Monthly Weather Review - Pitsford Hall

Headline: Cool for the first fortnight with a prevalence of northerly winds, then very warm. Rainfall well below normal.

May began with an area of low pressure moving south-eastwards across the UK from Northern Ireland. This brought a very unsettled day across the county on the 1st with 14.1mm of rain falling in just under 11 hours at Pitsford. However, as the low moved southwards, the UK came increasingly under the influence of high pressure south of Iceland. This high would maintain the cold northerly airstream already set up in April and with the clearer skies typical of anticyclonic conditions, overnight temperatures fell sharply, down to 1.5C at Pitsford on the 4th. The first few days were quite windy too adding to the cold feel. In fact, peak gusts reached or exceeded 30mph between the 1st and 3rd, recording 43mph on the 3rd.

By the 6th the Icelandic high had started to retreat westwards and this encouraged a run of frontal systems to move down from the north. The county remained dry on the 6th, although rain did fall on the 7th and 8th as a more easterly flow was set up drawing in weakened frontal systems from the continent.

High pressure over Scandinavia on the 7th, was gradually replaced by low pressure over the next few days. With high pressure still positioned south of Iceland, the impact of this low was to restore the cold northerly airflow across the UK. Daytime temperatures struggled in the low teens and a run of weak frontal systems introduced outbreaks of rain across the county on the 11th and 12th. Again, some particularly cold nights were recorded, the 13th especially with lows falling to 0.5C.

As the high pressure south of Iceland moved further south on the 13th, being replaced by a fairly intense low, it still ensured fine weather across England and Wales as a result of a ridge extending up from the south-west. However, this would break down the following day as a weak frontal system worked in from the west. This front was a fairly insignificant feature across Northamptonshire on the 15th, although on the 16th was followed by a more active system that brought some drizzle during the early morning.

High pressure quickly regained control from the south-west on the 17th and over the next few days would prevent a succession of Atlantic fronts from delivering their cargo of rain across the county. In fact, by the 21st this high had become resident across the British Isles steering any weather to the north. With some strong sunshine recorded during the daytime, temperatures finally started to rise exceeding 20C for the first time on the 19th and climbing still further towards a high of 26.7C on the 23rd. Between the 21st and 24th daily sunshine amounts exceeded 11 hours, with the most (12.5 hours) recorded on the 22nd.

By the 24th, high pressure had retreated from the UK and whilst pressure over the next few days remained generally slack, the northerly airstream responsible for the cool start to the month had returned. Daytime temperatures fell consistently over the days that followed and as frontal systems began to work southwards, rain brought to an end a long dry period on the 26th.

Air Temperatures    
The Highest Maximum: 26.7 C on 23rd
The Lowest Maximum: 8.3 C on 8th
The Highest Minimum: 13.6 C on 20th
The Lowest Minimum: 0.5 C on 13th
The Mean Maximum: 16.2 C  
The Mean Minimum: 6.9 C  
The Overall Mean: 11.6 C  
Difference from the Monthly Mean: 0.0 C  
    
Solar Radiation    
Maximum (at 0900): 850.0 W/m^2 on 4th
Mean (at 0900): 357.3 W/m^2  
    
Relative Humidity:    
Highest Relative Humidity (at 0900): 93.0 % on 2nd
Lowest Relative Humidity (at 0900): 52.0 % on 18th
Mean Relative Humidity (at 0900): 71.3 %  
    
Dew Point:    
The Highest Dew Point (0900): 14.5 C on 24th
The Lowest Dew Point (at 0900): -0.8 C on 11th
The Mean Dew Point (at 0900): 6.7 C  
    
Rainfall:    
Total: 27.3 mm  
Percentage of the Monthly Mean: 55.3 %  
Duration: 27.5 hrs  
Highest 24 hour fall (0900 to 0900): 14.1 mm on 1st
Rain Days (>/=0.2mm): 8   
Wet Days (>/=1.0mm): 4   
    
Sunshine:    
Total Duration of Bright Sunshine: 192.2 hrs  
Sunniest day: 12.5 hrs on 22nd
No. of days without sunshine: 3   
Percentage of the Monthly Mean: 103.9 %  
Cloud cover (mean at 0900): 5.3 oktas 66.3 %
    
Pressure (reduced to sea level):    
The Highest Pressure (at 0900): 1032.9 mb on 20th
The Lowest Pressure (at 0900): 1009.6 mb on 1st
Mean Pressure (at 0900): 1018.4 mb  
    
Winds    
Run of wind (mean over 24 hrs): 86.8 miles  
Mean daily wind speed: 4.7 mph  
Run of wind (cumulative): 2691.3 miles  
Highest Maximum Gust: 43 mph on 3rd
No. of gusts of 50mph or more: 0   
Highest wind strength (at 0900): 21.9 mph on 9th
Mean wind strength (at 0900): 9.7 mph  
    
Winds from the Following Directions:    

N 6 NE 4 E 4 SE 3 S 1 SW 2 W 3 NW 8 Calm 0
    
Concrete     
Lowest Concrete Minimum: 0.5 C on 4th
Mean Concrete Minimum: 7.4 C  
    
Evaporation    
Piche 87.2 ml  
Pan 84.69 mm    
 
Days with:    
Thunder: 0   
Hail <5mm: 0   
Hail >/=5mm: 0   
Snow or snow & rain: 0   
Snow lying: 0   
Fog: 0   
Air Frost: 0   
Gales: 0   

All data © Pitsford Hall weather station.

The weather station publishes a full Monthly Weather Report (ISSN 1741-4733) which is distributed to libraries across Northamptonshire. This report comprises a full UK weather diary, reports of extreme weather events across the county, statistics from Pitsford Hall's affiliated stations across the county as well as news from the weather station itself. Individuals may download this report for £2 or take out an annual subscription for the paper-based report for £25. Click here for further details.