Gaithersburg 2 WNW Maryland – January 2016 climate summary by NJWO member, Kevin Shaw observer

by Kevin Shaw, Observer in charge

Average high temperature 40.8° (+ 0.4°)
Average low temperature 23.0° (+ 0.6°)
Mean temperature 32.4° (+ 0.5°)
Precipitation 4.51″ (+ 1.46″)
Greatest daily amt(date) 2.21″ (23)
Year to date precip 4.51″ (+ 1.46″)
Snowfall 31.7″ (+ 23.1″)
Greatest daily amt (date) 23.7″ (23)
Greatest storm total (dates) 31.0″ (22-23)
Greatest depth of snow (date) 31″ (23)
High temperature month (date) 60° (31)
Low temperature month (date) 10° (25)
Highest barometric pressure (date) 30.69″ (5)
Lowest barometric pressure (date) 29.39″ (10)
Peak wind gust (date/direction): 27 (23/NNW)
Heating degree days for the month: 1010
Cooling degree days for the month: 0
Greatest diurnal range (date): 32.5° (25)
Least diurnal range (date) 4.9° (8)

Fog days: 6
Snow days: 7
Sunny/clear days: 10 Partly Cloudy days: 10 Cloudy days: 11

Days with measurable precipitation (=>.01″) = 10
Days with maximum temperatures of 32 or less = 6
Days with minimum temperatures of 32 or less = 26


January started 2016 with a bang with a record-setting
snowstorm on the 22nd and 23rd. The 31.0″ total is the greatest snowstorm total in my 38 year period of record (POR). The 23.7″ that fell on the 23rd set a daily record for snowfall, and also was the largest daily snowfall amount ever recorded during my 38 POR. The 2.21″ water equivalent total for the snowfall on the 23rd was the greatest amount for the month and set a daily record for the date and is the second largest daily amount ever, only surpassed by the 3.00″ that fell back on January 30, 2013. Only a few temp records were set, the monthly max of 60 on the 31st failed to set a record, but the 58 on the 10th did set a daily record. The high min temperature of 40 on the 9th tied a daily record with 2 previous years (1998, 2006). The total monthly precipitation amount of 4.51″ came in as eighth wettest January in my 38 year POR. The max and min temperature averages were a bit above normal but by less than 1°, not really significant. No minimum temperature records were set, as the 10° minimum temperature on the 25th, caused by great radiational
cooling from the big storm’s deep snow pack, still didn’t really come close to a record. The snow pack helped chill us the rest of the month, as it remained in place through the 31st and into the beginning of February.

The average maximum temperature for the month was 41.2° (+0.4°), the average minimum temperature was 23.6° (+ 0.6°). The resultant mean average temperature for the month was 32.4° (+ 0.5°). Much more normal
wintertime temperature patterns in January than the record mild December. The most persistent pattern of temperature was the below normal period from the 18th through the 25th which surrounded our biggest weather event of the month, our monster snowstorm that fell on the 22nd and 23rd.

The month’s total precipitation amount of 4.51″ was 1.46″ above the
normal January amount of 3.05″. Precipitation fell on 9 of the 15 days from the 9th through the 23rd and was just about all the precipitation that fell the entire month with basically dry periods at the beginning (1st-8th) and the end (24th-31st) when only 0.02″ fell one day and traces on a few other days. 10 days of measurable precipitation for the month compared favorably with the long-term average amount of 11.5 days. Total snowfall for the month of 31.7″ was the second greatest amount ever recorded in January, only surpassed by the 33.5″ that fell back in 1996.

The month’s highest barometric pressure reading of 30.69 on the 5th
interestingly enough occurred on the same day as in December. The 30.69″ reading occurred in the middle of our beginning of the month long dry spell of the month (a modest 8 day streak with only 2 trace amount days) between the 1st and 8th. The lowest pressure reading of the month was 29.39″ at the end of our first wet period of the month on the 10th, as the storm center passed by close to our area. Average barometric pressure for the month was 30.05″, within .01″ if you averaged the two extreme values (30.69″ and 29.39″). Based on this month and the last 9 months of 2015, it appears there is quite a
strong correlation between these two statistics. Not sure what it really is good for, but it is interesting to study and note the relationship.

The distribution of 10 sunny, 10 partly cloudy and 11 cloudy days correlated well with the above normal monthly precipitation total of 4.51″.

There were 1010 heating degree days (HDD) and 0 cooling degree days.
That was a bit more than double the amount of HDD I had in December. There were an about normal amount of 6 days with fog observed and no thunder days. The peak wind gust during January was 27 MPH out of the NNW on the 23rd in the middle of our monster snowstorm. I had a total of 9 days in January with PWG days of 20 MPH or more, pretty windy for my normally tranquil station.

My maximum temperature frequencies included 1 day of 60°, 6 days between 50° and 59°, 12 days between 40° and 49°, 7 days between 30° and 39°, and 5 days between 20° and 29°. On the minimum temperature frequency side of things, there were 11 days between 10° and 19°, 12 days between 20° and 29°, 7 days between 30° and 39°, and 1 day with a minimum of 40°.

The diurnal range average was a wee bit below normal (17.6° vs the normal 17.8°). The max daily range of 32.5° occurred on the 25th at the beginning of our warm up after the big snow when we had our coldest morning of the month (10°). The lowest daily temperature range of 4.9° occurred on the 7th on the first day of the first wet period of the month. We had 6 days with a diurnal range less than 10° (all on or before the 23rd of the month) and 7 days with ranges of 25° or more, interspersed fairly evenly throughout the month.

January 2016 really was quite a contrast in many respects to December 2015. From no snow at all in December to record-breaking amounts in January was the biggest change, though almost totally due to the one big snowstorm of the month on the 22nd-23rd. The record-breaking warm temperatures so frequent in December went away in January and were replaced with more normal winterlike temperatures. Similarly, however, precipitation was significantly above normal in January as it was in December. However, unlike December’s total being 100% attributable to
rain, a good part of January’s precipitation consisted of snow from our monster snowstorm. Unlike December’s predominantly mild WSW/SW flow (based on direction of peak wind gusts on each day of the month), January had just about half of the days with NW/NNW/WNW flow to help bring in the colder air to the region. Stay tuned in a few weeks for the February report. I still have not gotten my 2015 annual report out yet, I hope to produce that soon.

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