PITSFORD HALL WEATHER STATION

MONTHLY WEATHER REPORT - MAY 2001


Monthly Assessment

May opened on a cool note with air minima falling on consecutive nights 
producing ground frosts by the 4th and 5th as winds blew from a 
consistent north or north-easterly direction. Despite some rainfall on 
the 2nd and 5th, the first week or so was generally settled with pressure 
building off the coast of Scotland. Some good sunshine was recorded 
between the 5th and the 7th (10.5hrs on the 5th).

A marked warming trend began during the second week. By the 10th daytime 
maxima had reached 23.7C triggering some thundery showers. Further hikes 
in temperature over the following few days and the arrival of low pressure
 resulted in further thundery showers on the 13th and further heavy 
rainfall totals everyday until the 17th which was particularly unsettled 
with some heavy downpours and strong winds gusting to 52mph. During this 
particularly wet period, temperatures progressively fell. 

From the 18th onwards, high pressure became firmly established across the 
county giving a prolonged dry spell of weather. Temperatures recovered, 
but not to the very warm daytime maxima experienced during the second 
week, the predominant north-easterly wind direction keeping the 
temperatures pegged down. Several days did, however, notch up some good 
sunshine totals.

The high pressure had slipped away southwards sufficiently by the 27th 
to allow weather fronts to track across the county. However, rainfall 
totals were light and daytime temperatures remained warm, generally 
above 20C. From then on until the end of the month, the weather was 
generally settled. Clear spells by night forced a progress lowering 
of mean temperatures, although daytime values remained respectable. 
Some good sunshine was again recorded, 13.3hrs being clocked up on 
the 30th.


Climatological & Agromet Statistics - May 2001

Climatological Statistics - Pitsford Hall

Air Temperatures				
The Highest Maximum: 25.0C on 11th & 12th
The Lowest Maximum: 11.2C on 17th
The Highest Minimum: 14.5C on 28th
The Lowest Minimum: 1.2C on 5th

The Mean Maximum: 18.1C
The Mean Minimum: 7.3C
The Overall Mean: 12.7C
Difference from the Monthly Mean: +0.3C
				
Relative Humidity:				
Highest Relative Humidity (at 0900): 98.8% on 3rd
Lowest Relative Humidity (at 0900): 47.7% on 4th
Mean Relative Humidity (at 0900): 76.6%
    
Dew Point:				
The Highest Dew Point (at 0900): 15.2C on 28th
The Lowest Dew Point (at 0900): -0.6C on 4th
The Mean Dew Point (at 0900): 9.0C
				
Rainfall:				
Total: 59.2mm
Difference from the Monthly Mean: 118.9%
Duration: 25.9hrs
Highest 24-hour fall (from 0900): 11.4mm on 16th
Rain Days (>/=0.2mm): 10
Wet Days (>/=1.0mm): 8
Lowest pH: 6.20 on 9th
			
Sunshine:				
Total Duration of Bright Sunshine: 211.9hrs
Sunniest day: 13.3hrs on 30th
Sunless days: 2
Cloud cover (mean at 0900): 4.9 oktas (61.3%)
				
Pressure (reduced to sea level):				
The Highest Pressure: 1030.6mb on 8th
The Lowest Pressure: 995.6mb on 17th
Mean Pressure (recorded at 0900): 1018.6mb
		
Winds:				
Run of wind (mean over 24 hrs): 92.1 miles 
Mean daily wind speed: 5.0mph
Highest 24-hour Wind Speed: 9.1mph on 17th
Run of wind (to date): 2855.9 miles
Highest Maximum Gust: 52mph on 17th
Highest wind strength (at 0900): 18.4mph on 1st
Mean wind strength (at 0900): 8.3mph
		
Winds from the Following Directions:				
N 9, NE 6, E 4, SE 1, S 2, SW 4, W 1, NW 4, Calm 0
	
Days with:				
Thunder: 3
Hail less than 0.5mm: 0
Hail greater than/equal to 0.5mm: 0   
Snow or snow & rain: 0
Snow lying: 0
Fog: 0
Air Frost: 0
Duration of Air Frost: 0 hrs
Ground Frost: 2

Evaporation: 

73.27mm (Hook-gauge tank evaporimeter)	

	
Agro-Meteorological Statistics - Pitsford Hall Agromet Site 
(Brixworth)
				
Ground Temperatures:			 	
Lowest Grass Minimum: -3.9C on 5th
Mean Grass Minimum: 6.3C
Lowest Concrete Minimum: 0.6C on 4th
Mean Concrete Minimum: 8.0C
Lowest Bare Earth Minimum: 1.5C on 4th
Mean Bare Earth Minimum: 7.8C
				
Soil/Earth Temperatures (under grass):		 		
Surface mean: 11.6C
5cm mean: 11.1C  
10cm mean: 11.5C  
20cm mean: 12.4C  
30cm mean: 12.8C
40cm mean: 12.6C
50cm mean: 12.9C
100cm mean:  11.7C
	

				
Climatological observations made at 0900 UTC. Agro-meteorological 
observations made at 0700 UTC. Averages refer to the
period 1971-2000.