Guest analysis

Every morning, the Capital Weather Gang assigns the “Daily Digit”, a ‘somewhat  subjective’ rating of the day’s weather from 1 to 10. They have been doing this since December 16, 2009.

With this post, I extend the analysis back to the beginning, as well as include data all the way up to the present – June 30, 2015. A total 2,018 days are included in the analysis.*

Some key findings:

  • The average Daily Digit – approximately 6/10 – has increased over time
  • Saturday, on average, earns the highest digit
  • Tuesday, on average, earns the lowest digit
  • Months with the lowest average digits are associated with some of D.C.’s most extreme historical weather events over the last 5 years

While the current Daily Digit Range is 1 through 10, several zeroes have been assigned. There are 10 dates where a zero was used, such as June 30, 2012, the day after the 2012 Derecho. It was also used several more times during the summer of 2012, as well as on October 29, 2012, the day Superstorm Sandy hit. The last use of zero I could find was January 7, 2014 – when a bitter cold snap arrived.

Due to the relative infrequent use of zero, it is not included in most of the analysis below.

The mean digit assigned of all days was 6.023, vs. an expected mean of 5.5 if the digits were uniformly assigned. Below is a histogram, showing the distribution of each digit.


Number of days with digit ratings ranging from 0-10, Dec. 2009 to June 2015. (Chris Smolinski)

Below is a trend graph of the Daily Digit, smoothed slightly to make it more readable:


Time series showing daily digit December 2009 to June 2015. Best fit trend line included. (Chris Smolinski)

There is a very slight increase in the assigned digit over time, about 3.3% over five and a half years. This could be due to the weather actually getting nicer over time, or Daily Digit inflation.

Below is a graph of the Daily Digit averaged on a per month basis:


(Chris Smolinski)

Several months stand out as being particularly low: December 2010 (the month of Snowpocalypse), July 2012 (the second hottest July on record), and January 2014 and 2015 (both of which had punishing cold air outbreaks).

Below is a histogram of the average Daily Digit for each day of the week. There does appear to be a weekend bias, although there is a semi-regular rotation of CWG staff by day of week:


(Chris Smolinski)

Monday: Jason Samenow
Tuesday: Matt Rogers
Wednesday: Dan Stillman
Thursday: David Streit
Friday: Camden Walker
Saturday: Ian Livingston
Sunday: Brian Jackson

Sometimes there are changes to the staff rotation, so the histogram of average Daily Digit vs author is not exactly the same as the day of week histogram:


(Chris Smolinski)

The histogram of average Daily Digit by month shows Spring and Fall being the winners, with December, January, and July having the lowest average ratings:


(Chris Smolinski)

Below are histograms for each author. Some have a [relatively] normal distribution, some do not:


Histogram showing the count of the various digit values assigned by Jason Samenow Dec 2009 to June 2015. (Chris Smolinski)

Histogram showing the count of the various digit values assigned by Matt Rogers Dec 2009 to June 2015. (Chris Smolinski)

Histogram showing the count of the various digit values assigned by Dan Stillman Dec 2009 to June 2015. (Chris Smolinski)

Histogram showing the count of the various digit values assigned by David Streit Dec 2009 to June 2015. (Chris Smolinski)

Histogram showing the count of the various digit values assigned by Camden Walker Dec 2009 to June 2015. (Chris Smolinski)

Histogram showing the count of the various digit values assigned by Ian Livingston Dec 2009 to June 2015. (Chris Smolinski)

Histogram showing the count of the various digit values assigned by Brian Jackson Dec 2009 to June 2015. (Chris Smolinski)

And finally all of the authors on one histogram (yes, it is a busy graph):


Histogram showing the count of the various digit values assigned by all CWG authors Dec 2009 to June 2015. (Chris Smolinski)

Below are some statistics for each regular author:

Jason Samenow posts: 333 mean: 5.726727
Matt Rogers posts: 289 mean: 5.449827
Dan Stillman posts: 284 mean: 5.841549
David Streit posts: 268 mean: 6.156716
A. Camden Walker posts: 290 mean: 6.151724
Ian Livingston posts: 237 mean: 6.649789
Brian Jackson posts: 266 mean: 6.43985

Not included in the above histograms are authors with only a few posts:
Josh Larson – 7 posts
Kathryn Prociv – 17 posts
Rick Grow – 15 posts

There are also a few posts credited to more than one author, they also were not included.

I want to thank Justin Grieser who provided me with data from December 16, 2009 through December 16, 2012, as well as all of the members of the Capital Weather Gang for their work each day providing us with excellent forecasting and commentary on all topics related to the weather.

More daily digit reviews:

Previously, I analyzed the distribution of the Gang’s daily digits between March 19, 2013 through October 13, 2014:

A Statistical Analysis of A Somewhat Subjective Rating of the Day’s Weather

See also these earlier digit analyses from Justin Grieser…

Capital Weather Gang’s Daily Digit turns 3

Dissecting the daily digit: Forecaster averages, nice days, and best commentary (Part II)

Dissecting the daily digit: History, seasonal averages, temperature trends, and other trivia

* Five days are not included in the above analysis, because no Daily Digit was assigned: February 6 and 10, 2010, June 6, 2010, January 8, 2011, and April 24, 2011.