Monthly Weather Review - Pitsford Hall

Headline: A cold month – the coldest since 1995 in Northampton. Snowfall in the week before Christmas lying on the ground until Boxing Day.

The ridge of high pressure that produced the only dry day last month on the 30th November quickly disappeared as December opened. Low pressure centred to west would drive frontal systems across the British Isles introducing spells of rain. In fact, the first 10 days would be dominated by cyclonic conditions as a train of depressions worked their way eastwards, each one introducing spells of rain. These lows maintained a predominantly south-westerly airstream and relatively mild conditions across Northamptonshire. Daytime maxima climbed from 7.0C on the 1st to 12.0C on the 5th and then remained at or slightly above 10C until the 10th. There were a couple of overnight frosts initially, but nighttime temperatures remained above freezing throughout this period, only dropping to 0.7C on the 4th as a ridge of high pressure introduced clearer skies.

The situation changed on the 10th as high pressure, which had been resident over central Europe for much of the month, started to drive north-westwards towards the British Isles. High pressure became fairly stationary over the UK over the next few days before moving steadily towards Iceland on the 14th. The movement of this high saw a significant change in wind direction to a much colder north or north-easterly flow. Daytime maxima fell consistently day after day managing just 2.1C at Pitsford on the 15th and air frosts were resumed on the morning of the 16th (-1.9C). A fine sunny day was enjoyed across Northamptonshire on the 10th (6.5hrs) courtesy of the high, but as this moved towards Iceland and allowed weak frontal systems in from the east most days became rather cloudy. These systems also brought with them occasional showers of light rain or drizzle.

The next significant change occurred on the 16th. Although high pressure remained centred over Iceland, pressure now started to fall over the North Sea. Over the next few days, this encouraged a succession of frontal systems to work down from the north. However, on the 18th this low had retreated to southern England where it fuelled significant snowfall across the Midlands and Northamptonshire in particular. 6.0cm of snow was recording as lying at Pitsford at 0900 GMT. Snow showers continued throughout the rest of the day and temperatures struggled to climb much above freezing. As a new low developed north-east of Shetland and sank southwards through the North Sea over the next few days, the Arctic weather continued across Northamptonshire. Overnight lows sank to -6.5C on the 19th and the next few nights saw some severe frosts and daytime temperatures struggling to climb above freezing. Snow lay extensively on the ground until Christmas Day, but becoming increasingly icy and compacted.. Christmas Day itself saw outbreaks of rain overnight clearing to a grey and misty morning, although some spells of sunshine came through later. It was also relatively milder with highs reaching 5.5C. The milder, or more correctly, less colder weather continued for the next few days.

By the 28th, low pressure over Scandinavia began to inject another cold blast across the UK. However, with low pressure approaching from the south-west there was potential for heavy snowfall on attendant weather fronts as they worked their way across the county. As it happened, much of the snow fell as fairly heavy rain on the 29th, although a small amount of snow fell across Northamptonshire on the morning of the 30th. The year came to an end with the cold weather persisting, in fact New Year’s Eve was bitterly cold, the county caught in a cold Arctic airflow with lows overnight falling to -2.5C.

Overall this was the coldest December in Northampton since 1995 (1.9C average) and the second coldest since 1981 (1.0C average). However, last December recorded more days with air frost (14) than December 2009. With the combined impact of the snow in February, 2009 saw more snow than any other year for the past 10 years. .

Air Temperatures    
The Highest Maximum: 12.0 C on 5th
The Lowest Maximum: 0.0 C on 18th
The Highest Minimum: 6.1 C on 6th
The Lowest Minimum: -6.5 C on 19th
The Mean Maximum: 5.5 C  
The Mean Minimum: 0.4 C  
The Overall Mean: 3.0 C  
Difference from the Monthly Mean: -2.1 C  
    
Solar Radiation    
Maximum (at 0900): 118.0 W/m^2 on 19th
Mean (at 0900): 31.3 W/m^2  
    
Relative Humidity:    
Highest Relative Humidity (at 0900): 100.0 % on 11th, 18th, 22nd-25th, 28th-30th.
Lowest Relative Humidity (at 0900): 78.1 % on 16th
Mean Relative Humidity (at 0900): 95.0 %  
    
Dew Point:    
The Highest Dew Point (0900): 7.2 C on 6th
The Lowest Dew Point (at 0900): -6.4 C on 20th
The Mean Dew Point (at 0900): 1.6 C  
    
Rainfall:    
Total: 56.8 mm  
Percentage of the Monthly Mean: 105.7 %  
Duration: 77.2 hrs  
Highest 24 hour fall (0900 to 0900): 12.2 mm on 29th
Rain Days (>/=0.2mm): 21   
Wet Days (>/=1.0mm): 15   
    
Sunshine:    
Total Duration of Bright Sunshine: 44.3 hrs  
Sunniest day: 6.5 hrs on 10th
No. of days without sunshine: 10   
Percentage of the Monthly Mean: 69.8 %  
Cloud cover (mean at 0900): 4.7 oktas 58.8 %
    
Pressure (reduced to sea level):    
The Highest Pressure (at 0900): 1034.7 mb on 11th
The Lowest Pressure (at 0900): 985.6 mb on 22nd
Mean Pressure (at 0900): 1006.8 mb  
    
Winds    
Run of wind (mean over 24 hrs): 139.8 miles  
Mean daily wind speed: 7.6 mph  
Run of wind (cumulative): 4335.2 miles  
Highest Maximum Gust: 44 mph on 17th
No. of gusts of 50mph or more: 0   
Highest wind strength (at 0900): 21.9 mph on 27th
Mean wind strength (at 0900): 7.4 mph  
    
Winds from the Following Directions:    

N 3 NE 2 E 1 SE 3 S 6 SW 5 W 3 NW 5 Calm 2
    
Concrete     
Lowest Concrete Minimum: -7.3 C on 19th
Mean Concrete Minimum: -0.5 C  
    
Evaporation    
Piche 26.7 ml  
Pan Not available
    
Days with:    
Thunder: 0   
Hail <5mm: 0   
Hail >/=5mm: 0   
Snow or snow & rain: 5   
Snow lying: 10   
Fog: 3   
Air Frost: 11
Duration of Air Frost: 129hrs   
Gales: 0   

All data © Pitsford Hall weather station.

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.