December COOP Data Uploaded
3015 ViewsThe quality controlled Iowa COOP data for December 2015 has been
uploaded to the IEM. These observations are kindly provided by Harry
Hillaker, our state climatologist, who passes along these notes on the
month:
General Summary. Temperatures averaged 32.9° or 10.0° above normal while precipitation totaled 4.90 inches or 3.56 inches above normal. This ranks as the wettest and 7th warmest December among 143 years of records. The previous wettest December was recorded in 1982 with 3.43 inches. The last warmer December was recorded in 1965.
Temperatures. Unseasonably warm weather was the rule through nearly all of December. Only one day (the 31st) brought a statewide average temperature that was below normal. This warm pattern began on August 31 with only 25 of the last 123 days of 2015 averaging below normal. The final one-third of the year averaged 5.6° above normal. Only 1931 was warmer for this late year period (when September, November and December all ranked in the top 5 warmest for their respective months). Temperature extremes for the month ranged from highs of 64° at Donnellson and Keokuk on the 12th, Bloomfield and Keosauqua on the 13th and Keosauqua again on the 23rd while Sheldon, Sioux Center and Spencer recorded the lowest temperatures with -6° readings on the morning of the 31st. There were five days (10th, 12th, 13th, 14th and 23rd) during the month when temperatures exceeded 60° somewhere in the state while only two days (3rd and 31st) brought sub-zero readings.
Heating Degree Days. Home heating requirements, as estimated by heating degree day totals, averaged 24% less than normal and 13% less than last December. Heating degree day totals so far this season (since July 1) are running 23% less than last year and 22% below normal.
Precipitation. A storm system brought heavy snow to far northwest Iowa on the last day of November with light rain and snow persisting over much of Iowa into the first two days of December. There was a welcome mostly dry period from the 3rd through the 11th. However, an unseasonably warm and humid air mass brought widespread heavy rainfall from the evening of the 12th through the morning of the 14th. An amazing statewide average of 2.82 inches of rain fell during this event. Only three winter months (December 1982, February 1881 and February 1915) have brought more precipitation to Iowa than this one storm system. Grundy Center recorded 5.98 inches of rain during this storm which easily exceeded their December monthly record precipitation total of 3.74 inches. Another storm system brought widespread rain on the 23rd with some central and northeast Iowa locations receiving over an inch of rain. The extended period of unseasonably warm and wet weather appeared to make a White Christmas impossible. However, a compact Christmas Eve storm system brought snow from southwest, through central and into northeast Iowa. Heavy snow fell from Council Bluffs to Ames with 14 inches reported at Persia is Harrison County. Finally, another large storm system brought heavy winter precipitation to much of Iowa on the 28th into the morning of the 29th. Heavy snow fell across the northern one-third of Iowa where 6 to 10 inch amounts were common. Meanwhile copious amounts of sleet and freezing rain fell over much of east central and southeast Iowa. Monthly precipitation totals (rain plus the liquid equivalent of snow and sleet) varied from 1.72 inches at Rock Rapids to 8.20 inches at Grundy Center. Grundy Center's total has been exceeded only once in Iowa during December when Keokuk recorded 8.56 inches in 1873. Dozens of cities set records for greatest December precipitation totals with a partial list below. Cherokee, Shenandoah and Storm Lake set record maximum totals for both November and December. Only two locations, Rock Rapids and Fort Madison failed to record at least double their normal December precipitation total.
City Dec. 2015 (inches) Previous Dec. Record Period of Record Grundy Center 8.20 3.74 in 1982 123 years Denison 7.15 3.43 in 1984 120 years Glenwood 6.74 4.19 in 1984 127 years Atlantic 6.62 3.54 in 1982 126 years Clarinda 6.16 4.73 in 1913 132 years Carroll 6.09 3.88 in 1931 128 years Waterloo 5.92 3.77 in 1982 132 years Logan 5.80 4.76 in 1984 146 years Marshalltown 5.60 3.41 in 1982 134 years Iowa Falls 5.60 4.47 in 1982 131 years Oskaloosa 5.52 4.16 in 2007 137 years Belle Plaine 5.49 3.31 in 2007 126 years Dakota City 5.46 3.72 in 2009 129 years Des Moines 5.44 3.72 in 1931 140 years Sac City 5.42 4.40 in 1871 140 years Indianola 5.19 3.90 in 2009 129 years Decorah 4.79 3.29 in 2010 129 years Storm Lake 4.71 2.46 in 1931 126 years Cedar Rapids 4.49 3.84 in 1982 133 years Charles City 4.42 3.59 in 1891 134 years Mason City 4.22 3.26 in 1982 117 years Ottumwa 4.03 3.95 in 1895 125 years
December snow totals varied from only 0.4 inches at Fort Madison to 24.9 inches at Rock Rapids. The statewide average snowfall was 9.8 inches or 1.5 inches above normal and ranks as the 29th highest December total among 129 years of records.
The following is the number of new daily records set at COOP sites based on data back to 1951.
__________2015__________________________________
DEC NOV OCT SEP AUG JUL JUN MAY APR MAR
Maximum High: 244 85 75 130 25 22 69 28 34 182
Minimum High: 13 56 21 13 269 261 88 316 28 102
Maximum Low: 467 171 79 336 38 54 32 82 34 29
Minimum Low: 5 58 20 25 156 139 26 87 76 98
Maximum Precip: 439 316 162 150 158 214 151 155 122 17
The following is a table summarizing how well the IEM daily data estimator is working in comparison to the quality controlled data.
2015
DEC NOV OCT SEP AUG JUL JUN MAY APR
High Temp Bias 0.2 0.3 0.2 0.0 0.1 0.0 0.0 -0.1 0.0
High Temp STD 2.0 2.2 1.8 1.7 1.8 1.7 1.7 2.5 2.2
Low Temp Bias 0.1 0.2 0.1 0.0 0.2 0.2 0.2 0.1 0.3
Low Temp STD 2.2 2.7 2.6 2.1 2.1 2.0 2.0 2.0 2.7
Precip Bias -0.01 -0.00 -0.01 0.01 -0.01 0.00 0.00 -0.01 0.00
Precip STD 0.14 0.14 0.08 0.26 0.27 0.29 0.33 0.20 0.13