December & 2013 Annual Climate Data and MWN Forecast Accuracy

December was marked by huge temperature swings and periods of rain and thunderstorms with several days also seeing very light winter precipitation. When averaged out, temperatures averaged just below normal and precipitation was also below normal at the airport but above normal in other areas of the metro where precipitation was more persistent.  There were two periods of well above normal temperatures (70s), including a couple of record-setting days, while the colder days tended to be very cold with highs in the 30s. Climate details for December, as well as the year 2013, can be found below.

Memphis International Airport, Memphis, TN – December

The average temperature for the month of December was 43.0 degrees, or 0.6 degrees below normal. The average high temperature was 51.4 degrees (0.7 degrees below normal) and the average low was 34.6 degrees (0.5 degrees below normal). The coolest temperature of the month was 22 degrees, reached on the 7th, while the highest temperature was 76 degrees on the 4th and 21st. There were 17 days which saw low temperatures below 32 degrees and one day in which the high did not reach 32.  The low of 61 degrees on the 20th set a record (1931) for the warmest minimum temperature on record for that date. The high of 76 degrees on the 21st also set a record (1967) for the warmest temperature on record for that date.

Precipitation for the month totaled 4.82″, which was 0.76″ below the average monthly rainfall for Memphis International. There were 11 calendar days with measurable rainfall and one which saw 1″ or more.  The greatest 24-hour rainfall occurred on the 20th-21st with 1.95″ of precipitation. There were 4 days one which light freezing rain was recorded, 4 days with sleet recorded, and 2 days on which light snow fell.  In sum, 5 days had some form of winter precipitation, however totaling only a trace for the month.

The peak wind was 49 mph from the south on the 21st with an average wind speed for the month of 7.4 mph. The average relative humidity was 71 percent and average sky cover was 70 percent. Click here for a daily statistical recap for Memphis International Airport.

Memphis International Airport, Memphis, TN – 2013 Annual

For the year, the official mean temperature for Memphis was 62.1 degrees with an average high of 71.2 and an average low of 53.0.  The mean is 1.0 degrees below normal, while the average high was 1.3 degrees below normal and the average low 0.6 degrees below normal.  There were 62 days with temps of 90 or greater (2.3 below normal), 58 days with lows at or below 32 (15.2 days above normal), and 3 days with highs at or below 32 (1.4 below normal).

Periods of warm and cold weather are evident in the daily average temperature graphic, particularly in the running mean (shown below). Very warm weather started the year, followed by a cool spring, average summer, then warm early fall and cool start to winter.

Precipitation totaled 59.43″ for the year, which is 5.75″ above normal, but almost two feet more than 2012. There were 114 “rain days” (measurable precip recorded), which is 6.3 above normal, and 18 days with more than one inch of rain. The wettest day of 2013 was May 21, which recorded 4.18″ of rainfall. Snowfall totaled a trace (normal is 3.8″) with 11 days recording a trace of snow.

The last freeze in the spring was March 24th and the first fall freeze was November 12, resulting in a growing season of 232 days.  The average wind speed was 7.6 mph, the peak wind was southwesterly at 61 mph on January 29.  Average sky cover was 60%.  Average relative humidity was 65%.  For a summary of 2013 from NWS-Memphis for each of it’s climate locations, including Memphis, click here.

Cirrus Weather Solutions, Bartlett, TN – December

The average December temperature at Cirrus Weather Solutions was 41.9 degrees with a maximum of 76.1 degrees on the 4th and a minimum of 18.0 degrees on the 12th. There were 18 days with lows below 32 degrees and 1 day with a high below freezing.

Monthly precipitation was higher than at the airport and measured 5.26″ via the Cirrus automated gauge, as well as the manual gauge used for the CoCoRaHS program. Maximum daily precipitation was 1.66″ on the 21st on the automated gauge. The measured peak wind gust was 20 mph on the 4th. Average relative humidity was 81%. Click here for a daily recap on MemphisWeather.net.

Cirrus Weather Solutions, Bartlett, TN – 2013 Annual

For the year, the average temperature at MWN was 60.5 degrees with a maximum temperature of 98.9 degrees recorded on June 27th and a minimum of 17.9 degrees on November 28th.

The CoCoRaHS manual rain gauge recorded 56.78″ of precipitation, while the automated rain gauge recorded 54.80″.  The peak wind speed was 29 mph on March 24th with a dominant direction for the year of southwesterly.  The mean barometric pressure reading was 30.08″ and the mean relative humidity 76%.

MWN Forecast Accuracy

For the month of December, the average temperature error in all MWN temperature forecasts was 2.39 degrees, lower than all available computer data models and the National Weather Service forecasts. MWN’s forecasts extend out five periods (2.5 days, or roughly 60 hours). Over 62% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. For dewpoint accuracy, the MWN forecast averaged 2.80 degrees error and fell within 2 degrees of the actual dewpoint over 56% of the time.

For the year, the average temperature error in all MWN temperature forecasts was 2.13 degrees, lower than all available computer data models and the National Weather Service forecasts. Over 68% of the MWN temperature forecasts were within 2 degrees of the actual temperature. For dewpoint accuracy, the MWN forecast averaged 2.44 degrees error and fell within 2 degrees of the actual dewpoint over 62% of the time.

Historical accuracy statistics can be found here.

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