AUGUST 2013 – GAITHERSBURG 2 WNW MARYLAND
BRIEF SUMMARY STATISTICS
by Kevin Shaw, Observer in charge
Average high temp 80.4° (- 4.5°)
Average low temp 64.7° (+ 0.6°)
Mean temp 72.5° (- 2.0°)
Precipitation 1.76″ (- 1.91″)
Greatest daily amount 0.40″ (7)
Year to date precip 32.67″ (+ 2.72″)
High temperature for the month (date) 87° (27,30)
Low temperature for the month (date) 53° (15)
Highest barometric pressure (date) 30.42″ (25)
Lowest barometric pressure (date) 29.74″ (13)
Peak wind gust (date/direction): 15 (4,14/NE,NW)
Heating degree days for the month: 1
Cooling degree days for the month: 234
Greatest diurnal range (date): 24.6° (26)
Least diurnal range (date) 4.3° (28)
Fog days: 3
Sleet/Freezing Rain days: 0
Snow days : 0
Thunder days: 1
Sunny/clear days: 12 Partly Cloudy days: 11 Cloudy days: 8
Days with measurable precipitation (=>.01″) = 10
Days with minimum temperatures of less than 60 = 7
Days with maximum temperatures of 90 or more = 0
AUGUST 2013 MONTHLY SUMMARY – GAITHERSBURG 2 WNW MARYLAND
by Kevin Shaw, observer in charge
August 2013 somewhat reversed the general pattern of the past several months,
in that the average temperature was below normal (-4.5). It has been common to
have below average max temps, but not to record breaking numbers – I had my
coolest average max temp (80.4°) in my 35 years of records, surpassing the 80.5°
set back in 1982 and 1994. And for only the second time ever, I had no days of
max temps of 90 or greater, which only happened one other time, back in 1982.
The average min temp was still above normal, so that part fits in with my general
patterns of the past few years, but it was only 0.6° above normal, the least amount
all year. High humidity levels were quite present most of the month, I had 18 days
with dew points of 70° or greater recorded sometime during the day. Despite this
high humidity, rainfall was considerably below normal (-1.98″) with the monthly
total of 1.76″ tying 1992 as the fifth driest August of all time. 83% of total precip
was on 8/13 or before. Not very many records were set during the month, as only
2 lowest maximums (3rd with 74°/4th with 78°) and one high minimum (9th with
75°) were established as records.
Actual statistics for July 2013 shows an average maximum temperature of 80.4° (- 4.5°)
with the average minimum temperature of 64.7° (+ 0.6°) resulting in a mean monthly
temperature average of 72.5° (-2.0°). I had 12 days with maxs in the 70s and 7 days
with mins in the 50s.
It being a basically dry month, the stress on crops and lawns was mitigated by a few
factors. Precipitation was spread out in light amounts most of the month, particularly in
the first 13 days of the month when 83% of the total monthly precipitation fell. Though only
sporadic light amounts fell, spaced out over only 3 days, a combination of cool, dry and
warm, very humid days kept evaporation down a bit. There were a total of 10 days with
measurable rainfall, essentially a normal amount for August, based on my 35 year record
average of 9.5. The monthly precipitation total of 1.76″ was 1.91″ below the normal amount
of 3.67″. I am now running 2.72″ above the normal precipitation amount for the year through
August 31 (32.67″ vs. 29.95″).
The modest high barometric pressure reading for the month of 30.42″ on the 25th occurred
at the beginning of the month ending hot and humid period, punctuated by a light shower in
the middle of this period. The 29.74″ lowest pressure value of the month occurred on the
13th, a cool rainy day that ushered in our coolest weather of the month around the 15th.
The 15 MPH PWG (peak wind gust) for the month that came from a northerly component
occurred on the 4th and 14th, bringing in our two coolest spells of the month (a short one on
the 4th, longer one on the 14th). The distribution of 12 clear/sunny, 11 partly cloudy
and 8 cloudy days was very similar to July’s numbers in that regard, but did not yield the
same results otherwise.
There were only 3 days with fog. There were 234 cooling degree days and 1 heating degree
day. My maximum temperature frequencies included 0 days of 90 or above, 19 days from
80-89, and 12 days from 70-79. On the minimum temperature frequency side of things, there
were 7 days below 60, 16 days between 60-69 and 8 days of 70 or greater.
The diurnal range average was quite a bit below normal (15.6° vs a normal of 20.8°) with a max
daily range of 24.6° on the 26th. The 4.3° lowest monthly range occurred only 2 days later on
the 28th on a cloudy, light rainy day, one of only a few during the last half of the month. There
were only 3 days total with diurnal ranges less than 10°. Conversely there were 8 days with
diurnal ranges of over 20°. On those 8 dry days the temperature really spread apart from the
morning min to the afternoon max.
August 2013 was quite diverse with some really nice, dry pleasant days interspersed with very
muggy, cloudy days but with precious little rain. Tropical activity has been sub-par so far this
season, as I type this approaching the peak day of the season based on long-term averages.
There are some indications that activity will be increasing over the next few weeks. Much more
September analysis will be forthcoming about this time next month so stay tuned!