PITSFORD WEATHER STATION
NORTHAMPTON, UNITED KINGDOM

MONTHLY WEATHER REPORT - MAY 2002


Headline: A cool start, mostly unsettled. A short period of 
warmth around mid-month.

The month opened with scattered showers and patchy light rain 
until the 8th. It was also cool with temperatures falling steadily. 
Overnight temperatures had fallen to 2.3C on the 5th and some 
parts of the county were recording ground frosts (-2.1C grass 
minimum at Byfield on the 2nd). Clear nights and a general north 
or north-easterly air flow as the county came under the influence 
of a developing anticyclone over Scandinavia were largely 
responsible for the cool conditions.

The passage of an Atlantic low to the north-west of the county 
brought changed conditions on the 13th and 14th. Winds picked up 
from the south, later west, bringing rain. 6.6mm fell over a period 
of 5 hours at Pitsford Hall, but the gales experienced around 
western coasts were not felt in the county where rather modest 
gusts reached 29mph on the 14th. 

With the departure of the depression the county came under the 
influence of anticyclonic conditions centred on the continent. 
Temperatures climbed quite smartly, in fact it had become very 
warm by the 16th (23.7C). However, a change to unsettled weather 
quickly followed with 5.0mm of rain falling on the 17th as a 
vigorous Atlantic low deepened to the west.

The unsettled spell, accompanied by a deterioration in temperatures 
and frequent outbreaks of rain and blustery showers, lasted 
practically until the last few days of May. The 21st was a 
particularly wet day with 15.5mm of rain falling in just under 7 
hours. Winds were frequently moderate or fresh southerlies. Again, 
although gales were reported in coastal areas, gusts reached their 
highest of just 35mph (24th) here in Northamptonshire. Nevertheless, 
despite the rain some good sunshine managed to be recorded, 
frequently in excess of 10 hours a day between 22nd and 24th, and 
up to 11.7 hours on the 27th.

As May ended low pressure finally gave way to a ridge of high pressure 
from Europe which had become firmly established across the county by 
the 31st. The ridge brought with it a change to drier and warmer 
weather.



Climatological & Agromet Statistics - May 2002


Air Temperatures				
The Highest Maximum: 23.7C on 16th
The Lowest Maximum: 11.9C on 9th
The Highest Minimum: 12.3C on 21st
The Lowest Minimum: 2.3C on 5th

The Mean Maximum: 16.5C
The Mean Minimum: 7.7C
The Overall Mean: 12.1C
Difference from the Monthly Mean: -0.3C
				
Relative Humidity:				
Highest Relative Humidity (at 0900): 98.7% on 6th
Lowest Relative Humidity (at 0900): 60.1% on 25th
Mean Relative Humidity (at 0900): 80.8%
    
Dew Point:				
The Highest Dew Point (at 0900): 16.5C on 16th
The Lowest Dew Point (at 0900): 4.7C on 5th
The Mean Dew Point (at 0900): 9.6C
				
Rainfall:				
Total: 55.2mm
Difference from the Monthly Mean: 110.7%
Duration: 44.3hrs
Highest 24-hour fall (from 0900): 15.5mm on 21st
Rain Days (>/=0.2mm): 16
Wet Days (>/=1.0mm): 12
Lowest pH: 6.19 on 17th
			
Sunshine:				
Total Duration of Bright Sunshine: 191.1hrs
Sunniest day: 11.7hrs on 27th
Sunless days: 2
Cloud cover (mean at 0900): 6.0 oktas (75.0%)
				
Pressure (reduced to sea level):				
The Highest Pressure: 1025.5mb on 6th
The Lowest Pressure: 991.3mb on 22nd
Mean Pressure (recorded at 0900): 1011.1mb
		
Winds:				
Run of wind (mean over 24 hrs): 140.7 miles
Mean daily wind speed: 7.6mph
Highest 24-hour Wind Speed: 14.5mph on 22nd
Run of wind (to date): 4360.4 miles
Highest Maximum Gust: 35mph on 24th
Highest wind strength (at 0900): 17.3mph on 11th
Mean wind strength (at 0900): 11.1mph
		
Winds from the Following Directions:				
N 7 NE 1, E 1, SE 0, S 12, SW 3, W 3, NW 3, Calm 1
	
Days with:				
Thunder: 2: 2nd & 3rd
Hail less than 0.5cm: 1: 3rd
Hail greater than/equal to 0.5cm: 0   
Snow or snow & rain: 0
Snow lying: 0
Fog: 0
Air Frost: 0
Duration of Air Frost: 0.0hrs
Ground Frost: 0


Evaporation: 

Total evaporation (tank): 67.83mm

					
Ground Temperatures:			 	
Lowest Grass Minimum: 0.1C on 2nd & 5th
Mean Grass Minimum: 6.4C
Lowest Concrete Minimum: 1.9C on 2nd & 5th
Mean Concrete Minimum: 6.9
Lowest Bare Earth Minimum: 2.5C on 2nd
Mean Bare Earth Minimum: 7.7
				
Soil/Earth Temperatures:		 		
Surface mean: 14.7
5cm mean: 12.3C
10cm mean: 12.4C
20cm mean: 12.4
30cm mean: 12.7
40cm mean: 12.5C
50cm mean: 12.7C
100cm mean:  11.4C
	
Climatological observations made at 0900 UTC.  Averages refer to the period 1971-2000.