GAITHERSBURG 2 WNW MARYLAND – APRIL 2015 WEATHER STATION HIGHLIGHTS by Kevin Shaw, NJWO contr ibuting member

APRIL 2015 WEATHER HIGHLIGHTS, GAITHERSBURG 2 WNW MD
by Kevin Shaw, NJWO member and observer in charge

We had quite a contrast between April 2015 and April 2014.
We set several records last year, had some wild rainfall amounts,
setting new monthly records. This year virtually no records were
set either in temperature and rainfall, with a very insignificant
snowfall record tied with our 0 amount, the 16th April when that
has happened out of my 37 year period of record (POR). Being that
April 2015 featured a bit lower than normal precipitation amounts
compared with my long-term average, and a bit above normal
temperatures, the rankings show that it was not a remarkable
month, as it was the 15th driest month and it was the 10th
warmest in average temperature in my POR.

The only daily record set all month was the month’s warmest
minimum temperature, 59°, recorded early in the month on the
3rd. That officially goes down as a daily record maximum
minimum temperature. The 31° minimum temperature on the 1st
of the month, the only sub-freezing minimum temperature of the
month, was almost 3 weeks earlier than the long term average last
32 spring minimum temperature. (We have been nowhere close to
a 32° min so far in May.) After a cold March, leaf bud was behind
schedule on April 1, but by the end of the month caught up.

The average maximum temperature for the month was 67.2° (+1.0°),
the average minimum temperature was 44.2°(+2.5°) with the resultant
mean average temperature for the month of 55.7°(+1.7°). The highest
temperature recorded during the month was a modest 81° on the 18th,
which did not come close to setting or tying a daily record. The lowest
reading of the month was 31° on the 1st, which also did not come close
to setting a daily minimum record.

The month’s total precipitation amount of 3.01″ was 0.65″ below the
normal March amount of 3.66″. The 14 days of measurable precipitation
during the month was a bit above the long term average of 11.3 days.
The year to date (YTD) precipitation total of 13.88″ is 0.20″ above the
normal YTD average amount for this time of year of 13.68″. No snow fell
in April, and there hasn’t been any in May, so the final seasonal snowfall
total of 35.8″ was 7.3″ above the normal total seasonal snowfall amount
of 28.5″.

The monthly barometric pressure extremes were a modest 30.43″ on the
16th and 29.44″ just a few days later on the 20th on our wettest (0.86″)
day of the month. Average barometric pressure for the month was 30.00″,
not the same value you would get if you averaged the two extreme values
(29.94″) I had for the month but pretty close. In March they came out as
the same. Just trying to explore t his relationship for a few months to see
what kind of patterns develop, if any.

The distribution of 9 sunny, 11 partly cloudy and 10 cloudy days
corresponded somewhat with our drier than normal precipitation values
but more aligned with the above normal amount of measurable
precipitation days.

There was 281 heating degree days and 2 cooling degree days. There were
6 days with fog and 2 days with thunder.

My maximum temperature frequencies included 2 days at or above 80°,
11 days between 70°and 79°, 12 days between 60° and 69°, 4 days from
50°- 59°, and 1 day between 40°and 49°. On the minimum temperature
frequency side of things, there were 8 days below 40°, 15 days between
40°and 49°, and 7 days between 50°-59°.

The diurnal range average was a bit below normal (23.1° vs the normal
24.5°). The max daily range of 39.1° occurred on the 6th during one of
typical spring warmups bridging late winter leftover cold and early
spring warmth. The lowest daily temperature range of 5.6° occurred on
the 9th at the end of a rainy period with our coldest max temp of the
month (47°). There were only 2 days total with diurnal ranges lower
than 10° while there were 6 days with ranges of 30° or more, mostly in
the first half of the month.

The month of April had no real outstanding periods of cold or heat,
reflecting in the lack of daily records being set. Precipitation was below
normal, but light amounts were spread out throughout the month and
were frequent. Gardens and lawns got off to a good spring start with no
damaging late frosts occurring. With the lack of significant heat and
remaining winter cold, there was a lack ofthunderstorm activity that
normally starts to get going in April. May has started out warm, but
with still a lack of convective activity during this typically active month.

Monthly record precipitation amounts

January 3.00” 1/20/2013 February 2.80” 2/14/2007
2.12” 1/14/2005 1.81” 2/29/2012

March 2.86” 3/13/1993 April 4.15” 4/30/2014
2.43” 3/23/1991 4.08” 4/22/2006

May 2.75” 5/5/1989 June 4.09” 6/25/2006
2.71” 5/18/1988 3.11” 6/18/1996
2.67” 516/2014 3.01” 6/19/1996

July 2.79” 7/20/1986 August 4.68” 8/11/2001
2.57” 7/27/1994 3.71” 8/6/1995
3.58” 8/19/1979

Sept 5.41” 9/5/1979 Oct 5.20” 10/29/2012
5.20” 9/30/2010 3.50” 10/23/1990
4.92” 9/8/2011 3.22” 10/1/1979
4.31” 9/6/2008 3.07” 10/2/2012

Nov 3.03:11/27/1993 Dec 2.10” 12/7/2011

2.95”11/16/2006 2.09” 12/24/1986
2.71” 11/7/1997
2.58” 11/8/1996

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