ForecastAdvisor Weather Forecast Accuracy Blog

A Blog Documenting the Intersection of Computers, Weather Forecasts, and Curiosity
 Subscribe in a reader    Subscribe by email:   Delivered by FeedBurner


Wednesday, October 11, 2006

A Very Cool September

The September accuracy data has been aggregated and is now available. You should see the "Last month" accuracy values on your forecast page have updated. For Columbus, Ohio, for example, there wasn't much change...Weather Channel moved up from #3 to #2 while the National Weather Service did the opposite.

Temperature accuracy is beginning its seasonal dip. Overall high temperature accuracy was at its lowest in July, at 4.05 degrees error. In August it started moving back up to a peak in mid-winter. September continued the trend. Overall high temperature error in September was 4.57 degrees. You can read more about the seasonal nature of weather forecast accuracy in this blog entry.

One interesting thing to note is that it was a very cool September. ForecastWatch tracks how an unskilled climate forecast compares to weather forecasts by the weather forecast providers. But this also tells us how the climate is doing, because all we are doing is comparing climate normals with what actually happened. In September, for the about 800 observations locations we track, high temperatures were 2.33 degrees below 1971-2000 climate normals. Low temperatures, on the other hand, were only 0.14 degrees below normal. The National Climatic Data Center has said that September was the 31st coolest on record. There is more data from the NCDC here.

The map below is one available in ForecastWatch. Because it is from the perspective of the forecast, red means the forecast was too high, blue means the forecast was too low. If you want to look at it from the perspective of the actual temperatures, red areas are areas where temperatures were below climate normals, and blue where they were above.

The map shows how a climate normal forecast did in September. Red areas indicate areas where a forecast of the climate normal high was too high (in other words, the actual high temperature was below normal, on average). The blue areas are areas where the actual high temperature was above climate averages.

You can compare this map to the one produced by the NCDC. I think they are pretty comparable.



December 2005   January 2006   March 2006   June 2006   July 2006   August 2006   September 2006   October 2006   November 2006   December 2006   January 2007   February 2007   March 2009   September 2009   March 2010   April 2010   February 2011   April 2011   June 2011   February 2012   September 2012   June 2013   October 2013   February 2014   June 2016   Current Posts