Saturday, January 4, 2020

December 2019 Climate Data for Memphis, TN

December Climate Recap

Following one of the colder Novembers on record, the script flipped in December as a major pattern change over the U.S. resulted in very warm temperatures across the eastern 2/3 of the country, an area which had been well below average in November. The mid-month period featured relatively "average" temperatures, and even a couple of very minor frozen precipitation events. However, warmth to start, and especially end, the month set the tone. In fact, the week surrounding Christmas Day (Dec. 23-29) was one of the warmest such weeks on record. Overall, the month ended more than four degrees above average.

The U.S. temperature anomaly (departure from normal) for the month of December shows well above normal temperatures across much of the nation east of the Rocky Mountains, while predominantly below average temperatures were present in the western U.S. The pattern was nearly a completely reversal of November temperatures. (WeatherBell)
December precipitation typically averages just under six inches, being one of the wetter months of the year climatologically. In 2019, rainfall was fairly well spread out with no prolonged wet or dry periods. For the month, just over four inches fell. Thunderstorms occurred on the 6th and 16th, but no severe weather was reported, nor warnings issued. Heavy rain on the 16th prompted a Flood Advisory for the southern portion of the greater metro.

There were two minor winter precipitation events, both on the backside of rain events, on the 10th and 17th. Only a trace or sleet or snow was recorded on each day. The most impact-ful "cold weather" event though was a coating of black ice on elevated roadways the morning of the 18th, resulting in dozens of crashes and major bridges and overpasses shutting down until the ice melted. More on this heavy frost/black ice event can be found in this blog post.

Google traffic data from the morning of the 18th when black ice caused major issues city-wide.


Memphis International Airport, Memphis, TN


Temperature
Average temperature: 47.7 degrees (4.1 degrees above average)
Average high temperature: 56.7 degrees (4.6 degrees above average)
Average low temperature: 38.8 degrees (3.7 degrees above average)
Warmest temperature: 71 degrees (28th)
Coolest temperature: 26 degrees (11th, 18th)
Heating Degrees Days: 526 (139 below average)
Cooling Degree Days: 0 (2 below average)
Records set or tied: None.
Comments: Nine days recorded a low temperature at or below freezing, x.x days more than average for the month.

Precipitation
Monthly total: 4.04" (1.70" below average)
Days with measurable precipitation: 7 (2.7 days below average)
Wettest 24-hour period: 1.42" (16th)
Snowfall: Trace
Records set or tied: Record snowfall tied - trace (10th).
Comments: Two days had rainfall exceeding one inch. A trace of snow and sleet fell on the 10th and snow flurries fell on the 17th.

Miscellaneous
Peak wind: West/25 mph (29th)
Average wind: 7.0 mph
Average relative humidity: 73%
Average sky cover: 60%

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

Cirrus Weather Solutions / MemphisWeather.net, Bartlett, TN


Temperature
Average temperature: 46.1 degrees
Average high temperature: 56.0 degrees
Average low temperature: 36.8 degrees
Warmest temperature: 70.1 degrees (25th)
Coolest temperature: 23.8 degrees (19th)
Comments: None

Precipitation
Monthly total: 3.69" (automated rain gauge), 3.99" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 11
Wettest date: 1.43" (29th) (via automated gauge)
Snowfall: Trace
Comments: A bit of sleet and snow fell on the 10th and snow flurries fell on the 17th.

Miscellaneous
Peak wind: West/32 mph (29th)
Average relative humidity: 81%
Average barometric pressure: 30.08 in. Hg
Comments: None

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

MWN Forecast Accuracy

MWN average temperature error: 2.41 degrees
MWN forecast temperatures within 2 degrees of actual: 67%
MWN average dewpoint error: 2.50 degrees
MWN forecast dewpoints within 2 degrees of actual: 61%

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

Climate Outlook - January 2020

The January climate outlook for the United States from the Climate Prediction Center is shown below. Above average temperatures are forecast for the southeast, spreading north towards the Ohio Valley and west into the Southern Plains. Below average temperatures are expected in the western U.S. Odds favor above average temperatures for Memphis, at 43% (versus only a 24% chance of below average temperatures). Memphis averages 41.2 degrees for the month.



Wetter than normal weather is expected for the Ohio and Tennessee Valleys into the Mid-Atlantic and southeast U.S., as well as the High Plains. For Memphis, odds favor above average rainfall (43% chance), which historically averages nearly four inches.

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