Summary for September 2005

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

HEADLINE: VERY MILD & DRY OVERALL. FINE/WARM START THEN UNSETTLED.

(last updated: 25/1500 NOVEMBER)

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; ) Readings taken at 0900 and 1800 UTC. Where the NIGHT maximum

or DAY minimum are significantly different from figures hereunder, this will be noted in the accompanying text summary. There are now two mean daily 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 .. as kept formerly) .. 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.

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TEMPERATURES ETC.

Highest day maximum (date):... 27.5(04)

Highest 24hr maximum (date):.. 27.5(04)

Lowest night minimum (date):... 03.5(17)

Lowest 24hr minimum (date):... 03.5(17)

Lowest overnight grass minimum (date):... 01.9(17)

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

[ Lowest day maximum (date):... 15.1(29)]

[ Highest night minimum (date):... 17.6(05)]

A. Mean Day (09-18Z) maximum: ... 20.3

A. Mean Night (18-09Z) minimum: ... 12.0

A. Mean of Day Max & Night min: ... 16.1

B. Mean 24hr maximum:... 20.4 [+2.7]

B. Mean 24hr minimum:... 11.8 [+1.0]

B. Mean of 24hr max & min:... 16.1 [+1.9 anomaly on eLTA of 14.2degC]

(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:14

Nr of days maximum at 09UTC >=25degC:02

Nr of days maximum at 09UTC >=30degC:00

(Notes relating to temperature & allied observations:

see summary below)

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PRECIPITATION (PPN/mm)

Total rainfall/melted snow etc:... 47.0 [67% of eLTA of 70 mm]

Highest 24hr total:............... 15.7 (04)

No. days PPN total >= 0.2:11

No. days PPN total >= 1.0:08

No. days PPN total >=10.0:01

No. days PPN total >=25.0:00

(Notes relating to precipitation & allied observations:

[4th]: tl/r/R 2030-2130Z (see notes below);

[5th]: r/R 00-03Z; pr/r(slight) thereafter until at least 09Z, dying out by 0930Z; very light rain ~1330Z;

[9th]: pr(slight) 1815Z -> tlr(slight)/r 1828-1845Z;

[10th]: tl(slight),r(slight) 1910-1930Z; pr/R 2030-22Z;

[11th]: id(slight) off and on much of day & early evening;

[15th]: dr overnight, with ocnl r ~0530-0600Z, and again from 0820Z until early PM; then dr(slight) slowly dying out by mid-afternoon;

[15th/16th]: r/ocnl R overnight, clearing by 05Z;

[16th]: very light/scrappy rain showers;

[23rd]: r(slight), ocnl r 1030-1415Z;

[25th]: r(slight) ~0530-0730Z;

[27th]: r(slight)/r from early hours, ceased by 0530Z; pr(slight)/trough-line ~ 1430-1445Z;

[28th]: ir(slight) ~16Z to ~1730Z; periods r from ~1930Z to late evening;

[30th]: r(slight)/r/dr second half of night, csd by 0800Z; further idr(mainly slight) through day – csd by ~17Z; ocnl r evening, dying out by midnight;

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OTHER TOTALS

Number of days thunder heard: (dates).. 03 (04,09,10)

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 September, 2005

[4th]: slight-to-moderate tl 2030Z to 2130Z (thereafter, passing to N/NE as distant CC/IC event); moderate/heavy rain (high proportion of the latter) between 2045Z & 2130Z. Vast majority of lightning CC/IC, but a single local CG discharge close-by at height of storm, when the general discharge rate was around 1 every 5 to 8s.

[9th]: trace (measured) in gauge from overnight heavy dew/wet fog.

[9th]: slight thunderstorm (irregular / infrequent thunder/lightning) 1828-1845Z. Distant CC/IC lightning (infrequent) visible until well after 2030Z to north.

[10th]: tl(slight) 1745Z, with slight rain 1910-1930Z: thunderstorm/rain ceased here then, but lightning/very distant thunder evident well afterwards;

... 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 16.3 25.3 14.8 02.2 19.3 23.1 - - -

02 12.1 21.4 09.5 - 15.9 22.4 - -

03 14.1 21.5 12.8 - 18.0 25.3 - -

04 16.3 23.6 14.0 - 19.2 27.5 - 15.7

05 17.6 25.2 14.6 15.7 18.2 21.6 tr tr A

06 13.7 20.5 12.4 - 17.8 22.7 - -

07 12.3 21.7 10.3 - 17.2 24.5 - -

08 13.3 22.2 11.8 - 17.7 23.2 - tr B

09 12.0 21.3 10.4 tr(fw) 14.7 24.4 - 00.3

10 14.4 22.3 12.4 00.3 18.3 23.9 - 02.2

11 14.8 20.7 14.5 02.2 15.2 16.1 tr tr

12 13.9 15.9 13.3 tr 15.0 21.1 - -

13 12.2 20.0 09.6 - 17.0 22.0 - -

14 15.3 19.8 14.4 - 17.9 24.1 - 05.4

15 14.7 22.1 13.1 05.4 17.8 20.9 01.6 06.7

16 10.5 18.9 09.0 05.1 11.6 15.3 tr tr

17 03.5 12.5 01.9 - 09.2 15.6 - -

18 06.7 13.9 ---- - 12.3 16.8 - - C D

19 13.8 15.6 13.2 - 14.4 17.4 - -

20 10.0 15.8 07.7 - 15.1 21.1 tr -

21 13.7 19.3 10.6 - 15.6 20.5 - -

22 08.9 18.6 07.1 - 13.9 20.3 - -

23 12.5 18.5 09.8 - 15.4 17.6 02.1 02.1

24 05.0 15.7 03.3 tr(w) 09.7 17.2 - 00.2 E F

25 12.2 15.3 10.2 00.2 15.3 19.5 - - G

26 09.3 17.2 07.5 - 13.0 17.5 tr 03.9

27 13.3 16.8 12.4 03.9 14.5 18.9 tr tr

28 07.5 15.0 05.8 - 10.9 15.2 tr 07.0

29 07.5 12.9 05.6 07.0 10.5 15.1 - 02.8 H

30 11.3 16.3 09.4 02.8 16.3 19.5 00.2 00.7 I

Remarks:

A. grass min.(14.6) looks too low for some reason

B. trace of (measured) PPN at 09Z from heavy dewfall/wet fog

C. index stuck on grass min. 18th

D. day min.(12.3)/also 24hr min. 19th, occurred 18/09Z

E. tr of PPN from heavy overnight dewfall at 24/09Z

F. day min.(9.7)/also 24hr min. 25th, occurred 24/09Z

G. night max.(15.3) occurred 25/09Z

H. day min.(10.5)/also 24hr min. 30th, occurred 29/09Z

I. night max.(16.3)/also 24hr max. 29th, occurred 30/09Z

Number of occasions (24hr periods) THIS YEAR (2005)

maximum temperature >= 21degC (70degF) = 74

minimum temperature >= 16degC (61degF) = 11

[ notes re: September as a whole ]

[TEMPERATURE]

Using a composite Easthampstead Park / Tawfield series (1971-2005), this September just gone was the *second* warmest (using the 24hr max/min values) in those 35yr with the overall anomaly of +1.9degC. The warmest in that period was 1999 (+2.5degC).

In those 35 years, there have been 7 years with an anomaly >= +1.0degC, and all of them have occurred in the period from 1989 onwards (1989, 1991, 1998, 1999, 2000, 2004 & 2005).

Using the mean maximum (24hr) value ONLY, with an anomaly of +2.7degC, this places it equal 'top' in the list (with 2003), but that year, the overnight minima were *below* average, thanks to some cold nights during the last week. This September, the 24hr minimum anomaly was +1.0, with very few really chilly nights – hence the influx of Crane Flies and large house spiders!

[RAINFALL]

Of the 47.0mm of rainfall this month, the overwhelming bulk of same occurred in the period 18Z to 09Z (42.6mm 'overnight' plays 4.4mm during the 'day'): As well as being a 'dry' month overall ( 67% of eLTA 1971-2000 ), the bias to night-time rainfall emphasised the perception of a dry month. A third of the monthly total was produced in the period 04/2030 – 05/0300Z.

Martin.