News and Notes

The quality controlled Iowa COOP data for September 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 68.4° or 5.2° above normal while precipitation totaled 4.13 inches or 0.75 inches above normal.   This ranks as the 7th warmest and 47th wettest September among 143 years of state records.   A warmer September has been recorded only once since 1939 (1998 at 68.6°).

Temperatures. Above normal temperatures were the rule for most of the month as only seven days (11th-13th, 18th-20th and 30th) averaged cooler than usual.   The heat was characterized more by persistence than extremes as no daily record high temperatures were set.   The first seven days of the month were the warmest week of the year with temperatures averaging 10.6° above normal.   Afternoon high temperatures reached into the mid-nineties in some areas each day from the 3rd through the 6th.   Highest readings were 96° temperatures at Burlington 2 S, Glenwood, Muscatine and Sidney on the 6th.   On the other extreme, Cresco and Estherville recorded 33° minimums on the morning of the 30th.

Cooling Degree Days. Home air conditioning requirements, as estimated by cooling degree day totals, averaged 184% greater than last September and 115% greater than normal.    Cooling degree day totals for the year-to-date are running 15% greater than last year at this time and 3% less than normal.

Precipitation. Rain amounts were highly variable across Iowa with totals varying from 11.63 inches at Glenwood to only 0.83 inches near Badger (Webster County).   Glenwood’s total was second only to a 12.64 inch total in 1965 among 119 years of September records at that location.   Monthly rain totals were well above normal over most of the southwest one-half of Iowa while small areas of far southeast and far northeast Iowa, as well as the Fort Dodge area, saw less than one-third of normal rainfall.   Torrential rains fell over extreme western Iowa, centered upon the morning of the 23rd, with storm totals of 9.28 inches on the north edge of Council Bluffs and 6.80 inches at Glenwood.   Excessive rains also fell on the night of the 6th over northern Guthrie/southern Greene counties, as well as Taylor and Appanoose counties, with Bagley reporting the largest total during this event with 6.25 inches.

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

                 __________2015______________________________2014
                 SEP  AUG  JUL  JUN  MAY  APR  MAR  FEB  JAN  DEC
Maximum High:    130   25   22   69   28   34  182   13  113   84
Minimum High:     13  269  261   88  316   28  102  364   65   60
Maximum Low:     336   38   54   32   82   34   29   25  135  451
Minimum Low:      25  156  139   26   87   76   98  345  111   28
Maximum Precip:  150  158  214  151  155  122   17  113   67  121

The following is a table summarizing how well the IEM daily data estimator is working in comparison to the quality controlled data.

                      2015
                 SEP   AUG   JUL   JUN   MAY   APR   MAR   FEB   JAN
High Temp Bias   0.0   0.1   0.0   0.0  -0.1   0.0   0.3   0.3   0.2
High Temp STD    1.7   1.8   1.7   1.7   2.5   2.2   2.6   2.8   2.5
Low  Temp Bias   0.0   0.2   0.2   0.2   0.1   0.3   0.4   0.3   0.1
Low  Temp STD    2.1   2.1   2.0   2.0   2.0   2.7   2.9   2.9   2.6
Precip    Bias   0.01 -0.01  0.00  0.00 -0.01  0.00  0.01 -0.16  0.01
Precip    STD    0.26  0.27  0.29  0.33  0.20  0.13  0.13  0.05  0.04