December 2017: Winter Arrives On Cue

December was generally a mild month through the 21st, the winter solstice. Then, on December 22nd, the first full day of winter, things took an inevitable turn for the worse when frigid air finally made its presence known. Once the cold air arrived, a modified arctic air mass remained entrenched across the region, only to be replaced by periodic surges of true arctic air from the 26th right on through the end of the year.

Temperature Specifics: The first 21 days of December averaged 7 degrees above normal with an average high of 53 and average low 26. In contrast, the last 10 days of the month averaged 12 degrees below normal with an average high of 25 and average low of 10. For the month as a whole, the average high was 44 and average low 21. Normal is 42 and 21.

The warmest temperature of the month was 71 degrees on December 3rd and 4th, now only a vague and distant memory. The coolest reading of the month was 3 below zero, which also occurred on two occasions, once on the morning of the 27th and again just before midnight on New Years Eve. New Years Eve Day was the coldest day of the month with a high of 11 and low of 3 below zero. The mean temperature on the last day of the year was 4 degrees, 25 degrees below normal for the date.

Precipitation: For the second month in a row precipitation was lacking.

The biggest event of the month occurred during the predawn hours of December 17th when an average 0.32 inches of an inch of rain fell across town. This helped dampen the very dry and dusty ground conditions a bit in the last 5 mild days before the cold air surged in.

We even had a white Christmas – sort of. On December 24th, an average of 1.2 inches of fluffy, arctic snow fell across town which contained 0.06 inches of water equivalent. However, the light and airy snow compacted down a bit by Christmas Day. (The 20:1 ratio of snowfall to moisture content is typical of arctic type snowfall.)  This was reinforced a bit on the 26th when 0.7 inches of snow fell that contained 0.04 inches of moisture.

The rain event on the 17th combined with the two light snowfall events bookending Christmas day brought precipitation for the month to 0.42 inches.  Normal for December is 1.47 inches.

Yearly Precipitation:  For the calendar year, an average of 44.66 inches fell in Lawrence among our city reporting rainfall sites. This compares to an annual average of 38.55 inches.

Our city total of 44.66 inches differs considerably from the reported Lawrence Airport total of 34.37 inches. This is because the automated measuring equipment at the airport has issues of missing data during equipment outages or mechanical malfunctions that are not corrected or accounted for.   Over time (if not with every event), this missing and unaccounted for precipitation renders the officially reported accumulated total at the airport significantly on the low side.  Lawrence is by no means the lone ranger in this regard.  The same type of errors occur with many such  ‘2nd order’ NWS climate stations.

An excellent alternative source for precipitation data in these situations is a network of citizen volunteers that make up the Community Collaborative Rain, Hail and Snow Network. The acronym is CoCoRaHS.  Precipitation data and information about this network of precipitation observers is available online.

Monthly Outlook:  For January, the NWS monthly outlook calls for below normal temperatures and above normal precipitation for our region.  Normally the driest month of the year, January averages 1.01 inches of precipitation and about 5 inches of snowfall.

January is also the month when we normally bottom out in average temperature. The average daily mean temperature reaches a minimum of 28.7 from the 2nd to the 11th of the month.  By the end of January, the average daily mean rises to 30.7, two degrees higher than the early January minimum.

So, cheer up!

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December 17th:  Looking across Perry Lake just before sunset on a mild, calm day.

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December 17th:  Bare trees along the shore of Perry Lake lit up by the setting sun.  Some rain the previous night accented the lichens on the bark a bit.   This was a mild day with a high near 50 degrees, and followed welcome wetting rain early that morning.  There was not a lot of rain, but enough to dampen down the dust for awhile and add some moisture to the air for a day or two.

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Winter Solstice Day (Dec 21st), the last mild day of the month.   Here, at the Baker Wetlands, a flock of Canada Geese depart their previously tranquil pond as I approach.   The temperature was a mild 53 as I snapped this photo at 3:15 PM.  Just an hour later, the first surge of arctic air pushed in on stiff north winds.  Reinforcing arctic surges then continued for the rest of the month and right on into the new year.  

 

 

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December 24th along the shore of Clinton Lake.  A light snowfall of about an inch fell early in the day.  The high was 27 and the low 13.

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December 30th.  A couple of eagles perch along the shore of Clinton Lake.  Unfortunately, it was hard to hold the camera still as the temperature was in the high teens with northwest winds blowing about 15-20 MPH.  Winds gusted as high as 29 MPH at the airport earlier in the day.

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December 31st:  A brave soul walks the dog at the Rotary Arboretum.   True arctic air continued to surge in, resulting in the coldest day of the month on New Years Eve.   The high was 11 degrees and the low, which occurred right at the ringing in of the new year, was 3 below zero.  Northwest winds gusting to more than 20 MPH added further insult to misery.

 

 

$$

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