News and Notes

The quality controlled Iowa COOP data for September 2014 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 62.1° or 1.1° below normal while precipitation totaled 4.37 inches or 0.99 inches above normal. This ranks as the 45th coolest and 40th wettest September among 142 years of records.

Temperatures. Temperatures were on the cool side of normal for 17 of the first 23 days of the month. Most noteworthy was an unseasonably cold period from the 11th through the 16th. Daytime high temperatures on the 12th were only in the forties as far south as Ringgold and Union counties. At Dubuque their calendar day high of 48° on the 12th came a full week sooner than the previous earliest sub-50° maximum in 140 years of records in that city. The next morning frost was scattered across much of the state with the lowest official readings of 31° recorded at Elkader, Estherville, Mason City, Sheldon, Sioux Center, Spencer, Stanley and Webster City. These were the lowest temperatures recorded for so early in the season in Iowa since Elkader recorded 29° on September 10, 1976. Frost was also reported in a few areas on the morning of the 16th when official temperature readings bottomed out at 33° at Battle Creek, Elkader, Sheldon and Stanley. However, a brief warm-up came on the 4th when nearly one-half of Iowa saw temperatures in the nineties with highest readings of 94° at Donnellson, Glenwood, Shenandoah and Sidney. Little Sioux and Sioux City also reached 90° on the 19th. Finally, temperatures frequently climbed into the eighties from the 25th through the 29th.

Precipitation. September began with a widespread rain event exiting the state and ended with another large rain event entering Iowa. Rain was frequent over the first twelve days of the month with the largest event coming on the night of the 9th. Rain amounts of three to five inches were widespread with this event across the southern one-third of the state with a maximum of 5.41 inches reported near Hartford in Warren County. Thanks to the frequent early month rains the September 16 edition of the U.S. Drought Monitor had Iowa 100% free of even an 'abnormally dry' designation for the first time since July 12, 2011. Little, if any, rain fell across much of east central and southeast Iowa during the last one-half of the month. Monthly rain totals varied from 1.35 inches at Rock Rapids to 8.63 inches near Norwalk. At Denison above normal rainfall each month from April through September, including a record wet calendar month in August, has pushed their annual precipitation total through September 30 to 45.74 inches. With three months to go in the year, this breaks their previous annual record of 45.08 inches set in 1993 (115 years of data).

Cooling Degree Day Totals. Home air conditioning requirements, as estimated by cooling degree day totals, averaged 26% less than normal and 59% less than during the very warm September of 2013. Air conditioning requirements for the 2014 season are running 15% less than normal and 22% less than last year.

Summer Summary Summer temperatures averaged 70.2° or 1.4° below normal while precipitation averaged 19.31 inches or 5.60 inches above normal. This ranks as the 28th coolest and 4th wettest summer among 142 years of records.

The following is the number of new daily records set at COOP sites based on data back to 1951.

                 __________2014_____________________________2013_
                 SEP  AUG  JUL  JUN  MAY  APR  MAR  FEB  JAN  DEC
Maximum High:     25   25    4   27   79  118   24   26   79   21
Minimum High:    267  161  399   37  235  174  406  306  219  141
Maximum Low:      86  113    8  122  102   40    7    7   22   14
Minimum Low:     180   33  330   58  171  209  439  379  194  177
Maximum Precip:  176  182  134  342   92  187   29   91   36   41

The following is some bulk statistics on how well IEM's daily COOP data estimator is performing on a monthly basis versus this QC'd dataset.

                 ___________2014_______________________________
                 SEP   AUG   JUL   JUN   MAY   APR   MAR   FEB
High Temp Bias   0.2   0.0   0.2   0.1   0.2   0.4   1.3   1.4
High Temp RMSE   0.8   0.7   0.8   0.7   0.8   0.8   1.8   1.7
Low  Temp Bias   0.2   0.1   0.2   0.1   0.1   0.2   2.1   2.7
Low  Temp RMSE   0.9   0.8   1.0   0.8   0.9   1.0   2.4   2.9
Precip    Bias   0.33  0.39  0.2   0.13  0.20  0.14  0.36  0.31
Precip    RMSE   0.75  1.11  0.92  1.39  0.64  0.63  0.46  0.56