December 2015 Weather and Its Impacts on Missouri
Pat Guinan
State Climatologist
Commercial Agriculture/University of Missouri Extension
Historic flooding impacted Missouri during December with eastern and southern sections of the state experiencing the brunt of the extreme weather. A highly unusual cold season heavy rainfall event from December 26-29 dropped 7.5-10 inches of rain along a 60-mile wide corridor extending from just south of Joplin to St. Louis, Figure 1. Antecedent conditions were saturated following the state's wettest November on record and another widespread heavy rain event on Dec 13-14. Rivers and streams reacted quickly to the post-Christmas rainfall event, and flash flooding was widespread with hundreds of water rescues reported, especially over the southern half of the state. Sadly, 15 flood fatalities were reported in December, all vehicle-related, with 7 of the drownings occurring in Pulaski county. There were 18 flood-related fatalities in Missouri for 2015, the highest total since 1993.
Transportation was severely impacted by the flooding, with portions of major interstates (I-44, I-55, and I-70) closed for a period of time. Amtrak service was temporarily suspended and barge traffic along the Mississippi River at St. Louis was shutdown. Record flood crests were reported along parts of the Mississippi (Cape Girardeau, Thebes), Meramec (Pacific, Eureka, Valley Park, Arnold) and Gasconade Rivers (Jerome), among other streams and tributaries. Thousands of homes and hundreds of businesses were flooded as President Obama designated Missouri a federal disaster area on Saturday, January 2.
Preliminary precipitation data for the state indicate a statewide average December total of 7.37 inches, slightly more than 5 inches above average, or 315% of normal. It was the second wettest December on record, and the wettest December since 1982, Figure 2. The combined November-December statewide average precipitation total for Missouri was 15.23 inches, nearly 3 times the long-term average and by far the wettest November-December period in 121 years, Figure 3.
Exceptional wetness earlier this year in May, June and July, combined with unprecedented November-December precipitation, contributed toward an unusually wet year for the state, Figure 4. Preliminary data indicate an average statewide annual total of just over 55 inches, which will likely be the 4th wettest year on record, Figure 5.
December temperatures in Missouri were also extreme with the state reporting its warmest December since official records began in 1895, Figure 6. According to preliminary data, the statewide average temperature was 42.0°F, or 9.0° above the long-term average. The September through December period this year was the second warmest on record with an average temperature of 55.1°, Figure 7. Only September-December 1931 was warmer, recording an average statewide temperature for the period of 57.1°F.
It should be noted an exceptionally warm December also occurred in 1889, but weather stations in the state were sparse during that time and these early data are not contained in the official period of record. For comparison, Figures 8 and 9 show daily temperatures in Columbia during December 1889 and December 2015. December 1889 is in a league of its own when it comes to unparalleled warmth.
The record December warmth translated to substantial savings in heating bills, but winter retail clothing sales were down. Saturated conditions were reported statewide at the end of the month with significant flooding ongoing. The damp conditions will stick around for the rest of winter considering cold season temperatures, short day length, dormant vegetation and minimal evaporation rates.
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Source: Pat Guinan, 573-882-5908