PITSFORD HALL WEATHER STATION NORTHAMPTON, UNITED KINGDOM MONTHLY WEATHER REPORT - SEPTEMBER 2005 Headline: Beginning generally warm, but turning distinctly autumnal towards the end. Rainfall totals were locally high due to some thundery downpours and active frontal systems. The month opened as a weak cold front slipped away eastwards on the 1st. A ridge of high pressure developed across the region in its wake which brought a spell of warm and fine weather with daytime maxima climbing to 28.6C on the 4th. Most days saw some good spells of sunshine with 11.2 hrs of bright sunshine recorded on the 3rd. The fine weather soon broke down on the 4th as a trough followed on by a cold front worked through the county bringing some thundery showers totaling 4.3mm over just over 2hrs. Although it remained reasonably warm over the few days that followed, the county didn’t receive the warmth that other localities experienced particularly on the 6th and 7th when maxima recorded locally were a good few degrees below the highs reported elsewhere, notably in Kent where daytime temperatures reached 26.7C on the 7th compared with just 23.1C at Pitsford. A weather front worked south-eastwards on the 8th bringing a good deal of cloud. Areas further south held on to some very warm temperatures, whereas in Northants temperatures struggled in the low 20s. Nevertheless, there was sufficient warmth here to trigger some thundery showers with 7.5mm delivered in the space of 2.4hrs on the 9th. Further showers broke out on the 10th, although there were no reports of excessive downpours in the county comparable with other places, e.g. Surrey and parts of Berkshire. Trace amounts of rain were recorded on the 11th due mainly to a weak weather front, but otherwise a dry interlude followed as pressure built across the region. The 12th, 13th and 14th saw some good sunshine and temperatures recovered with a high of 24.5C recorded on the 13th. Later on the 14th a weather front worked south-eastwards through the county followed on by a further frontal system that delivered a significant amount of rain. In the 24 hours from 0900hrs GMT on the 15th 27.5mm of rain was recorded. This event reached a peak intensity of 159mm/hr at 1510 GMT with 6.9mm of rain delivered in the space of 10 minutes. The rain cleared on the 16th to leave a cool north-westerly airflow in its wake. Temperatures dropped markedly from highs exceeding 20C on the 15th to the mid teens thereafter. Despite the cool temperatures it remained dry as high pressure began to develop across the region. Clear skies overnight associated with this high was responsible for the first ground frost of the autumn season on the morning of the 17th (grass minima at Pitsford -0.3C). Thereafter daytime maxima were rather modest and, although weather fronts did work across the county they did so as weak features delivering negligible amounts of rain. Another weak weather front worked across the county on the 23rd producing just trace amounts of rainfall. However, the cooler air which followed it resulted in another more significant ground frost with grass minima falling to -1.3C on the morning of the 24th. Air minima also fell markedly to 3.2C. The month ended on a fairly typical autumnal theme. For much of the month wind speeds had been generally rather light, but 24 hour mean wind speeds topped 10 mph on the 26th, with gusts reaching 27mph on a good few days. Temperatures were rather modest, occasionally in the high teens and there were some beefy showers, notably 14.0mm in just under 4 hours on the 28th. Air Temperatures The Highest Maximum: 28.6C on 4th The Lowest Maximum: 14.7C on 16th The Highest Minimum: 17.0C on 10th The Lowest Minimum: 3.2C on 24th The Mean Maximum: 20.3C The Mean Minimum: 10.7C The Overall Mean: 15.5C Difference from the Monthly Mean: +1.5C Relative Humidity: Highest Relative Humidity (at obs): 97.8% on 11th Lowest Relative Humidity (at obs): 71.3% on 6th Mean Relative Humidity (at obs): 86.0% Dew Point: The Highest Dew Point (at obs): 17.9C on 14th The Lowest Dew Point (at obs): 4.2C on 17th The Mean Dew Point (at obs): 13.1C Rainfall: Total: 76.6mm Difference from the Monthly Mean: 135.1% Duration: 32.8hrs Highest 24 hour fall (obs to obs): 27.5mm on 15th Rain Days (>/=0.2mm): 13 Wet Days (>/=1.0mm): 10 Sunshine: Total Duration of Bright Sunshine: 148.9hrs Sunniest day: 11.2hrs on 2nd Days without sunshine: 2 Cloud cover (mean at obs): 5.1oktas (63.8%) Pressure (reduced to sea level): The Highest Pressure: 1029.5mb on 3rd The Lowest Pressure: 1007.8mb on 25th Mean Pressure (recorded at obs): 1018.1mb Winds Run of wind (mean over 24 hrs): 81.6miles Mean daily wind speed: 4.4mph Highest mean daily wind speed: 10.1mph on 26th Run of wind (to date): 2446.7miles Highest Maximum Gust: 32mph on 15th Highest wind strength (at obs): 13.8mph on 16th Mean wind strength (at obs): 4.7mph Winds from the Following Directions: N 3 NE 1 E 3 SE 1 S 6 SW 7 W 4 NW 2 Calm 3 Ground Temperatures: Lowest Grass Minimum: -1.3C on 24th Mean Grass Minimum: 7.1C Lowest Concrete Minimum: 4.0C on 17th Mean Concrete Minimum: 10.8C Lowest Bare Earth Minimum: 3.7C on 24th Mean Bare Earth Minimum: 10.6C Soil/Earth Temperatures: Surface mean: 14.8C 5cm mean: 14.7C 10cm mean: 15.2C 20cm mean: 15.4C 30cm mean: 16.3C 40cm mean: 16.1C 50cm mean: 16.5C 100cm mean: 16.0C Days with: Thunder: 2 Hail less than 0.5mm: 0 Hail greater than/equal to 0.5mm: 0 Snow or snow & rain: 0 Fog 2 Air Frost: 0 Ground Frost: