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

by Kevin Shaw, Observer in charge

Average high temperature 87.8° (+ 2.9°)
Average low temperature 69.2° (+ 5.1°)
Mean temperature 78.5° (+ 4.0°)
Precipitation 2.97″ (- 0.70″)
Greatest daily amount (date) 1.51″ (17)
Year to date precipitation 31.23″ (+ 1.28″)
High temperature for the month (date) 97° (13,14)
Low temperature for the month (date) 60° (23)
Highest barometric pressure (date) 30.37″ (23)
Lowest barometric pressure (date) 29.76″ (6)
Peak wind gust (date/direction): 18 (14/WSW)
Heating degree days for the month: 0
Cooling degree days for the month: 419
Greatest diurnal range (date): 25.2° (7)
Least diurnal range (date) 11.3° (3)

Fog days: 0
Thunder: 4
Sunny/clear days: 10 Partly Cloudy days: 17 Cloudy days: 4

Days with measurable precipitation (=>.01″) = 6
Days with maximum temperatures of 90 or more = 9
Days with minimum temperatures of 70 or more = 15

by Kevin Shaw, observer in charge

Once again this month of August was warmer than normal, and
also drier than normal. There were several daily records set, mostly with maximum low temperatures with many very warm,
muggy overnights. I had the warmest August mean temperature
(78.5°) and the warmest average minimum temperature (69.2°)
ever. The maximum average temperature (87.8°) only came in as the sixth warmest ever. The 9 days with maximum temperatures of 90 or greater was actually just about normal. 6 days with measurable precipitation was predictably below the normal of about 9 days. The wettest day of the month of 1.51″ on the 17th failed to break a daily record, but the 1.31″ that fell on the 15th did break a daily record, the only such record in this dry month. An all-time record high dew point temperature of 82 was set on the 12th (records on this variable only go back through 2013 unfortunately). The highest temperature of the month of 97°
was reached on the 13th and 14th. Only the reading on the 13th went into the record book as a tied daily max temp value with the reading recorded back in 2002. Numerous daily record high
minimum temperatures were either set or tied, including 5 days in a row during our hottest temperatures of the month between the 10th and 14th, and also on the 6th, 17th and 26th.

The average maximum temperature for the month was 87.8°
(+2.9°), the average minimum temperature was 69.2° (+ 5.1°). The resultant mean average temperature for the month was
78.5° (+ 4.0°).

The month’s total precipitation amount of 2.97″ was 0.70″
below the normal August amount of 3.67″. My current year to date precipitation total of 31.23″ through August 31 is 1.28″ above the normal amount of 29.95″. All measurable amounts of precipitation fell between the 12th and 21st. Trace amounts also fell on the 8th and 9th. 6 days of measurable rain at my station was below the long-term normal amount of 8.9 days.

The month’s highest barometric pressure reading of 30.37″ on the 23rd occurred on the day with our lowest monthly minimum air (60°) and dew point (57°) temperatures of the month. The modest lowest pressure reading of the month of 29.76″ on the 6th occured during a bit of a cloudy period (but without rain) from the 5th to the 9th.

The distribution of 10 sunny, 17 partly cloudy and only 4 cloudy days fit in with the dry conditions found during most of the month, particularly at the beginning and end of the month. With plenty of muggy dew points around, there was plenty of fuel around for cloud formation; they just didn’t develop into many full overcasts at all.

There were 419 cooling degree days (CDD) and 0 heating degree days. I didn’t observe any fog in August, but with the dew points frequently as high as they were, I probably missed early morning fog occurrences when I was sleeping. There were essentially a normal amount (4) of thunderstorm days, all occurring during our wettest period of the month between the 14th and 17th. The peak wind gust during the month was a very modest 18 MPH out of the WSW on the 14th during evening light thunderstorm activity that mostly missed the station. It was a generally calm month as only 19 days recorded a PWG of 10 MPH or more. The dominant daily wind direction was 16 days with a W/SW/WSW component, followed by 11 days with an
easterly component and 4 days with a northerly component.

My maximum temperature frequencies included 9 days at or above 90°, 21 days between 80° and 89° (including 11 days with max temps of either 88° or 89°), and 1 day with 79°. On the minimum temperature frequency side of things, there were 16 days between 60° and 69° and 15 days with minimum temperatures of 70° or greater.

The diurnal range average was below normal (18.6° vs the normal of
20.8°). The max daily range of 25.2° occurred on the 7th at the end of the beginning of the month dry period (with a dew point of 58° recorded that day – 89°-64°). There were an additional 10 days with daily ranges at or above 20°, The lowest daily temperature range of 11.3° (80°-69°)
occurred on a non-descript partly cloudy August 3rd day. There were only a total of 6 days during August with daily temperature readings less than 15°.

Late July finished up relatively cool with a long 90°+ streak broken that continued into August 2016 with the first 9 days failing to reach 90° but then on August 10 we started a streak of 8 straight days of 90° or more, along with dew point temperatures well up into the 70s and even low 80s. This was probably the most oppressive period of August, if not the entire summer. Only the thunderstorms from the 14th-17th provided any sort of relief. The rest of the month finished moderately hot and muggy, but without needed rain. The tropics appear to be getting active finally as we head into September, and perhaps will be transporting needed moisture into our area in September. We shall see. Check back later to see how September works out. Please continue to watch the tropics closely for the next several weeks.

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