Summary for March 2006

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

HEADLINE: COLD OVERALL BUT MILD END. WET SECOND & LAST WEEKS: OFTEN WINDY

(last updated: 01/0900 APRIL)

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):... 14.6(31)

Highest 24hr maximum (date):.. 14.6(31)

Lowest night minimum (date):... –05.2(04)

Lowest 24hr minimum (date):... –05.2(04)

Lowest overnight grass minimum (date):... –06.8(04)

[ number of days grass minimum < 0degC: ... 12 ]

[ Lowest day maximum (date):... 03.2(16)]

[ Highest night minimum (date):... 10.8(27)]

A. Mean Day (09-18Z) maximum: ... 08.4

A. Mean Night (18-09Z) minimum: ... 02.6

A. Mean of Day Max & Night min: ... 05.5

B. Mean 24hr maximum:... 08.6 [-1.3 anomaly on eLTA of 9.9degC]

B. Mean 24hr minimum:... 02.4 [-1.0 anomaly on eLTA of 3.4degC]

B. Mean of 24hr max & min:... 05.5 [-1.2 anomaly on eLTA of 6.7degC]

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

Nr of days minimum at 09UTC <0.0degC:10[dates: 01-06,12-13,22-23]

Nr of days maximum at 09UTC >=21degC:00

Nr of days maximum at 09UTC >=25degC:00

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

(Notes relating to temperature & allied observations:

none, but see notes at end re: cold Marches etc.)

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PRECIPITATION (PPN/mm)

Total rainfall/melted snow etc:... 56.1 [108% of eLTA of 52mm]

Highest 24hr total:............... 09.3(07)

No. days PPN total >= 0.2:15

No. days PPN total >= 1.0:11

No. days PPN total >=10.0:00

No. days PPN total >=25.0:00

(Notes relating to precipitation & allied observations:

2nd: phs(slight snow pellets) ~mid-afternoon;

3rd: ps(very slight/few flakes) ~1340Z;

5th: ps(slight – no appreciable cover)): ps(very slight) ~16Z;

6th: ir(very slight) ~18Z; r(slight), ocnl r 18-20Z;

7th: r(slight)/(r) from ~06Z until mid-afternoon, then ocnl d/r (slight) through evening & night 7th/8th;

8th: r/d(slight/moderate), off/on through day, ocnl R short periods afternoon; further periods rain evening/early hours 9th;

9th: rain, ocnl moderate, late-morning to early afternoon; pr(R) / tl(slight)r/R(short period small hail & squall) between 1508 & 1530Z, then slight rain, csd by 1540;

10th: ir(very slight/few spots) ~0830Z; ocnl r/pr(all light) afternoon / early evening;

11th: a couple of very light pr afternoon – no impact;

14th: sporadic rh(slight rain/ice pellets mixed) from ~06Z, with moderate fall ~0914/0916Z, then sporadic r(slight)/r until early evening;

16th: idr(very light) late AM onwards, but persistent after ~17Z & through early evening;

17th: sh(snow grains) from ~08Z, ocnl moderate until just after 09Z, then id(very slight) until midday;

18th: phs(very light shower snow pellets)~0830-0845Z;

24th: r(slight)/r from early hours to ~08Z; id(very light) 09-11Z; pr(slight) ~14Z;

24th/25th: r(slight)/r (isol R) mid/late evening, csd by ~2330Z; ir(slight) early hours;

25th: r(slight) ~15Z, soon ocnl r, bec. ir(slight) by 1730Z – further mainly light r early part of night 25th/26th;

26th: ir(very light) 10-12Z, r(slight), ocnl r 12Z-18Z;

26th/27th: ocnl r(R) through night;

27th: ir/d(slight, ocnl moderate) through day until ~15Z;

27th/28th: pr(mainly light) evening & early night;

28th: pr(slight)/r PM, with single-rumble ts(slight) 1330Z AFTER heavy shower cell had passed to east;

28th/29th: pr(slight)/pr evening & overnight;

29th/30th: r, ocnl R evening & early night, ceased by ~02Z;

30th: pr(slight) PM;

30th/31st: pr(slight, ocnl moderate) earlier in night;

31st: pr(slight) from late AM;

31st/1st(April): ocnl r(slight)/r overnight: pr(R) 0630-0700Z (to March total);

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OTHER TOTALS

Number of days thunder heard: (dates).. 02 (09,28)

Number of days hail < 0.5cm diameter:.. 02

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

Number of days snow/rain & snow:....... 05

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 March, 2006

[optical]

22nd: strong LH parhelion/22deg ~08Z in patch of dense Cirrus/COTRA

[thunder]

9th: slight thunderstorm (two claps of thunder only) ~1510Z, accompanied by heavy rain / small hail & short-lived squall;

28th: slight thunderstorm (single rumble thunder only) ~1330Z, after cell had passed us and was to our east;

[snow]

2nd: phs(slight snow pellets) ~mid-afternoon;

3rd: ps(very slight/few flakes) ~1340Z;

5th: ps(slight – no appreciable cover); ps(very slight) ~16Z;

17th: sh(snow grains) from ~08Z, ocnl moderate until just after 09Z;

18th: phs(very light shower snow pellets)~0830-0845Z;

... 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 -02.7 00.6 -04.2 tr -00.8 04.6 - - -

02 -03.9 01.5 -05.0 - -01.5 04.8 tr tr

03 -02.1 02.0 -04.3 - -00.9 04.5 tr tr

04 -05.2 02.2 -06.8 - -01.9 04.3 - tr

05 –02.2 02.0 -05.7 tr 02.0 06.8 tr tr A

06 -00.5 05.6 -03.7 - 02.8 08.0 tr 01.3

07 01.2 07.1 -01.0 01.3 04.0 05.0 08.2 09.3 B

08 04.8 10.2 04.3 01.1 10.2 12.4 06.3 07.2 C

09 07.2 10.5 06.0 00.9 06.3 10.3 07.9 07.9

10 03.2 07.9 02.4 tr 06.2 08.9 tr tr

11 03.5 06.3 01.7 tr 03.8 05.4 tr tr

12 -01.2 04.3 -02.7 - 00.5 05.0 - -

13 -00.5 02.7 -01.8 - 01.2 05.0 - 00.2

14 00.7 03.5 -00.8 00.2 03.5 07.6 00.5 00.6

15 03.5 06.4 02.8 00.1 04.5 09.2 - -

16 00.7 07.1 00.0 - 01.7 03.2 tr tr

17 01.1 02.2 00.9 tr 01.4 05.5 tr tr

18 01.1 03.7 01.0 tr 02.3 06.8 - -

19 01.4 04.5 01.1 - 03.2 09.8 - -

20 02.0 07.4 00.4 - 04.6 06.1 - -

21 02.4 04.6 01.9 - 03.7 05.1 - -

22 -00.9 04.1 -02.9 - 03.0 06.9 - -

23 -01.5 05.1 -03.1 - 02.7 09.9 - 03.2 D

24 05.5 08.5 04.7 03.2 08.5 13.2 tr 04.2 EF

25 08.8 11.9 07.5 04.2 09.9 12.5 01.1 01.6 G

26 10.6 11.6 09.4 00.5 11.6 14.0 02.3 04.6 H

27 10.8 13.7 10.0 02.3 10.7 12.3 00.4 00.6

28 07.0 11.3 05.6 00.2 08.6 12.3 02.5 05.1

29 06.4 09.4 05.0 02.6 08.8 13.1 tr 07.0

30 08.5 11.8 07.9 07.0 11.7 13.9 tr 00.5

31 09.8 11.7 08.0 00.5 11.4 14.6 tr 02.8

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.(2.0), also 24hr max. 4th, occurred 05/09Z

B. day min.(4.0), also 24hr min. 8th, occurred 07/09Z

C. night max.(10.2), also 24hr max. 7th, occurred 08/09Z after air mass change

D. day min.(2.7), also 24hr min. 24th, occurred 23/09Z

E. night max.(8.5) occurred 09Z .. air mass change after lengthy cold spell

F. day min.(8.5), also 24hr min. 25th, occurred 24/09Z

G. day min.(9.9), also 24hr min. 26th, occurred 25/09Z

H. night max.(11.8) occurred 30/09Z

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

maximum temperature >= 21degC (70degF) = 00

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

Rolling 12 month temperature anomaly: +0.4 (was +0.6 end last month)

Rolling 12 month rainfall anomaly: 88% (was 86% end last month)

Rolling 24 month rainfall anomaly: 87% (was 86% end last month)

[ A note re: cold Marches ]

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

Using a composite Easthampstead (aka Beaufort) Park & Tawfield record:

1971-2005

Cold March months (by anomaly c.f. 1971-2000 LTA)

1987 -2.2

1996 -2.0

1985 &

1971 -1.9

1980 -1.8

1984 &

1976 -1.7

1975 -1.5

These 35 years can be broadly split between:

1970's to mid 1980's: cold such-named months were frequent, culminating in the series low of –2.2 in 1987;

1988 onwards: marked reversal, with a string of notably mild Marches, spoilt only by the second-coldest in the series (-2.0) in 1996.

This month (-1.2) we were the coldest March since 1996 (-2.0); however, up until the end of the third week of the month, the anomaly was running at around –3degC, and if this had continued, the month would have been the coldest in this series – the much higher temperatures from the 24th, particularly overnight, 'corrected' this sharply. Perhaps of more significance is that is has made a significant dent in the 12 month running anomaly – down to +0.4, from values of +0.8 or higher up to the end of 2005.

[ A note re: winter-half (October to March) rainfall ]

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Based on a composite Easthampstead Park / Tawfield record (since 1971)

2005/06 (current) = 341.2mm / 91%

2004/05 = 312.5mm / 84%

Although we have had two successive drier-than-average such periods (but only just in the case of the current one), in the previous 7 such periods at this site, 6 achieved average or above-average rainfall, including the series wettest (702mm / 193%) season 2000/01.

The driest winter-half periods in this series (1971/72 to 2004/05)

(by anomaly)

1975/76: 45%

1991/92: 52%

1972/73: 55%

1988/89: 69%

so we were a long way away from entering that illustrious list.

Looking at dry *consecutive* winter-half periods over the same record gives:

(by anomaly)

1990/91 & 1991/92: 475.3mm / 65%

1991/92 & 1992/93: 515.0mm / 71%

1972/73 & 1973/74: 527.8mm / 73%

1971/72 & 1972/73: 536.0mm / 74%

again, even pairing up dry winter-half periods, this one (653.7mm / 88%) does not come close to these previously dry episodes.

Moreover, despite all the 'angst' surrounding supposed declining winter-time rainfall, in this area, the *reverse* is happening, at least over this 35 year period as follows:

10 year average 1971/72 – 1980/81 = 344mm

10 year average 1981/82 – 1990/91 = 353mm (+2.6% on previous)

10 year average 1991/92 – 2000/01 = 393mm (+11.3% on previous)

and 10 years ending 2005/06 = 405mm

The trend for 'winter-half' rainfall for this area of SE England is 'up'; unfortunately, the trend-line for water use is also upward, at a much steeper rate!

Martin.