December 2018 was a bit warmer and wetter than normal, based on new normals for my station developed out of the PRISM program out of Oregon State Univ. My max temp (46.3°) was 1.1° above normal, my min temp (33.4°) was 5.2° above normal, and my mean temperature (39.9°) was 3.2° above normal. My total precipitation of 7.35″ was 4.25″ above the newly computed normal precipitation December value for my station of 3.10”. There was no snowfall during the month. Snow normals are not computed by PRISM that I know of but this zero amount was considerably below normal for December.

There were no really unusually cold or warm periods during the month. There were 12 days with measurable precipitation, highlighted by the monthly maximum of 3.24″ on the 15th, occurring at the end of our longest dry period of the month between the 3^rd and the 13^th. Other notable daily rainy days was 0.98” on the 21^st when our highest temp of the month was reached (64.8°) and the lowest pressure was recorded (29.17”) and a week later on the 28^th when 1.01” was recorded. Oddly enough the day before that rain I reached my highest pressure reading of the month (30.63” on the 27^th).

The highest temperature reached during the month was 64.8° on the 21st while the lowest temperature in December was a modest 22.1° early on the 8th. The highest dew point temperature reached during the month was 61° on the 21st while the lowest dew point temperature value reached during the month was another modest reading of 18°, recorded 4 straight days beginning on the 7^th.    

December had 14 cloudy days, 12 partly cloudy days, and 5 clear/sunny days. There were 770 heating degree days and 0 cooling degree days during the month. There were 8 foggy days, 1 windy day, and no frozen precipitation days nor thunder heard during the month.  The windy day category is subjective with no personal real data values to back it, just based on my descriptive email daily weather posts that are posted on weathertogether.net.

Daily max/min temperatures didn’t vary as much as they did in November. My maximum temperature frequencies included 1 day above the 60° mark, 8 days between 50° and 59°, 16 days between 40° and 49° and  6 days between 30° and 39°, 5 of which occurred during the first 10 day period of the month.  On the minimum temperature frequency side of things, there were 11 days between 20° and 29°, 15 days between 30° and 39°, and 5 days between 40° and 49°. The coldest daily max temperature was 31.9° on the 9th while the warmest daily min temp of 44.9° was on the 15th.   

The diurnal range daily monthly average was 13.0°. Our greatest daily range of temperature was 26.2° on the 20th, formed from a high of 58.7° and the low of 32.5°. We had a total of only 4 days with daily ranges above 20.0°. Our lowest range of temperature was 3.2° (31.9°-28.7°) on the 9^th during a cloudy, cold, dry day when I had my only sub-freezing max temp day of the month. There were a significantly above normal 9 total days with diurnal temperature ranges of less than 10.0° throughout the month. 14 cloudy days during the month and low sun angle helped to suppress this month’s daily diurnal ranges.

Fortunately I’ve had no more problems with my VP2 weather station as I did earlier in the year. I am constantly checking on my data quality frequently, along with discussion and data comparison with several of my Maryland weather cohorts and reliable online close-by observer data locations. I finally have deployed my snow board, just ahead of our biggest snowstorm of the season so far on Jan 12-13,  I continue to occasionally (as time allows) submit GLOBE Cloud observations, complete with submission of sky pictures at the time of the observation, usually timed with the passage of satellites and/or solar noon (about 70 minutes past actual EDT noon).  Please ask me any questions you want at any time about my station setup and/or my data through any means available to you.

 

My December data spreadsheet can be downloaded and viewed by clicking on this link: 

2018-12-Rockville-2.8-WNW

 

 

DECEMBER 2018 – ROCKVILLE 2.8 WNW MARYLAND – SUMMARY STATISTICS

 

Average high temperature                         46.3° (+1.1°)

Average low temperature                           33.4° (+5.2°)

Mean temperature                                      39.9° (+3.2°)

 

Precipitation                                               7.35″ (+4.25” – long-term PRISM normals)

Greatest daily amount (date)                     3.24″   (15)

Greatest storm total (dates)                     3.74”   (14-16)

2018 year-to-date precipitation total       66.16″ (+24.25”)

 

High temperature for the month (date)      64.8°  (21)

Low temperature for the month  (date)      22.1°  (8)

 

Highest barometric pressure (date)           30.63” (27)

Lowest barometric pressure (date)            29.17” (21)

 

Peak wind gust (date/direction):                  N/A

 

Heating degree days for the month:            770

Cooling degree days for the month:              0

 

Greatest diurnal range (date):                     26.2°  (20)

Least diurnal range (date)                             3.2°   (9)

 

Number of days:

 

Fog                                     8                  

Windy                                 1

Thunder                              0     

Cloudy                                14

Partly Cloudy                      12

Sunny/Clear                        5

Max temp ≥ 50°                   9

Min temp  =<  32°               13        

Precip ≥  0.01”                    12