Sunday, October 5, 2014

September 2014 Weather Recap and MWN Forecast Accuracy

September Recap

A ten month streak of below normal temperatures was broken in August. September saw those above normal temperatures continue, averaging 1.0 degree above normal.  Despite the warmer than average month, the average temperature for the year through September ranks 30th coolest on record (a span of 140 years).

Precipitation-wise, it was a rather odd month. The summer dry pattern continued on 29 of the 30 days, but historic flooding in the metro and record rainfall at the airport on September 11th left the month wetter than an average September. However, a total of just 0.30" of rain fell for the month if one disregarded that single day. And after September 11, only a trace of rain was recorded. For the year, precipitation is still 126% of normal, or exactly 10" above normal. Severe weather was limited to the significant flooding event on the morning of September 11. We posted a thorough recap of the event previously on the blog. You can find it here.

Precipitation totals from the September 11, 2014 Flash Flood event.

Memphis International Airport, Memphis, TN

Average temperature: 76.2 degrees (1.0 degrees above average)
Average high temperature: 85.6 degrees
Average low temperature: 66.7 degrees
Warmest temperature: 95 degrees (4th, 5th)
Coolest temperature: 54 degrees (23rd)
Records set or tied: None
Comments: 10 days had maximum temperatures at or above 90, two above the climatological average. For the year, the average temperature at Memphis is 64.0 degrees, which is 2.1 degrees below average.

Monthly total: 4.75" (1.66" above average)
Days with measurable precipitation: 4
Wettest 24-hour period: 4.45" (September 11)
Records set or tied: 4.45" on September 11 broke the previous record of 1.87" in 1965.
Comments: Besides September 11, only one other day had more than 0.02" (0.27" on the 6th). As of the end of September, the yearly precipitation has been 48.47", which is 10.00" above (or 126% of) average.

Peak wind: Southwest/35 mph (11th)
Average wind: 6.0 mph
Average relative humidity: 67%
Average sky cover: 50%

Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 73.2 degrees
Average high temperature: 85.8 degrees
Average low temperature: 62.7 degrees
Warmest temperature: 96.5 degrees (4th)
Coolest temperature: 46.7 degrees (23rd)
Comments: 9 days had high temperatures at or above 90. The warmest low temperature was 77.1 on the 10th.

Monthly total: 8.39" (automated rain gauge), 8.46" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 5
Wettest date: 7.62" (11th) (via automated gauge)
Comments: As in Memphis, the vast majority of the rain fell on September 11 (91%). There was only one other day with more than 0.03" (0.71" on the 6th). Over 7" of rain fell in 3.5 hours on the morning of the 11th, with Bartlett one of the epicenters of historic flooding. For the period July-September, excluding September 11, Bartlett received only 4.25" of rain, or 40% of the normal Memphis average for that period.

Peak wind: Southwest/16 mph (10th)
Average relative humidity: 80%

Click here for a daily statistical recap for Bartlett, TN.

MWN Forecast Accuracy

MWN average temperature error: 1.64 degrees
MWN forecast temperatures within 2 degrees of actual: 81%
MWN average dewpoint error: 2.02 degrees
MWN forecast dewpoints within 2 degrees of actual: 70%

MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). Historical accuracy statistics can be found here.

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