PITSFORD HALL WEATHER STATION NORTHAMPTON, UNITED KINGDOM MONTHLY WEATHER REPORT - DECEMBER 2003 Headline: Changeable. Dry and cold spells alternating with mild and wet weather. December began on a very wet note with a depression to the south bringing a wet couple of days on the 1st and 2nd. High pressure then became established to the north and a generally dry spell ensued, although turning significantly colder from the 6th onwards as a cold front slipped southwards. Although the high moved off into the continent in the second week a ridge was maintained across the county helping to maintain the fine weather until the 10th. Clear skies overnight on the 7th/8th resulted in a hard frost with grass minima falling to –6.6C. After freezing fog on the morning of the 10th, the weather became influenced by depressions passing to the north. These brought bands of rain which were heavy and prolonged at times, particularly on the 12th when 8.7mm was recorded over nine and a half hours. With a predominantly south-westerly airflow it also turned appreciably milder with highs approaching 13C recorded on the 12th and 13th, a good few degrees above normal for mid-December. The mild conditions ended fairly abruptly on the 14th as winds veered north-westerly. Anticyclonic conditions had returned by mid month. It remained generally dry with overnight minima falling consistently below freezing between the 15th and 19th and with a grass minimum of –6.9C noted on the 16th. Morning visibilities remained generally good and sunshine totals especially on the 17th and 18th were very respectable for December (6.9hrs and 6.7hrs respectively), although fairly extensive fog was reported on the 20th. A depression developed across the UK on the 20th and tracked south-eastwards bringing spells of heavy rain over the next few days. As winds veered north-westerly on the 21st, temperatures remained pretty low with air and ground frost recorded on most days. Some showers fell as snow in areas further north or east, although none was recorded in the county. A second low tracked to the north over the Christmas period, maintaining mild and damp conditions with winds coming in from the south-west. Christmas Day saw a high of 10.1C and was generally dry despite some drizzly spells, whilst Boxing Day was very unsettled with 4.5mm of rain recorded over 2.6hrs. Winds were also pretty strong gusting to 36mph. In addition it was a pretty grey Christmas with no sunshine being recorded from the 23rd until the 27th. December came to a close with a cold snap. Daytime maxima reached only 2.5C on the 29th & 30th and, although air frosts weren’t particularly severe, grass minima fell to around –6C. The cause was a switch to colder northerly winds as the Christmas low tracked eastwards to Scandinavia. The passage of a frontal system across the cold air on the 30th saw the first recordable snowfall of the winter at Pitsford , although amounts were slight and were soon wiped out by heavy and prolonged rain on the 31st. Air Temperatures The Highest Maximum: 12.8C on 13th The Lowest Maximum: 2.5C on 29th & 30th The Highest Minimum: 8.5C on 26th The Lowest Minimum: -3.2C on 10th & 11th The Mean Maximum: 7.6C The Mean Minimum: 1.3C The Overall Mean: 4.5C Difference from the Monthly Mean: -1.0C Relative Humidity: Highest Relative Humidity (at 0900): 100.0% on 19th & 31st Lowest Relative Humidity (at 0900): 81.1% on 14th Mean Relative Humidity (at 0900): 93.1% Dew Point: The Highest Dew Point (at 0900): 11.8C on 13th The Lowest Dew Point (at 0900): -3.6C on 22nd The Mean Dew Point (at 0900): 3.1C Rainfall: Total: 60.5mm Difference from the Monthly Mean: 96.2% Duration: 54.5hrs Highest 24 hour fall (from 0900): 11.3mm on 31st Rain Days (>/=0.2mm): 14 Wet Days (>/=1.0mm): 12 Sunshine: Total Duration of Bright Sunshine: 59.7hrs Sunniest day: 6.9hrs on 17th Days without sunshine: 14 Cloud cover (mean at 0900): 5.1oktas (63.8%) Pressure (reduced to sea level): The Highest Pressure: 1031.8mb on 7th The Lowest Pressure: 994.4mb on 27th Mean Pressure (recorded at 0900): 1016.2mb Winds Run of wind (mean over 24 hrs): 136.7 miles Mean daily wind speed: 7.4 mph Run of wind (over month): 4238.8 miles Highest Maximum Gust: 38mph on 13th Highest wind strength (at 0900): 19.6mph on 26th Mean wind strength (at 0900): 9.0mph Winds from the Following Directions: N 1 NE 2 E 6 SE 3 S 7 SW 1 W 1 NW 9 Calm 1 Ground Temperatures: Lowest Grass Minimum: -6.9C on 16th Mean Grass Minimum: -2.2C Lowest Concrete Minimum: -3.5C on 22nd Mean Concrete Minimum: 0.4C Lowest Bare Earth Minimum: -3.5C on 31st Mean Bare Earth Minimum: 0.8C Soil/Earth Temperatures: Surface mean: 4.0C 5cm mean: 4.0C 10cm mean: 4.4C 20cm mean: 5.1C 30cm mean: 5.2C 40cm mean: 5.3C 50cm mean: 5.9C 100cm mean: 6.9C Days with: Thunder: 0 Hail less than 0.5mm: 0 Hail greater than/equal to 0.5mm: 0 Snow or snow & rain: 1 Fog 3 Ground frost: 22 Air frost: 14 Duration of air frost: 73.0hrs Evaporation (tank): Not recorded.