Summary for May, 2006

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

HEADLINE: CHILLY START, SOON WARMER; UNSETTLED, COOL, WET AFTER MID-MONTH

(last updated: 04/1800 JUNE)

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; )

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

TEMPERATURES ETC.

Highest day maximum (date):... 26.6(04)

Highest 24hr maximum (date):.. 26.6(04)

Lowest night minimum (date):... 04.2(02)

Lowest 24hr minimum (date):... 04.2(02)

Lowest overnight grass minimum (date):... 02.1(02)

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

[ Lowest day maximum (date):... 14.1(23)]

[ Highest night minimum (date):... 13.7(27)]

A. Mean Day (09-18Z) maximum: ... 17.8

A. Mean Night (18-09Z) minimum: ... 09.3

A. Mean of Day Max & Night min: ... 13.5

B. Mean 24hr maximum:... 17.8 [+0.5]

B. Mean 24hr minimum:... 09.2 [+1.7]

B. Mean of 24hr max & min:... 13.5 [+1.1 anomaly on eLTA of 12.4degC]

(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:05

Nr of days maximum at 09UTC >=25degC:01

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

(Notes relating to temperature & allied observations:

4th: Day maximum (also 24hr maximum): 26.6degC; this is the highest such value for the first 10 days of May in our short / 7 year record, and the earliest date to equal / exceed 25degC in that same period.)

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

PRECIPITATION (PPN/mm)

Total rainfall/melted snow etc:... 89.1 [154% of eLTA of 58mm]

Highest 24hr total:............... 14.5(19)

No. days PPN total >= 0.2:16

No. days PPN total >= 1.0:15

No. days PPN total >=10.0:04

No. days PPN total >=25.0:00

(Notes relating to precipitation & allied observations:

1st: (r/R overnight – see April summary): pr(few drops) ~0915Z;

5th: r(slight) for a short time ~0100Z (fragmenting cold-front);

6th: pr/r 1100-1230Z [ estimated/away in Poole ];

6th/7th: r(slight)/r for a time overnight;

8th: r(slight) 0450Z, soon r/R, with tl(slight/discharge every 5 to 8 mins), between 0510 & 0545Z: at 09Z ob, rain had been steady moderate, isol R since 0545Z, then r>r(slight) ~ 0840Z, csd by ~1015Z;

9th: ir(few droplets) ~09Z;

10th: r(slight) for a short time early hours;

15th: ir(slight) from ~0655Z, becoming persistent by 0830Z, with a short-period moderate, before ceasing by 1050Z. Then, ir(slight) until early afternoon, and pr(slight) late afternoon;

16th: r(slight), with short-periods r, between 1350 & 1740Z;

17th: r(slight), ocnl r, from ~1130Z, becoming r/R for about an hour early evening, then r -> r(slight), then ceased by late evening;

18th: dr(slight/moderate) 0820Z – 0840Z; frequent pr(slight/isol moderate) AM, then isol. pr(slight) PM, with lengthy dry periods: no collection in gauge; pr(slight) early evening;

18th/19th: r/pr(slight, isol moderate) overnight;

19th: further pr/r(slight) through day, but lengthy dry spells;

19th/20th: r/R for lengthy periods evening 19th to early hours 20th;

20th: pr(slight) ~08Z; further pr(slight/isol moderate) AM;

21st: r(slight) from ~0840Z, bec r(slight)/r (isol R) until 1420Z. r(R) 1525-1550Z. pr(slight) ~ 1710Z. pr 1815-1830Z;

22nd: r/R early hours. Further ocnl r after 0400Z until early afternoon, then ir/d(slight) afternoon;

22nd/23rd: r(slight)/r through evening 22nd until early hours 23rd;

23rd: pr(slight/moderate) through day but also dry/sunny spells; pr 1800-1815Z;

23rd/24th: pr(slight/moderate) early hours;

24th: further pr (slight/moderate) period 07 -> early afternoon; r(slight) began ~1705Z, bec r ~1740Z, then r(R) until around midnight 24th/25th;

25th: ir/d(slight) 0630Z – 0830Z;

26th: r(slight)/r from ~04Z, with short period r/R 0630Z-0700Z, bec d/r (slight) by 0930Z, csd ~1045Z;

27th: id/r (very light) ~08/0830Z: r/d(slight), ocnl r/dr, between 1140 & 1620Z;

29th: ir(slight)/r [ex medium-level instability] 04-05Z; pr/R 0815-0840Z;

pr/R [with phr/R] 0940-0954Z, small hail only, and low proportion of total fall; further pr(slight, ocnl moderate) remainder of day until ~1630Z; pr(slight) early evening;

30th: pr(very light) from late morning to mid-afternoon;)

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

OTHER TOTALS

Number of days thunder heard: (dates).. 03 (08,10,13)

Number of days hail < 0.5cm diameter:.. 01

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

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

Additional comments on the weather in May, 2006

8th: r/R = 14.3mm (~0500 to ~0840Z) is probably our wettest few hours since 1st December, 2005.

9th/10th: atmosphere very hazy – elevated haze on 10th at 0900Z ensured sky had a very milky look; on a scale 0 (very white) to 5 (deeply blue), estimate sky-colour around 1 or 2.

26th: Possible Noctilucent cloud (NLC) seen around 0130/0200Z.

29th: phr/HR 0940-0954Z, small hail only (dia.<5mm), and low proportion of total fall – hail melted rapidly on hitting ground.

[thunder]

8th: tl(slight / discharge every 5 to 8 mins), between 0510 & 0545Z, associated with trough / moderate or heavy rain, moving very slowly north. CG discharges visible for a time, but mainly CC/IC activity.

10th: tl(slight) 1525Z – 1730Z (when decaying cells seen retreating to west), with tl(moderate discharge rate/1 per 45s to 60s), between 1640-1645Z. Main discharge frequency (CC/IC) circa 1 per 2 or 3 mins; no CG seen here, but then main activity was always well to the north of us, running in an arc from E/ENE, through N to W/WNW. The individual cells developed and decayed quickly.

13th: tl(slight/distant) 0120Z – 0140Z, probably from passing storm complex & mainly mid-level activity; max discharge rate ~1 per 3 to 5 mins: no PPN.

[snow]

NIL.

... 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 08.3 11.4 08.0 11.9 11.4 14.7 tr tr AB

02 04.2 13.4 02.1 - 12.4 15.2 - -

03 08.0 13.9 05.6 - 13.9 20.7 - - C

04 12.4 19.1 09.7 - 19.1 26.6 - tr

05 10.3 22.5 08.1 tr 15.3 21.1 - -

06 05.3 18.7 03.5 - (11.7)(16.5)(02.1) 02.7 D

07 10.6 13.1 10.4 00.6 13.1 17.7 - 14.3

08 11.2 16.3 10.5 14.3 11.9 15.8 tr tr

09 08.6 14.2 07.6 tr 11.8 18.6 tr tr

10 09.7 17.3 09.0 tr 12.8 22.5 - -

11 07.4 18.2 05.5 - 16.3 23.6 - -

12 08.1 21.9 05.7 - 18.3 24.4 - -

13 10.6 21.7 09.1 - 13.4 18.0 - -

14 10.9 16.8 10.7 - 13.5 16.9 - tr

15 09.8 15.5 09.3 tr 13.8 17.1 01.1 01.1

16 11.1 15.1 09.1 - 13.6 17.3 01.7 01.7

17 10.3 14.4 09.1 - 14.0 17.2 01.0 06.9 E

18 11.3 14.6 10.5 05.9 13.8 17.9 tr 01.3

19 11.0 14.9 10.4 01.3 12.3 16.8 tr 14.5

20 10.2 12.7 08.9 14.5 11.2 15.5 00.6 00.6

21 10.7 14.6 10.2 tr 11.7 14.5 06.3 10.9

22 09.8 13.8 08.4 04.6 11.3 15.2 02.1 06.9

23 05.6 12.2 04.6 04.8 09.3 14.1 02.6 04.3

24 08.5 12.3 07.4 01.7 11.2 15.1 01.0 12.1 F

25 09.0 12.1 08.6 11.1 12.1 19.6 - 03.1 G

26 12.9 17.7 12.0 03.1 14.4 19.4 tr tr

27 13.7 17.2 13.2 tr 14.8 16.4 02.8 02.8

28 09.3 15.7 08.1 - 14.4 17.7 - 02.3

29 09.3 16.3 08.0 02.3 08.7 15.1 03.5 03.6

30 04.9 12.1 03.3 00.1 11.0 14.9 tr tr H

31 04.7 12.7 02.4 - 11.6 16.6 - -

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 max.(11.4) occurred 01/09Z

B. NB: 24hr min for 1st May (6.7) occurred 30th April/09Z

C. night max.(13.9) occurred 03/09Z

D. (in Poole – returning evening/ observation at 1940Z .. probably made little difference to figures compared to 'normal' observation time of 18Z)

E. night max.(14.4) occurred 17/09Z

F. night max.(12.3) occurred 24/09Z

G. night max., day min & 24hr min 26th (12.1) occurred 25/09Z

H. night max.(12.1) occurred 30/09Z

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

maximum temperature >= 21degC (70degF) = 05

minimum temperature >= 16degC (61degF) = 00

Rolling 12 month temperature anomaly: +0.5 (was +0.4 end last month)

Rolling 12 month rainfall anomaly: 95% (was 85% end last month)

Rolling 24 month rainfall anomaly: 86% (was 83% end last month)

------------------------------------------------------------

Total rainfall for this year (2006) so far: 265 mm, representing 97% of the 'average' that we should have by the end of May.

------------------------------------------------------------

[Rainfall]

Although it has been a wet month, given the final total (89 mm), in the last 35 years, there have been 5 wetter Mays. It is the wettest May since 2000 hereabouts, when 129.0mm was recorded, of which 48.3mm was due largely to the 'Bracknell Storm'. I record rainfall in two segments: 09-18Z & 18-09Z; this month, the 'weight' of rainfall was heavily biased to the 'night-time' segment (64.3mm/18-09 plays 24.8mm/09-18).

It is the wettest *any* named month since October 2004 (124.8 mm).

[TEMPERATURE]

Monthly +ve anomaly heavily biased to the 24hr minimum element. Minima were never particularly low, even over the final days of the month, and we have not recorded an air or ground frost. Looking at a composite local record (since 1971), the overall mean *minimum* figure was the highest since 2000, the years 1998, 1999 & 2000 having the warmest, and equal second-warmest mean night minima in that record.

More importantly for the perception of this month, after a promising start during the first-half when temperatures rose to 26.6degC on the 4th, the second half of the month failed to live up to this promise with 20degC being approached (but not reached/exceeded) on only a couple of days. It is this fact, plus the cloudy, damp weather that prevailed, that brought spring abruptly to a halt [insects, some plants etc.], at least in this part of the country. (see details under temperature above.)

------------------------------------------------------------

Spring summary:

meanTn(anom) meanTx(anom) mean24h(anom) totRain(anom)

Mar: 02.4 (-1.0) 08.6 (-1.3) 05.5 (-1.2) 56.1 (108%)

Apr: 05.6 (+0.9) 13.4 (+0.5) 09.5 (+0.7) 40.8 (78%)

May: 09.2 (+1.7)(17.8) (+0.5)(13.5) (+1.1) 89.1 (153%)

Season: (+0.5) (-0.1) (+0.2) 186.0 (115%)

> Relative 'warmth' of season overall shows up primarily in the minima not being too low;