PITSFORD HALL WEATHER STATION NORTHAMPTON, UNITED KINGDOM MONTHLY WEATHER REPORT - APRIL 2004 Headline: Changeable – periods of heavy rain alternating with dry spells. Warm during the penultimate week. April opened with a depression dominating the weather over the first week. Frontal systems tracked eastwards across the county bringing showers and longer spells of rain. Conditions were thundery on the 2nd and falls of hail were noted on the 5th and 6th. The month also began on a fairly warm note, but temperatures then fell as winds veered from south-west to north-west. Despite the rain there were a few days that saw some good sunshine, notably the 4th and 7th with over 7 hours. A ridge of high pressure extended across the region from the mid-Atlantic in the second week. This brought a spell of settled weather, chilly at first with some air and ground frosts but then warming up. Winds were generally light and, although some good sunshine was recorded on the 9th (9 hours) and 14th (7.1 hours) the county kept a good deal of cloud in common with more northern areas. A second spell of unsettled weather linked to a series of depressions tracking close to or across the region followed in the third week. Although warm at first, in fact temperatures reached 19C on the 16th, a succession of fronts and fairly heavy rain brought temperatures tumbling on the 17th and 18th. Rainfall on the 18th amounted to 16.5mm over 5.5hrs and, in parts of the Midlands, gave rise to localized flooding. As pressure built up from the 22nd, a very warm spell of weather developed. Temperatures exceeded 20C on the 24th and 25th and with pretty lengthy sunshine (nearly 12 hours on 23rd) the county enjoyed an early taste of summer. The month ended with low pressure to the south. There were some heavy and persistent spells of rain, the 28th recording 14.7mm over 20 hours, although the county escaped some of the problematic downpours and lightning strikes which affected many other areas. Air Temperatures The Highest Maximum: 21.0C on 24th The Lowest Maximum: 9.4C on 10th The Highest Minimum: 9.7C on 17th The Lowest Minimum: -0.8C on 9th The Mean Maximum: 14.5C The Mean Minimum: 5.3C The Overall Mean: 9.9C Difference from the Monthly Mean: 0.8C Relative Humidity: Highest Relative Humidity (at 0900): 98.7% on 29th Lowest Relative Humidity (at 0900): 57.9% on 23rd Mean Relative Humidity (at 0900): 80.2% Dew Point: The Highest Dew Point (at 0900): 11.8C on 24th The Lowest Dew Point (at 0900): 2.7C on 7th The Mean Dew Point (at 0900): 7.0C Rainfall: Total: 68.7mm Difference from the Monthly Mean: 130.9% Duration: 59.9hrs Highest 24 hour fall (from 0900): 16.5mm on 18th Rain Days (>/=0.2mm): 16 Wet Days (>/=1.0mm): 12 Sunshine: Total Duration of Bright Sunshine: 142.2hrs Sunniest day: 11.9hrs on 23rd Sunless days: 4 Cloud cover (mean at 0900): 5.8oktas (72.5%) Pressure (reduced to sea level): The Highest Pressure: 1026.0mb on 24th The Lowest Pressure: 976.8mb on 18th Mean Pressure (recorded at 0900): 1011.2mb Winds Run of wind (mean over 24 hrs): 128.6miles Mean daily wind speed: 7.0mph Highest mean daily wind speed: 15.3mph on 3rd Run of wind (to date): 3856.7miles Highest Maximum Gust: 38mph on 3rd Highest wind strength (at 0900): 17.3mph on 7th Mean wind strength (at 0900): 7.4mph Winds from the Following Directions: N 5 NE 1 E 0 SE 2 S 10 SW 2 W 2 NW 6 Calm 2 Ground Temperatures: Lowest Grass Minimum: -4.0C on 9th Mean Grass Minimum: 2.2C Lowest Concrete Minimum: -1.0C on 9th Mean Concrete Minimum: 4.3C Lowest Bare Earth Minimum: 0.5C on 9th Mean Bare Earth Minimum: 5.1C Soil/Earth Temperatures: Surface mean: 10.0C 5cm mean: 9.1C 10cm mean: 9.4C 20cm mean: 9.9C 30cm mean: 10.0C 40cm mean: 9.9C 50cm mean: 10.0C 100cm mean: 8.6C Days with: Thunder: 1 Hail less than 0.5mm: 2 Hail greater than/equal to 0.5mm: 0 Snow or snow & rain: 0 Fog: 1 Air Frost: 1 Duration of Air Frost: 1hr Ground Frost: 7 Total Evaporation (tank) 46.65mm