PITSFORD HALL WEATHER STATION NORTHAMPTON, UNITED KINGDOM MONTHLY WEATHER REPORT for FEBRUARY 2001 Low pressure dominated the scene during the first week of February. A succession of weather fronts resulted in a very wet period from the 1st until the 5th and as the low intensified on the 6th, winds gusted up to 39mph with observations of thunder. The month also started off pretty cold with overnight frosts on the 1st and 2nd, but temperatures then recovered as far as the 7th as south-westerly winds brought in milder air. A ridge of high pressure began building on the 8th and 9th which sent temperatures tumbling under clear overnight skies. The high was short-lived, however, and gave way to a further low on the 11th and 12th which brought some significant rainfall totals including 12.5mm on the 12th. Winds also picked up with gusts recorded in excess of 30mph. A more extensive area of high pressure built up over the next week leading to a dry period until the 23rd. Clear skies overnight resulted in a succession of frosts. Calm conditions and very light winds after the 17th allowed the development of mist and fog which became quite dense in the mornings of the 19th and 20th. From the 21st onwards, high pressure gave way to a developing low to the north-east which brought in a stream of colder air across the United Kingdom. Although cloudy at first, sunshine totals gradually recovered and by the 25th clear skies and the northerly airflow had allowed overnight air temperatures to fall to -4.2C with -9.2C being recorded on the ground (grass). The month ended with some falls of snow as milder air associated with a low to the west met the colder air over the United Kingdom. Falls were slight on the 24th, 25th and 28th with a thin covering remaining on the ground on the 25th (2cm) and 28th (<1cm). Climatological Statistics - February 2001 Air Temperatures The Highest Maximum: 12.7C on 11th The Lowest Maximum: 2.4C on 28th The Highest Minimum: 6.3C on 7th The Lowest Minimum: -4.2C on 25th The Mean Maximum: 7.9C The Mean Minimum: 0.9C The Overall Mean: 4.4C Difference from the Monthly Mean: -0.1C Relative Humidity: Highest Relative Humidity (at 0900): 100% on 3rd, 4th, 18th Lowest Relative Humidity (at 0900): 70.7% on 26th Mean Relative Humidity (at 0900): 92.6% Dew Point: The Highest Dew Point (at 0900): 10.4C on 11th The Lowest Dew Point (at 0900): -3.6C on 25th The Mean Dew Point (at 0900): 2.4C Rainfall: Total: 72.3mm Difference from the Monthly Mean: 191.8% Duration: 49.1hrs Highest 24-hour fall (from 0900): 12.5mm on 12th Rain Days (>/=0.2mm): 17 Wet Days (>/=1.0mm): 10 Lowest pH: 5.30 on 27th Sunshine: Total Duration of Bright Sunshine: 87.2hrs Sunniest day: 8.7hrs on 25th Sunless days: 8 Cloud cover (mean at 0900): 5.5 oktas (68.8%) Pressure (reduced to sea level): The Highest Pressure: 1043.3mb on 12th The Lowest Pressure: 984.5mb on 6th Mean Pressure (recorded at 0900): 1016.9mb Winds: Run of wind (mean over 24 hrs): 131.4 miles Mean daily wind speed: 7.1mph Highest 24-hour Wind Speed: 17.9mph on 12th Run of wind (to date): 3679.72 miles Highest Maximum Gust: 39mph on 6th Highest wind strength (at 0900): 26.5mph on 11th Mean wind strength (at 0900): 9.1mph Winds from the Following Directions: N 6, NE 0, E 1, SE 2, S 6, SW 0, W 0, NW 12, Calm 1 Ground Temperatures: Lowest Grass Minimum: -9.1C on 25th Mean Grass Minimum: -2.6C Lowest Concrete Minimum: -4.1C on 25th Mean Concrete Minimum: 0.3C Lowest Bare Earth Minimum: -3.1C on 25th Mean Bare Earth Minimum: 0.5C Soil/Earth Temperatures: 5cm mean: 2.6C 10cm mean: 2.9C 20cm mean: 3.4C 30cm mean: 4.2C 40cm mean: 4.5C 50cm mean: 4.9C 100cm mean: 5.1C Days with: Thunder: 0 Hail less than 0.5mm: 2: 6th & 23rd Hail greater than/equal to 0.5mm: 0 Snow or snow & rain: 3: 23rd, 24th & 28th Snow lying: 3 Fog: 7 Air Frost: 14 Duration of Air Frost: 41 hours Ground Frost: 20 Evaporation: Suspended until next summer. Observations made at 0900 UTC. Averages refer to the period 1971-2000.