September 2008

A Dartmoor landscape on a warm September day with hazy sunshine.
A Dartmoor landscape on a warm September day with hazy sunshine caused by anticyclonic conditions.

Summary for September 2008

Mean Max: 18.4C (-0.1C)
Mean Min: 10.1C (+0.2C)
Mean: 14.3C (+0.1C)
     
High Max: 21.3C 19th
Low Max: 14.4C 30th
High Min: 13.6C 9th
Low Min: 5.9C 28th
Mean Grass Min: 7.9C  
Grass Min: 3.3C 29th
     
Rain Total (gauge): 70.9 mm (200%)
Rain Total (tipping bucket): 86.5 mm (244%)
Rain Days >0.2 mm: 11 Days  
Rain Days >1.0 mm: 8 Days  
Max 24 hrs: 32.2 mm 5th
Days without any rain: 19  
     
Air Frost: 0 Days  
Ground Frost: 0 Days  
Snow Falling: 0 Days  
Snow (50%) @ 9am: 0 Days  
Thunder Heard: 0 Days  
Hail <5 mm: 0 Days  
Hail >5 mm: 0 Days  
Fog @ 9am: 1 Days  
     
Total Monthly Sunshine: 143h:42m  
Total Monthly Sunshine: 144.2 Hours  
Most Sunshine in a Day: 11h:34m 20th
Average Daily Sunshine: 04h:47m  
Sunless Days: 3 Days  
Cloudless Days: 3 Days  
Total Possible Sunshine: 377h:45m  
Percentage of Total Sun: 38%  
     
Mean Soil Temp @ 30 cm: 14.0C  
Min Soil Temp @ 30 cm: 12.9C 29th
Max Soil Temp @ 30 cm: 15.2C 7th
Mean Soil Temp @ 100 cm: 14.1C  
Min Soil Temp @ 100 cm: 13.4C 30th
Max Soil Temp @ 100 cm: 15.2C 1st
     
Mean 10 Min Wind >39 mph: 0.1 Days  
N: 4.38 Days  
NE: 3.19 Days  
E: 3.20 Days  
SE: 2.90 Days  
S: 4.29 Days  
SW: 3.69 Days  
W: 2.83 Days  
NW: 2.53 Days  
Calm: 6.98 Days  
Mean Wind: 4 mph  
Max Gust: 39 mph 5th
     
Mean Cloud Cover: 61%  
Mean RH @ 9am: 88%  
Rain Duration >0.1mm/hour: 40.8 Hours  
Frost Duration: 0.0 Hours  
Max Frost Duration in a Day: 0.0 Hours  
     
Mean Sea Temperature: 16.5C  
Normal for Month:    
Max Sea Temperature: 17.3C 13th
Min Sea Temperature: 15.9C 30th
     
Mean Pressure @ 9am: 1016.4 hPa (-1.6 hPa)
Mean Pressure: 1016.7 hPa (-1.3 hPa)
Max Pressure: 1034.7 hPa 26th
Min Pressure: 983.2 hPa 5th
     
Max Dewpoint: 14.9C 14th
Min Dewpoint: 2.6C 28th
Mean Dewpoint: 9.1C  
     
Max Humidity: 92% 5th
Min Humidity: 47% 20th
Mean Humidity: 76% (-5)

As with July it was a month of two halves. The first 2 weeks were dominated by very wet, dull and cool conditions but after the 12th it started to become more settled and slightly warmer with a dry and generally sunny weather regime becoming established.

This September had no really warm days carry on a trend from August. The temperature failed to exceed 20C until the 12th whilst during September 2007 10 of the first 12 days had temperatures greater than 20C with 25.9C being the warmest day. The maximum temperature for the whole of this September only reached 21.3C on the 19th and only 5 days exceeded 20C.

Rainfall, as with July & August was well above the average with a total of 86.5 mm, most of which fell during the first week. This brought the total for the 3 months of July, August & September to 326.7 mm.
As usual in a summer month there were no air or grass frosts. Thunder was recorded on two occasions but there were none of the usual spectacular thunderstorms associated with an average August.
After a very dull start the sun started to make a regular appearance, especially from the 18th onwards and the month ended with 144 hours of sunshine, which was an improvement on August's total of 120 hours but well down on last year's September total of 187 hours.
Soil temperatures were variable throughout the month due mainly to the high amount of rainfall.
Winds dominated from the south and north sectors representing the cyclonic first half of the month and the anticyclonic conditions thereafter until the last few days.
For such a wet month it was actually raining for only 41 hours.
Sea temperatures fell gradually throughout the month and on the whole were around average or slightly below average, especially at the end of the month.
Mean pressure was was -1.6 hPa below normal.
Dewpoints were generally quite low throughout.
With the month being dominated from the 12th onwards by relatively dry anticyclonic the humidity levels ended up rather below the average.

 

Weather Data for Otter Valley, Devon.  September 2008  
  Temp (oC) Hum (RH%) Dewpoint (oC) Wind (mph) Rain Pressure (hPa) Grass Sun  
  Min Max Ave Min Max Ave Min Max Ave Max Ave Run mm Min Max Ave Min Hours Observations
1 10.9 19.5 15.2 67 91 79 7.7 12.8 10.3 28 5.4 129 0.0 1008 1014 1011 9.8 3.2 Sunny ints, rain evening
2 11.6 18.8 15.2 62 91 77 8.8 13.3 11.1 31 5.3 127 9.6 1001 1008 1005 10.5 8.0 Sunny ints, showers pm
3 9.5 17.7 13.6 57 89 73 6.5 9.8 8.2 24 5.3 128 1.2 1000 1004 1002 9.1 6.1 Sunny ints, showers pm
4 12.6 17.4 15.0 70 87 79 8.7 11.6 10.2 20 5.3 126 3.4 998 1001 1000 11.1 1.2 Sun and showers all day
5 13.1 17.1 15.1 82 92 87 10.4 13.7 12.1 39 9.7 233 26.8 983 999 991 12.3 1.3 Rain am, showers pm
6 12.2 17.7 15.0 75 91 83 9.5 13.5 11.5 23 3.7 90 7.2 985 1000 992 10.6 3.8 Sun and showers all day
7 13.5 17.9 15.7 65 86 76 7.9 11.1 9.5 28 8.4 202 0.0 1000 1012 1006 12.9 4.6  
8 7.3 16.7 12.0 66 91 79 4.0 10.6 7.3 14 2.0 48 0.0 1012 1014 1013 6.7 1.1  
9 13.6 17.3 15.5 80 92 86 9.3 14.2 11.8 29 6.3 150 15.0 1006 1013 1009 11.3 0.0  
10 13.2 18.6 15.9 76 91 84 10.0 14.2 12.1 26 6.3 152 0.4 1006 1011 1009 11.1 2.0  
11 13.3 19.4 16.4 62 92 77 9.5 14.0 11.8 29 7.1 170 5.2 1003 1009 1006 11.2 0.0  
12 7.2 20.1 13.7 58 92 75 4.4 13.4 8.9 13 1.7 41 0.6 1009 1015 1012 6.6 0.0  
13 10.3 20.2 15.3 64 91 78 6.5 13.3 9.9 9 1.1 25 0.0 1016 1022 1019 9.1 8.9 Sunny intervals all day
14 7.1 20.1 13.6 66 92 79 3.9 14.9 9.4 12 1.6 38 0.0 1022 1024 1023 5.7 8.3 Sunny am, sunny ints pm
15 13.4 17.4 15.4 67 88 78 7.9 12.1 10.0 12 1.9 47 0.0 1023 1024 1024 10.8 1.6 Cloudy am, sunny ints pm
16 8.1 16.9 12.5 62 91 77 4.8 10.6 7.7 12 1.8 43 0.0 1022 1024 1023 5.7 2.5 Sunny intervals all day
17 10.6 16.8 13.7 69 83 76 6.4 10.9 8.7 11 1.7 40 0.0 1021 1023 1022 9.4 0.1 Sunny int am, cloudy pm
18 7.6 19.0 13.3 55 91 73 4.3 10.6 7.5 13 1.8 44 0.0 1022 1024 1023 4.4 9.4 Sunny am, sunny ints pm
19 7.1 21.3 14.2 49 90 70 3.1 12.3 7.7 11 0.8 19 0.0 1024 1030 1027 4.6 9.3 Sunny intervals all day
20 7.2 19.6 13.4 47 91 69 2.9 10.9 6.9 15 1.8 44 0.0 1028 1031 1029 4.5 11.6 Sunny all day
21 9.5 19.2 14.4 50 88 69 4.6 10.9 7.8 17 3.4 82 0.0 1024 1028 1026 5.2 11.4 Sunny all day
22 9.4 20.1 14.8 52 88 70 4.5 10.6 7.6 20 3.0 72 0.0 1024 1026 1025 4.1 5.2 Sunny am, sunny ints pm
23 12.6 17.4 15.0 63 83 73 7.5 10.0 8.8 20 6.5 155 0.0 1024 1026 1025 10.3 6.0 Sunny intervals all day
24 11.1 18.8 15.0 65 83 74 5.9 11.4 8.7 21 5.1 124 0.0 1024 1027 1025 7.2 2.8 Sunny intervals all day
25 12.6 19.4 16.0 54 85 70 8.2 11.1 9.7 13 3.2 76 0.0 1027 1033 1030 7.8 2.7 Sunny intervals all day
26 8.2 18.4 13.3 52 89 71 4.3 10.0 7.2 20 2.9 69 0.0 1033 1035 1034 3.8 11.2 Sunny all day
27 7.1 19.5 13.3 57 90 74 3.2 12.4 7.8 8 1.0 25 0.0 1028 1033 1031 4.4 6.7 Misty am, sunny pm
28 5.9 19.4 12.7 59 91 75 2.6 13.1 7.9 10 0.7 17 0.2 1024 1029 1027 4.6 7.6 Foggy early am then sunny
29 6.7 17.3 12.0 56 89 73 3.4 8.5 6.0 17 3.2 76 0.0 1019 1024 1022 3.3 7.5 Sunny am, sunny ints pm
30 11.7 14.4 13.1 78 89 84 7.5 10.7 9.1 26 6.0 144 3.4 1005 1019 1012 9.3 0.3 Cloudy am, sunny ints pm
10.1 18.4 14.3 63 89 76 6.3 11.9 9.1 19 3.8 2734 73.0 1014 1019 1017 7.9 144.25  
 
Graphs for September 2008
Figure 1. Temperature and Rainfall for September 2008.
Figure 2. Sunshine, air pressure and mean wind speed for September 2008.
Figure 3. Wind direction for September 2008.
Figure 4. Soil & sea surface temperature (SST) for Lyme Bay for September 2008.
Figure 5. Wind run, maximum gusts and mean pressure for September 2008.