WEATHER REVIEW - December 2006

Headline: A strong cyclonic influence resulted in very mild temperatures and high rainfall over the first half of the month. A protracted period of anticyclonic gloom then followed across the Christmas period.

December opened with a deep area of low pressure centred over Iceland. For the first week at least low pressure to the north of the British Isles was the dominant influence with a succession of frontal systems crossing the UK accompanied by strong winds. The 1st and 2nd were particularly wet days across the county as was the 6th and on  the 3rd the strength of the wind was sufficient to register as a rare gale at Pitsford. Winds consistently reached peak gusts of 35mph or more between the 2nd and 7th with some days recording winds over 45mph. The wind, coming from the south-west, made for exceptionally mild temperatures for early December with a daytime maximum on the 4th reaching 13.5C with no danger of ground or air frost overnight.

Pressure began to increase on the 8th which led to a couple of fine days with lighter winds. Some good sunny spells on the 9th led to clear skies overnight and the first ground frost of December (-3.3C) at Pitsford. With the increase in pressure came a switch to a north-westerly airstream and a consequent reduction in daytime temperatures, although only back to where they should be for the time of year. The cooler airflow was sufficient to allow a slight air frost on the 10th.

A return to cyclonic conditions occurred on the 10th as a frontal system accompanied once again by strong winds drove eastward.  Additional fronts marched in from the west on the 11th making for a couple of particularly wet days. Over the next few days the UK became sandwiched between high pressure over the continent and low pressure south of Iceland. The result moderate south-westerly airflow allowed temperatures to recover once again becoming unseasonably mild. In fact, night-time minima on the 14th scarcely fell below 10.0C.  Despite the mild air, skies remained pretty cloudy with little or no sunshine recorded. In fact the 3 days from the 13th saw no sunshine at all.  The cloud was due largely to a frontal wave which remained across the county on the 15th delivery some 8.2mm of rain in just over 6 hours.

Over the next few days high pressure gradually built in across the UK from the south-west becoming firmly established on top of the British Isles on the 19th.  This was to produce a protracted period of anticyclonic gloom which continued right through the Christmas period finally giving way to frontal systems and a fair amount of rain on the 27th. Winds throughout this period remained very light and variable and the skies remained grey with no sunshine recorded for 7 days from the 20th. With the lack of insolation, daytime temperatures tumbled with maxima on the 22nd only reaching 0.6C at Pitsford. Air frosts, largely absent until now, became a frequent occurrence.

As December came to a close a  strong cyclonic influence was a established with a deep low developing in the vicinity of Iceland. Strong south-westerly winds brought a return to very mild conditions. On the 29th winds gusted to 55mph and continued strong through the New Year period. Coupled with the wind was the inevitable rain, 7.1mm on the 29th and a further 8.6mm on the 30th.

Despite the mild conditions, the prolonged spell of anticyclonic gloom was sufficient to return overall temperatures to just 0.7C above average and rainfall amounts also were close to the average for December despite the succession of active frontal systems.


Air Temperatures    
The Highest Maximum:  13.6C on 29th
The Lowest Maximum:  0.6C on 22nd
The Highest Minimum:  10.0C on 14th
The Lowest Minimum:  -2.3C on 22nd
The Mean Maximum:  8.7C  
The Mean Minimum:   3.6C  
The Overall Mean:   6.2C  
Difference from the Monthly Mean: +0.7C  
    
Relative Humidity:    
Highest Relative Humidity (at 0900): 100.0% on 20th
Lowest Relative Humidity (at 0900): 80.1% on 5th
Mean Relative Humidity (at 0900): 92.1%  
    
Dew Point:    
The Highest Dew Point (0900):  11.2C on 11th
The Lowest Dew Point (at 0900): -2.3C on 22nd
The Mean Dew Point (at 0900): 4.7C  
    
Rainfall:    
Total:    64.3mm  
Difference from the Monthly Mean: 102.2%  
Duration:    41.0hrs  
Highest 24 hour fall (0900 to 0900): 8.6mm on 30th
Rain Days (>/=0.2mm):  15   
Wet Days (>/=1.0mm):  13   
    
Sunshine:    
Total Duration of Bright Sunshine: 31.9hrs  
Sunniest day:   4.3hrs on 17th
No. of days without sunshine:  15   
Difference from the Monthly Mean: 82.4%  
Cloud cover (mean at 0900):  6.3oktas (78.8%)
    
Pressure (reduced to sea level at 0900):    
The Highest Pressure:  1044.4mb on 22nd
The Lowest Pressure:  983.7mb on 8th
Mean Pressure:   1018.4mb  
    
Winds    
Run of wind (mean over 24 hrs): 168.7 miles  
Mean daily wind speed:  9.1 mph  
Run of wind (cumulative):  5229.2 miles  
Highest Maximum Gust:  55 mph on 29th
No. of gusts of 50mph or more: 1   
Highest wind strength (at 0900): 27.7 mph on 5th
Mean wind strength (at 0900):  9.1 mph  
    
Winds from the Following Directions:    

N 0 NE 2 E 2 SE 1 S 9 SW 11 W 3 NW 2 Calm 1
   
    
Ground Temperatures:     
Lowest Grass Minimum:  -5.1C on 10th
Mean Grass Minimum:  0.4C  
Lowest Concrete Minimum:  -2.5C on 10th
Mean Concrete Minimum:  1.8C  
Lowest Bare Earth Minimum:  -2.4C on 10th
Mean Bare Earth Minimum:  2.4C  
    
Soil/Earth Temperatures:     
Surface mean:   5.7C  
5cm mean:   5.7C  
10cm mean:   6.0C  
20cm mean:   6.6C  
30cm mean:   6.8C  
40cm mean:   6.8C  
50cm mean:   7.4C  
100cm mean:   8.2C  
    
    
Days with:    
Thunder:    0   
Hail <5mm:   0   
Hail >/=5mm:   0   
Snow or snow & rain:  0   
Fog:    4   
Air Frost:    6
Duration of Air Frost:  38.0hrs   
Ground Frost:   12   
    
Total (Tank) Evaporation:  9.26mm

All data © Pitsford Hall weather station.
Click here to view the full climatological register for December  2006. 
Click here to view the full AWS weather record for December 2006.
Click here to view the statistical summary for 2006.

The weather station publishes a full Monthly Weather Report (ISSN 1741-4733) which is distributed to libraries across Northamptonshire. This report comprises a full UK weather diary, reports of extreme weather events across the county, statistics from Pitsford Hall's affiliated stations across the county as well as news from the weather station itself. Individuals may download this report for £2 or take out an annual subscription for the paper-based report for £25. Click here for further details.