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| Why is the official temperature for Denver recorded at Denver International Airport (DIA)? |
| Denver’s official temperatures along with all other weather information except snowfall, is recorded at DIA because commercial airports are the origin of regular weather observations in the United States. This is mandated by the National Weather Service and the Federal Aviation Administration. 9NEWS is not involved in the process of determining the location of official weather observation stations. |
| Why is snowfall not recorded at DIA? |
| Official snowfall for Denver is measured at the former Stapleton International Airport site to provide continuity of records. In addition, the Automated Surface Observation Station (ASOS) at DIA is not capable of recording snow depth. |
| Where, when, and how is snow measured at the former Stapleton International Airport site? |
| Snow measurements are taken at several locations around the former National Weather Service facility on East Smith Road (just east of Quebec St). The average of all the measurements is used to determine the official snow depth for Denver. This measurement is recorded daily at approximately 6 a.m. If snow falls at the measurement site after 6 a.m. it won’t be recorded until the next day. For example, if 10 inches of snow falls between 7 a.m. and 9 p.m. on December 15th, and no snow fell on December 14th, the official weather report for Denver will indicate no snow on December 15th and 10 inches on December 16th. |
| How many days of sunshine does Denver really get? |
| Regardless of what you may hear, each year Denver averages 115 mostly sunny days, 130 partly cloudy days, and 120 mostly cloudy or cloudy days. If you consider partly cloudy days to be “sunny”, then Denver averages 235 days of sunshine each year. The popular claim of 300 days of sunshine each year in Denver is only true if every day with at least some sunshine is considered a “sunny” day. |
| What is wind chill and how is it calculated? |
| Heat produced by the human body radiates out of our skin and into the surrounding air. When there is no wind, this thin layer of heat partially insulates us from the full effect of the cold surrounding us. When conditions are windy, this layer of heat is swept away from the body and thus the full impact of the cold air is felt on our skin. Even though the actual air temperature is the same when conditions are windy, it "feels" colder. The wind chill temperature gives a comparison to what it would feel like at a lower temperature if there were no wind. Wind chill only applies humans and other living things; it has no effect on objects such as vehicles. Click here for more information. |
| Where can I find historical weather data for Denver? |
The “Climate” page on the Denver-Boulder National Weather Service website offers historical weather data for Denver going back five years. Click here and then click on “Preliminary Climatology Data (CF6)” to find daily information about temperature, precipitation, snowfall, wind speed, etc.
For historical weather data beyond five years ago or for locations other then Denver, refer to the National Climatic Data Center website. The NCDC may charge a fee for data.
You may also be able to obtain information from the Colorado Climate Center at Colorado State University in Fort Collins.
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| What weather related educational materials are available on the Internet for teachers? |
| Our partners at the USA TODAY have developed a website with links to a wide variety of weather related material especially for teachers. Click here. |
| What is high pressure and what does it mean for Colorado weather? |
| When the atmospheric pressure is above 1013.25 millibars (the equivalent of 29.92 inches of mercury), we are considered to be under high pressure. This implies that the atmosphere is "denser" and therefore the air tends to sink. Winds flow in a clockwise motion around the center of high pressure. Sinking air under an area of high pressure generally means a lack of cloud cover, precipitation, and wind. During the summer months, temperatures are usually warm, while the opposite is true in the winter. |
| What is low pressure and what does it mean for Colorado weather? |
| When the atmospheric pressure is below 1013.25 millibars (the equivalent of 29.92 inches of mercury), an area is considered to be under low pressure. This implies that the atmosphere is "less dense" and therefore the air tends to rise. Winds flow in a counter-clockwise motion around the center of low pressure. Since the air is rising under an area of low pressure, it cools and condenses generally causing clouds and possibly precipitation. |
| What does “radiational cooling” mean? |
| When skies are clear and winds are light or calm, the heat accumulated during the day rapidly rises, or radiates, upwards. This results in a quick drop in temperatures shortly after sunset. |
| What is the difference between “partly cloudy” and “partly sunny” |
| At 9NEWS we use six different explanations to describe daytime sky conditions: Sunny means no clouds are present in the sky
Mostly Sunny means clouds cover less than 10% of the sky
Partly Cloudy means clouds cover between 10% and 50% of the sky
Partly Sunny means clouds cover between 50% and 75% of the sky
Mostly Cloudy means clouds cover between 75% and 99% of the sky
Cloudy means clouds cover the entire sky |
| What is the difference between “isolated” and “scattered” precipitation? |
| Forecasts on 9NEWS will often include both of these terms. Scattered is a more common occurrence than isolated. In other words, you are more likely to see rain or snow when there is a chance of "scattered showers" than when there is a chance of "isolated showers". |
| What is a “Chinook” wind and why does it bring warmer temperatures to Denver? |
| A “Chinook” or “downsloping” wind refers to a westerly wind that descends the leeward side of a mountain range. As Chinook winds force an air mass down the east slope of the Front RangeMountains, the air mass encounters stronger atmospheric pressure causing it to warm. This generally results in gusty winds causing warm, dry conditions for the Denver area. Chinook winds where named after the Chinookan Indians who lived in present day Oregon and Washington since the wind origination in the direction of their country. They occur all along the Front Range of the Rocky Mountains from Alberta, Canada to Albuquerque, New Mexico. |
| What do you mean by “upslope” and why does it bring precipitation to Denver? |
| 9NEWS Meteorologists will often use the term “upslope” during weathercasts as an easy way to refer to “orographic lift”. Orographic lifting occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. This occurs frequently in Colorado when an easterly wind is present over the Eastern Plains. As an air mass moves west it encounters the mountains it is forced upward. As the air gains altitude, it expands and cools. Cold air can’t hold moisture as well as warm air and therefore moisture contained within the air is forced out through a process called “condensation” which changes invisible water vapor into a liquid. As the air condenses, it creates clouds and often precipitation. The process can bring significant snow to Denver in the winter and heavy rain in the summer. |
| Where can I find information about pursuing a career in Meteorology? |
| We recommend that you check out the Career Guide put together by the American Meteorological Society. A list of colleges and universities that offer courses in meteorology, atmospheric science and weather forecasting can be found here. |
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