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MAY 2009 daily and monthly summary

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MAY 2009
June
1st - 7th
1st, HP 1030 hPa southern Sweden stretching eastwards, weak ridge over S England from HP of 1030 hPa west of Portugal, LP 972 hPa south of Iceland. 3rd, HP 1039 hPa to W of UK, HP 1027 hPa over central Europe. 4th, some very light and short lived showers pm gave trace of rain. 5th, S England under influence of HP ridge 1025 hPa, LP 972 hPa WNW of Scotland. 7th, cloudy and dull with trace of rain from showers.
8th - 13th
8th, LP 976 hPa to N of Scotland, cold front and troughs bring moderate/heavy showers am. HP 1025 hPa NW of Ireland, LP zone from W of Portugal across C Europe. 12th, HP 1033 hPa near Shetland, LP 1012 hPa northern France. 13th, drizzle early morning, daytime dull and overcast.
14th - 19th
15th, HP 1033 hPa Norwegian Sea, Lp 1001 hPa over southern England with many fronts and troughs associated, moderate showers from midnight to 2.30am, moderate rain from 19.30 to 21.00. 17th, LP 988 hPa W of Ireland with fronts circulating over UK. HP dominates to far N Atlantic, rain am and showers mid afternoon. 18th, light/moderate showers early am. 19th LP filling 1004 hPa north of Scotland, moderate/heavy showers early morning.
20th - 24th
More settled with weak HP ridging from SW bringing sunny periods but also cloudy spells each day. 24th, HP ridge 1020 hPa from SW with slack LP to south and LP 979 hPa S of Iceland.
25th - 27th
25th, LP 1012 hPa over central France, mid-morning rain from warm front followed by thundery showers in mid afternoon from convection tracking from northern France. 26th: HP 1033 hPa W of Galicia, LP 1001 hPa over Denmark showers from cold fronts am. 27th, mainly dull with light rain late morning into early afternoon.
28th - 31st
29th, HP 1036 hPa North Sea and Scandinavia, long sunny periods. Virtually cloudless and unbroken sunshine 30th & 31st. 31st. HP 1033 hPA from Mid Atlantic through S Norway to Baltic states, LP 998 hPa Azores.
MONTHLY SUMMARY MAY 2009
ACTUAL TEMPERATURE
 AVERAGE
 Daily Maximum
18.2
  ºC ( +0.7C)*
 Daily Minimum
8.8
  ºC ( +0.4C )*
 Daily Mean
13.18
  ºC ( +0.7C)
 EXTREMES
 High Maximum
24.4
  ºC ( 29th )
 Low Minimum
3.4
  ºC (   4th )
 Low Maximum
13.7
  ºC ( 13th )
 High Minimum
12.5
  ºC ( 28th )
 
   
 Days with max => 20 °C
8
   ( -1 )
 Days with max in range 15 - 20 °C
18
   ( +3 )*
 Days with max < 15 °C
5
   ( -2 )*
 
PRECIPITATION
 Monthly Total
25.8
  mm ( 55% )*
 Days with measurable precip
10
  Days ( -1 )*
   ...of which, days with >= 1.0 mm
8
  Days ( -1 )*
   ...and days with hail observed
0
  Days  
 
   
 Days with Thunder
1
  Days  
 RAIN RATE & EXTREMES
 High Rain Rate
19.3
  mm/hr (   8th )
 High Rain Total in 1 day
6.3
  mm ( 15th )
 High Rain Total in 1 hour
4.1
  mm ( 15th, 20.40h)
 EVAPO-TRANSPIRATION
 Total for month
93.9
  mm  
 High Total for 1 day
4.6
  mm ( 30th )
APPARENT TEMPERATURE
 Low Wind Chill
3.4
  ºC (   4th )
 DAVIS HEAT INDICES THW & THSW
 Low Temp/Hum/Wind Index
3.2
  ºC (   4th )
 High Temp/Hum/Wind Index
24.4
  ºC ( 29th )
 High Temp/Hum/Sun/Wind Index
31.6
  ºC ( 29th )
 
DEWPOINT & HUMIDITY
 High Dewpoint
15.5
  ºC ( 29th )
 Low Dewpoint
-3.1
  ºC (  3rd )
 Average Dewpoint at 14h
6.8
  ºC  
 Low Relative Humidity
28
  % ( 23rd )
 Average RH at 14h
52
  %  
WIND SPEED & DIRECTION
 Monthly Average
2.40
  mph  
 Windiest day (Average)
5.1
  mph ( 18th )
 Highest Gust
26
  mph ( 18th )
 Dominant Direction
SW
  ( 36% )
 
BAROMETER
 Monthly Mean
1017.4
  hPa  
 High Barometer
1031.4
  hPa ( 29th  )
 Low Barometer
1000.8
  hPa ( 15th )
SUNSHINE
 Max Sensor Exposure to direct sun
9.5
  hours/day ( 14-15 possible )
 Calculated Monthly Sunshine Hours
159.0
  hours  
 Estimated Actual Hours (approx)
194.0
  hours  
 Sunniest Day Measured
9.3
  hours ( 30th )
 Days with no sunshine
1
  Days  
 
FOG
 Number of Days with Fog
0
  Days  
NEW RECORDS SET THIS MONTH
 
* Difference from site average 1984 - 2008
‡ SUN: Sunshine hours are calculated approximately and solely from solar radiation readings, but note that the solar sensor's exposure to sunshine is limited. The sensor receives only up to 70% 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"

   DAILY STATS MAY 2009
 
TEMPERATURE ºc
HUMIDITY
SUN ‡
PRESSURE
RAINFALL
WIND SPEED
DIRECTION
  WEATHER
 NOTES ‡
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 ‡
                       
1st
 7.4 19.4 16.3 62 9.0 7.0 1022.9 RS 0.0 2.1 13 SW  Sunny
2nd
 9.9 19.0 18.7 34 2.5 7.7 1027.1 FS 0.0 1.8 12 SW  Sunny
3rd
 9.2 15.1 14.4 34 -1.2 4.8 1025.5 ST 0.0 2.2 18 N  Fair
4th
 3.4 14.3 11.6 70 6.3 1.8 1025.6 FS 0.0 2.2 16 SW  Cloudy
5th
 10.4 19.2 19.0 49 8.0 3.5 1019.6 F 0.0 3.3 20 SSW  Cloudy
6th
 10.5 20.2 20.2 47 8.5 5.7 1016.6 FS 0.0 3.7 19 SW  Fair
7th
 9.0 14.2 13.4 72 8.5 0.2 1013.5 FS 0.0 4.4 17 SW  Cloudy, dull
8th
 8.8 15.4 14.8 45 2.9 5.7 1011.9 R 1.8 4.9 22 SW  Showers am
9th
 5.8 17.7 17.3 41 3.9 7.2 1014.0 FS 0.0 1.8 14 SW  Sunny pm
10th
 5.2 20.6 19.4 41 5.8 7.5 1017.2 FS 0.0 0.9 13 SW  Sunny
11th
 8.9 15.0 14.8 50 4.4 8.0 1020.5 ST 0.0 3.3 21 ENE  Sunny
12th
 8.4 15.8 15.6 50 5.2 4.7 1017.7 FS 0.0 3.3 20 ENE  Fair
13th
 11.1 13.7 13.2 90 11.6 0.0 1012.5 FS 0.8 0.8 10 SE  Drizzle
14th
 10.1 18.4 17.7 60 9.9 0.3 1005.8 FS 0.0 0.4 8 SE  Cloudy
15th
 10.8 14.8 13.9 58 5.8 2.7 1001.6 RS 6.3 3.7 20 SW  Rain evening
16th
 7.1 15.6 15.4 48 4.5 5.5 1006.7 RS 0.8 4.0 25 SW  Showers am
17th
 8.7 15.6 14.4 54 5.2 3.0 1006.6 RS 3.8 3.6 21 SW  Rain am
18th
 9.0 15.4 14.3 58 6.2 5.7 1013.9 RS 2.5 5.1 26 SW  Showers am
19th
 9.3 16.5 14.7 59 6.7 5.2 1017.0 ST 2.5 3.5 21 SW  Showers am
20th
 7.1 18.6 18.3 44 5.8 7.0 1018.0 F 0.0 1.7 13 SW  Sunny periods
21st
 7.7 19.8 19.4 37 4.4 6.8 1012.7 FS 0.0 1.8 16 SSW  Sunny periods
22nd
 7.1 18.3 17.9 53 8.2 5.5 1016.9 RS 0.0 2.4 17 SW  Sunny spells
23rd
 6.9 19.7 19.0 43 6.1 5.5 1015.2 F 0.0 1.0 12 SW  Sunny am
24th
 7.7 24.2 23.7 39 8.9 8.7 1018.7 ST 0.0 0.9 12 SE  Sunny
25th
 10.9 22.4 21.6 59 13.4 3.0 1012.5 F 2.8 0.7 19 SE  Rain am, thunder pm
26th
 10.3 16.9 16.3 39 2.3 6.2 1015.4 R 3.0 2.4 18 WNW  Rain am
27th
 7.9 14.0 11.8 86 9.5 0.3 1020.4 F 1.5 3.9 21 SW  Rain am/pm
28th
 12.5 22.2 22.1 55 12.6 3.2 1029.8 RS 0.0 1.3 11 SSW  Sunny pm
29th
 11.2 24.4 23.3 47 11.4 8.2 1029.6 FS 0.0 1.0 13 SE  Sunny
30th
 9.8 23.4 22.8 30 4.3 9.3 1024.2 FS 0.0 1.2 16 SE  Sunny
31st
 11.1 24.1 23.1 45 10.5 9.3 1023.4 ST 0.0 1.3 16 N  Sunny
                         
‡ 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 approx 65% of total possible sunshine exposure 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†
‡ Weather Notes use METAR codes: OVC = overcast; SHRA = rain showers; '+' = heavy;