JANUARY 2018 MONTHLY SUMMARY ROCKVILLE 2.8 WNW MARYLAND

                              By Kevin Shaw, Observer in Charge

January 2018 started my second year at my apartment observing the weather and living at this location in West Rockville MD. The month started off with a bang, as I had my coldest week ever (1st-7th) and coldest days, with the first days of maximums in the teens on the 5th and 6th and my coldest min ever of 2.9° on the morning of the 7th. Combined with the last 5 days of 2017, the 12 day period from December 27th-January 7th is easily the longest sub-freezing max temperature period in my short period of record. But even with much longer duration official stations in the area, this snap was quite epic and near the all-time record long period of cold. The rest of the month was generally much warmer, with only a few seasonably cold days and many days with highs in the 50s and 60s (66.5° max on the 12th was the highest). Rainfall and snowfall was below normal, with only a few days of snow, all less than an inch. There were 9 days with measurable precipitation, probably just a bit below normal, topped off by the 0.90″ that also occurred on the 12th. The highest barometric pressure reading of the month (30.74″) on the 26th was actually the highest since early March, but on a seasonable day with temperatures topping off in the mid 40s. The lowest barometric pressure reading of the month (29.37″) occurred just after midnight on the 13th and was associated with by far our wettest two days of the month (1.35″).  The month was pretty cloudy despite the meager precipitation, with 6 clear days logged along with 15 partly cloudy and 10 cloudy days. The general reversal of that very cold pattern at the start of the month balanced out temps to be just a bit below normal values at the three first-order stations at the 3 major DC area airport locations.

There were 991 heating degree days (HDD) and 0 cooling degree days (CDD) during the month. There were only 4 days with fog, 4 days with snow, and a new category, 9 windy days. That is a subjective category with no real data values to back it, just based on my email daily weather posts that is also posted on weathertogether.net. There was 1 day with sleet and 1 day with glaze (on the 8th as we were getting out of the deep freeze).  

Daily max/min temperatures varied widely throughout the month. My maximum temperature frequencies included 5 days between 60° and 69°, 5 days between 50° and 59°, 6 days between 40° and 49°, 8 days between 30° and 39°, 5 days between 20° and 29°, and 2 days colder than 20°.  On the minimum temperature frequency side of things, there was 3 days lower than 10°, 11 days between 10° and 19°, 7 days between 20° and 29°, 6 days between 30° and 39°, 3 days between 40° and 49°, and 1 day 50° or above. The coldest daily max temperature was 16.8° on the 5th and warmest daily min temp was 56.2° on that “busy” day on the 12th. 

The diurnal range daily monthly average was 17°.  Our greatest daily range of temperature was 41.5°, formed from a high of 60° and low of 19° as a strong cold frontal passage dropped temperatures quickly after a warm start. This was the only day with a range over 40°, only one other day had a range over 30° but we had an additional 8 days with daily ranges at or above 20°. Our lowest range of temperature was 6.7° on our coldest max day of the month on the 5th, formed from a high temperature of 17° and a low temperature of 10°. There were a total of 6 days with diurnal temperature ranges less than 10.0°, a decrease of 1 over last month. The distribution of these days was spread out over the month, on both warm and cold days.

With yet another month to study the most recent instrument changes made in mid-August, data appears to be stable and an overall data quality improvement success. I am still constantly checking on my data quality frequently along with some of my Maryland weather cohorts. With the paucity of snow, my recently installed snowboards have not gotten much action this winter so far. With the recent warm spell I have returned the inner tube and funnel to my cocorahs rain gauge setup, as below freezing temps do not appear to be returning the rest of February into early March.  I have been swapping out gauges when frozen precipitation occurs to allow for casual, comfortable melting inside my apartment. Unfortunately the “snow stake” was pulled out early in February when high winds knocked it over partially at a significant angle and has not been placed back outside through the current time. I did get a new hand-held anemometer that is especially sensitive to light winds, a good thing as that is a persistent trait at my relatively calm location. I also have resumed taking daily GLOBE observations, complete with submission of sky pictures at the time of the observation, usually timed with the passage of satellites if at all possible. If not, I try to take the observation around the time of solar noon, about 20 minutes past actual 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.

 

Here is a link to my January 2018 data spreadsheet file: 

https://files.acrobat.com/a/preview/6ee955c3-c479-4a16-938c-63556618b40a

 

 

JANUARY 2018 – ROCKVILLE 2.8 WNW MARYLAND – SUMMARY STATISTICS

 

Average high temperature                         41.5°

Average low temperature                           24.5°

Mean temperature                                      33.0°

 

Precipitation                                                1.83″

Greatest daily amount (date)                      0.90″ (12)

Snow                                                            1.4″

Greatest daily amount (date)                       0.7”   (17)

2018 year-to-date precipitation total           1.83″

Seasonal snowfall total as of 1/31/2018      5.2″

 

High temperature for the month (date)       66.5°  (12)

Low temperature for the month  (date)         2.9°    (7)

 

Highest barometric pressure (date)             30.74”   (26)

Lowest barometric pressure (date)              29.37”   (13)

 

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

 

Heating degree days for the month:             991

Cooling degree days for the month:                0

 

Greatest diurnal range (date):                       41.5°     (13)

Least diurnal range (date)                               6.7°     (5)

 

Number of days:

 

Fog                                  3                  

Windy                              9

Snow                               4     

Cloudy                             6

Partly Cloudy                 15

Sunny/Clear                   10

Max temp => 70°            0

Min temp =<  32°           23       

Max temp =<  32°          10