Monday, September 28, 2015

Feels-Like Temperature Range 2014-2015.

Earlier in the summer I posted maps showing the "typical" range of temperatures during a climatological period. This post is a little different as it uses the "feels like" temperatures during the last year to depict the actual range of apparent temperatures. I use the conventional measures of Heat Index for warm temperatures and Wind Chill for cold temperatures. Only those stations that had sufficient observations to measure both a summer Heat Index and a winter Wind Chill were utilized. That required valid temperature, dewpoint (for Heat Index) and wind (for Wind Chill) measurements.

Heat Index:

The first map (Figure 1) shows the highest Heat Index recorded at ASOS station during the summer of 2015. The Heat Index was computed from hourly ASOS observations using the temperature and dew point (Steadman formula). The maximum dew point for 2015 is shown in Figure 2.

Figure 1. Highest Heat Index recorded in 2015 at ASOS stations.

Figure 2. Highest dew point temperature recorded in 2015 at ASOS stations.

Wind Chill:

Wind Chill is the apparent temperature based on the combined effect of temperature and wind. As many readers know, the wind chill formula was updated in 2001 (Osczevski 2001). In this analysis, I looked as hourly ASOS observations and computed wind chills for every hour during the 2014-2015 winter (November through March). The results are shown in Figure 3.
 Figure 3. Lowest Wind Chill recorded in the 2014-2015 winter at ASOS stations.


Unsurprisingly, continental climates experience the greatest range of annual temperatures (see interior Alaska and the northern Great Plains. While interior Alaska has the greatest annual temperature range in the U.S. based on climatology, several stations in North Dakota won the feels-like temperature lottery. In Alaska, the coldest temperatures are usually accompanied by calm winds and the warmest summer temperatures usually are so dry that the apparent temperature is 5°F-10°F lower than the actual temperature.

The other surprising aspect to the map is the range in Iowa is greater than the range in neighboring Nebraska.
Figure 4. Difference between highest Heat Index and Lowest Wind Chill at ASOS stations during the last year (summer minus winter).

Figure 5. ASOS stations used in the analysis depicted in Figures 1-4.

1 comment:

  1. Thank you for your maps. They are useful in finding good places to live.

    I would like to see a Number of Miserable Days map. I know you've done dreary. To me miserable would mean any one of the following:

    1. Heat index > 90
    2. Wind chill < 10
    3. Cloudiness > 90%


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