The
Weather Records of
Chepstow,
Monmouthshire, S.E. Wales, U.K.
2011
Annual Review
Statistics
and Averages
2011 Annual Report
Rainfall
Looking
back across through the year only five months received a respectable rainfall totals
for their relevant months. The first half of the year would reflect a
significant dry period spanning across the winter and spring months.
Taking
into account December 2010 as part of the winter climate season, up to May,
only February within that group had average rainfall. Admittedly there were two
reasonable falls within February on the 18th and 25th that helped.
December
2010 on the other hand was very dry and cold and contributed little towards
rainfall for the winter period, having merely 62% of normal. The Winter 2011
period was the driest since 2006 and the 4th driest in the last 20 years.
The
spring months of March April and May yielded little rain compared with the long
term 30 year averages with only 18 ‘wet days’ being registered.
Air
Pressure during this time was significantly higher over the spring season than
at any time over the year being about 4 m/bar higher than average and bore an
influence on the weather. May faired the best month for spring precipitation at
58% of average but with a March total of 31% and a very low April at just 9%,
it became the lowest total rainfall total for spring since 1974.
Overall
only 33% of expected rainfall fell for the spring season, the lowest since 1990
and the second lowest in over 100 years. Records dug out show this spring was
the 4th lowest total in a series dating back to 1893.
Rainfall
up to the first six months of the year also showed rainfall was still rather
low at just 69% of normal for the area. There was a bit of a recovery in the
second half of the year with the summer months replenishing a little of the now
receding reservoirs, streams and rivers. June led the way with nearly one and
half times its average making for a good start. August 99% and July at 84% gave
weight to the small recovery, which weighed in with an overall 107% for the
summer season.
The
wettest days of year fell in the summer months with the 12th June receiving
25.43mm and August 24th having 23.27mm respectively.
September
ended an average month but October and November were below standard for
rainfall amounts bringing autumn to three quarters of normal. December provided
a good total so annually there a small recovery for the second half as annual
rainfall reached 78% of long-term average for Chepstow at 807.2mm.
Temperatures
This
turned out to be a record year for temperature surpassing the previous record
held in 2006. The annual mean of 11.69c was derived from a mixed bag of
unexpected monthly mean temperatures, which generally did not reflect expectant
averages. It was an odd year for temperature not dissimilar to a roller coaster
in respect of many months fluctuated wildly off their mark. The winter season
was cold as you would expect but well below average. The bitter month of
December was an exceptional one with a 120 years interval before you found a
colder one. January delivered another cold one but February broke the mould
with a mild, dull cloudy month.
The
spring months of March, April and May all brought average or above normal
temperatures. April set a new record of 13.3c breaking the old 2007 record, as
spring was 11.5c, some 1.0c above average overall.
Roll
on summer for warmer months were the call of the now expectant public. June
disappointed with limited warm days turning unsettled by and large.
Taking
in June, the first six months initially did not illustrate that this would be
an exceptional year for temperature being only 5%above average. Summer
temperature meanwhile had itself in a rut. July and August delivered poor
results as a lot of cloud cover rolled in at times. The summer had already
reversed the good work done this spring.
September
looked like being an average month halting the poor summer trend. It was indeed
about average helped by some exceptional warm final days that turned up out of
the blue. October had a very warm first half but it was November that grabbed
everyone as yet another record was broken for warmth. It broke the record held
in 1994 and recorded a mean of 10.2c.
December
was again a mild month this reflected around the garden, as oddly unseasonably
flowers still remained in bloom in small quantities. It would be certainly an
eventfully year anyway but would it be a record year.
It
was touch and go but when the figures were double checked 2011 registered
11.69c, 53.04f confirming the record but only just, breaking the 2006 record
held here. The Meteorological Office UK reported that the temperature for the
whole country was just short of the 2006 record therefore recording the 2nd
warmest in their database that stretches back to 1910 some 111 years.
Sunshine
There
were poor amounts of sunshine this winter season with just 70% of the short
term average. December and February particularly poor with only January
delivering good amounts. A total 45 days in the winter period, nearly half,
received no bright sunshine at all and total sunshine generally has seen a
decline over the last 4 years at the site.
Mimicking
the temperature, the spring season was very good for sunshine with a new record
of 534 hours set at the station. All spring months were above average for
sunshine with April the best month of the year at 117%.
The
summer reflected the amount of cloud cover that was around in August but the
other months gave summer a just below average dowsing of sun.
More
cloud cover affected November this year giving a low amount of sunshine but
both October and December rallied to give an standard autumn season. Annually
1347 hours would reflect the last four years as an average.
Extreme
elements
Winter had more than 60% extra frost, the highest since 1996. This was due to the extreme months of December and January. Spring and autumn in contrast hardly received any. There was a total of just 16 days of air frost recorded this calendar year which sees the lowest since 2002. Hail was more frequent this winter helped by diamond dust events but a total of 5 days annually was equal to 2005’s low total.
Snowfall events were very few with only 5 days recorded this again equalling the total in 2005. Of the 5 days of snowfall only one ‘snow lying’ day was recorded on January 4th.
Mist was more frequent this year up 10% on average, but fog was more in evidence. January and February this year more frequency occurred whilst November recorded 7 days, the highest amount for that month for at least two decades.
Thunderstorms were few a far between again at the site as they were last year in 2010, a trend perhaps.
The
Months
Note: The first six months show that sunshine was 99.9% of short-term average, whilst the temperature mean was 105% of average.
January,
February and March
January was below average month for all of the main climate elements. A milder mid month phase was sandwiched between colder days especially towards the latter part of the month. Diamond dust a form of hail was recorded this month.
This was recorded over the hours prior to and after midnight on the 20th and 21st.
February on the other hand had some mild temperatures including several overnight ones dropping no lower than 9c. It was the mildest February since 1998, but with this it was damp, raising humidity levels to over 90%, high for February.
Mist and fog was evidently present throughout and overall cloud cover was an issue. Okta observations taken at 9am showed cloud cover to be at their highest since the station started recording the element back in January 2007. This became reflective in poor sunshine amounts for the month in general.
For March there were two most striking features that leapt out. The first was the March minimum mean temperature was lower than the preceding month of February. Not an odd thing you may think but the last time this event happened locally was back in 1995 and clearly illustrates the mild overnight temperatures that were on offer in February. The other fact to come out was how dry it was. Just over 24.3mm brought about the driest March for 21 years helped by good amounts of sunshine.
April,
May and June
An
exceptionally warm April this year with a new record temperature mean of 13.3
Celsius this surpassing the previous 2007 record. It also recorded record
sunshine amounts at the site for April with 229.2 hours. Many of the days
enjoyed lengthy spells of sunshine.
It
turned out to be a very dry April with only 6.25mm, the driest since 1974
locally. In addition, 26 of the 30 days this April some 87%, were classed as
‘dry days’ an exceptionally high total.
The
exceptionally warm April brought out many butterflies early so consequently
hardly any butterflies were of note this May.
May turned
out to be a windy month as gusts of 32mph on the 2nd and a 35mph gust on the
26th contributed it to a windy monthly average of 3.0 mph, the highest for the
year. There was no mist registered this May probably due the constant breeze
circulating. It was yet another below average rainfall month. The mean
temperature was about average but oddly the second half of the month was 0.4c
colder than the first.
The
cool trend continued, as it became the coldest June month for a decade. It felt
frequently cold and wet and some cool overnight temperatures were recorded.
Rainfall for this month was good though being above average but not too good
for any people taking the time off for a holiday. It became the wettest June
since 1998 here with the wettest day of the year occurring in this month on the
12th as the gauge recorded 25.43mm. Towards the end of the month, the
temperature on the 26th rose to 28.6c, 83.4f also highest recording of the
year.
July,
August, and September
July was another cool month to follow on from June. Temperatures ranged on average around 1c colder than expected for this month and contrasted to last year. The 14th produced a cool overnight temperature of 8.8c one the coldest minimum’s for July since 2004. Rainfall appeared to be not too far below average and sunshine was up slightly on what had been recorded in the short term.
August continued the cooler theme for the summer months. Cloud cover or showery spells depressed many daytime temperature maximums to low levels. In between, short-lived drier interludes temperatures managed to struggle into the low twenty’s at best. Sunshine was also affected notably by cloud with just 106 hours.
September ended the cooler trend despite the showery nature of the month. It turned out to be the warmest September for 5 years. It was bolstered by a surprising and exceptionally warm last three days helped by a large anticyclone which drew warm air up from Spain and Portugal. Temperatures reached 24-25c, in what was an unanticipated late summer show for the public who had given up hope on any hot days.
October,
November and December
The
exceptional end to September continued into October as temperatures again rose
to 24-25c. Temperatures in that range for this month had not been heard of for
at least twenty years locally. It helped contribute to a record month for
temperature plus sunshine was up on previous years in a fairly settled first
three weeks.
Exceptional
warmth and mild days would be recorded during November with a new record mean
temperature of 10.2c. This surpassed the record held back in 1994. It was also
humid taken as a whole with mist and fog common.
The
highest rainfall total for one hour occurred on the 4th of this month at
14.1mm. Twelve of the days this November received no sunshine, which was high
compared to the last five years of data.
December
again was an overall very mild month cementing a record year for temperature.
Predominate westerly wind brought in much needed rain and the warm flow stemmed
the development of any air frost.
|
Temperatures Celsius |
Ranges |
|||||||||||
|
Month |
Max |
Min |
Mean Max |
Mean Min |
Overall Mean |
Mean Range |
0 =< |
<15 |
15+ |
20+ |
25+ |
30+ |
|
Jan |
12.1 |
-4.0 |
6.63 |
2.04 |
4.34 |
4.59 |
11 |
31 |
|
|
|
|
|
Feb |
13.0 |
-2.1 |
9.47 |
4.61 |
7.04 |
4.86 |
2 |
28 |
|
|
|
|
|
Mar |
16.9 |
-1.6 |
11.49 |
4.39 |
7.94 |
7.10 |
2 |
28 |
3 |
|
|
|
|
Apr |
24.8 |
4.3 |
18.20 |
8.44 |
13.32 |
9.76 |
|
5 |
16 |
9 |
|
|
|
May |
22.9 |
4.8 |
17.65 |
9.16 |
13.40 |
8.49 |
|
1 |
29 |
1 |
|
|
|
Jun |
28.6 |
6.3 |
19.44 |
10.58 |
15.01 |
8.86 |
|
1 |
21 |
6 |
2 |
|
|
Jul |
25.8 |
8.8 |
21.24 |
12.44 |
16.84 |
8.80 |
|
|
10 |
19 |
2 |
|
|
Aug |
24.8 |
8.4 |
20.17 |
12.81 |
16.49 |
7.36 |
|
|
16 |
15 |
|
|
|
Sep |
25.4 |
7.0 |
19.20 |
12.40 |
15.80 |
6.80 |
|
|
21 |
8 |
1 |
|
|
Oct |
25.5 |
3.1 |
16.49 |
10.25 |
13.37 |
6.24 |
|
10 |
18 |
1 |
2 |
|
|
Nov |
15.4 |
2.3 |
12.66 |
7.83 |
10.24 |
4.83 |
|
27 |
3 |
|
|
|
|
Dec |
12.7 |
-0.4 |
9.45 |
3.70 |
6.57 |
5.75 |
1 |
31 |
|
|
|
|
|
Total |
|
|
|
|
|
|
16 |
163 |
137 |
59 |
7 |
0 |
|
Ave |
20.6 |
3.07 |
15.17 |
8.22 |
11.69 |
6.95 |
|
|
|
|
|
|
<0.2
includes trace days that register
|
Precipitation Mm |
Ranges |
||||||||
|
Month |
Total |
Max 24hr |
Month Ave |
<0.2 |
0.2+ |
1.0+ |
10+ |
20+ |
30+ |
|
Jan |
80.62 |
14.73 |
2.60 |
2 |
|
13 |
2 |
|
|
|
Feb |
80.55 |
20.44 |
2.87 |
5 |
3 |
11 |
1 |
1 |
|
|
Mar |
24.39 |
8.38 |
0.78 |
1 |
2 |
7 |
|
|
|
|
Apr |
6.25 |
2.38 |
0.20 |
1 |
1 |
3 |
|
|
|
|
May |
42.02 |
15.54 |
1.35 |
1 |
6 |
7 |
1 |
|
|
|
Jun |
93.04 |
25.43 |
3.10 |
3 |
4 |
9 |
2 |
1 |
|
|
Jul |
60.31 |
13.97 |
1.94 |
1 |
5 |
6 |
2 |
|
|
|
Aug |
76.91 |
23.27 |
2.48 |
1 |
5 |
8 |
2 |
1 |
|
|
Sep |
76.10 |
14.54 |
2.53 |
1 |
3 |
12 |
3 |
|
|
|
Oct |
84.56 |
19.35 |
2.72 |
1 |
2 |
9 |
3 |
|
|
|
Nov |
71.68 |
17.49 |
2.38 |
1 |
7 |
10 |
2 |
|
|
|
Dec |
110.79 |
17.58 |
3.57 |
1 |
7 |
12 |
4 |
|
|
|
Total |
807.22 |
|
|
19 |
45 |
107 |
22 |
3 |
0 |
|
Aves |
67.26 |
|
2.21 |
|
|
|
|
|
|
|
|
Wind speed MPH |
Humidity % |
Air pressure |
Dew point |
||||||||
|
Month |
Ave Speed |
Dominate Direction |
Max Gust |
Ave Gust |
Max |
Min |
Ave |
Max |
Min |
Ave |
Max |
Min |
|
Jan |
2.4 |
NNE |
26 |
15.51 |
100 |
67 |
89.62 |
1040.7 |
985.0 |
1018.23 |
11.7 |
-5.0 |
|
Feb |
2.2 |
W |
28 |
16.50 |
100 |
60 |
90.01 |
1035.2 |
989.3 |
1012.97 |
11.7 |
-2.5 |
|
Mar |
2.7 |
NNE |
28 |
15.32 |
98 |
41 |
79.96 |
1041.2 |
995.0 |
1021.81 |
11.7 |
-3.3 |
|
Apr |
2.8 |
N |
26 |
15.90 |
98 |
40 |
71.95 |
1031.7 |
1004.2 |
1019.03 |
13.9 |
0.0 |
|
May |
3.0 |
W |
35 |
18.77 |
97 |
33 |
72.79 |
1028.6 |
1003.4 |
1016.89 |
15.2 |
-2.3 |
|
Jun |
2.5 |
W |
25 |
16.63 |
100 |
45 |
75.65 |
1034.4 |
996.7 |
1014.65 |
20.0 |
3.9 |
|
Jul |
1.9 |
WNW |
23 |
14.58 |
99 |
38 |
73.59 |
1027.6 |
990.7 |
1012.74 |
17.2 |
5.0 |
|
Aug |
1.7 |
WNW |
27 |
14.51 |
99 |
44 |
77.90 |
1026.4 |
1000.1 |
1012.56 |
19.4 |
7.2 |
|
Sep |
1.6 |
W |
27 |
14.40 |
100 |
52 |
82.36 |
1028.2 |
996.3 |
1012.36 |
19.4 |
6.1 |
|
Oct |
1.9 |
W |
28 |
15.16 |
100 |
54 |
83.80 |
1030.3 |
987.5 |
1015.83 |
17.8 |
2.2 |
|
Nov |
2.1 |
NE |
24 |
14.93 |
100 |
62 |
91.36 |
1028.5 |
988.2 |
1014.99 |
14.4 |
1.9 |
|
Dec |
2.2 |
W |
29 |
18.90 |
100 |
59 |
88.38 |
1033.4 |
983.2 |
1011.19 |
11.7 |
-1.1 |
|
Aves |
2.3 |
W |
|
15.92 |
|
|
81.44 |
|
|
1015.27 |
|
|
|
Temperatures |
C. |
F. |
Dates |
Times |
|
Mean
Maximum |
15.17 |
59.30 |
|
|
|
Mean
Minimum |
8.22 |
46.79 |
|
|
|
Overall
Mean |
11.69 |
53.04 |
|
|
|
Highest
Maximum |
28.6 |
83.4 |
26th June |
2.36pm |
|
Lowest
Maximum |
1.3 |
34.3 |
28th January |
12.00am |
|
Highest
Minimum |
17.6 |
63.6 |
10th September |
(9th) 11.28am |
|
Lowest
Minimum |
-4.0 |
24.8 |
31st January |
5.41am |
|
Absolute
Range |
32.6 |
58.6 |
|
|
|
Maximum
Range |
14.6 |
26.2 |
19th April |
|
|
Minimum
Range |
0.5 |
0.9 |
14th November, 28th December |
|
|
Precipitation |
Mm |
Ins |
Days |
% |
Date |
|
Annual
Total |
807.22 |
32.288 |
365 |
|
|
|
Highest
rainfall day |
25.43 |
1.017 |
|
|
12th June |
|
Most
rainfall in 1hour |
14.11 |
0.564 |
|
|
4th November |
|
Wet
Days =>1.0mm |
|
|
134 |
36.7 |
|
|
Rain
Days =>0.2mm |
|
|
179 |
49.0 |
|
|
Precipitation
(- trace) |
|
|
194 |
53.2 |
|
|
Trace
days (<0.05) |
|
|
38 |
10.4 |
|
|
Condensation |
2.42 |
0.096 |
32 |
|
|
|
Longest
rain period |
|
|
8 |
|
10th-17th January |
|
Daily
rainfall average |
2.21 |
0.088 |
365 |
|
|
|
Ave.
precipitation fall |
4.14 |
0.165 |
194 |
|
|
|
Dry
Days (+ trace) |
|
|
171 |
46.8 |
|
|
Longest
dry period |
|
|
16 |
|
14th-29th April |
|
Extreme Weather Elements |
|||||||||||||
|
|
Jan |
Feb |
Mar |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov |
Dec |
Total |
|
Air
Frost |
11 |
2 |
2 |
|
|
|
|
|
|
|
|
1 |
16 |
|
Grass
Frost |
21 |
8 |
12 |
|
|
|
|
|
|
2 |
4 |
15 |
62 |
|
Fog |
4 |
5 |
|
|
|
|
|
1 |
|
1 |
7 |
|
18 |
|
Mist |
6 |
13 |
14 |
9 |
|
3 |
7 |
2 |
9 |
11 |
13 |
3 |
90 |
|
Snow
Falling |
3 |
|
|
|
|
|
|
|
|
|
|
2 |
5 |
|
Snow
Lying |
1 |
|
|
|
|
|
|
|
|
|
|
|
1 |
|
Hail |
3 |
|
|
|
|
|
|
|
|
|
|
2 |
5 |
|
Thunder
Heard |
|
|
|
|
1 |
|
1 |
1 |
|
|
|
1 |
4 |
|
Thunderstorms |
|
|
|
|
1 |
|
1 |
1 |
|
|
|
1 |
4 |
|
Gale |
|
|
|
|
|
|
|
|
|
|
|
|
0 |
|
Ice
Day |
|
|
|
|
|
|
|
|
|
|
|
|
0 |
|
Air conditions |
% |
Mbar |
Dates |
Times |
|
Highest
Humidity |
100 |
|
|
|
|
Lowest
Humidity |
33 |
|
2nd, 3rd May |
2.06pm, 6.34pm |
|
Average
Humidity |
81.4 |
|
|
|
|
Absolute
range humidity |
67 |
|
|
|
|
Maximum
Air pressure |
|
1041.2 |
23rd March |
9.14am |
|
Minimum
Air pressure |
|
983.2 |
16th December |
3.59am |
|
Average
Air pressure |
|
1015.2 |
|
|
|
Absolute
range pressure |
|
58.0 |
|
|
|
Sunshine Hours and Distribution |
Hour Ranges |
||||||||
|
Month |
Total |
Daily Ave |
Max Hrs |
Days of No Sun |
0.1+ |
3+ |
6+ |
9+ |
12+ |
|
Jan |
36.15 |
1.16 |
5.89 |
16 |
10 |
5 |
|
|
|
|
Feb |
32.51 |
1.16 |
7.18 |
12 |
7 |
3 |
2 |
|
|
|
Mar |
131.00 |
4.22 |
10.90 |
3 |
11 |
8 |
3 |
6 |
|
|
Apr |
229.20 |
7.64 |
13.24 |
2 |
4 |
6 |
4 |
9 |
5 |
|
May |
173.90 |
5.60 |
13.66 |
0 |
8 |
5 |
9 |
2 |
3 |
|
Jun |
168.93 |
5.63 |
15.02 |
4 |
4 |
8 |
8 |
2 |
3 |
|
Jul |
162.34 |
5.23 |
14.52 |
1 |
9 |
8 |
5 |
4 |
2 |
|
Aug |
106.04 |
3.42 |
9.64 |
1 |
9 |
9 |
5 |
2 |
|
|
Sep |
124.95 |
4.16 |
10.09 |
1 |
10 |
10 |
3 |
4 |
|
|
Oct |
106.64 |
3.44 |
9.34 |
3 |
12 |
5 |
7 |
2 |
|
|
Nov |
41.60 |
1.38 |
6.96 |
12 |
10 |
5 |
2 |
|
|
|
Dec |
34.37 |
1.10 |
3.66 |
11 |
14 |
6 |
|
|
|
|
Annual |
1347.63 |
|
|
66 |
108 |
80 |
48 |
31 |
13 |
|
Wind |
Mph |
Knots |
Date |
Times |
Direction at Observational hour (9 GMT) |
||||||||
|
Maximum
Wind gust |
35.0 |
30.4 |
26th May |
3.13pm |
N |
NNE |
NE |
ENE |
E |
ESE |
SE |
SSE |
Calm |
|
|
|
|
|
|
22 |
37 |
13 |
12 |
16 |
10 |
10 |
8 |
43 |
|
|
|
|
|
|
S |
SSW |
SW |
WSW |
W |
WNW |
NW |
NNW |
|
|
|
|
|
|
|
18 |
18 |
69 |
32 |
26 |
17 |
8 |
6 |
|
Copyright ©Nick Felstead 2004-2011