[summer '85]

The data for that day when Rickmansworth recorded that large diurnal range.

GMT Temp F
1am 38.8
2am 37.9
3am 36.2
4am 35.1
5am 34.4
6am 35.5
7am 46.7
8am 58.3
9am 70.7
10am 74.1
11am 78.0
12pm 80.9
1pm 83.0
2pm 84.5
3pm 84.5
4pm 83.1
5pm 79.7
6pm 69.2
7pm 56.8
8pm 51.1
9pm 47.7
10pm 46.6
11pm 45.7
12am 44.1

The lowest reading for the thermometers in the standard screen were 34.0F and the highest reading was 84.9F

The radiation thermometers ranged from 26.3F to 150.4F

[Matt D]

Interesting. In Celcius terms, it rose from 1.3C to 29.1C, a rise of just under 28C in less than 12 hours. That was a very cold start for August!

[Dave W]

..and at that 6am it was 1C , at 9am 21C !

[summer '85]

A thermograph in a smaller Stevenson screen 15ft to the south of the main one had a minimum of 35.3F at about 5.45am GMT and a maximum of 84.6F at 14.30pm GMT

Sunshine duration that day was 12.6hrs  [91% of the possible maximum]

Relative humidity at 9am was 56% and at 1pm was 28%

The next day had  a diurnal range from 39.5F to 81.3F

[Matt D]

Yeah thats a stonking rise. Guess the only way this could have happened is when a rather cool airmass was quite quickly replaced by rising thicknesses (advection of warm, continental air etc) during the morning under strong sunshine. The 'frost hollow' nocturnal inversion looks to have been eroded very quickly!

[Dave W]

29th Aug 1936 00Z

[summer '85]

According to reports at the time this was the 67th day [the 30th August 1936] since May 1929 that Rickmansworth recorded a diurnal range of at least 40.0F or more.

23 of these occasions were in August, 13 in July and 11 in June

[BUTTERFLY]

The date should be 29th, not 30th, August 1936. Even higher diurnal ranges have been recorded in Scotland, e.g. 29.0 deg. C., from -7.0 deg. C. to +22.0 deg. C. at Tummel Bridge, Perthshire, on 9th May 1978 (see http://www.personal....ther_in_may.htm) and 28.9 deg. C. from -27.2 deg. C. to +1.7 deg. C. on 30th December 1995 at Altnaharra, NW Scotland (see http://www.personal....in_december.htm).
On 20th March there was quite a high range of temperature in the far north of Scotland; http://www.met.rdg.a...gge/mintemp.png shows a minimum of -4.5 deg. C. in the 12 hours ending 0600 on 20.3.2009 (the lowest figure on the map) and http://www.met.rdg.a...gge/maxtemp.png shows a maximum figure 18.5 deg. C. (in the 12 hours ending 1800 on 20.3.2009) at what seems to be the same place (the highest temperature on the map). http://www.ukweather...posts=4&start=1 shows that on 20th March 2009 Altnaharra recorded a maximum of 18.5 deg. C. and a minimum of -3.0 deg. C., with Aboyne in Aberdeenshire recording -4.2 deg. C. , giving a range of 21.5 deg. C. at Altnaharra.

[Dave W]

The date we were discussing WAS the 29th?

[summer '85]

Quote

Dave W - 22/3/2009 08:03 The date we were discussing WAS the 29th?

The title of the thread is a bit of a giveaway

"The large diurnal temperature range at Rickmansworth for 29th August 1936"

 

The 30th of August 1936 referred to is that there was a large diurnal range for that day as well which was mentioned earlier in the thread and was the 67th day since May 1929 that there was a diurnal range of 40F or more for that station. The 29th of August 1936 being the 66th such day.

[Dave W]

Incidentally, when would you ever get that kind of detail in the papers today? I remain convinced of the 'dumbing down' in the press of weather reporting in recent decades..

[BUTTERFLY]

The home page of http://www.ukweatherworld.co.uk/ states that on 20th March 2009, Altnaharra ranged from -4.5 deg. C. to +18.5 deg. C., a range of 23 deg. C. (although http://www.ukweather...w.asp?tid=29... gives a minimum at Altnaharra on 20th of -3.0 deg. C., and -4.2 deg. C. at Aboyne, Aberdeenshire (no -4.5 deg. C. is given). Which is right I cannot say, though clearly there was a big range of temperature at Altnaharra of at least 21.5 deg. C.

In the last 15 years or so, I have very rarely recorded daily ranges of more than 20 deg. C. either at my place of work or in my garden. I think the highest was in late May 1994 when (in my garden) it ranged from 0.6 deg. C. to about 23.2 deg. C.; at my place of work I cannot remember the exact figures but I think a range of around 19 deg. C. was recorded in August 1995 and 1 or 2 of 20 deg. C. or more in July (perhaps 1999) and September (latter possibly 1998). A few years ago in 2003, Altnaharra had a range of 28.2 deg. C. on http://www.personal....er_in_april.htm, falling from 24.5 deg. C. on Good Friday, 18th April, to -3.7 deg. C. the following night. On 16th February 2003 a minor example of a large daily range of 18 deg. C. occurred at Altnaharra, which had both the lowest (-9.0 deg. C.) and the highest temperature (9.0 deg. C.) in the UK on the same day, presumably a rare event in itself (see http://www.met.rdg.a...y2003.html#0302).

Clearly high daily ranges can occur for a variety of reasons and at all seasons (perhaps more frequently in spring or very late summer) and both in the English lowlands and Northern Scotland.

[BUTTERFLY]

I should have said that I don't know of any published large daily ranges of temperature (say around 23 - 25 deg. C.) in Ireland although it is likely that these have occurred on occasion. In some occasions (e.g. at Altnaharra on 30.12.1995 and probably at Tummel Bridge on 9.5.1978) it was presumably caused by a change of air mass, though this may not have been the case at Rickmansworth in August 1936. It is a pity that the latter site no longer maintains weather records; I have seen a table showing a list of the highest and lowest temperatures in each month; it actually showed 1 or 2 maximum monthly records which were as high or higher than the official British record.

Other currently known frost hollows (e.g. Benson in Oxfordshire, Redhill in Surrey, Katesbridge in Co. Down) though often noted for low minima, seldom seem to produce particularly high maxima (as far as I know whereas according to Gordon Manley in his New Naturalist Book on Weather, Rickmansworth, being in a constricted valley, tended to be warmer than elsewhere during the day (though he said that dahlias were often lost in August whereas a quarter of a mile away they survived until November!

[Matt D]

Quote

BUTTERFLY - 22/3/2009 12:55 The home page of http://www.ukweatherworld.co.uk/ states that on 20th March 2009, Altnaharra ranged from -4.5 deg. C. to +18.5 deg. C., a range of 23 deg. C. (although http://www.ukweather...w.asp?tid=29... gives a minimum at Altnaharra on 20th of -3.0 deg. C., and -4.2 deg. C. at Aboyne, Aberdeenshire (no -4.5 deg. C. is given). Which is right I cannot say, though clearly there was a big range of temperature at Altnaharra of at least 21.5 deg. C. 

Altnaharra recorded a high of 18.5C on Fri 20th and then that night, into the morning of Sat 21st, it recorded a minimum of -4.5C.

[BUTTERFLY]

Table 20 on page 126 of Robin Stirling's book "The Weather of Britain" (Faber and Faber 1992) shows the extreme maxima and minima for each month at "Two Frost Hollows", Rickmansworth in Hertfordshire from 1938-1950 and at Santon Downham in Norfolk from 1958n onwards. The figures are shown below:

RICKMANSWORTH

Jan 14.4/-20.0 Feb 18.3/-19.4 Mar 22.8/-17.2 Apr 30.1/-8.9 May 33.3/-8.3 June 34.4/-2.8 July 35.0/0.0 Aug 34.4/-2.2 Sep 32.2/-3.9 Oct 25.6/-9.4 Nov 21.7/-10.6 Dec 15.0/-18.9 Year 35.0/-20.0

The April and May figures are higher than the accepted British records of 29.4 deg. C. in 1949 and 32.8 deg. C. in 1922 and 1944 respectively and the November one equal to the 1946 record of 21.7 deg. C.

SANTON DOWNHAM

Jan 14.5/-19.9 Feb 18.3/-15.0 Mar 25.0/-12.2 Apr 25.6/-10.6 May 28.3/-6.7 June 30.0/-5.6 July 33.3/-1.1 Aug 33.5/-1.7 Sep 29.2/-5.6 Oct 26.7/-5.0 Nov 17.8/-11.1 Dec 15.8/-16.1 Year 33.5/-18.9

Santon Downham holds the British record for high March temperature and the lowest June temperature. The September and October figures are correct, although over a longer period the extreme minimum for October will be lower than that for September.

[Big Rich]

A 23.8c rise in Altnaharra today. Interesting.

[BUTTERFLY]

Can you give the actual figures relating to the 23.8 deg. C. rise at Altnharra for 8th/9th? Seems reminiscent of 30.12.1995, when the temperature fell from a low just after midnight on 30th of -27.2 deg. C. (the joint British record, along with Braemar on 11.2.1895 and 10.1.1982) to +1.7 deg. C. on the afternoon of 30th, giving a range of 28.9 deg. C. (alost the same as the 29 deg. C. range from -7.0 deg. C. to +22.0 deg. C. at Tummel Bridge, Perthshire, on 9th May 1978; a wind got up in the small hours of 30th which prevented a potential low of -30 deg. C. or so, and there was also a 20.2 deg. C. rise from -21.2 deg. C. at mid-day on 30th to -1.0 deg. C. in 3 hours. Altnaharra also fell from +24.5 deg. C. on 18th April 2003 to -3.7 deg. C. the following night (see http://www.personal....er_in_april.htm, http://www.personal....ther_in_may.htm and http://www.personal....in_december.htm)

[Big Rich]

I believe it was -22.5 to 1.3c at the time I posted. Since then there was another diurnal range as big as that at Altnaharra.

[BUTTERFLY]

Someone ought to do an article (e.g. in "Weather" magazine") about Altnaharra, especially the large temperature ranges on occasions. Incidentally is it in Sutherland or Wester Ross?

[Bluebreezer54]

That was a particularly interesting read regarding Rickmansworth since I live approximatley 4 miles from there. Am I right in thinking that until quite recent times it was an official reporting station ?

Im not too suprised by the low temperature recordings as it it lies in a locally well known frost hollow, It is quite literally situated in a bowl. Would the rapid rise result from warm air flowing down the valley slopes later in the day at that time of year ?