Friday, October 4, 2013

September 2013 Climate Data and MWN Forecast Accuracy

Climatological fall starts in September but it didn't feel like autumn with temperatures well above normal and precipitation highly variable. At the official observing site at Memphis International, rainfall was below normal, but on the north side of the county, at MWN headquarters in Bartlett, rainfall totaled nearly 2" more than at the airport. Climate details for September can be found below.

Memphis International Airport, Memphis, TN

The average temperature for the month of September was 78.2 degrees, or 3.0 degrees above normal. The average high temperature was 87.4 degrees (2.3 degrees above normal) and the average low was 68.9 degrees (3.7 degrees above normal). The coolest temperature of the month was 59 degrees, reached on the 15th, 22nd, and 23rd, while the highest temperature was 98 degrees on the 8th. This also was the hottest temperature recorded all summer in Memphis. There were 14 days which saw high temperatures at or above 90, which is 6.3 more than normal.

Precipitation for the month totaled 2.69", which was 0.40" below the average monthly rainfall for Memphis International. There were nine calendar days with measurable rainfall, but only two which recorded at least 0.1" and one which saw 1" or more.  Through September 30, annual precipitation at Memphis is 48.64", which is 10.17" above the 30-year average.  The maximum 24-hour rainfall was 1.87" on the 20th.

The peak wind was 30 mph from the east on the 1st with an average wind speed for the month of 6.7 mph. The average relative humidity was 62 percent and average sky cover was 40 percent. Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions, Bartlett, TN

The average September temperature at Cirrus Weather Solutions was 74.1 degrees with a maximum of 97.7 degrees on the 8th and a minimum of 49.4 degrees on the 15th (which was also the only morning low below 50 for the month). September precipitation was much higher than at the airport and measured 4.59" via the Cirrus automated gauge and 4.79" in a manual gauge used for the CoCoRaHS program. Much of this was recorded on 3 days which each saw 0.85" of rain or more. For the year, the CoCoRaHS gauge at MWN has recorded 46.11" of precipitation. The measured peak wind gust was 21mph on the 9th and again on the 10th. Average relative humidity was a muggy 79%. Click here for a daily recap on

MWN Forecast Accuracy

For the month of September, the average temperature error in all MWN temperature forecasts was 1.64 degrees, lower than all available computer data models and the National Weather Service forecasts with the exception of the LAMP short-range model, which only extends 25 hours into the future. MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). Over 81% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. For dewpoint accuracy, the MWN forecast averaged 2.17 degrees error and fell within 2 degrees of the actual dewpoint 63% of the time. Historical accuracy statistics can be found here.

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