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DECEMBER 2008 daily and monthly summary

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DECEMBER 2008
January 2009
1st - 6th
1st. Complex LP area 995-990 hpa, N France to Genoa Gulf, drifting slowly towards Baltic Sea. Light rain before dawn clearing to give a bright day. Dry days but cloudier 2nd and 3rd. LP 995 hpa, Southern North Sea, drifting NE while filling. Light/moderate rain 07.00 to 10.00h of 4th, clearing to give sunshine. 5th, LP 974 hpa, close E to Scotland, drifting towards N Germany while filling.
7th - 12th
7th, HP cell 1026 hpa, English Channel, drifting towards Switzerland at first, and moving away E. A sunny and cloudless day (rainfall from melted frost). 9th, LP 996 hpa W of Bergen, Norway; HP 1039 hpa NE of Azores, light rain midnight to 3am. 11th, Slack LP cells 1008 hpa North Sea and Biscay. 12th, freezing fog lasting to mid-morning with some rime frost.
13th - 18th
13th (Saturday), LP 975 hpa near Faeroe Is tracking SE with associated warm and occluded fronts crossing UK bringing prolonged and moderate/heavy rainfall from the early hours to evening. Dense fog morning of 14th. 15th UK lies in a col with HPs over Azores and Russia, and LPs near Iceland and Balearics. Fog on 16th morning and remaining rather misty and murky for the whole day. Drizzle / light rain early hours of 17th followed by a sunny day. 19th, LP 967 hpa to NW of Scotland, HP 1034 hpa ridging ENE of Azores to Germany.
19th - 24th
19th, LP 967 hpa to NW of Scotland, HP 1034 hpa ridging ENE of Azores to Germany, shower just after midnight. 22nd, High 1038 hpa over France, drifting very slowly north while weakening slightly. Overcast and gloomy 23rd & 24th.
25th - 31st
HP 1045 hpa over S Norway dominates and brings a fine spell as the airmass becomes colder, drier and continental in origin. The main HP moves SE toward Romania with a 1035 hpa ridge by Benelux and the UK. Precipitation in this period from frost melt only. 31st was a dull and overcast day

MONTHLY SUMMARY DECEMBER 2008
ACTUAL TEMPERATURE
 AVERAGE
 Daily Maximum
6.0
  ºC ( -1.8C )*
 Daily Minimum
1.8
  ºC ( -1.8C )*
 Daily Mean
3.84
  ºC (c. -1.8C )
 EXTREMES
 High Maximum
12.6
  ºC ( 20th )
 Low Minimum
-5.8
  ºC ( 30th )
 Low Maximum
2.1
  ºC ( 16&29th )
 High Minimum
9.9
  ºC ( 22nd )
 
   
 Days with max => 10 °C
5
    
 Days with max <= 5 °C
15
    
 Days with Air Frost
11
    
 
PRECIPITATION
 Monthly Total
33.2
  mm ( 45%)*
 Days with measurable precip
10
  Days ( -5 )*
   ...of which, days with >= 1.0 mm
5
  Days ( -6 )*
   ...and days with snowfall observed
0
  Days  
 Days with Snow Cover
0
  Days  
 Days with Thunder
0
  Days  
 RAIN RATE & EXTREMES
 High Rain Rate
12.0
  mm/hr ( 13th )
 High Rain Total in 1 day
20.3
  mm ( 13th )
 High Rain Total in 1 hour
3.3
  mm ( 13th, 12.20)
 EVAPO-TRANSPIRATION
 Total for month
11.1
  mm  
 High Total for 1 day
0.9
  mm ( 21st )
APPARENT TEMPERATURE
 Low Wind Chill
-5.8
  ºC ( 30th )
 DAVIS HEAT INDICES THW & THSW
 Low Temp/Hum/Wind Index
-5.9
  ºC ( 30th )
 High Temp/Hum/Wind Index
12.2
  ºC ( 20th )
 High Temp/Hum/Sun/Wind Index
14.1
  ºC ( 20th )
 
DEWPOINT & HUMIDITY
 High Dewpoint
8.8
  ºC ( 22nd )
 Low Dewpoint
-7.6
  ºC ( 30th )
 Average Dewpoint at 14h
2.1
  ºC  
 Low Relative Humidity
67
  % ( 24&29th )
 Average RH at 14h
78
  %  
WIND SPEED & DIRECTION
 Monthly Average
1.8
  mph  
 Windiest day (Average)
4.2
  mph ( 13th )
 Highest Gust
28
  mph ( 13th )
 Dominant Direction
SW
 ( 27% )
 
BAROMETER
 Monthly Mean
1017.3
  hPa  
 High Barometer
1036.7
  hPa ( 26th)
 Low Barometer
978.4
  hPa (   4th )
SUNSHINE
 Max Sensor Exposure to direct sun
2
  hours/day (8 possible)
 Calculated Monthly Sunshine Hours
21.7
  hours  
 Estimated Actual Hours (approx)
69.0
  hours  
 Sunniest Day Measured
2.0
  hours ( 30th )
 Days with no sunshine
8
  Days  
 
FOG
 Number of Days with Fog
3
  Days  
NEW RECORDS SET THIS MONTH
 
* deviation from average 1984 - 2007
‡ SUN: Sunshine hours are calculated approximately and solely from solar radiation readings, but note that the solar sensor's exposure to sunshine is very limited during November. The sensor receives approx 50% of total possible sunshine exposure this month, and there is no allowance for calculated or measured 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
   DAILY STATS DECEMBER 2008
 
TEMPERATURE ºc
HUMIDITY
SUN ‡
PRESSURE
RAINFALL
WIND SPEED
DIRECTION
DATE
Minimum
(21-09h)
Maximum
(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)
High Gust
(mph)
Dominant
(Compass)
                     
1st
 2.7 4.9 4.7 70 -0.3 1.7 1002.7 RS 1.5 3.1 20 N
2nd
 0.2 5.5 5.2 78 1.7 0.5 1002.5 F 0.3 1.6 16 SSW
3rd
 -1.3 2.3 2.1 84 -0.3 0.3 1001.9 R 0.0 0.5 11 SSW
4th
 -1.1 8.4 8.3 70 3.2 1.0 980.0 RS 6.9 3.2 22 SW
5th
 0.4 6.6 6.4 76 2.5 1.7 988.2 R 0.0 1.2 13 SW
6th
 4.2 6.6 6.4 74 2.1 1.2 1014.3 R 0.0 1.5 16 N
7th
 -2.0 5.1 4.9 89 3.3 1.5 1027.8 ST 0.3 0.0 4 SW
8th
 -1.8 6.6 6.6 83 3.9 0.1 1019.4 F 0.0 0.5 11 SW
9th
 1.2 4.7 4.7 77 1.0 0.1 1016.4 FS 1.8 1.7 13 N
10th
 -0.7 4.0 3.9 69 -1.2 1.5 1014.8 F 0.0 1.1 12 SSW
11th
 0.4 3.6 3.4 84 1.0 1.7 1009.9 ST 0.0 0.8 6 SW
12th
 -4.3 6.6 5.4 88 3.6 0.1 1011.1 F 0.3 1.9 25 SW
13th
 3.8 4.8 3.8 90 2.3 0.0 987.2 F 20.3 4.2 28 SE
14th
 -0.2 3.7 2.8 92 1.7 0.0 1000.1 R 0.0 1.1 11 N
15th
 3.7 4.8 3.9 88 2.1 0.0 1017.6 RS 0.0 1.7 13 N
16th
 0.8 2.1 1.9 92 0.7 0.0 1013.8 F 0.0 0.7 7 SSW
17th
 2.4 7.2 6.4 71 1.5 1.5 1015.1 RS 1.0 0.6 8 SSW
18th
 1.9 10.1 9.9 82 7.0 0.0 1016.7 FS 0.0 2.6 17 SW
19th
 3.6 9.2 6.1 72 1.4 0.1 1024.8 FS 0.5 3.2 22 SW
20th
 9.2 12.6 12.3 77 8.4 0.3 1024.2 ST 0.0 3.7 20 SW
21st
 9.3 10.9 10.8 69 5.3 0.3 1029.9 FS 0.0 4.0 22 SW
22nd
 9.9 11.8 11.8 81 8.7 0.2 1033.4 FS 0.0 1.2 14 SW
23rd
 9.4 10.4 9.9 78 6.3 0.0 1034.7 ST 0.0 0.2 7 SSW
24th
 7.3 7.4 7.3 67 1.6 0.0 1032.9 F 0.0 0.3 6 N
25th
 4.8 7.3 7.3 75 3.1 0.7 1032.7 FS 0.0 0.8 17 N
26th
 0.8 4.7 4.6 70 -0.4 1.3 1035.3 FS 0.0 1.4 12 S
27th
 0.7 3.2 3.0 73 -1.4 1.0 1033.2 FS 0.0 1.0 14 SE
28th
 -0.7 3.3 3.2 72 -1.3 1.5 1027.2 FS 0.0 0.7 12 SE
29th
 -3.7 2.1 2.0 67 -3.5 1.3 1027.4 FS 0.0 0.1 7 SE
30th
 -5.8 3.2 2.7 88 0.9 2.0 1028.8 FS 0.3 0.0 5 WNW
31st
 -0.9 2.6 2.6 81 -0.4 0.0 1026.4 FS 0.0 0.6 8 N
                       
‡ SUN: Sunshine hours are calculated approximately and solely from solar radiation readings, but note that the solar sensor's exposure to sunshine is rather limited. The sensor receives no more than 2 hours out of a possible 8 hours this month, 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