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JANUARY 2009 daily and monthly summary

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JANUARY 2009
February 2009
1st - 10th
HP 1041 hpa east of Iceland, drifting south, HP 1029 hpa C and SE Europe. 4th: HP 1027 hpa ridging from Azores to SW of UK and across to C Europe, LP 1012 hpa near Denmark linked to LP 1004 hpa over Belarus, more HP to N and NE. 5th, light snow and snow showers early morning giving a covering of 0.5cm at 09.00, thawing quickly. 6th, HP 1030-1028 hpa, British Isles to Russia, weakening from the east. 9th, HP 1040 hpa Romania, LP 994 hpa Finland. Freezing fog lasting until 12.30 then sunny.
11th - 16th
LPs 963 hpa S of Iceland and 960hpa Norwegian Sea, HP 1037 hpa, Hungary. Milder conditions push in around 6 am of 11th after another hard frost, precipitation from frost melt. 12th, outbreaks of light rain from series of fronts from NW. 13th, heavy showers mid afternoon. Precipitation from lingering fog on 14th. Overcast and gloomy days 15th and 16th with some drizzle.
17th - 25th
Start of a very unsettled period for much of the UK; 17th, LP 945 hPa to NW of Scotland, light rain early hours followed by heavy showers around 8am then dry until warm front rain late evening. Squally showers around 5am of 18th as cold front passes. Light/Moderate rain 19th from 3.30 to 9.00am. LP 958 hPa near Outer Hebrides with many secondary LPs. 22nd. LP 942 hPa S of Iceland deepening to 937 hPa. 23rd, LP 964 hPa tracks across SE England with heavy rain overnight until midday. 25th, twin centre LP 966 hPa near Donegal and 968 hPa near Kerry/Cork coast brings light then moderate rain from warm and cold fronts from 3am continuously to late evening.
26th - 31st
HP building over S Scandinavia, LP to SW and NW. 28th dull and gloomy with light rain or drizzle from 8am to early afternoon.

MONTHLY SUMMARY JANUARY 2009
ACTUAL TEMPERATURE
 AVERAGE
 Daily Maximum
5.2
  ºC ( -2.1C )*
 Daily Minimum
0.4
  ºC ( -2.5C )*
 Daily Mean
2.69
  ºC ( -2.2C )*
 EXTREMES
 High Maximum
9.7
  ºC ( 22nd )
 Low Minimum
-7.7
  ºC ( 10th )
 Low Maximum
-1.7
  ºC ( 10th )
 High Minimum
8.0
  ºC ( 13th )
 
   
 Days with max => 10 °C
0
    
 Days with max < 0 °C ("Ice Day")
1
    
 Days with Air Frost
14
    
 
PRECIPITATION
 Monthly Total
78.0
  mm ( 101% )*
 Days with measurable precip
18
  Days  
   ...of which, days with >= 1.0 mm
12
  Days  
   ...and days with snowfall observed
1
  Days  
 Days with Snow Cover
0.3
  Days  
 Days with Thunder
0
  Days  
 RAIN RATE & EXTREMES
 High Rain Rate
15.2
  mm/hr ( 17th )
 High Rain Total in 1 day
14.5
  mm ( 25th )
 High Rain Total in 1 hour
4.6
  mm ( 23rd, 02.50h)
 EVAPO-TRANSPIRATION
 Total for month
12.3
  mm  
 High Total for 1 day
0.9
  mm ( 17th)
APPARENT TEMPERATURE
 Low Wind Chill
-7.7
  ºC ( 10th )
 DAVIS HEAT INDICES THW & THSW
 Low Temp/Hum/Wind Index
-9.0
  ºC ( 10th )
 High Temp/Hum/Wind Index
9.4
  ºC ( 13th )
 High Temp/Hum/Sun/Wind Index
14.2
  ºC ( 26th )
 
DEWPOINT & HUMIDITY
 High Dewpoint
8.3
  ºC ( 22nd )
 Low Dewpoint
-11.6
  ºC (   6th )
 Average Dewpoint at 14h
0.5
  ºC  
 Low Relative Humidity
38
  % (   6th )
 Average RH at 14h
76
  %  
WIND SPEED & DIRECTION
 Monthly Average
1.9
  mph  
 Windiest day (Average)
6.6
  mph ( 12th )
 Highest Gust
30
  mph ( 17th )
 Dominant Direction
SW
  ( 40% )
 
BAROMETER
 Monthly Mean
1011.3
  hPa  
 High Barometer
1030.2
  hPa (  2nd )
 Low Barometer
963.8
  hPa ( 23rd )
SUNSHINE
 Max Sensor Exposure to direct sun
3
  hours/day (8-9 possible)
 Calculated Monthly Sunshine Hours
27.2
  hours  
 Estimated Actual Hours (approx)
60.0
  hours  
 Sunniest Day Measured
2.7
  hours ( 29th )
 Days with no sunshine
7
  Days  
 
FOG
 Number of Days with Fog
3
  Days  
NEW RECORDS SET THIS MONTH
  • First January in site records without max temp reaching 10 °C
* deviation from 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 30% 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 JANUARY 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
 0.8 3.2 3.1 77 -0.5 0.0 1028.5 FS 0.0 0.1 5 N
 OVC day
2nd
 1.7 4.8 4.7 68 0.7 0.7 1028.2 ST 0.3 0.4 11 NNW
 SHRA, late pm
3rd
 -4.1 2.6 2.6 60 -4.4 1.5 1027.8 FS 0.0 0.0 6 SE
 Sunny
4th
 -5.2 0.2 0.1 73 -4.2 0.2 1020.9 F 0.0 0.4 6 SW
 Cloudy
5th
 -0.6 2.4 1.3 66 -4.3 0.1 1020.9 RS 1.0 1.5 17 NE
 SN, RASN am
6th
 -5.0 1.2 0.9 39 -11.5 1.7 1024.9 FS 0.0 0.1 10 NE
 Sunny
7th
 -7.0 2.4 2.3 81 -0.6 0.7 1024.4 ST 0.0 0.3 6 W
 Cloudy
8th
 0.1 3.7 3.7 84 1.3 0.5 1027.6 F 0.0 0.0 6 ESE
 Mist
9th
 -4.3 0.1 0.1 92 -1.1 1.7 1027.6 FS 0.0 0.1 5 ESE
 Freezing Fog am
10th
 -7.7 -1.7 -2.9 90 -4.4 0.1 1025.8 FS 0.0 0.1 8 N
 Mist
11th
 -5.2 8.2 8.1 55 -0.5 1.2 1022.2 F 0.3 4.0 20 SW
 Fine
12th
 6.6 9.0 7.5 90 6.0 0.0 1010.1 F 4.8 6.6 22 SW
 Rain
13th
 8.0 9.6 9.4 81 6.3 0.8 1007.7 FS 1.8 2.4 17 SW
 SHRA+ pm
14th
 -1.9 2.3 1.9 92 0.7 0.0 1014.0 ST 0.3 0.1 7 SE
 Fog
15th
 -0.1 4.6 4.6 81 1.6 0.0 1013.3 ST 0.0 1.0 11 SE
 OVC
16th
 3.3 7.6 6.8 91 5.4 0.0 1013.4 FS 1.0 2.3 19 SW
 Drizzle, OVC
17th
 6.2 9.3 9.1 62 2.2 1.0 1009.3 FS 7.9 5.9 30 SW
 Rain, SHRA+
18th
 3.7 6.6 6.4 65 0.3 1.3 996.1 R 5.1 4.5 28 SW
 SHRA+ am.
19th
 4.6 7.7 6.8 71 1.9 0.5 977.8 FS 10.7 4.6 26 SW
 Rain, am
20th
 2.0 5.0 4.6 82 1.7 0.5 991.0 RS 0.8 1.8 14 SW
 SHRA, am
21st
 -2.3 6.4 6.2 63 -0.3 1.7 1002.7 FS 1.8 1.4 22 SW
 Rain, eve
22nd
 4.8 9.7 8.6 78 4.9 0.5 984.7 R 11.4 4.0 27 SW
 Rain, am
23rd
 5.2 6.6 5.7 66 -0.1 1.2 997.7 RQ 13.2 2.7 29 N
 Rain+, am
24th
 -1.4 4.9 4.6 79 1.2 1.5 991.2 RS 0.0 0.8 11 SW
 Hazy sunshine
25th
 2.8 6.6 5.7 89 4.0 0.0 985.2 ST 14.5 2.9 29 SW
 Rain, all day
26th
 1.9 7.7 7.1 90 5.6 1.0 999.8 RS 0.5 0.1 6 S
 SHRA-, am
27th
 -0.6 7.3 7.0 91 2.3 1.5 1013.1 ST 0.0 0.7 10 SSW
 Fair
28th
 3.9 5.9 5.7 91 4.4 0.0 1013.8 ST 2.3 0.6 10 SE
 Rain, drizzle
29th
 1.8 5.9 5.7 64 -0.6 2.7 1015.8 F 0.0 1.0 13 SE
 Sunny
30th
 -1.4 6.1 6.1 67 0.4 2.3 1014.7 F 0.3 0.7 14 SE
 Frost melt
31st
 0.8 5.3 4.9 64 -1.3 2.3 1010.2 FS 0.0 1.0 16 SE
 Hazy sun
                         
‡ 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; CAVOK = no cloud below 5000 ft & visibility> 10 km & no fog, precipitation or snow; SN = snow; RASN = Rain and snow