Summary for July, 2006

======================

HEADLINE: EXCEPTIONALLY WARM: LENGTHY HOT/DRY SPELLS. SOME THUNDERY RAIN

(last updated: 02/1500 AUGUST)

Location: Tawfield/Wooden Hill area of SW Bracknell, Berkshire, UK

Altitude 80 m (other location details see elsewhere on web site.)

(temperatures [standard screen] degC; rainfall/melted snowfall mm; snow depths cm; )

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TEMPERATURES ETC.

Highest day maximum (date):... 35.7(19)

Highest 24hr maximum (date):.. 35.7(19)

Lowest night minimum (date):... 11.0(14)

Lowest 24hr minimum (date):... 11.0(14)

Lowest overnight grass minimum (date):... 09.5(14)

[ number of days grass minimum < 0degC: ... 00 ]

[ Lowest day maximum (date):... 21.2(07)]

[ Highest night minimum (date):... 19.9(22)]

A. Mean Day (09-18Z) maximum: ... 27.6

A. Mean Night (18-09Z) minimum: ... 15.5

A. Mean of Day Max & Night min: ... 21.5

B. Mean 24hr maximum:... 27.6 [+5.0 anomaly on eLTA]

B. Mean 24hr minimum:... 15.5 [+2.8 anomaly on eLTA]

B. Mean of 24hr max & min:... 21.5 [+3.9 anomaly on eLTA 1971-2000]

(data below relate to 24 hr day beginning 09Z on date given)

Nr of days minimum at 09UTC <0.0degC:00

Nr of days maximum at 09UTC >=21degC:31

Nr of days maximum at 09UTC >=25degC:22

Nr of days maximum at 09UTC >=30degC:11[dates: 02-04,16-21,25-26]

(Notes relating to temperature & allied observations:

19th: day / 24hr max 35.7degC, beats the previous highest (any-month) value for us set on the 10th August, 2003 of 35.6degC: record starts 2000.)

22nd: temperature dropped from the day max.(28.7 which occurred late morning), to 21.2degC by 1300Z as thunderstorm / rain arrived.

(26th: possible problem with max. thermo: behaving as an ordinary thermometer – will check against alternate: update 29th – checks over past days show no apparent problem, but will exchange with new unit end-month)

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PRECIPITATION (PPN/mm)

Total rainfall/melted snow etc:... 41.9 [93% of eLTA]

Highest 24hr total:............... 11.0(26)

No. days PPN total >= 0.2:11

No. days PPN total >= 1.0:10

No. days PPN total >=10.0:01

No. days PPN total >=25.0:00

(Notes relating to precipitation & allied observations:

5th: r(slight) from ~0600Z (with thunder – see below), becoming r for a time until 0645 (thunder ceased), and again from 0820Z onwards, with r / R 0840-0902Z, then r(slight),dying out by~1030Z. Further pr(mainly light) thereafter until early evening;

6th: r(slight)/dr(slight), ocnl dr, 0705-0840Z; pr/r (very light) AM;

7th: r(slight), ocnl r, from ~0840Z – 1230Z. pr(slight)~16Z;

8th/9th: r(slight), ocnl r/dr, from ~23Z, dying out by~ 10Z;

10th: id(very light) from~ 0840Z to early afternoon, then r(slight), ocnl r, 1330Z-1730Z; r(slight) off/on evening, csd by~24Z;

13th: ir(few drops) ~12Z;

22nd: very few drops~04Z, assw tl(slight) between 03 & 0430Z; r(slight)/r between 1153Z & 1430Z, in association with thunderstorm (see below);

23rd: pr(very light) ~1130 & 15Z;

26th: ir(R) 0030-0230Z, with short period weak / infrequent thunder 0020-0030Z; period r/R (assoc. with tl(slight)/tl) between 2215 & 2345Z .. see further note below under 'thunder');

27th: pr(R) 1420-1445Z (contributed to the bulk of rainfall reported in 09-18Z period); r(slight), ocnl r, (assoc. with tl(slight/see below)) 1602Z to 1810Z;

29th: ir(very light)~1645/1650Z;

29th/30th: ocnl r(slight), tempo. r, overnight;

30th: pr(few spots)~1640Z;

31st: pr(slight) from ~12Z – early evening; r(slight), ocnl r between 22 & 24Z, pr(slight) early hours 1st: rainfall (1.7mm) credited to this month.):

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OTHER TOTALS

Number of days thunder heard: (dates).. 04 (05,22,26,27)

Number of days hail < 0.5cm diameter:.. 00

Number of days hail >=0.5cm diameter:.. 00

Number of days snow/rain & snow:....... 00

Number of days snow lying at 09UTC:.... 00

Deepest snow cover (date,s):........... -

Number of days fog (visibility < 1km @ 09UTC).. 00

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Additional comments on the weather in July, 2006

[rainfall]

Although the monthly total of 41.9mm was close to the estimated long-term average (1971-2000) of 45mm, there were lengthy dry periods with the rainfall being made up of 'short, sharp bursts' rather than prolonged frontal-type rainfall. There was also a bias towards the rainfall coming along in the 18-09Z period (65% of all rainfall) as opposed to the 09-18Z period: Neither of the two 'high-yield' rain events (8.6mm/~dawn 5th & 11.0mm/late PM 26th thundery activity) troubled the daytime 'score-board')

[thunder]

5th: tl(slight) 0518Z (first distant thunder heard) to ~0645Z (10 mins elapsed since last thunder). Light, short-period moderate, rainfall, with discharge rate at maximum ~4-5 per minute. Discharges appeared to be CC/IC & 'medium level'. A 'true' Cb could not be seen (though it probably had a high base amongst the extensive Ac canopy).

22nd:

(i): tl(slight/high-base, medium-level) 03-0430Z, with only a trace of rain recorded. Mainly IC ('sheet') lightning, infrequent;

(ii): t(1145Z), with tl(slight)r(slight), ocnl tlr (moderate thunder/rain) between 1153Z & 1340Z. Maximum discharge rate (IC/medium level) ~ one per 30 or 40s at it's height ~12Z, otherwise discharges (IC/medium level) every 1 to 5 mins in the main, with no CG strikes noted locally. [NB: more significant activity just to our west at Wokingham].

26th:

(i): period weak / infrequent thundery activity (CC/IC) ~0020/0030Z.

(ii): tl(slight)/tl between 2215 & 2310Z, with peak activity 2225-2235Z, when discharge rate (CC/CG) somewhere around 1 per 5 to 8 seconds. Lightning in evidence for a little while before, and a long time afterwards. Periods of moderate or heavy rainfall (11.0mm) within ~90mins, much of it in less than 30mins. [ see note at bottom added from local paper ]

27th: t 1530Z, then tl(slight/IC or CC activity) from 1602Z to 1640Z, cells decaying / forming in vicinity, slow-moving, with no CG activity detected.

[snow]

(none)

... these data can also be viewed at:-

http://homepage.ntlworld.com/booty.weather/metinfo/wxdata/climintro.htm

Tn Tx Tg RR Tn Tx RR RR24hr Remark code (below)

(09Z) (09Z) (09Z)(18-09Z) (18Z) (18Z) (09-18Z) (from 09Z today)

01 13.1 26.2 10.2 - 24.4 29.9 - - -

02 18.6 28.5 16.8 - 26.6 31.5 - -

03 16.9 29.6 14.3 - 25.5 31.4 - -

04 18.1 28.6 16.4 - 22.8 31.0 - 08.6

05 17.1 28.8 14.9 08.6 18.6 21.8 01.8 02.7

06 17.0 19.3 16.3 00.9 17.6 24.9 tr tr

07 16.1 22.6 14.7 tr 17.5 21.2 01.9 01.9

08 13.5 20.7 12.1 - 19.4 21.9 - 02.2

09 13.7 19.4 13.2 02.2 15.7 22.6 tr tr

10 13.5 20.4 11.7 tr 18.1 22.0 01.1 01.4

11 15.4 19.7 13.8 00.3 19.7 25.2 - -

12 11.7 23.6 10.2 - 21.1 26.8 - -

13 12.7 24.6 11.3 - 18.8 23.2 tr tr

14 11.0 22.4 09.5 - 17.2 23.5 - -

15 11.8 21.6 10.5 - 17.9 25.9 - -

16 13.1 23.9 11.9 - 21.2 30.1 - -

17 12.6 27.9 09.9 - 24.9 32.0 - -

18 15.1 30.6 11.8 - 25.3 33.5 - -

19 17.3 30.9 15.5 - 26.5 35.7 - -

20 19.7 32.3 17.3 - 24.7 30.5 - -

21 17.1 28.7 15.8 - 24.7 31.5 - tr

22 19.9 29.5 18.7 tr 19.9 28.7 05.0 05.0

23 15.8 22.7 14.7 - 19.7 26.1 tr tr

24 13.3 24.5 10.8 - 22.6 29.5 - -

25 16.9 27.3 14.4 - 24.2 33.4 - 01.6

26 18.8 (31.0) 17.5 01.6 25.2 31.1 - 11.0 ABC

27 18.6 29.6 17.7 11.0 22.2 28.5 04.9 04.9

28 15.2 22.2 14.1 tr 22.1 28.6 - -

29 15.2 26.8 14.0 - 21.1 25.2 tr 00.9

30 17.2 21.6 16.2 00.9 19.8 25.0 tr tr

31 15.8 21.8 14.6 - 20.4 23.3 tr 01.7

Readings taken at 0900 and 1800 UTC. Where the NIGHT maximum or DAY minimum are significantly different from 24hr values, this will be noted in the listing against a 'Remarks' letter. There are two mean temperatures shown: the first is the mean of the average day maximum and average night minimum (A), and the second is the average of the 24hr maximum and 24hr minimum (B) .. the anomalies are shown for this latter figure from 1971-2000 estimated Long Term Averages. Rainfall is credited to the 24hr day beginning 0900 UTC.

Remarks:

A. Night maximum recorded is an estimate to maintain continuity; we were in Poole that day, returning ~2100Z.

B. (see comments re: max. thermo. under temperature above).

C. (day max. checked against frequent actuals – seems OK at this moment: new maximum thermometer ordered, and should be with us 27th: UPDATE: new thermo. arrived, but not brought into use yet as existing seems fine. Probably start 1st August).

Number of occasions (24hr periods) THIS YEAR (2006)

maximum temperature >= 21degC (70degF) = 58

minimum temperature >= 16degC (61degF) = 17

Rolling 12 month temperature anomaly: +0.8 (was +0.5 end last month)

Rolling 12 month rainfall: 91% of eLTA (was 93% end last month)

Rolling 24 month rainfall: 86% of eLTA (was 85% end last month)

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Total rainfall for this year (2006) so far: 322.0 mm, representing 87% of the 'average' that we should have by the end of July (372mm).

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NOTES RE: PERIODS WITH MAXIMA >=25DEGC FOR THREE OR MORE DAYS (FOR ME, A 'HOT' SPELL).

(2006 ONLY – FOR OTHERS, SEE THE 2006 JUNE FILE)

[2006/INCOMPLETE]

07JUN-12JUN (6 DAYS): 26.9,26.9,26.5,28.9,26.9,31.5

16JUN-18JUN (3 DAYS): 25.0,28.3,25.1

29JUN-04JUL (6 DAYS): 25.9,28.5,29.9,31.5,31.4,31.0

15JUL-30JUL (16 DAYS): 25.9,30.1,32.0,33.5,35.7,30.5,31.5,28.7,26.1,29.5,33.4,31.1,28.5,28.6,25.2,25.0

[Note re: overall warmth of July in context]

Using a composite record for Easthampstead Park / Tawfield (1971-2005), the previous warmest July (& warmest any-named month) occurred in 1983, with a value of 20.0degC. This year (2006), with a value of 20.6degC, we have comfortably exceeded this value.

Using that same series, looking at June & July combined, the previous warmest two such pairings occurred in 1976 (17.8degC) & 1983 (17.5degC). This year, with a value of 18.6degC (provisional), again we have comfortably exceeded these values.

[Note re: extended hot spell second-half July, 2006]

July, 2006 as a whole will go into the 'books' as a classic, exceptionally warm summer month, with extended dry spells.

In this part of the country (mid-section Thames Valley), of particular note is the period 15th – 30th July (16 days), when every day experienced maxima >=25degC, the majority (12) >=28degC & no less than 8 having day maxima exceeding 30degC, and a run of 6 consecutive such days (16th-21st).

The mean day/09-18Z maximum temperature over this spell (15th – 30th) was 29.7degC, around 7degC above the all-month 1971-2000 estimated long-term mean.

The mean night minimum (18-09Z) over this period was 16.1degC (or approx. 3.4degC above the all-month mean min), and on 8 nights, the temperature failed to fall below 16degC: the highest night minimum temperature was 19.9degC on the 22nd.

As to rainfall, the total over this spell was a seemingly respectable 22.5mm, representing 57% of the whole-month total (as of 1600Z/29th), but over those 16 days, rain only occupied ~8hr (or roughly 2% of the total), with two event occurring after dark: On 13 of those days, in the period 09-18Z, either there was no rain recorded, or only a 'trace'.

And finally, in many previous 'hot' spells, the visibility & sky clarity has been moderate at best: this time around, visibilities have often been good to excellent, with only temporary periods of 'milky' skies.

Martin.

[additional note: re: thundery activity late evening 26th / Wednesday]

From Bracknell 'Midweek' paper .. (extracts only: no doubt distressing for those involved, but somewhat 'over-egged' as to amount of 'devastation': Only two (known) direct hits by lightning, rather than the 'trail' described in the accompanying headline!)

" A thunderstorm hit Bracknell and left a trail of devastation after houses were struck by lightning bolts. Two families cheated death when their homes, in Ullswater, Great Hollands, were hit . . . at the height of the terrifying storm . . . A retired couple were left shaken but unharmed after their home was hit. The bolt hit the TV aerial of their bungalow – leaving a hole in their living room wall. Only a few doors away another house was hit – this time a young father was electrocuted. He was unhurt from the shock but the family's television blew up in the strike . . . in another strike . . . (a couple) were shutting their windows during the storm when (the householder) received an electric shock. "