MONTHLY WEATHER REPORT

from PITSFORD HALL WEATHER STATION

released at 10:07 AM on Thursday, 05 February 2009

REVIEW OF JANUARY 2009

Headline: Anticyclonic and very cold for much of the first half of the month, becoming increasingly unsettled with frequent frontal systems bringing rain working through during the second half.

The weather for the first week and a half of January was dominated by essentially anticyclonic conditions. High pressure initially placed with its centre to the north of Scotland gradually drifted southwards across the British Isles during the period.  With winds coming in from a mainly northerly direction, the exceptionally cold which marked December continued into January. A cold front worked in against the high from the north-east on the 4th introducing snow showers, a situation which repeated itself on the 7th, although the snow on this occasion was slight.  Daytime temperatures struggled with air maxima struggling to climb above 2.0C on several days with some hard frosts overnight. With snow lying on the ground, some severe frosts were recorded overnight leading into the 6th (-5.5C) and into the 7th (-5.2C). With the exception of some good sunshine on the 6th, it remained generally overcast with some mist and fog occasionally experienced during the morning.

The cold weather finally released its grip on the county on the 11th with winds swinging round to a milder south-westerly direction. Active frontal systems piled into northern and western Britain introducing some significant rainfall totals. However, rainfall amounts in the county were slight by comparison. The 12th saw some wet and windy weather with gusts at Pitsford reaching 44mph.

A ridge of high pressure developed across the British Isles on the 13th and 14th. As a consequence, freezing fog was recorded widely across the county on the 14th. Winds remained generally light ahead of quite a contrast in the weather that was to follow on the 15th.

From the 15th onwards the county experienced quite a disturbed spell of weather.  Frontal systems linked to some deep lows worked eastwards across the region in quick succession bringing frequent outbreaks of rain and some strong winds, the strongest gusts reaching 49mph at Pitsford on the 17th. Barometric pressure associated with this particular low dropped to 946mb at its centre north of Scotland at midnight on the 17th.  There were some reports of minor structural damage on a building site in Kingsthorpe, Northampton. Although temperatures remained around average during the period, snow still managed to fall on the 23rd, albeit without accumulation.  Apart from the 25th, most days did manage to record a small amount of sunshine.

As the month came to a close, high pressure took up residence over Scandinavia. This introduced a south or south-easterly airflow across the region and without the warming influence of the Atlantic temperatures began to fall with frosts being experienced overnight into the 27th and 28th. Initially, this high did not prevent outbreaks of rain spreading towards the county, most notably on the 27th. However, by the 30th the high had a strong influence over much of the eastern half of the UK and would remain in place introducing an influx of significantly colder weather and heavy snowfall during the first few days of February.

Thanks to the cold snap at the beginning of the month, this month was the coldest January in Northampton since 2001 and the second coldest since 1987. Rainfall amounts were below average in common with many eastern areas, but not significantly so.  Nationally, January recorded above average sunshine. However, across the county we came in with marginally below average totals.  

Climatological Statistics

Air Temperatures   
The Highest Maximum:    9.6 C on 22nd
The Lowest Maximum:    1.2 C on 4th
The Highest Minimum:    5.4 C on 17th
The Lowest Minimum:   -5.5 C on 6th
The Mean Maximum:    5.8 C 
The Mean Minimum:   0.1 C 
The Overall Mean:    3.0 C 
Difference from the Monthly Mean:  -0.8 C 
   
Black Bulb   
Maximum (at 0900):    8.3 C on 22nd
Mean (at 0900):    2.3 C 
   
Relative Humidity:   
Highest Relative Humidity (at 0900):  100.0 % on 10th, 14th, 19th, 27th
Lowest Relative Humidity (at 0900):  74.3 % on 17th
Mean Relative Humidity (at 0900):  94.0 % 
   
Dew Point:   
The Highest Dew Point (0900):   8.3 C on 22nd
The Lowest Dew Point (at 0900): -6.0 C on 6th
The Mean Dew Point (at 0900):   1.5 C 
   
Rainfall:   
Total:      35.9 mm 
Percentage of the Monthly Mean:  68.6 % 
Duration:     35.2 hrs 
Highest 24 hour fall (0900 to 0900):  5.7 mm on 27th
Rain Days (>/=0.2mm):    14  
Wet Days (>/=1.0mm):    11  
   
Sunshine:   
Total Duration of Bright Sunshine:  41.0 hrs 
Sunniest day:     6.2 hrs on 18th
No. of days without sunshine:   12  
Percentage of the Monthly Mean:  92.3 % 
Cloud cover (mean at 0900):   6.5 oktas (81.3 %)
   
Pressure (reduced to sea level):   
The Highest Pressure (at 0900):  1031.8 mb on 1st & 2nd
The Lowest Pressure (at 0900):   972.3 mb on 23rd
Mean Pressure (at 0900):   1010.4 mb 
   
Winds   
Run of wind (mean over 24 hrs):  154.2 miles 
Mean daily wind speed:    8.4 mph 
Run of wind (cumulative):   4781.3 miles 
Highest Maximum Gust:   49 mph on 17th
No. of gusts of 50mph or more:   0  
Highest wind strength (at 0900):  25.4 mph on 11th
Mean wind strength (at 0900):   8.0 mph 
   
Winds from the Following Directions:   

N 2 NE 2 E 1 SE 4 S 11 SW 5 W 2 NW 2 Calm 2
   
Concrete    
Lowest Concrete Minimum:   -8.0 C on 8th
Mean Concrete Minimum:   -2.2 C 
   
Evaporation   
Piche      32.3 ml 
Pan     Not available
   
Days with:   
Thunder:     0  
Hail <5mm:     0  
Hail >/=5mm:     0  
Snow or snow &amp; rain:    3  
Snow lying:     3  
Fog:      3  
Air Frost:     15  
Duration of Air Frost:   102 hrs
Gales:      0 

Notable Weather Events Across Northamptonshire

6 January

Temperatures at Pitsford Hall overnight on the 5th into the 6th fall to -5.5C making this the coldest January night since -7.0C was recorded on 4th January 2002. Some parts of the county record even lower temperatures including Thrapston with an air minimum of -7.1C. Dozens of people are admitted to A & E at Northampton General Hospital having fallen on the ice on untreated surfaces. 12 car accidents are reported on the county's roads.

17 January

Strong winds and spells of heavy rain affect much of the county as a deep low tracks past the north of Scotland. Although there are no reports of structural damage, winds gust to in excess of 50mph across many areas.

Station Notes