PITSFORD HALL WEATHER STATION NORTHAMPTON, UNITED KINGDOM MONTHLY WEATHER REPORT - MAY 2004 Headline: Generally rather warm and dry although unsettled at the beginning and end. The month opened with low pressure dominating the weather across the county. Showers, some heavy, broke out frequently. The 3rd was a particularly wet day with 8.1mm of rain recorded over 6.8hrs. Despite the showers and rain some days recorded appreciable sunshine, 6.5hrs on the 3rd and 7.7hrs on the 4th. For many places thunder accompanied the showers although no recording was made at Pitsford. The start of the second week saw the centre of the low track eastwards giving rise to a predominantly northerly airflow. Showers continued to mark the weather with the first completely dry day in May not being reached until the 10th. From the 11th the Azores high extended across much of the UK. A fine settled spell of weather ensued with temperatures climbing. By the 17th daytime maxima had topped 24C. Daily sunshine totals progressively increased exceeding 12hrs on 16th, 18th and 19th. The high finally receded westwards by the 20th allowing a cold front to slip southwards producing a marked downturn in the temperatures. In fact, temperatures had fallen so much by the 22nd to produce the only ground frost recorded in May at Pitsford. Spells of rain also accompanied the front. High pressure had gained control again by the 23rd resulting in a return to fine settled weather. There were some good sunny days, although showery outbreaks on the 26th produced over 7mm of rain and a fairly dull and cool day. However, the warming trend resumed the following day. The month ended as it had begun with low pressure dominating the scene pushing a system of fronts across the county bringing showers on the 29th. The Bank Holiday was essentially dry, warm and sunny with the rain earlier forecast not reaching the county until overnight and through the 31st. In fact nearly 12mm were recorded over a little over 9hrs at Pitsford. Air Temperatures The Highest Maximum: 24.1C on 17th The Lowest Maximum: 12.6C on 1st The Highest Minimum: 11.6C on 29th The Lowest Minimum: 2.1C on 22nd The Mean Maximum: 17.5C The Mean Minimum: 7.5C The Overall Mean: 12.5C Difference from the Monthly Mean: 0.0C Relative Humidity: Highest Relative Humidity (at 0900): 97.5% on 11th Lowest Relative Humidity (at 0900): 47.2% on 24th Mean Relative Humidity (at 0900): 77.1% Dew Point: The Highest Dew Point (at 0900): 13.7C on 17th The Lowest Dew Point (at 0900): 4.1C on 5th The Mean Dew Point (at 0900): 9.8C Rainfall: Total: 43.6mm Difference from the Monthly Mean: 87.6% Duration: 37.2hrs Highest 24 hour fall (from 0900): 11.9mm on 31st Rain Days (>/=0.2mm): 12 Wet Days (>/=1.0mm): 10 Sunshine: Total Duration of Bright Sunshine: 194.0hrs Sunniest day: 12.8hrs on 16th & 18th Days without sunshine: 3 Cloud cover (mean at 0900): 5.1oktas (63.8%) Pressure (reduced to sea level): The Highest Pressure: 1029.7mb on 16th The Lowest Pressure: 976.6mb on 5th Mean Pressure (recorded at 0900): 1015.2mb Winds Run of wind (mean over 24 hrs): 84.3miles Mean daily wind speed: 4.6mph Highest mean daily wind speed: 10.5mph on 7th Run of wind (to date): 2612.9miles Highest Maximum Gust: 30mph on 7th Highest wind strength (at 0900): 18.4mph on 8th Mean wind strength (at 0900): 5.0mph Winds from the Following Directions: N 11 NE 1 E 2 SE 2 S 3 SW 1 W 1 NW 10 Calm 0 Ground Temperatures: Lowest Grass Minimum: -0.4C on 22nd Mean Grass Minimum: 5.2C Lowest Concrete Minimum: 2.7C on 22nd Mean Concrete Minimum: 7.4C Lowest Bare Earth Minimum: 3.6C on 23rd Mean Bare Earth Minimum: 7.9C Soil/Earth Temperatures: Surface mean: 14.2C 5cm mean: 13.0C 10cm mean: 13.2C 20cm mean: 13.5C 30cm mean: 13.6C 40cm mean: 13.4C 50cm mean: 13.5C 100cm mean: 11.7C Days with: Thunder: 0 Hail less than 0.5mm: 0 Hail greater than/equal to 0.5mm: 0 Snow or snow & rain: 0 Snow lying: 0 Air Frost: 0 Ground Frost: 1 Fog 1 Total Evaporation (tank) 79.14 mm