Friday, June 3, 2011

May 2011 Climate Data and MWN Forecast Accuracy

As in April, May was again marked by multiple severe weather events across the region. The month started with heavy rainfall (nearly 7" at the WXLIVE! station in Bartlett on May 1-2), just as it did a year ago when a 500-year flood impacted west and middle TN. The last week of the month featured additional strong tornadoes with the highest-profile being the Joplin, MO EF-5 that killed 134. That system brought a high risk event to the Memphis area on May 25. A tornado-warned rotating supercell with pronounced wall cloud and picturesque beaver tail cloud passed over the north half of Shelby County with this system. Fortunately, damage was limited in the metro area.

The most noteworthy event in the city in May was the vast Mississippi River flooding that took place. The river crested at 47.8' at the Memphis gauge on May 9, less than a foot from the all-time record set during the Great Flood of '37, and forced the relocation of the Memphis in May World Championship Barbecue Cooking Contest from flooded Tom Lee Park to Tiger Lane.

Memphis International Airport, Memphis, TN

The average May temperature was 70.2 degrees, which was 0.4 degrees below normal. The average high temperature was 79.6 degrees and the average low was 60.9. The coolest temperature of the month was 46 degrees on the 5th and 17th and the highest temperature was 93 degrees on the 30th. There were 4 days in which the temperature reached 90 degrees or higher.

Precipitation for the month of May totaled 7.12", which was 1.97" above the normal of 5.15". There were 13 days with measurable rainfall (on 2 of those days more than an inch fell) and the maximum 24-hour total was 3.18" on the 2nd-3rd. The peak wind gust was 46 mph on the 25th during a severe thunderstorm with an average wind speed for the month of 8.9 mph. Click here for a daily statistical recap for Memphis International for May.

Bartlett, TN

The average temperature for May at the WXLIVE! station in north Bartlett was 69.0 degrees with a maximum of 93.6 degrees on the 31st and a minimum of 41.3 degrees on the 5th.

May precipitation ended above normal with a total of 9.66", or more than 2.5" greater than at Memphis International. A co-located manual gauge used for the CoCoRaHS program measured 10.76". The peak wind gust was 46 mph on the 1st. Average relative humidity was a high 70%. Click here for a daily recap on

MWN Forecast Accuracy

For the month of May, the average temperature error in all MWN temperature forecasts was 1.71 degrees, lower than all compared computer models, including the National Weather Service, by nearly 10%. Over 78% 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 beat all data sources, averaging 2.35 degrees error and falling within 2 degrees of the actual dewpoint nearly two-thirds of the time. Historical accuracy statistics can be found here.

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