PITSFORD HALL WEATHER STATION NORTHAMPTON, UNITED KINGDOM MONTHLY WEATHER REPORT - DECEMBER 2001 Headline: Very dry and sunny with foggy mornings under prolonged anticyclonic conditions. The beginning and end of December saw vigorous lows bringing damaging winds. A cold end to the month with snow showers and severe frost. A succession of Atlantic lows brought mild but unsettled weather for the beginning of December. The 3rd and 4th were particular wet as low pressure moved eastwards across northern England. Strong winds on the 5th saw trees being uprooted in many areas. Winds gusted to 51mph at Pitsford Hall. The period from the 6th to the 18th saw a prolonged dry spell as anticyclonic conditions prevailed. Sea level pressure rose to 1041.4mb on the 10th and remained consistently between 1035 and 1041mb throughout. Some good sunshine was recorded by day, but clear skies overnight resulted in a succession of foggy mornings from the 8th to 11th and the occasional slight frost. Dense fog on the morning of the 10th reduced visibility to less than 100m across much of the county. An accident involving 30 vehicles caused a 7-mile tail-back on the A14 near Naseby. 9 people were injured, 3 seriously. The daytime maximum on the 10th rose to just 4.0C as the fog persisted. High pressure finally gave way to a series of lows tracking southwards from Norway from the 19th. The southward moving cold air brought frequent air frosts and some severe ground frosts across the county, especially on the 22nd, 23rd (air minimum -4.1C, grass minimum -7.0C) and 24th. Many eastern counties experienced some snow showers, although these were largely absent in Northamptonshire until the final week. Christmas Day in the county began with some wintery showers, but was mainly dry and overcast; the cloud breaking up overnight resulting in a penetrating frost on Boxing Day morning. The final few days of December from the 27th saw a deep low track south-eastwards from Iceland to Denmark. Strong winds, gusting to severe gale force on the 28th, caused some structural damage across the county. In Northampton, the tennis dome on the Racecourse collapsed and parts of the roof of the newly constructed Sol Central leisure complex were lost. Snowfall finally arrived in the county on the 29th with further flurries on the 30th. However, accumulations were modest amounting to just 1cm. With the arrival of the snow the last few days were bitterly cold. Temperatures climbed no higher than 1.8C on the 29th whilst on the 31st overnight air minima had fallen to -4.7C with -8.0C recorded as a grass minimum. Nationally, this was the sunniest December on record. In Northampton this December was the driest since 1963 (11.4mm) and the coldest since 1995 (1.9C). Climatological & Agromet Statistics - December 2001 Air Temperatures The Highest Maximum: 10.7C on 1st The Lowest Maximum: 1.8C on 29th The Highest Minimum: 8.6C on 1st The Lowest Minimum: -4.7C on 31st The Mean Maximum: 5.9C The Mean Minimum: 0.3C The Overall Mean: 3.1C Difference from the Monthly Mean: -2.2C Relative Humidity: Highest Relative Humidity (at 0900): 100.0% on 5th, 19th & 18th Lowest Relative Humidity (at 0900): 65.3% on 28th Mean Relative Humidity (at 0900): 92.5% Dew Point: The Highest Dew Point (at 0900): 9.0C on 5th The Lowest Dew Point (at 0900): -6.7C on 31st The Mean Dew Point (at 0900): 1.6C Rainfall: Total: 16.5mm Difference from the Monthly Mean: 26.2% Duration: 14.1 hrs Highest 24-hour fall (from 0900): 4.9mm on 4th Rain Days (>/=0.2mm): 11 Wet Days (>/=1.0mm): 4 Lowest pH: 6.05 on 24th Sunshine: Total Duration of Bright Sunshine: 85.6 hrs Sunniest day: 6.6 hrs on 14th Sunless days: 8 Cloud cover (mean at 0900): 5.2 oktas (65.0%) Pressure (reduced to sea level): The Highest Pressure: 1041.4mb on 10th The Lowest Pressure: 996.9mb on 28th Mean Pressure (recorded at 0900): 1024.7mb Winds: Run of wind (mean over 24 hrs): 109.6 miles Mean daily wind speed: 5.9mph Highest 24-hour Wind Speed: 10.9mph on 3rd & 27th Run of wind (to date): 3399.1 miles Highest Maximum Gust: 54mph on 27th Highest wind strength (at 0900): 28.8mph on 28th Mean wind strength (at 0900): 8.0mph Winds from the Following Directions: N 7 NE 4, E 1, SE 0, S 4, SW 1, W 5, NW 7, Calm 2 Days with: Thunder: 0 Hail less than 0.5mm: 0 Hail greater than/equal to 0.5mm: 0 Snow or snow & rain: 2: 29th & 30th Snow lying: 2: 30th & 31st Fog: 2 Air Frost: 14 Duration of Air Frost: 169 hrs Ground Frost: 22 Evaporation: Total evaporation (tank): 9.49mm Ground Temperatures: Lowest Grass Minimum: -8.0C on 31st Mean Grass Minimum: -1.9C Lowest Concrete Minimum: -8.4C on 31st Mean Concrete Minimum: -1.6C Lowest Bare Earth Minimum: -3.4C on 31st Mean Bare Earth Minimum: -0.2 Soil/Earth Temperatures: Surface mean: 2.7C 5cm mean: 2.9C 10cm mean: 3.6C 20cm mean: 4.5C 30cm mean: 4.9C 40cm mean: 5.0C 50cm mean: 5.6C 100cm mean: 6.8C Climatological observations made at 0900 UTC. Averages refer to the period 1971-2000.