October 2016 Gaithersburg 2 WNW Maryland weather summary and statistics for the NJWO blog

by Kevin Shaw, Observer in charge

Average high temperature 68.7° (+ 3.5°)
Average low temperature 49.9° (+ 6.0°)
Mean temperature 59.3° (+ 4.7°)
Precipitation 0.78″ (- 2.72″) Greatest daily amount (date) 0.40″ (1)
Year to date precipitation 34.91″ (- 2.74″) High temperature for the month (date) 84° (19)
Low temperature for the month (date) 33° (26)
Highest barometric pressure (date) 30.52″ (11,26)
Lowest barometric pressure (date) 29.60″ (21)
Peak wind gust (date/direction): 26 (22/SW)
Heating degree days for the month: 204
Cooling degree days for the month: 28
Greatest diurnal range (date): 35.5° (29)
Least diurnal range (date) 2.9° (1)
Number of days:
Fog 3
Thunder: 0
Sunny/clear days: 13 Partly Cloudy days: 11 Cloudy days: 7

Days with measurable precipitation (=>.01″) = 5
Days with maximum temperatures of 80° or more = 5
Days with minimum temperatures in the 30s = 3

by Kevin Shaw, observer in charge

October 2016 was noticeably dry and warm. It was the second
driest October ever, only surpassed by the meager 0.29″ that fell in all of October 2000. The mean temperature 59.3° was
the third warmest October in my 38 year period of record
(POR), only being surpassed by October 1984 (61.0°) and
October 2007 (62.1°). Several record daily high temperatures were set during the month, as were several high minimum
temperatures. The minimum temperature for the month (33.2°)
failed to reach the freezing mark for the ninth time in my POR, including a fifth time in very recent times, since 2009. I hit the 80° maximum temperature threshold five times during the month, including 4 times in a row during our mid-month heat wave from the 17th through the 20th. Similarly, I had 5 days during the month when I had minimum temperatures above the 60° mark.
Conversely, I only had 3 days during the month with minimum
temperatures in the 30s. Only the 33.2° reading on the 26th
managed to produce frost at my location. Fall colors were
delayed this season once again, and are only now approaching peak color in early November, forestalled by the mild overnight temperatures and lack of frost during the month.

October 2016 featured more near record-breaking warmth with
regard to average monthly temperatures for my 38 year period of record (POR). The average high temperature wasn’t quite as extreme but was the 5th warmest ever. 3 daily record high
temperatures were recorded – 83° on the 18th, 84° on the 19th, and 80° on the 30th. 2 daily record high minimum temperatures were set – 61° on the 19th and the warmest min of the month of 66° on the 20th of 66°. The average min temperature of 49.9° turned out to be the 3rd warmest in my POR, only surpassed by the 51.8° set in 2007 and 51.5° set back in 1984.

No other daily temperature or precipitation records were set during the month.

The entire month was warm and dry as only 0.78″ (-2.72″) of
rain fell to go along with the warm temperatures already discussed. Measurable rain fell on only 5 widely scattered days through out the month, only about half of the long-term average amount of 9.5 days. My current year to date precipitation total of 34.91″ through October 31 is 2.74″ below the normal amount of 37.65″.

The average maximum temperature for the month was 68.7°
(+3.3°), the average minimum temperature was 49.9° (+ 6.0°). The resultant mean average temperature for the month was
59.3° (+ 4.7°).

The month’s highest barometric pressure reading of 30.52″ twice, on the 11th on the first day of the month with min temperatures in the 30s, and then again on the 26th on the coolest day of the month. The lowest pressure reading of the month of 29.60″ on the 21st occurred on one of the rare rainy days of the month and when we transitioned out of our late season heat wave finally into more normal fall-like temperatures.

The distribution of 13 sunny, 11 partly cloudy and 7 cloudy days fit in with the generally dry conditions better than in September.

There were 204 heating degree days (HDD) and 28 cooling degree days. I managed to catch a few foggy days in October (3) during the slightly more damp first part of the month. There were no thunder storm days, below normal but fit in with the dry conditions during the month. The peak wind gust during the month was 26 MPH out of the SW on the 22nd was during our transitional period from summer warmth to more typical fall chill. I had two other days with PWG readings above the 20 MPH mark (25 on the 9th and 23 on the 30th). It was a generally calm month as 11 days recorded a PWG of 9 MPH or less, all but one of those days occurring in the first half of the month. The dominant daily wind direction was 16 days with a westerly component, followed by 13 days with a easterly component, 1 day with a northerly component, and 1 day with a southerly component. The first half of the month had more easterly component winds, and the second half conversely had more westerly component winds.

My maximum temperature frequencies included 5 days at or above 80°, 8 days between 70°and 79°, 16 days between 60° and 69° and 2 days below 60°. On the minimum temperature frequency side of things, there were 3 days between 30° and 39°, 13 days between 40° and 49°, 10 days between 50° and 59°, and 5 days 60° or above.

The diurnal range average was below normal (18.8° vs the normal of 21.5°). The max daily range of 35.5° occurred on the 29th (74°-38°) on the first transition day out of the biggest cool snap of the month into the last brief heat wave of the month. on the day before the final day of the month with an 80° max temp. There were no more days with ranges in the 30s, but an additional 12 days with daily ranges at or above 20°, including 9 days in a row (11th-20th during our mid-month heat wave). The lowest daily temperature range of 2.9° (63°-60°) occurred on our wettest day of the month on the 1st. The 1st and 2nd combined with the last 3 days of September into a modest streak of 5 days in a row with daily temperature ranges less than 10°. There were 2 additional days during October with minimum daily temperature ranges less than 10°.

The tropics really got active in late September with powerful Hurricane Matthew, ravaging Haiti and other Caribbean islands before moving into
the SE US areas in early October, and threatening our area briefly. With adjoining (but weaker) hurricane named Nicole interacting, we did have a generally damp, warm period during the first 10 or so days of the month, then giving way to a drier but continued warm spell for the next 10 days. Not till the last third of the month did we start getting more traditional fall-like weather but without much frost or any freezing temperatures. Fall color has finally been developing, a few weeks delayed in early November. Check back in a few weeks to see how the rest of November works out. I believe that tropical activity is basically over for this season. But watch out for our first snowflakes of the season, not far away !!!

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