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APRIL 2009 daily and monthly summary

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APRIL 2009
May
1st - 7th
1st, HP 1026 hPa centred in the North Sea, LPs 986 hPa SW of Iceland and 1007 hPa over Balearics. 2nd and 3rd, low cloud and mist respectively until after 13.00h followed by sunshine. 4th, LP 1006 hPa Outer Hebrides, cold front passage during morning, trace of rain. 5th - 7th long periods of sunshine.
8th - 14th
Becoming unsettled with LP from the W. 8th, rain during early morning clearing by 9am. 9th, Dull with drizzle, clearing late pm. Easter weekend is mild but cloudy and often dull with outbreaks of rain or showers. 10th LP 982 hPa NW of Hebrides, cold front brings light rain during pm. 12th, weak HP over Wales with LP to W, N and E. Trailing warm front over the E of UK, light rain am, moderate rain late evening. Thundery showers after 22h on 14th.
15th - 17th
16th, LP to E and W of England, slow moving warm front lies across southern England, moderate rain after 21h. 17th, front is now occluded and moves slowly southwards, light and moderate rain during early hours, drizzle later. Trough brings heavier rain from late afternoon to late evening.
18th - 24th
Long sunny periods during this fine, warm spell, sometimes hazy. 19th, HP 1031 hPa in Norwegian Sea, weak HP ridge over France. 21st, HP 1031 hPa ridge from Azores, HP 1029 hPa over Baltic states. 23rd, HP 1026 hPa Denmark, LP 980 hPa S of Iceland.
25th - 30th
Becoming less warm. 25th, HP 1029 hPA over E Europe, LP systems surround UK, shower am then fine and sunny. 27th, LP 989 hPa over Scotland, light to moderate rain during the middle of the day from warm and cold fronts. 28th; fog am, heavy showers pm. 29th; fog am clearing to sunny spells and the 30th rather more cloudy.

MONTHLY SUMMARY APRIL 2009
ACTUAL TEMPERATURE
 AVERAGE
 Daily Maximum
16.3
  ºC ( +2.5C )*
 Daily Minimum
6.5
  ºC ( +1.3C )*
 Daily Mean
10.88
  ºC ( +1.7C )*
 EXTREMES
 High Maximum
22.8
  ºC ( 15th )
 Low Minimum
1.4
  ºC ( 28th )
 Low Maximum
10.2
  ºC ( 17th )
 High Minimum
10.7
  ºC ( 13&16th )
 
   
 Days with max => 15 °C
21
    
 Days with max in range 10 - 15 °C
9
    
 Days with Air Frost
0
    
 
PRECIPITATION
 Monthly Total
38.3
  mm ( 71% )*
 Days with measurable precip
12
  Days ( -1 )*
   ...of which, days with >= 1.0 mm
8
  Days ( -2 )*
   ...and days with snowfall observed
0
  Days  
 Days with Snow Cover
0
  Days  
 Days with Thunder
1
  Days  
 RAIN RATE & EXTREMES
 High Rain Rate
25.9
  mm/hr ( 28th )
 High Rain Total in 1 day
14.5
  mm ( 17th )
 High Rain Total in 1 hour
3.6
  mm ( 17th, 02.30h)
 EVAPO-TRANSPIRATION
 Total for month
67.1
  mm  
 High Total for 1 day
3.6
  mm ( 24th )
APPARENT TEMPERATURE
 Low Wind Chill
1.3
  ºC ( 28th )
 DAVIS HEAT INDICES THW & THSW
 Low Temp/Hum/Wind Index
1.3
  ºC ( 28th )
 High Temp/Hum/Wind Index
21.9
  ºC ( 15th )
 High Temp/Hum/Sun/Wind Index
29.8
  ºC ( 15th )
 
DEWPOINT & HUMIDITY
 High Dewpoint
12.6
  ºC ( 15th )
 Low Dewpoint
-4.7
  ºC ( 26th )
 Average Dewpoint at 14h
5.9
  ºC  
 Low Relative Humidity
26
  % ( 26th )
 Average RH at 14h
56
  %  
WIND SPEED & DIRECTION
 Monthly Average
1.3
  mph  
 Windiest day (Average)
4.1
  mph ( 8th )
 Highest Gust
21
  mph ( 8th )
 Dominant Direction
SW
  ( 25% )
 
BAROMETER
 Monthly Mean
1012.3
  hPa  
 High Barometer
1026.6
  hPa ( 20th )
 Low Barometer
994.5
  hPa ( 27th )
SUNSHINE
 Max Sensor Exposure to direct sun
9
  hours/day (12-13 possible)
 Calculated Monthly Sunshine Hours
149.1
  hours  
 Estimated Actual Hours (approx)
170.0
  hours  
 Sunniest Day Measured
8.8
  hours ( 22nd )
 Days with no sunshine
2
  Days  
 
FOG
 Number of Days with Fog
4
  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 75% 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 APRIL 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
 4.6 15.6 14.9 54 5.7 7.8 1020.8 FS 0.0 1.2 18 WNW  Sunny
2nd
 7.1 15.9 14.4 58 6.2 5.2 1018.1 F 0.0 1.0 13 N  Cloudy am.
3rd
 5.3 12.6 9.9 77 6.0 3.0 1016.0 FS 0.0 1.3 8 SW  Mist
4th
 7.2 16.6 16.3 48 5.3 5.5 1017.8 ST 0.0 1.9 16 SSW  OVC am, sunny pm
5th
 3.1 17.6 17.1 37 2.2 6.8 1020.8 F 0.0 0.8 19 SE  Sunny
6th
 6.4 18.4 17.8 44 5.4 7.8 1006.6 F 0.0 1.4 17 SW  Sunny
7th
 8.3 14.6 13.7 47 2.5 6.5 1008.4 ST 0.0 3.6 18 SW  Sunny
8th
 7.8 16.3 15.9 40 2.3 8.7 1007.1 RS 3.6 4.1 21 SW  Rain am, sunny
9th
 6.6 14.7 13.8 71 8.7 1.7 1008.4 FS 0.3 1.7 14 SW  Drizzle, OVC
10th
 8.1 15.3 12.9 76 8.8 0.5 1001.7 ST 1.3 0.8 11 SW  Lt rain pm.
11th
 9.5 13.9 12.8 80 9.4 0.3 1007.9 RS 0.8 0.4 12 N  Showers
12th
 10.2 14.3 13.9 80 10.5 0.5 1012.9 ST 1.5 0.3 8 N  Rain eve
13th
 10.7 17.5 15.4 59 7.4 4.8 1009.1 F 0.0 0.7 11 SW  Sunny pm
14th
 8.1 17.2 16.5 66 10.1 0.2 1008.0 FS 1.5 0.4 7 SE  Thunder night
15th
 8.6 22.8 22.7 40 8.4 7.0 1002.7 FS 0.8 1.2 19 SE  Mist am
16th
 10.7 15.6 14.6 72 9.6 0.8 1005.4 ST 3.3 0.5 13 N  Rain eve
17th
 8.3 10.2 10.0 90 8.4 0.0 1009.5 RS 14.5 0.8 10 N  Rain
18th
 5.5 14.9 14.9 49 4.3 8.0 1016.6 RS 0.0 1.9 17 N  Sunny
19th
 4.6 16.9 16.7 55 7.6 6.2 1022.4 ST 0.0 1.3 12 N  Sunny pm
20th
 6.0 18.8 17.9 49 7.1 7.0 1025.9 ST 0.0 0.6 8 N  Sunny pm
21st
 3.8 20.6 20.2 36 4.7 8.2 1024.7 FS 0.0 0.7 11 N  Sunny
22nd
 7.4 19.9 19.5 33 2.8 8.8 1024.5 F 0.0 1.0 13 SW  Sunny
23rd
 6.1 18.8 18.4 35 2.6 7.7 1021.7 F 0.0 1.0 13 SE  Sunny
24th
 5.5 18.7 18.3 37 3.3 7.2 1013.1 F 0.0 1.7 19 SE  Sunny
25th
 7.9 15.1 14.8 42 2.0 7.0 1008.0 R 0.3 2.3 18 SW  Sunny pm
26th
 3.7 18.1 17.8 31 -0.4 7.5 1005.4 FS 0.0 1.3 16 SW  Sunny
27th
 6.2 10.4 8.6 86 6.4 0.0 995.0 FS 6.6 2.0 19 SW  Rain
28th
 1.4 11.6 10.1 77 6.2 2.3 1000.7 RS 3.8 0.3 7 N  Fog am. SHRA+
29th
 1.6 17.3 15.4 47 4.2 6.8 1009.7 RS 0.0 1.3 13 SW  Fog am, sunny pm
30th
 4.7 17.4 17.1 57 8.5 5.3 1015.2 RS 0.0 1.4 16 SW  Sunny spells
                         
‡ 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;