WEATHER ANALYSES FOR 2009

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MONTHLY WEATHER REVIEWS AND CLIMATOLOGICAL SUMMARIES

Headline: Anticyclonic and very cold for much of the first half of the month, becoming increasingly unsettled with frequent frontal systems bringing rain working through during the second half.

February

March

Headline: A month of alternating unsettled and settled weather although becoming overall drier, warmer and sunnier than normal.

April

Headline: Very warm with below average rainfall. Long sunny periods, especially in the second half.

May

Headline: Changeable, but drier than normal with a wet unsettled spell around mid-month.

June

Headline: Cool and unsettled during the first half of the month, increasingly warm and humid later.

July

August

September

Headline: Wet at the start, but then a protracted dry spell broken only by drizzle later in the month. Warmer than usual

October

November

December

Headline:  A cold month – the coldest since 1995 in Northampton. Snowfall in the week before Christmas lying on the ground until Boxing Day.

CLIMATOLOGICAL STATISTICS FOR 2009

Air Temperatures     
The Highest Maximum: 30.0 C on 30th June
The Lowest Maximum: 0.0 C on 18th December
The Highest Minimum: 17.1 C on 5th August
The Lowest Minimum: -6.5 C on 19th December
The Mean Maximum: 14.1 C   
The Mean Minimum: 6.4 C   
The Overall Mean: 10.3 C   
Difference from the Yearly Mean: 0.4 C   
     
Solar Radiation (from 1st May)     
Maximum (at 0900): 784.0 W/m^2 on 20th June
Mean (at 0900): 244.4 W/m^2   
     
Relative Humidity:     
Highest Relative Humidity (at 0900): 10th,14th,19th,27th January; 18th,20th February; 13th March; 3rd April; 21st,24th,27th July; 21st, 22nd,24th-30th October; 9th-11th November; 11th,18th,22nd-25th,28th-30th December
Lowest Relative Humidity (at 0900): 46.4 % on 6th July
Mean Relative Humidity (at 0900): 84.3 %   
     
Dew Point:     
The Highest Dew Point (0900): 18.4 C on 3rd July
The Lowest Dew Point (at 0900): -6.4 C on 20th December
The Mean Dew Point (at 0900): 7.3 C   
     
Rainfall:     
Total: 509.3 mm   
Percentage of the Yearly Mean: 84.8 %   
Duration: 454.5 hrs   
Highest 24 hour fall (0900 to 0900): 20.9 mm on 9th February
Rain Days (>/=0.2mm): 158    
Wet Days (>/=1.0mm): 113    
     
Sunshine:     
Total Duration of Bright Sunshine: 1407.8 hrs   
Sunniest day: 14 hrs on 30th May
No. of days without sunshine: 55    
Percentage of the Yearly Mean: 86.7 %   
Cloud cover (mean at 0900): 5.5 oktas   
     
Pressure (reduced to sea level):     
The Highest Pressure (at 0900): 1038.8 mb on 11th September
The Lowest Pressure (at 0900): 972.3 mb on 23rd January
Mean Pressure (at 0900): 1013.8 mb   
     
Winds     
Run of wind (mean over 24 hrs): 119.8 miles   
Mean daily wind speed: 6.5 mph   
Run of wind (cumulative): 43630 miles   
Highest Maximum Gust: 50 mph on 25th March
No. of gusts of 50mph or more: 1    
Highest wind strength (at 0900): 29 mph on 19th November
Mean wind strength (at 0900): 8.9 mph 

Winds from the Following Directions:     
North 31   
North-east 24 
East 20 
South-east 43    
South 87    
South-west 51    
West 38   
North-west 54    
Calm 15 

     
Concrete     
Lowest Concrete Minimum: -8 C on 8th January
Mean Concrete Minimum: 5.8 C   
     
Evaporation     
Piche 879.6 ml  
Pan Not available 
     
Days with:     
Thunder: 11    
Hail <5mm: 2    
Hail >/=5mm: 1    
Snow or snow & rain: 19    
Snow lying: 29    
Fog: 17    
Air Frost: 39    
Duration of Air Frost: 332 hrs   
Gales: 0    
       
Wettest month: 81.3 mm in  July
Driest month: 14.3 mm in  September
Warmest month: 17.1 C~ in  August
Coolest months: 3.0 C~ in  January and December
Sunniest month: 194.3 hrs in  May
Dullest month: 41.0 hrs in  January
Windiest month: 10.3 mph~ in  November
Calmest month: 4.4 mph~ in  June
     
~ averages