PITSFORD HALL WEATHER STATION
NORTHAMPTON, UNITED KINGDOM

MONTHLY WEATHER REPORT for JANUARY 2001


Monthly Assessment - January 2001


January 2001 was a particularly cold month at Pitsford Hall. Average 
temperatures balanced out at 3.0C, -1.2C below the new long-term average 
(1971-2000). Air frosts were recorded on 18 days with 26 days recording
a ground frost. Snow fell on 2 days (19th & 21st) remaining on the
ground for 3 days. Despite the cold, this January was particularly sunny
with 86.6 hours of bright sunshine recorded.

The first few days of the month were quite mild. Low pressure pushed
eastwards bringing some notable wet days (7.8mm on the 3rd). There then
followed a prolonged dry period associated with a developing high
pressure system to the south of Iceland.  Temperatures fell
substantially from the 16th with severe overnight frosts (-4.5C air
minimum, -8.7C grass minimum on 16th). A weak low pressure system moving
through the region triggered snowfall on the 19th and again on the 21st.
Snow depth was modest at just 1cm, in contrast to the heavy falls
experienced in the last week of December 2000. 

The 21st onwards saw a significant change in the weather. Temperatures
recovered together with some fairly brisk south-westerly winds. The
change to milder weather brought some misty and foggy mornings. Much of
the fog was persistent throughout the day. Eventually some sunny periods
broke through (4.4hrs on 23rd) alternating with some fairly hefty
showers (6.6mm also on 23rd). The last days of January from the 27th saw
some overnight frosts and overnight mist and fog. A damp day on the 30th
was associated with a fairly static occlusion. 


Climatological Statistics - January 2001

Air Temperatures				
The Highest Maximum: 11.2C on 23rd
The Lowest Maximum: 1.6C on 16th
The Highest Minimum: 7.2C on 2nd
The Lowest Minimum: -4.5C on 16th

The Mean Maximum: 6.2C
The Mean Minimum: -0.2C  
The Overall Mean: 3.0C  
Difference from the Monthly Mean: -1.2C
				
Relative Humidity:				
Highest Relative Humidity (at 0900): 100% on 4th, 5th, 10th, 20th, 22nd & 31st
Lowest Relative Humidity (at 0900): 78% on 11th
Mean Relative Humidity (at 0900): 94.5%
    
Dew Point:				
The Highest Dew Point (at 0900): 8.7C on 2nd
The Lowest Dew Point (at 0900): -4.7C on 16th
The Mean Dew Point (at 0900): 1.6C
				
Rainfall:				
Total: 36.8mm
Difference from the Monthly Mean: 70.4% 
Duration: 25.5hrs
Highest 24-hour fall (from 0900): 7.8mm on 3rd
Rain Days (>/=0.2mm): 10
Wet Days (>/=1.0mm): 9
Lowest pH: 5.40 on 2nd
			
Sunshine:				
Total Duration of Bright Sunshine: 86.6hrs
Sunniest day: 7.5hrs on 25th
Sunless days: 10
Cloud cover (mean at 0900): 5.5 oktas (68.8%)
				
Pressure (reduced to sea level):				
The Highest Pressure: 1036.1mb on 14th
The Lowest Pressure: 976.1mb on 24th
Mean Pressure (recorded at 0900): 1008.3mb
		
Winds:				
Run of wind (mean over 24 hrs): 147.5 miles  
Mean daily wind speed: 8.0mph
Highest 24-hour Wind Speed: 15.1 mph on 23rd   
Run of wind (to date): 3743.65 miles
Highest Maximum Gust: 40mph on 11th
Highest wind strength (at 0900): 26.5mph on 11th
Mean wind strength (at 0900): 9.0mph
		

		
Winds from the Following Directions:				
N 2, NE 4, E 4, SE 3, S 10, SW 0, W 3, NW 4, Calm 1	
		
				
Ground Temperatures:			 	
Lowest Grass Minimum: -8.7C on 16th
Mean Grass Minimum: -3.3C
Lowest Concrete Minimum: -5.9C on 16th
Mean Concrete Minimum: -1.7C
Lowest Bare Earth Minimum: -6.5C on 16th
Mean Bare Earth Minimum: -1.5C
				
Soil/Earth Temperatures:		 		
5cm mean: 1.1C  
10cm mean: 1.6C  
20cm mean: 2.2C  
30cm mean: 2.8C  
40cm mean: 3.1C  
50cm mean: 3.7C  
100cm mean: 4.6C 
				
Days with:				
Thunder: 1 on 23rd 
Hail less than 0.5mm: 0
Hail greater than/equal to 0.5mm: 0   
Snow or snow & rain: 2: 19th & 21st
Snow lying: 3
Fog: 6
Air Frost: 18
Duration of Air Frost: 156 hours
Ground Frost: 26   

Evaporation: 

Suspended until next summer.
				
Observations made at 0900 UTC. Averages refer to the
period 1971-2000.