Tuesday, August 6, 2013

July 2013 Climate Data and MWN Forecast Accuracy

As one might expect in July, rainfall across the metro was unevenly distributed thanks to pop-up thunderstorms that brought heavy rain to small areas.  However, the month was unusual from a big weather picture perspective as it was dominated more by northwest flow weather events than a strong Bermuda High and afternoon airmass storms. Though many of the showers and thunderstorms moved north and east of the metro, their presence in the region resulted in below average temperatures for the month due to increased cloud cover. Severe weather was negligible. Climate details for July can be found below.

Memphis International Airport, Memphis, TN

The average temperature for the month of July was 80.5 degrees, or 2.2 degrees below normal. The average high temperature was 89.1 degrees and the average low was 71.8 degrees. The coolest temperature of the month was 64 degrees on the 2nd, while the highest temperature was 96 degrees on the 11th and 17th.  For the year, Memphis is 1.1 degrees below average temperature-wise and, compared to last July, this month averaged 4.8 degrees cooler than July 2012 with a heat index that averaged 8 degrees cooler (93 in 2013 vs 101 in 2012).

Precipitation for the month totaled 3.73", which was 0.86" below the average monthly rainfall. No daily rainfall records were set.  There were eight calendar days with measurable rainfall, three of which recorded at least 0.5" and one which saw 1" or more.  Through July 31, annual precipitation at Memphis is over 11" above the 30-year average.

The maximum 24-hour rainfall was the record 1.82" on the 22nd-23rd. The peak wind was a 33 mph thunderstorm-induced gust from the northeast on the 18th with an average wind speed for the month of 6.8 mph. Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions, Bartlett, TN

The average July temperature at Cirrus Weather Solutions was 78.1 degrees with a maximum of 96.1 degrees on the 9th and a minimum of 59.4 degrees on the 13th. July precipitation measured only 2.98" via the Cirrus automated gauge and 3.15" in a manual gauge used for the CoCoRaHS program. The measured peak wind gust was 16 mph on the 14th. Average relative humidity was a muggy 78%. Click here for a daily recap on MemphisWeather.net.

MWN Forecast Accuracy

For the month of July, the average temperature error in all MWN temperature forecasts was 1.76 degrees, lower than all available computer data models and the National Weather Service forecasts. Nearly 75% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). For dewpoint accuracy, the MWN forecast averaged 1.62 degrees error and fell within 2 degrees of the actual dewpoint 77% of the time. Historical accuracy statistics can be found here.

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