Friday, October 1, 2010

September Climate Data and MWN Forecast Accuracy

Memphis International Airport, Memphis, TN
September typically marks the transition from the heat of a Memphis summer to the much more pleasant conditions of fall. While that transition did take place this month, it was much later in than any Mid-Southerner could have hoped for, especially after a very long and hot summer. Multiple high temperature records were again broken in September, including a week-long stretch of record heat from the 18th to the 24th, including the latest 100 degree day in recorded history, reached on September 20. Finally, on the 25th, an autumn cold front moved through and brought an end to the "Summer of 2010!" In addition, very dry conditions persisted and parts of the metro area were classified as being in a "moderate drought" by the end of the month.

For the month, the average temperature was 79.1 degrees, which was 4.3 degrees above normal. The average high temperature was 90.6 degrees and the average low was 67.7, with 19 days reaching a high of at least 90. Typically, only 7 days in September reach 90 degrees (making the average high of 90.6 even more incredible). The maximum temperature for the month was 100 degrees on the 20th and the lowest was 54 on the 28th.

Precipitation for the month of September totaled only 0.14", or 3.17" below normal, making this month the 3rd driest September on record, trailing only 1928 [0.06"] and 1897 [0.00"]. There were just 6 days with measurable rainfall, the maximum one day total being just 0.06". There were no days in which thunder was recorded. The peak wind gust was 37 mph on the 16th, while the average wind speed for the month was 6.9 mph. Click here for a daily statistical recap for September.

Bartlett, TN
Bartlett also saw a very warm and dry month. The average temperature for September at the WXLIVE! station in north Bartlett was 75.1 degrees with a maximum of 98.2 on the 20th and a minimum of 45.7 degrees on the 28th.

September precipitation ended up well below normal with a precipitation total of 0.12" and only 4 days of measurable rainfall. A co-located manual gauge used for the CoCoRaHS program measured 0.13" in September. The peak wind gust was 23 mph on the 16th. Average relative humidity was 65%. Click here for a daily statistical recap on

MWN Forecast Accuracy
For the month of September, the average temperature error in all MWN temperature forecasts was only 2.06 degrees, beating all compared computer models, including the National Weather Service, by 10% or more. Nearly 65% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. MWN's forecasts extend out five periods (or 2.5 days). For dewpoint accuracy, the MWN forecast was also the best of the data sources at 2.45 degrees average error and was within 2 degrees of the actual dewpoint nearly 65% of the time. More detailed accuracy statistics can be found here.

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