1997 No. 52 Part 1 - Bedfordshire Natural History Society

Bedfordshire Naturalist for 1997, No. 52 (Part 1) (1998)
very quickly so this rainfall will have contributed very little to ground waterlevels.
There were also two extreme and localised weather events in May which are described
in detail below. 1997 was certainly not without interest "meteorologically.
All the figures in the above report are taken from Silsoe unless otherwise stated and a
summary ofthe readings from this site appears inTable 1.The table has been modified
from the format ofprevious years. Figures for ground frost were no longer available so
the opportunity has been taken to show how the montWy means and totals compare
with the longer term average, in this case for the period 1951-1980 at the original
recording site inWrest Park. Thirty years is the standard period over which longer term
averages are calculated. It would be appropriate to use the more recent period of
1961-1990, but the original site atWrest Park was closed down before the end of
1990, and there is no single station in this area which provides a continuous record
over the required period. Readers should also bear in mind that the data inTable 1 is
from Silsoe College, about halfa mile from the original Wrest Park site, so the comparison
with the long term means should be taken as indicative rather than absolute.
Mean Mean Highest Lowest Rainfall Sunshine Air
Max Min Temp Temp Frost
°c °c °C °c mm hours days
January 5.5 (-0.5) -1.5 (-2.0) 11.2 -10.2 13.2 (29%) 54.2 (103%) 20~
February 10.5 (+4.0) 3.3 (+2.7) 13.8 -3.0 56.9 (159%) 66.3 (102%) 3
March 13.3 (+3.9) 4.5 (+2.9) 17.3 -1.2 9.7 (25%) 1?1.9 (136%) 2
April 14.5 (+2~1) 3.4 (-0.2) 22.2 -5.4 24.8 (34%) 186.0 (127%) 7
May 17.8 (+1.7) 5.3 (-1.1) 25.1 -1.5 34.6 (86%) 257.3 (134%) 2
June 19.1 (-0.3) 10.3 (+1.3) 25.5 5.9 112.5 (235%) 153.0 (76%) 0
July 22.8 (+1.8) 11.4 (+0.3) 27.3 6.3 32.8 (67%) 223.2 (121% 0
August 26.1 (+5.3) 14.3 (+3.4) 32.0 9.1 30.4 (51%) 195.3 (115%) 0
September 20.2 (+1.8) 9.9 (+0.7) 24.1 2.0 20.0 (45%) 174.0 (120%) 0
October 15.4 (+1.0) 5.2 (-1.3) 25.1 -8.0 58.6 (125%) 155.0 (148%) 8
November 12.0 (+2.6) 5.0 (+1.8) 15.8 -4.0 51.7 (102%) 63.0 (99%) 5
December 8.5 (+0.7) 3.0 (+1.4) 14.5 -1.8 52.4 (102%) 31.2 (63%) 6
Year 15.5 (+2.1) 6.2(+0~9) 32.0 -10.2 499.3 (91%)1710.4 (1160/0) 53
Table 1.Weather data for 1997 as recorded at Silsoe College
The Events of 17th May 1997
There were two separate but related weather events which occurred on Saturday
17th May 1997. One was the occurrence ofvery large hail almost a year after a similar
event on 7thJune 1996· (Williams 1997); the second was a major tornado ofstrength
T3 on the TORRO Scale (Meaden 1976).The Recorder was out ofthe county on the
relevant date (and subsequently) and the information presented here is from other
sources.
The 17th May was Cup Final day, and the afternoon saw the outbreak ofsevere
thunderstorms and two (possibly three) tornadoes across the country.The Bedfordshire
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