The Weather Wire
December 2009 Volume 17 Number 12
Avg High - 56.4
Avg Low - 28.8
Snow - 9.3"
Season Snow - 26.5"
Precipitation - 0.49"
Avg High - 44.1
Avg Low - 16.4
Avg Snow - 8.7"
Avg Precip - 0.63"
Wind Chill Overview
Now that we are entering the coldest part of the winter season we will be dealing with wind chill more often. Just last week there were Wind Chill Advisories posted for much of the Front Range and many questions were asked about what the effects are and how the cold affects humans and machinery alike. Below are typical questions asked about wind chill and answers provided by NWS/NOAA.
What is wind chill temperature?
6. Avoid Overexertion
A. Your heart is already working overtime in cold weather. The strain from the cold and the hard labor of shoveling heavy snow, walking through drifts or pushing a car may cause a heart attack. Sweating from overexertion could lead to a chill and hypothermia.
7. Is there a Celsius version of the chart?
A. We will look into adding a Celsius version to the web page calculator. In the mean time, you can go to http://www.wrh.noaa.gov/slc/projects/wxcalc/windChill.php
8. Wind chill factor vs. wind chill temperature.
A. These terms are almost the same. The wind chill factor describes what happens to a body when it is cold and windy outside. As wind increases, heat is carried away from the body at a faster rate, driving down both skin temperature (which can cause frostbite) and eventually the internal body temperature (which can kill).
Wind chill temperature is a unit of measurement to describe the wind chill factor. Wind chill temperature is a measure of the combined cooling effect of wind and temperature. Since you and your husband ride motorcycles, you can insert your driving speed to estimate the wind speed and the outside temperature. These two parameters combined will give you the wind chill temperature, or how it feels to you skin. On the bottom of the wind chill chart is the updated wind chill temperature formula.
9. Is it possible to get frostbite if the temperature is above freezing but the wind chill is below freezing?
The air temperature has to be BELOW freezing in order for frostbite to develop on exposed skin. Wind chill can bring the temperature to below freezing for humans and animals.
10. How is the Wind chill is calculated?
The wind chill temperature is calculated using the following formula:
Wind chill (ºF) = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16)
T = Air Temperature (F)
Wind chill Temperature is only defined for temperatures at or below 50 degrees F and wind speeds above 3 mph. Bright sunshine may increase the wind chill temperature by 10 to 18 degrees F.
11. When does the National Weather Service issue a Wind chill Advisory or Warning?
Criteria for issuing Wind chill Warnings and Advisories are set locally. For the Rochester, NY area, Wind chill Warnings are issued when the Wind chill Temperature is expected to fall at or below -25 F. Wind chill Advisories are issued when the wind chill temperature is expected to fall between -15F and -24F.
12. Does wind chill only apply to people and animals?
Yes. The only effect wind chill has on inanimate objects, such as car radiators and water pipes, is to more quickly cool the object to cool to the current air temperature. Object will NOT cool below the actual air temperature. For example, if the temperature outside is -5 degrees Fahrenheit and the wind chill temperature is -31 degrees Fahrenheit, then your car's radiator will not drop lower than -5 degrees F.
13. Does humidity or being near a large water body affect on wind chill?
When we tested the new Wind chill Temperature Index (WCTI), our researchers applied the new index to 12 test subjects. The results of the tests showed that relative humidity was an insignificant weather parameter, less than one degree at worst. To simplify the calculation, relative humidity was left out of the formula.
We did research a wet wind chill or blowing water spray. This research was to simulate a person near a body of water or a mariner. These findings are being finalized and may be incorporated for the winter season 2003-2004.
14. How does this chart apply to children?
The tests that were done on Wind chill were conducted on adult subjects. For legal and safety reasons, NWS could not ask for child volunteers. Use the existing chart as a starting point and be even more cautious with children, seniors and persons with compromised health.
Q + A was taken from: http://www.nws.noaa.gov/os/windchill/windchillglossary.shtml
With the widespread precipitation of the last several months over much of Colorado, though some dry areas have developed in southwestern Colorado.
The map below shows forecasted temperature deviances for December 2009. As can be seen, the eastern 1/3 of Colorado is expected to have below normal temperatures with the remainder of the state seeing normal temperatures.
The map below shows forecasted precipitation deviances for December 2009. All of Colorado is expected to have normal precipitation for December 2009.
Little in the way of drought remains in Colorado, with the exception of a small area in far southwest Colorado.
November of 2009 was relatively tame weather wise with above normal temperatures and below normal snowfall and precipitation. The average highs was 56.4 and the average low was only 28.8 resulting in a monthly mean temperature of 42.6 degrees which is 5.1 above the normal of 37.5. Being Denver's 2nd snowiest month, November of 2009 came in a little low in snowfall with 9.3" measured at DIA compared to 10.7" on average. Still for the year though we are 8.3" above normal thanks to a snowy October. Sadly % of possible sunshine is no longer recorded, but I would have to think that there was above normal sunshine with the above normal temperatures.
Well, since we are already through the first week and a half of the month it would be easy to think that with all the cold weather so far this will be a very cold and snowy month. But as we know by living in Colorado you don't have to wait long for the weather to change and I would expect a warmer and drier weather regime through at least Christmas. There may be another unsettled and cold outbreak towards the end of the month, but current weather trends indicate that most of the snow will remain on the western half of the state leaving the Front Range relatively dry for a couple weeks. The official start of Winter will be on the 21st at 10:47am. Amazing to think we have not even started winter yet and many areas from the Palmer Divide northward already have over 50-60% of an entire winters worth of snow! We have already logged above normal precipitation for the year with 17.67" at the start of the month which is 3.51" above normal.
Sunrise/Sunset (Jul - December Denver area)
Sept 2009 to Apr 2010