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

by Kevin Shaw, Observer in charge

Average high temperature 88.8° (+ 2.0°)
Average low temperature 69.8° (+ 4.1°)
Mean temperature 79.3° (+ 3.1°)
Precipitation 5.88″ (+ 2.14″)
Greatest daily amount (date) 1.51″ (30)
Year to date precipitation 28.26″ (+ 1.98″)
High temperature for the month (date) 98° (25)
Low temperature for the month (date) 62° (11,21)
Highest barometric pressure (date) 30.25″ (20)
Lowest barometric pressure (date) 29.79″ (8)
Peak wind gust (date/direction): 24 (19/ENE)
Heating degree days for the month: 0
Cooling degree days for the month: 443
Greatest diurnal range (date): 28.3° (21)
Least diurnal range (date): 5.7° (4)

Fog days: 5
Thunder: 7
Sunny/clear days: 4 Partly Cloudy days: 17 Cloudy days: 10

Days with measurable precipitation (=>.01″) = 11
Days with maximum temperatures of 90 or more = 17
Days with minimum temperatures of 70 or more = 18

by Kevin Shaw, observer in charge

July 2016 featured plenty of heat and humidity, along with an abundance of precipitation with a late month rally of heavy
rainfall from numerous thunderstorms and downpours.
Numerous records were set of many types. Two record high
temperatures were recorded on the 14th (96°) and the hottest day of the month on the 25th (98°). 17 days with maximum
temperatures of 90° or greater was considerably above the
normal amount of 10 days, but not a record (22 days in July
1999). 18 days with minimum temperatures of 70° or greater
was well above normal I am sure, though I don’t keep track
of that statistic in the long term. A cool wet July 4th helped set a record low max for the date (71°). There were 6 days
with record high mins set. Rainfall was running below normal through the 27th, but then a late month rally between the 28th and 31st when 3.05″ of rain fell brought the month to 5.88″, fifth wettest all-time, and over 2 inches above normal. Daily precipitation records were set on my birthday, the 29th
(0.93″) and the wettest day of the month on the 30th (1.51″). On that day record rains fell nearby in the Ellicott City MD area with incredible devastating floods of epic proportions. NOAA declared it a 1 in a 1000 year rainfall event.

The average maximum temperature for the month was 88.8°
(+2.0°), the average minimum temperature was 69.8° (+ 4.1°). The resultant mean average temperature for the month was
79.3° (+ 3.1°).

The month’s total precipitation amount of 5.88″ was 2.14″
above the normal July amount of 3.74″. My current year to
date precipitation total of 28.26″ through July 31 is 1.98″
above the normal amount of 26.28″. Precipitation was a bit
scarce the first 27 days of the month, with 7 day (July 9-15) and 8 day (July 20-27) dry streak periods and a total of
only 2.83″ rain falling. But the previously mentioned end of month wet period of 3.05″ between July 28 and July 31 put
us above normal for the month. 11 days of measurable rain at my station was essentially normal (long term average of 10.7)

The month’s modest highest barometric pressure reading of 30.25″ on the 20th occurred at the start of our longest dry streak of the month and our hottest temperatures of the month during that streak. The equally modest lowest pressure reading of the month of 29.79″ on the 8th occurred during a generally lower pressure time of July, started around the wet 4th of July.

The distribution of 4 sunny, 17 partly cloudy and 10 cloudy days fit in with the muggy, wet conditions commonly found during much of the month. There was definitely a good deal of clouds around most of the month with the rather low amount of sunny days.

There were 443 cooling degree days (CDD) and 0 heating degree days. There were a below normal amount of 5 days with fog and a bit above normal amount (7) of thunderstorm days. The peak wind gust during the month was a modest 24 MPH out of the ENE on the 19th, during a mid-evening thunderstorm. It was a generally calm month as this day was the only day of the month with a PWG over 20 MPH. There were a large amount of days (17) during the month with a daily PWG of under 10 MPH. The dominant daily wind direction was 22 days with a SW/WSW component, followed by a much lower 8 days with an easterly component and 1 day with a northerly component.

My maximum temperature frequencies included 17 days at or above 90°, 11 days between 80° and 89°, and 3 days between 70° and 79°. On the minimum temperature frequency side of things, there were 13 days between 60° and 69° and 18 days with minimum temperatures of 70° or greater.

The diurnal range average was a bit below normal (19.1° vs the normal of
21.1°). The max daily range of 28.3° occurred on the 20th at the beginning of our longest hot spell of the month (90° – 62°) on our hottest day of the month (94°- 60°). There were an additional 14 days with daily ranges at or above 20°, The lowest daily temperature range of only 5.7° (71°-65°) occurred on July 4th when we had our 2nd highest daily rainfall amount during the month. There was only 1 additional day during July with daily temperature readings less than 10°.

July 2016 started out relatively cool and wet, but that general pattern changed around the 9th and we were mostly dry and hot through the 27th. Hopefully this pattern will break down during August and we will have a more moderate rest of the summer. The wet period at the end of July initially broke our consecutive days of 90° max temperatures and has followed us into early August so far. We shall see. Check back in a few weeks to see how August finishes out. Don’t forget we are now in Hurricane Season! We just had a lull through most of July but Hurricane
Earl has brought us a hurricane in early August, and the tropical Atlantic has started to get active once again. So pay close attention to the tropics and beware!

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