WEATHER ANALYSES FOR 2009

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MONTHLY WEATHER REVIEWS AND CLIMATOLOGICAL SUMMARIES
January

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

Headline: Bitterly cold first half with frequent heavy snowfalls. Mild, but dull second half.

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

Headline: Mostly cyclonic and wet. Warm at first, but then mostly cool and breezy.

August

Headline: Changeable, but with most of the rain falling during the first week.

September

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

October

Headline: More settled and anticyclonic than some recent Octobers rainfall below average and temperatures close to the norm.

November

Headline: Mildest November for 10 years. High frequency of southerly winds and rain recorded nearly every day.

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