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Weather logSeptember 2010An unremarkable month

Weather – Novem

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Mean sea-level pressure (mbar). Dotted lines show anomalies with respect to the 1961–1990 average.

Mean 500mbar height (dam).

1000–500mbar thickness anomalies (dam) with respect to the 1961–1990 average.

All the charts on these pages are © Crown Copyright, Met Office.Charts on this page are based on NCEP Re-analysis data provided by the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, USA.

September 2010 was an episodic month with a succession of weather types, none of which lasted as long as a week. On the mean monthly chart, a brisk westerly flow across the Atlantic between latitudes 40 °N and 60 °N became a markedly diffluent southwesterly flow across the British Isles. Mean sea-level pressure anomaly ranged from +3mbar in Shetland to –2mbar in Cornwall and southwest Ireland.

An anticyclone over the UK on the 1st drifted slowly to Scandinavia over the next few days, allowing a southeasterly airflow to develop, while weak fronts affected western districts. The weather remained fine until the 3rd with cool nights and rather warm days; Kinloss (Morayshire) logged 13.2h bright sunshine on the 2nd and the temperature reached 24.5 °C at Kinlochewe (Wester Ross) on the 3rd. The 4th and 5th were cloudier with a freshening breeze, and western districts had occasional rain.

Active fronts moved northwards over the UK on the 6th and 7th preceded by strong easterly winds, and they brought widespread rain, heavy in places: largest totals were in Northern Ireland where Lough Fea (Co. Tyrone) collected 107mm and Killowen (Co. Down) 102mm in the 60h to 0900  UTC on the 7th. Showers, locally heavy and thundery, followed the general rain. A southwest-erly flow brought a succession of fronts from the 9th–11th. There was only a little rain in southern England, but heavy falls in south and mid Wales, with 73mm in 36h at Sennybridge (Breconshire). A transitory ridge gave England and Wales a fairly sunny day on the 12th, but further Atlantic fronts crossed the country on the 13th and 14th accompanied by strong winds and heavy orographic rain: 100mm fell in 48h at Cluanie Inn in Glen Shiel (Wester Ross). From the 15th to the 17th a strong, cold, northwesterly flow covered the country, bringing showers and sunny intervals; the month’s highest gust of 59kn was recorded at Capel Curig (Caernarfon) on the 15th.

A moderate southwesterly flow returned on the 18th–19th, delivering copi-ous amounts of rain to western and northern districts with 68mm in 48h at both Stonyhurst (Lancs) and Capel Curig, but little rain fell in southern, mid-land and eastern counties of England. A southerly airstream developed between the 20th and 22nd, and it became fine and warm in central and eastern England with 24.6 °C at Gravesend/Broadness (Kent) on the 22nd; western districts were less settled, and Bishopton (Renfrewshire) collected 60mm of rain on the same day. Heavy showers and thunderstorms in associa-tion with a southeastward-moving depression affected many places on the 23rd, then strong northerly winds developed between the 24th and 27th and there were further outbreaks of rain in eastern counties. It became cold: the lowest maximum was 7.6 °C at Braemar (Aberdeenshire) on the 24th, but maxima of 10–12 °C in southern and central England on both the 24th and 26th were the lowest in September at several sites since 1994. Tyndrum (Stirlingshire) and Kinbrace (Sutherland) reported minima of –4.4 °C on the 26th and 27th respectively – the lowest anywhere in the UK in September since 1993. Further rain, heavy at times, spread slowly from west to east dur-ing the 28th and 29th, followed by a brighter day on the 30th.

Both mean maximum and mean minimum temperatures were up to 1.0  degC above the 1971–2000 mean in all regions. Rainfall was within 40% of the average over much of the country, but southern counties from Dorset to Sussex were dry with barely half the normal amount, while parts of eastern Scotland and northeast England had twice the average. Sunshine duration ranged from 10–20% above normal in northern and western Scotland to 5% below locally in the Midlands, East Anglia and Southeast England.

© Philip Eden

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WEDNESDAY THURSDAY FRIDAY SATURDAY

Atmospheric circulation September 2010Mean sea-level pressure and fronts, 1200 UTC daily

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Because of a technical problem, the map for 7 September is not available in the usual format.

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SUNDAY MONDAY TUESDAY

Weather log

September 2010

An unremarkable month

Weather – Novem

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eather log

UK monthly data: September 2010Areal averagesRegion Max. temp. Min. temp. Mean temp. Sunshine Rainfall

Actual (°C)

Anom. (degC)

Actual (°C)

Anom. (degC)

Actual (°C)

Anom. (degC)

Actual (hours)

Anom. (%)

Actual (mm)

Anom. (%)

UKEnglandWalesScotlandN Ireland

Long-running time-seriesSeptember 2010 Anomaly

Central England Temperature (CET) 13.9 °C +0.2 degCEngland and Wales Rainfall (EWR) 88.3mm 110%The CET is supplied by Philip Eden; the series runs from 1659. The EWR (which runs from 1910) and the areal averages are supplied by the Met Office (http://www.metoffice.gov.uk/climate/uk/).Max, min and mean temps are analysed separately; as a result, occasionally an areal mean temp may not be exactly (max + min)/2.All figures are provisional and all anomalies relate to the averages for the period 1971–2000.

16.5 +0.4 9.1 +0.6 12.8 +0.5 129.1 104 114.6 11417.7 +0.3 9.7 +0.5 13.7 +0.4 138.6 103 79.2 10816.5 +0.3 9.4 +0.6 13.0 +0.5 140.1 110 145.3 11714.6 +0.7 7.9 +0.7 11.2 +0.7 112.6 107 156.3 11216.3 +0.6 9.5 +1.2 12.9 +0.8 116.2 102 163.4 173

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Data supplied by the Met Offi ce: www.metoffi ce.gov.uk§ Averages for sunshine and rainfall are all

for the period 1961–1990. Averages for temperature are the most up to date available, usually within the period 1971–1990; these averages are gradually being updated to the period 1961–1990.

The assistance of the Met Offi ce in producing the maps and tables is gratefully acknowledged.DOI: 10.1002/wea.723

SELECTED EUROPEAN STATIONS

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EUROPE TEMPERATURE SUNSHINE RAINFALLM

ean m

aximum

(°C)

Diff. from

average § (degC)

Mean

minim

um (°C)

Diff. from

average § (degC)

Highest

maxim

um (°C)

Date(s)

Lowest

minim

um (°C)

Date(s)

Total form

onth (hours)

% of average §

Total form

onth (mm

)

% of average §

Wet days

(days with ≥1m

m)

Diff. from

average wet

days (≥1mm

rain)

Alt. (m)

1 Murmansk2 Moscow3 Kiev4 Reykjavik5 Oslo6 Stockholm7 Helsinki8 Copenhagen9 De Bilt10 Paris11 Marseille12 Warsaw13 Berlin14 Munich15 Prague16 Budapest17 Bucharest18 Belgrade19 Lisbon20 Madrid21 Majorca22 Gibraltar23 Rome24 Malta25 Athens26 Istanbul27 Casement28 Valentia

CLIMATIC DATA FOR September 2010TEMPERATURE SUNSHINE RAINFALL

Days w

ith snow

lying at 0900

Days w

ith fog (vis <200 m

at 0900)

Mean m

aximum

(°C)

Diff. from

1971–2000 average (degC)

Mean m

inimum

(°C)

Diff. from

1971–2000 average (degC)

Highest m

aximum

(°C)

Date(s)

Lowest m

aximum

(°C)

Date(s)

Lowest m

inimum

(°C)

Date(s)

No. of air frosts

No. of days w

ith grass m

in <0°C

Total for month (hours)

% of 1971–2000 average

Maxim

um duration

(hours)

Date(s)

Days w

ith no sunshine

Total for month (m

m)

% of 1971–2000 average

Max. fall in 24h from

0900 (m

m)

Date(s)

Days w

ith no rain (≤0.1m

m)

Map no. and place Alt. (m)

1 Stornoway

2 Aviemore

3 Dyce

4 Leuchars

5 Bishopton

6 Eskdalemuir

7 Durham

8 Woodford

9 Valley

10 Waddington

11 Lowestoft

12 Cambridge

13 Shawbury

14 Aberporth

15 Lyneham

16 Heathrow

17 St Athan

18 Hastings

19 Hurn

20 Camborne

21 Aldergrove

Sunshine readings in the above table are taken from electronic sensors except at Lowestoft and Hastings.

46 10.4 +0.9 6.2 +1.9 16.4 11 2.9 25 46 52 56 105 11 +0156 16.5 +1.0 7.4 +0.3 25.2 2 –1.3 30 – – 70 114 10 +0179 20.2 +1.1 10.2 +0.2 27.8 15 6.4 10 – – 51 110 6 –2

61 13.1 +3.0 7.9 +2.9 17.2 1 0.4 22 110 87 92 137 12 –1204 14.5 +0.7 5.4 –0.7 18.5 12 –1.3 30 – – 74 77 6 –5

11 15.5 +0.4 9.3 +0.3 19.0 8 3.2 30 162 105 73 132 10 +056 14.9 +1.0 8.5 +2.2 20.0 9 1.4 29 92 68 54 73 9 –2

5 16.4 –0.4 10.8 +0.8 19.6 1 5.2 22 – – 42 66 9 –14 17.8 –0.9 9.0 –0.4 23.3 11 4.3 27 141 106 90 134 11 +1

96 20.6 –0.1 10.4 –0.2 26.0 22 4.0 19 197 – 60 109 9 +136 25.2 +0.3 14.3 –0.8 30.5 4 7.6 29 284 112 30 63 4 +0

107 16.6 –1.5 8.9 +0.3 22.0 24 3.5 20 186 151 89 217 13 +546 17.6 –1.6 9.3 –0.5 24.6 24 4.6 30 150 93 123 273 11 +3

529 17.6 –1.8 7.0 –1.8 23.4 23 2.6 20 165 99 59 86 6 –3369 16.7 –2.3 7.9 –0.7 22.0 12 2.5 7 145 90 73 182 8 +1139 19.0 –3.1 11.5 +0.0 23.0 24 6.6 21 129 65 144 360 10 +5

91 24.9 +0.3 10.9 –0.2 32.0 8 4.6 22 206 92 24 57 3 –2132 23.2 –0.5 13.4 +0.4 30.4 8 8.8 30 191 94 52 100 6 +0105 26.1 –0.3 17.9 +0.9 32.9 10 14.6 28 277 106 5 26 1 –3582 26.8 +0.9 15.8 +0.8 33.3 14 10.4 26 – – 12 40 1 –3

8 27.4 –0.2 15.8 +0.2 30.2 3 12.4 28 254 115 34 72 2 –25 25.5 –0.6 20.4 +1.1 29.6 6 16.2 30 241 91 11 78 5 +33 26.2 +0.2 15.7 –0.1 29.8 11 9.0 30 – – 6 8 1 –4

91 27.0 –1.0 21.0 +0.9 30.4 19 18.7 25 251 97 75 187 7 +415 29.1 +0.9 20.4 +0.7 33.0 9 16.0 23 239 86 31 344 2 +137 26.6 +1.6 18.3 +2.8 32.7 26 15.8 3 – – 16 39 5 +133 17.4 +0.6 9.5 +0.5 22.2 2 1.4 25 130 107 103 174 17 +714 17.3 +0.6 12.4 +1.7 21.1 1 6.1 18 107 99 123 98 16 +1

15 14.8 +0.8 9.7 +1.1 20.5 4 10.2 25 3.0 27 0 1 104 109 12.9 2 6 129 114 20.2 19 10 – 0

228 15.1 +0.2 6.9 +0.4 22.2 3 8.9 24 –1.2 27 1 2 92 97 11.0 3 5 107 134 16.2 14 7 – 0

65 15.0 –0.5 9.1 +1.0 20.8 10 10.7 24 2.1 27 0 1 97 92 10.4 3 7 – – – – – 0 0

10 16.5 +0.3 9.3 +0.9 21.3 9 12.3 24 3.3 26 0 4 142 122 11.2 2 4 114 185 32.2 22 14 0 0

59 16.9 +1.2 9.4 +1.0 21.7 3 12.1 27 1.6 25 0 3 135 139 11.7 2 7 185 142 59.6 22 9 – 0

242 15.9 +1.3 7.8 +0.9 20.7 3 11.8 25 –0.2 25 1 3 97 110 10.0 3 4 152 110 29.6 22 8 0 0

102 17.8 +1.1 9.8 +1.2 21.4 3,9 11.9 24 4.9 25,30 0 0 – – – – – 76 132 16.8 6 12 – –

88 17.4 +0.3 9.4 –0.4 21.2 2 12.0 24 –0.2 25 1 5 117 111 11.9 1 5 90 121 15.2 23 11 – 0

10 17.3 +0.4 11.8 +0.7 22.9 2 12.5 25 5.1 26 0 2 130 103 12.4 3 3 94 129 22.8 28 13 0 0

68 17.9 +0.2 10.6 +0.8 22.1 22 12.2 24 5.3 25 0 0 123 100 12.1 1 3 75 146 20.6 23 12 0 0

18 18.5 +0.1 10.9 –0.2 22.0 9 14.4 25 5.4 18 0 1 131 88 11.0 1 6 66 133 14.3 6 17 0 0

26 19.0 +0.1 10.5 +0.4 24.4 22 13.2 26 5.8 25 0 0 – – – – – 43 85 10.3 6 12 – –

72 18.0 +0.4 9.6 +1.0 22.0 10 12.4 24 3.0 25 0 1 132 119 12.2 2 2 59 97 12.6 10 8 0 0

133 16.6 +0.5 11.5 +0.8 21.6 3 12.6 24 4.9 26 0 0 143 116 12.1 2 4 62 82 10.8 6 13 0 0

145 18.0 +0.3 9.8 0.0 21.7 10 11.9 24 2.9 26 0 1 134 106 12.5 1 3 52 82 9.6 22 14 0 0

25 19.4 –0.1 11.2 +0.2 23.9 22 13.8 26 5.4 25 0 0 129 101 12.3 1 5 38 70 9.8 23 15 – 0

49 17.8 0.0 11.2 +0.1 21.5 2 14.5 24 4.2 26 0 0 145 113 12.0 1,2 3 70 69 14.8 30 14 – 0

45 17.9 –0.4 11.0 –1.0 21.0 12 13.1 26 5.0 25 0 0 140 87 10.4 1,3 3 35 51 8.3 26 20 0 0

10 19.0 +0.2 9.0 –0.1 22.0 2 13.9 25 1.5 18 0 3 124 91 10.4 1 3 58 81 15.2 30 10 – 0

87 17.3 +0.3 12.2 +0.8 20.8 4 13.4 26 6.5 18 0 0 145 108 11.4 1 6 84 96 24.0 22 14 0 0

63 16.8 +0.7 10.6 +1.5 21.5 3 11.4 25 2.9 27 0 0 102 99 11.6 2 4 110 137 26.2 6 9 – 0