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DECEMBER 2009
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| 1st - 7th | 1st, HP 1013 hPa S Norway, LP 974 hPa S of Iceland. 2nd, drizzle and light rain very early am followed by heavy and sometimes prolonged showers from midmorning. 3rd light rain just after midnight with light rain showers mid morning. 4th, light rain starting 20.00h. 5th, sunny morning, light intermittent rain from 17.00 to 23.00h from warm front. 6th, LP 953 hPa NW of Donegal, moderate/heavy showery rain from cold front from 04.00 to 10.00h. 7th, light rain pm. |
| 8th - 14th | Becoming more settled though mainly cloudy, light rain and drizzle from evening of 8th overnight into 9th. LPs near greenland and W Atlantic, HP 1029 hPa Spain. 10th, light rain shower early am then sunny, HP 1032 hPa Wales, 1029 hPa French Alps. 11th, sunny periods. 12th, very light rain showers am, light rain and drizzle evening. 13th HP 1036 hPa N Scotland to 1034 hPa S Norway, intermittent light drizzle night and early pm. 14th, intermittent drizzle early am, sunny periods from mid morning. |
| 15th - 23rd | 15th, light snow pm giving a slight and patchy dusting, turning to sleet and rain by evening. 16th, LP 1002 hPa N of Netherlands, HP 1037 hPa from S of Iceland to C Norway. 17th LP moves SSW toward Starights of Dover, light snow showers pm, moderate snow late evening and night. 18th, heavy snowfall before dawn giving 10 - 12 cm snow cover. 19th, sunny with some haze. 20th, LP 979 hPa W of Shetland, LP 989 hPa southern North Sea, occlusion brings another snowfall of about 3 cm before sunrise - total snow cover still around 10cm. 21st, new December record minimum temperature which rises quckly with a slight thaw later as warm front crosses giving some sleet and light rain. Snow cover about 6cm where undisturbed but icy 2 - 3 cm and rather patchy elsewhere. 22nd, a sunny day - slight thaw continues, freezing fog after nightfall. 23rd, LP Northern UK and Ireland, freezing fog to start followed by sleet then rain later - temperature rose above freezing only after midday, sunny pm. |
| 24th - 31st | 24th, light rain after midnight followed by heavier showers, snow cover now very patchy and max depth of 2.5cm where completely undisturbed. 25th, LP 980 hPa N Germany, LP 978 hPa 20°W of Ireland. 26th, passage of trough and cold front am with moderate rain (what little remaining snow/ice gone), and intermittent rain through the day and evening. 27th, some light rain just after midnight followed by a dry, cloudy day. 29th, LP 978 hPa 50°N 10 °W - very dull, light rain at first from warm front after 06.00 then spells of light/moderate rain intermittently all day from occlusion lasting well into the night. 30th more intermittent outbreaks of rain, night and into the daytime, light to moderate, overcast and very dull again. 31st, a quiet day with a late rain shower at night. |
| DECEMBER 2009 MONTHLY SUMMARY |
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| ‡ SUN: Sunshine hours are calculated approximately and solely from solar radiation readings, but note that the solar sensor's exposure to sunshine in Midwinter is very limited. The sensor receives only up to 25% of total possible sunshine exposure this month due to obstruction. There is no allowance for sunshine by visual observation only, so the sunniest day figures above can be very significantly less than the actual daily sunshine duration. THW = Shaded Heat Index calculated with cooling/warming effect of wind and humidity to give an apparent temperature. THSW = Unshaded Heat Index calculated with cooling/warming effect of wind, humidity and full direct sunshine to give an apparent temperature. EVAPO-TRANSPIRATION is drying effect due to sun and wind, and is equivalent to "negative rainfall" |
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DAILY STATS DECEMBER 2009 |
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TEMPERATURE ºc |
HUMIDITY |
SUN ‡ |
PRESSURE |
RAINFALL |
WIND SPEED |
DIRECTION |
WEATHER NOTES ‡ |
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DATE |
Low (21-09h) |
High (09-21h) |
Temp at 14.00z |
RH % at 14.00z |
Dewpoint ºc at 14.00z |
Bright sun hrs |
hPa at 14.00z |
Day Total (mm) |
Average (mph) |
Max Gust (mph) |
Dominant (Compass) |
Precipitation type etc ‡ |
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1st |
0.3 | 5.5 | 5.4 | 78 | 1.9 | 0.2 | 1010.5 | F | 0.0 | 0.9 | 14 | SSW | Sunny am |
2nd |
2.9 | 9.9 | 9.3 | 88 | 7.4 | 0.2 | 996.2 | F | 10.7 | 1.1 | 18 | SE | SHRA++ |
3rd |
7.1 | 7.6 | 5.4 | 80 | 2.2 | 0.0 | 997.5 | R | 1.5 | 1.8 | 16 | SSW | Rain am |
4th |
1.8 | 6.9 | 6.3 | 70 | 1.2 | 0.5 | 1007.4 | FS | 1.0 | 1.4 | 14 | WNW | Rain night |
5th |
5.2 | 11.3 | 10.1 | 77 | 6.3 | 0.1 | 1000.5 | RS | 5.3 | 4.0 | 19 | SW | Rain eve |
6th |
9.9 | 12.3 | 10.4 | 64 | 3.9 | 1.5 | 997.6 | RQ | 7.1 | 5.5 | 29 | SSW | Rain am |
7th |
8.1 | 10.6 | 10.1 | 78 | 6.4 | 0.0 | 997.2 | F | 3.3 | 3.9 | 25 | SW | Rain pm |
8th |
4.9 | 9.3 | 9.2 | 73 | 4.6 | 0.1 | 1012.1 | RS | 0.8 | 2.3 | 19 | SSW | Rain eve |
9th |
8.5 | 12.0 | 11.9 | 88 | 10.0 | 0.1 | 1018.1 | RS | 0.5 | 1.1 | 14 | SSW | Rain night |
10th |
6.4 | 9.4 | 9.4 | 69 | 4.0 | 1.2 | 1027.8 | RS | 0.3 | 1.3 | 16 | SSW | SHRA am, Sunny |
11th |
1.3 | 6.6 | 6.5 | 88 | 4.7 | 1.2 | 1030.9 | ST | 0.0 | 0.4 | 10 | N | Sunny periods |
12th |
4.4 | 7.8 | 7.5 | 62 | 0.7 | 1.3 | 1029.2 | FS | 0.8 | 1.5 | 13 | N | SHRA |
13th |
3.7 | 5.0 | 4.8 | 85 | 2.5 | 0.0 | 1024.6 | F | 0.5 | 1.0 | 13 | N | Rain am/eve |
14th |
1.7 | 5.3 | 5.2 | 74 | 0.9 | 1.3 | 1020.1 | FS | 0.5 | 0.1 | 8 | N | Drizzle am |
15th |
-3.6 | 0.1 | 0.1 | 90 | -1.3 | 0.8 | 1017.7 | FS | 0.0 | 0.0 | 3 | SE | Haze |
16th |
-6.1 | 1.0 | 0.2 | 86 | -1.9 | 0.1 | 1009.3 | F | 1.5 | 0.2 | 6 | SSW | Snow pm |
17th |
0.6 | 3.7 | 3.7 | 69 | -1.5 | 1.0 | 1006.9 | ST | 0.5 | 4.7 | 25 | N | SHSN pm/Snow eve |
18th |
-1.7 | 0.3 | 0.2 | 87 | -1.9 | 0.8 | 1013.2 | ST | 0.8 | 1.4 | 12 | N | Heavy snow am |
19th |
-3.1 | -0.2 | -0.7 | 81 | -3.6 | 1.3 | 1009.5 | F | 0.0 | 1.4 | 13 | N | Sunny |
20th |
-2.4 | 0.3 | -0.3 | 73 | -4.6 | 1.5 | 997.5 | FS | 0.5 | 0.7 | 11 | SW | Snow am |
21st |
-7.4 | 1.9 | 1.1 | 90 | -0.3 | 0.0 | 988.3 | F | 1.3 | 0.0 | 5 | WNW | Sleet/Rain pm |
22nd |
-0.2 | 2.2 | 1.4 | 90 | -0.1 | 1.5 | 986.9 | RS | 0.3 | 0.3 | 10 | SSW | Rain am, sunny pm |
23rd |
-5.1 | 4.2 | 2.4 | 92 | 1.3 | 1.8 | 989.8 | FS | 1.8 | 0.6 | 14 | SE | Rain am |
24th |
1.8 | 5.1 | 4.5 | 91 | 3.2 | 0.0 | 986.2 | F | 3.8 | 0.4 | 14 | SE | Rain am |
25th |
2.0 | 3.1 | 3.0 | 86 | 0.9 | 0.2 | 1000.3 | R | 0.0 | 1.5 | 14 | WNW | Cloudy |
26th |
-0.3 | 7.9 | 7.6 | 86 | 5.4 | 0.0 | 999.7 | FS | 9.1 | 4.5 | 19 | SW | Rain |
27th |
5.1 | 7.1 | 6.4 | 69 | 1.1 | 0.2 | 997.7 | R | 0.3 | 4.0 | 20 | SW | Rain am |
28th |
-1.5 | 4.7 | 4.2 | 84 | 1.7 | 2.0 | 1002.7 | F | 0.0 | 0.2 | 7 | SW | Sunny spells |
29th |
-0.3 | 3.8 | 3.7 | 91 | 2.4 | 0.0 | 990.7 | F | 14.0 | 0.3 | 10 | SE | Rain |
30th |
3.8 | 5.3 | 5.1 | 93 | 4.0 | 0.0 | 990.3 | RS | 5.6 | 0.5 | 6 | NW | Rain |
31st |
3.1 | 3.7 | 3.6 | 82 | 0.8 | 0.0 | 997.0 | ST | 0.3 | 2.6 | 17 | N | Shower night |
| ‡ SUN: Sunshine hours are calculated approximately and solely from solar radiation readings, but note that the solar sensor's exposure to sunshine in midwinter is very limited. The sensor receives less than 25% of total possible sunshine exposure this month - none in the morning - and there is no allowance for sunshine by visual observation only, so the figures above can be very significantly less than the actual daily sunshine duration. |
| Barometer trend (previous 3 hours) : F = falling, ST = steady, R = rising; Q = quickly, S = slowly |
| ‡ Weather Notes use METAR codes: SHRA = rain showers; SHSN = snow showers; SN = snow; RASN = Rain and snow; '+' = heavy; |