Back in June 2008, I did a post titled Color and Temperature: Perception is everything.
One WUWT reader, Jes Simon noticed that since that time, something changed in the way NOAA was presenting the CONUS surface temperature, he worked up this comparison at right, and magnified below. I located the full size graphics as well, and he is correct, there has been a change, but the reason isn’t what he concluded.
Here is the original image from 2008, seen at left in the above image.
And here is an image I got from NOAA’s forecast database on 5/27/2014 that has a similar distribution of temperature:
Now some might say that something insidious is going on here, that NOAA has purposely adjusted the color scale, they’d be half right.
What we have here is a sliding scale where the units change range, but the color range stays the same. Compare the two scales side-by-side:
The reason for this is some small pockets of 110F+ temperatures in the 2008 map, in and near Death Valley, seen magnified below, and with the scale and arrow placed so that it is obvious.
So the point here is that just one station, plotting a single pixel of 110F+ temperature is enough to change the entire sliding scale. NOAA isn’t really doing a purposeful adjustment of color here to alter anyone’s perception, it is just the program adjusting the numeric scale based on the range of temperatures within the CONUS.
A better way to handle this problem is to create a set of fixed colors for temperature, much like Dr. Ryan Maue did for WeatherBell’s CONUS temperature images:
Now, NOAA is about to redo the presentation with a new look, like this:
Note that they say:
Below is a proposed replacement of the National Weather Service Graphical Forecast Page, a product of the National Digital Forecast Database. Comments are encouraged and can be done by taking our survey.
The survey can be taken here http://www.nws.noaa.gov/survey/nws-survey.php?code=wxmap
Comments can be left. This might be a good time to suggest a color scale that doesn’t give hot yellows and reds for 70-80F temperatures.
UPDATE: 5/29/14 Reader Rick W. sends along this image and notes:
So is one pixel enough to slide NOAA’s magical scale as Anthony claims? Apparently not. Here is the NOAA high temperature map for May 29th at 8 p.m. EDT. Note the temperature scale goes from 0 to 100 degrees.
The coldest point on this map is the Mount Rainer area in Washington State. It is showing a deep blue pixel indicating a temperature in the low 30s.
The hottest area on this map is the southwest. It is showing temperatures between Phoenix, Yuma and Indio above 100 degrees. This is not a pixel we’re talking about; it is several thousand square miles of temperatures above 100 degrees.
Note the temperature scale does not go above 100 degrees in any of these maps.
So rather than speculate as to how the NOAA system works, I’m going to ask NOAA directly rather than speculate further. When I get an answer on why the map scale/colors are not representative of actual surface temperatures at the high end, I’ll post either an update here or a new post about it. – Anthony