent with the times in which they provide their reports.
- Location: In some cases, weather stations are quite far away from the city, so weather conditions may differ there.
Where Does the Weather Data Come From?
CustomWeather provides the weather data on timeanddate.com. They use weather stations at airports, stations run by the World Meterological Association (WMO), and MADIS weather stations which are typically a community effort.
What Is Weather?
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Weather is defined as the state of the atmosphere with respect to heat or cold, wetness or dryness, calm or storm, clearness, or cloudiness. It includes temperature, pressure, humidity, clouds, wind, precipitation, and fog.
While weather relates to mostly temperature and precipitation on a day-to-day basis, climate is the term for average atmospheric conditions over longer periods of time.
While most scientists are revered for making sense of our complex universe (Einstein is practically a hero), meteorologists often face ridicule. How can we put a person on the moon or foretell planetary alignments years in advance, yet still fail to put together accurate weather forecasts?
First, to give credit where credit is due: Weather forecasters have improved their game significantly over the last 20 years. The three-day forecasts they deliver today are better than the one-day forecasts they delivered 20 years ago. They're also much better equipped to provide advanced warnings of severe weather, doubling the lead times for tornado warnings and giving people an extra 40 minutes to escape flash floods.
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Modern meteorologists wouldn't be nearly so accurate without numerical forecasting, which uses mathematical equations to predict the weather. Such forecasting requires powerful computers and lots of observational data collected from land, sea and air. A single weather station would never be able to collect so much information. Instead, thousands of stations across the globe are linked and their data pooled. Some of these stations -- ground-based wind gauges (what meteorologists call anemometers), rain collectors and temperature sensors -- resemble those used by amateur weather watchers. Others lie far out at sea, strapped to buoys. And still others travel on commercial airliners or shipping vessels, collecting weather data as passengers and goods are moved from point A to point B. Finally, weather satellites and balloons provide information from the upper regions of the atmosphere. Satellites photograph Earth's weather from their orbit in space, while balloons monitor upper-air data over a particular location.
Collectively, all of these sensors and gauges produce more than 1 million weather-related observations every day. A normal computer -- the kind you buy at your local electronics store -- would choke on all of this data. Luckily, meteorologists can rely on supercomputers, crazy-fast machines that perform millions of calculations per second. In the United States, these computers are housed at the National Centers for Environmental Prediction (NCEP), located in Camp Springs, Md. There, weather observations stream into a supercomputer's brain, which uses complex mathematical models to predict how, based on the incoming data, weather conditions might change over time. The computer's output form the basis of almost every forecast broadcast on radio and television channels across America.
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You might think that the National Centers for Environmental Prediction's supercomputers could never make mistakes, but even their abilities aren't up to the enormous challenge of weather forecasting. That's because they must take into account several large-scale phenomena, each of which is governed by multiple variables and factors. For example, they must consider how the sun will heat the Earth's surface, how air pressure differences will form winds and how water-changing phases (from ice to water or water to vapor) will affect the flow of energy. They even have to try to calculate the effects of the planet's rotation in space, which moves the Earth's surface beneath the atmosphere. Small changes in any one variable in any one of these complex calculations can profoundly affect future weather.
In the 1960s, an MIT meteorologist by the name of Edward Lorenz came up with an apt description of this problem. He called it the Butterfly Effect, referring to how a butterfly flapping its wings in Asia could drastically alter the weather in New York City. Today, Lorenz is known as the father of chaos theory, a set of scientific principles describing highly complex systems, such as weather systems, where small changes in initial conditions radically change the final results. Because of chaos, there is a limit to how accurate weather forecasts can be. Lorenz set this limit at two weeks.
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Modern meteorologists use state-of-the-art technology and techniques to tame chaos, such as the ensemble forecast, which consists of several forecasts, each one based on slightly different starting points. If each prediction in the ensemble looks the same, then the weather is likely to 'behave.' If any prediction looks radically different, then the weather is more likely to 'misbehave.'
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Meteorologists also rely on Doppler radar to monitor weather conditions more effectively and improve forecasts. Doppler radar requires a transmitter to emit radio waves into the sky. The waves strike atmospheric objects and bounce back. Clouds moving away from the transmitter return different kinds of waves than clouds moving toward the transmitter. A computer in the radar converts data about the reflected radio waves into pictures showing cloud coverage and bands of precipitation, as well as wind speeds and direction.
Because of this technology, meteorologists can now predict the weather better than ever, especially when they limit how far they look into the future. For example, up to 12 hours out, meteorologists offer fairly reliable forecasts of general conditions and trends. Unfortunately, thanks to chaos, they will never be able to predict the weather with absolute certainty, which is how surprise storms -- tornadoes and torrential, flooding rains -- continue to devastate communities with little warning. For this reason, it might be best to carry an umbrella, even on days forecasted to be bright and sunny.
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Sources
- Dye, Lee. 'Can We Control the Weather? Maybe.' ABC News. Aug. 3, 2005 (June 29, 2010)http://abcnews.go.com/Technology/DyeHard/story?id=1001079&page=1
- Monastersky, Richard. 'Forecasting is No Picnic.' Scientific American Presents Weather: What We Can and Can't Do About It. Spring 2000.
- Rosenfeld, Jeffrey. 'The Butterfly That Roared.' Scientific American Presents Weather: What We Can and Can't Do About It. Spring 2000.
- Williams, Jack. The Weather Book. Vintage Books, 1997.