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MONTHLY WEATHER REPORT

APRIL 1999

TEXT-ONLY VERSION


Hard copy versions of this report, including graphics, can be obtained from the weather
station at the following address:

Pitsford Hall weather station
Pitsford Hall
Moulton Lane
Pitsford
Northampton NN6 9AX

Enclosing a stamped address A4 envelope.

The full register can be downloaded separately to this report from this web site. If you
encounter any problems in downloading data or viewing the files, please contact the
station via the answerphone on 07967 438314. 

For official purposes, data entries should always be double checked with the station
office.
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Pitsford Hall Weather Station

Office:

Pitsford Hall
Northamptonshire Grammar School
Pitsford
Northampton
NN6 9AX

Tel. 01604 880306
Fax. 01604 882212
E-mail weather@brixworth.demon.co.uk
Web site http://www.brixworth.demon.co.uk/weather



Registered member of the Climatological Observers Link
Station grading: A

Climatological Station No: 91012

Station Manager: M J Lewis, BSc(Hons), FRGS

Observers:

Christopher Cockrell
Simon Fleming
Benjamin Goodyear
Alexander Jackman
Andrew Sunderland

Honorary Foundation Observers:

Paul Dickens
William Keggin
Martin Sheehy
Andrew Stanton

Technician:  Mrs S West
Groundsman: Mr R Marshall



 
Statistical Analysis of Air Observations - April 1999
Temperatures:
Mean Max: 14.5C
Mean Min: 5.3C
Mean Temp: 9.9C (mean comparison: +2.0C)
Highest Max: 19.0C on 9th
Lowest Max: 10.1C on 6th 
Highest Min: 7.6C on 13th
Lowest Min: -2.1C on 14th

Relative Humidity:
Humidities observed at 0830hrs:
Max: 97% on 20th
Min: 73% on 8th
Mean: 86.2%
All Humidities (hygrograph record):
Max:98% on 16th and 17th
Min:30% on 21st

Rainfall:
Total for Month: 68.4mm (mean comparison: 69.7%)
Max: 12.2mm on 26th
Rain Days: 18
Wet Days: 11
Duration: 50.0hours

Rainfall acidity: 
Lowest pH: 5.70 on 17th
Mean pH:6.25 

Winds:
Max Max Gust: 57mph on 13th
Mean wind speed at observation: 7.1mph
Mean 24 hour wind speed: 6.3mph
Directions: north 3, northeast 5, east 2, southeast 5, south 0, southwest 5, west 2, northwest 8, calm 0, variable 0 

Pressures:
Max: 1026mb on 28th
Min: 992mb on 12th and 20th
Mean: 1011.5mb

Sunshine:
Total: 154.8 hours
Most in a day: 11.1 hours on 27th
No of sunless days: 1

Cloud Cover:
Mean cloud cover at observation: 75%

Other observations:
Days with fog recorded at 0830 hours: 3
Mean visibility: 6 (moderate, up to 7km)
Days with air frosts: 1
Duration of air frost: 2 hours on 14th


Days with snow falling: 1; 13th: slight.
Days with snow lying at observation: 0
Days with hail observed: 4
Days with thunder heard: 1 
Days with lightning observed: 1
Gales: 3


Note: The climatic averages (temperature and rainfall) at Pitsford Hall are based on the averages of a number of adjacent climatalogical stations over the period 1961-90.









United Kingdom Climatological Analysis - April 1999


Small cloud amounts over much of England and Wales led to a ground frost in places there by dawn on the 1st. Cloudy overnight conditions in Scotland and Ireland persisted for much of the day. This cloud pushed into wales and much of W England during the day, but the E had sunny spells. A SE breeze resulted in a cool day in some E coast districts, although it was warm in S England away from the coast. (Northolt 21C, Tynemouth 9C max, Farnborough 3C min, Stornoway 6mm, Clacton 11.4h.) 

On the 2nd patchy bands of rain moved from the SW to NE across Ireland, Wales and England, becoming weaker as they moved N. In the Gloucester area there was a spectacular display of lightning around 0300 GMT from a line of thunderstorms that developed along a cold front. Cloud in Scotland cleared overnight to give a light frost in places by dawn, followed by warm conditions during the day except along the E coast where a cool sea kept temperatures low again. Away from the rain, England and Wales remained mainly cloudy. (Lusa 20C, Aboyne -1C, Prestatyn 14mm, Cromer 9.9h.) 

There were fog patches by dawn on the 3rd in parts of S Scotland, N England, the Midlands and Cent S England with visibility down to 100m in places. Fog persisted in places nearly all day along the NE coast of England. During the day much of S England was cloudy with light rain and drizzle, while in N England and Scotland light rain gradually died out. (Leeds 19C, Tynemouth 7C max, Altnaharra -3C, Jersey 7mm, Lerwick 9.2h.) 

The 4th was a cloudy day in most parts of the British Isles. Clearing skies overnight led to fairly widespread fog patches in Scotland and N England by dawn. Further bands of light rain and drizzle spread across much of the British Isles from the SW during the day. (Cleethorpes 19C, Aboyne 0C, Capel Curig 9mm, Cleethorpes, Lerwick and Scarborough 7.3h.) 

The 5th saw a continuation of the recent mild, cloudy conditions over the British Isles with fronts and troughs bringing rain and drizzle to most areas. There was mist and fog in places around dawn, notably in SW Wales where visibility fell to 100m in places. (Chivenor 18C, Lerwick 6C, Lusa 15mm, Jersey 5.5h.) 

There was rain (some heavy) overnight in Scotland, and light rain in S England the Midlands by dawn on the 6th. During the daytime it remained mainly cloudy across the British Isles with the two rain areas gradually clearing as the wind veered round to a W direction everywhere. (Herne Bay 19C, Aviemore 6C, Eskdalemuir 29mm, Leeds 8.0h.) 

Pressure rose slowly during the 7th as a weak ridge became established over the British Isles. There were rain showers over Scotland and light rain and drizzle over Ireland. England and Wales were mainly cloudy but dry, with sunny intervals. (Boulmer 15C, Redesdale 4C, Loch Glascarnoch 9mm, Newcastle 9.0h.) 

Skies cleared over parts of England and Wales overnight by dawn on the 8th leading to a touch of ground frost in places, although Scotland remained cloudy with light rain falling from a warm front. Light rain and drizzle that affected Ireland overnight moved E and many areas of England and Wales received some light precipitation during the day. (Aberdeen 20.2C, Benson 0C, Lowestoft 4mm, Folkestone 10.3h.) 

A weak ridge of high pressure over the British Isles on the 9th resulted in a mainly dry day. The exception to this was Scotland, where there was light rain in the S overnight, and light rain and drizzle in places in the W and N by day. Ireland, Wales and England were mainly cloudy in the morning, but they became sunnier in the afternoon. (Great Malvern 20C, Fylingdales 7C, Stornoway 4mm, Shrewsbury 7.5h.) 

A cold front brought a period of mainly light rain to most places across the British Isles on the 10th as it moved E, preced by thickening cloud and followed by clearer skies and showers in W districts. Fresh to strong winds over Scotland and Ireland were accompanied by gusts to 40 kn. (Skegness 16C, Benson 6C, Sella Ness 6mm, Fishguard 10.5h.) 

Mainly clear skies overnight led to lower temperatures than of late by dawn on the 11th over much of the British Isles. However, thickening cloud over Scotland and Ireland was followed by rain by lunchtime in W districts there; the rain continued to move SE to affect most of England and by midnight. (Poole 16C, Altnaharra 1C, Tiree 11mm, Isle of Wight 12.0h.) 

The 12th was dominated by a showery NW airstream with embedded troughs, giving heavy showers of rain and hail, and occasional thunder, to most parts of the British Isles. The thunder was mainly restricted to N England (especially Yorkshire), the East Midlands and East Anglia, and SE England. There were gales in exposed areas in the W, and gusts to 50kn in S Ireland and SW England. At 1500 GMT there was a report of a funnel cloud near the Humber Bridge. (Herne Bay 15C, Lerwick 6C max, Wick 1C min, Capel Curig 59mm, Bognor Regis 9.9h.) 

The 13th did not feel like a spring day over most of the British Isles. A depression crossing from N of Ireland to East Anglia was accompanied by gales on its S flank, and snow and hail showers. In Fife snow made driving difficult during the morning rush-hour. These wintry showers (quite blustery with gusts to 50 kn in places) persisted after the passage of the low, and were felt over most parts of the British Isles - although in SW England and S Ireland precipitation was mostly of rain. In Chelmsford hail the size of marbles fell around 1050 GMT, while cricket at Durham was cancelled due to a snow-covered ground. Later in the evening, skies cleared everywhere. 
(Penzance 13C, Loch Glascarnoch 2C max, Lerwick -1C min, Buxton 13mm, Torquay 11.2h.) 

The 14th dawned with 6cm of lying snow at Dublin at 0600 GMT (which had mostly melted by 1300 GMT), and a widespread air frost following clear skies overnight. Morning cloud in SW England and S Wales was accompanied by heavy snow for a while in places and wintry showers were widespread during the rest of the day in W districts and over Ireland. Thunder was reported in NE England, although many E districts remained sunny for most of the day. At Weston Coyney (Staffs.) the minimum of -4.2C was the lowest in April since -4.2C on 11 April 1978. In one hour from 2230 GMT 3.5cm of snow fell in 1 hour at Bradninch (Devon), while at Wells (Somerset) snow fell from about 0700 GMT to 1400 GMT. A waterspout was observed from 1600 to 1605 GMT outside Rocquaine Bay (approx. 1 mile SW of Pleinmont Point) off Guernsey; it was moving S ahead of a heavy shower of soft hail. At Pentlow (Essex) a tornado lifted a dog out of its kennel and destroyed a few greenhouses. (Torquay 11C, Loch Glascarnoch 3C max, Redesdale -7C min, Altnaharra 19mm, Aberdeen 12.2h.) 

The 15th dawned with some roads closed in Wales (A4107, A965, M4) and Scotland (A93). 0600 GMT snowdepths included 2cm at Eskdalemuir, while on the Mendips snow lay approximately 10cm deep during the morning. Clear skies led to a widespread frost with minima including -4.2C at Buxton (Norfolk). Early rain and drizzle over Central and S Scotland and N England largely cleared by early afternoon, but scattered showers continued almost everywhere for most of the day. These showers were wintry (of snow or hail) as far S as Hampshire with reports of 5cm of snow on the Isle of Wight. A funnel cloud was observed near Jersey at around 0700 GMT. (Northolt 12C, Sella Ness 5C max, Aviemore 20mm, Penzance 11.7h.) 

Snowfall overnight led to blocked roads in Cumbria (A592 Kirkstone Pass) and West Yorkshire (M62, A6024) by dawn on the 16th, while in S England light winds allowed patchy, but thick, fog to form. By the afternoon there was a covering of 10-15 cm of snow on the top of Holme Moss (Yorks). Heavy thundery rain fell in Lincolnshire during the afternoon, and there was thunder in the Midlands. Northern England experienced rain or snow for much of the day from a persistent trough, while snow showers were fell over the higher ground in Scotland. Elsewhere, it was mainly dry but with scattered (often heavy) showers especially in SW Ireland, S Wales and SW England later in the day. (Poole 13C, Bingley 2C max, Tulloch Bridge -6C min, Waddington 28mm, Tiree 12.5h.) 

Clearing skies overnight led to a frost in places by dawn on the 17th; the exception to this was N England where a slow-moving trough continued to give some rain. In S England there were fog patches by dawn. This wet, cloudy area persisted all day, spreading to the Midlands, North Wales (for a while) and East Anglia. Many areas had a day with sunny spells (although some heavy, at times thundery, showers occurred in places) although low pressure over Scotland resulted in some light rain with snow on higher ground. Near Dunstable, a glider was hit and downed by reported ball lightning which flew out from cumulonimbus - the glider was under a clear sky at the time - the two pilots managed to bale out with only minor injuries. (Bognor Regis 14C, Buxton (Derbyshire) 5C max, Altnaharra -4C min, Coningsby 30mm, Aspatria 11.5h.) 

The 18th saw a continuation of the general weather pattern, with a slack pressure gradient and troughs, this time over W districts and in the E. Further rain in East Anglia overnight led to the flooding of the A134 by daybreak in the Bury St. Edmunds area, and along the A11 near Newmarket. After early fog patches, in S England and the Midlands, cloud soon developed in most areas and there were further heavy showers with snow, rain and hail. A thunderstorm with snow and heavy hail near Southend around 1800 GMT resulted in about 7 to 10cm of snow and ice on the A127 road, and several accidents. The best of the sunshine was over Ireland and in W districts after the clearance of early cloud. Following recent falls some small patches of snow were still visible on the hills to the W and NW of Newport and Cwmbran (above about 350m amsl) in S Wales. (Penzance 13C, Baltasound 5C max, Aboyne -4C min, Margate 21mm, Tiree 12.7h.) 

Skies cleared everywhere by dawn on the 19th (leading to a frost in places), except in East Anglia and Kent, and in parts of E Scotland where there was some light rain. Cloud soon developed in most places with the SE wind hearlding the approach of a frontal system from the 

SW. The system brought rain to SW England and S Ireland by midday, and the rain pushed into most of S Ireland, S Wales, Cent S England by midnight. There were showers of rain or snow of Cent and N Scotland, but the remainder of the British Isles was largely dry. (Colwyn Bay 13C, Castlederg -5C, Manston 21mm, Tiree 13.1h.) 

The rain continued to spread NE during the night and by dawn on the 20th covered all but N and Cent Scotland. By midnight the rain had reached Orkney, and was particularly heavy for a while in Cornwall and Devon. The rain was followed by blustery showers over Ireland in the SE airflow. Pressure fell to 969 mb by 2100 GMT, and gusts over 40kn were widespread in N Ireland and S Scotland; 58kn gusts were reported from Malin Head at 1200 GMT. (St Angelo (N Ireland) 14C, Altnaharra -3C, Dundrennan 40mm, Lerwick 11.8h.) 

The rain and showers diminished over England and Wales overnight with rainfall being largely confined to Scotland by dawn on the 21st. An advancing low resulted in still-falling pressure during the morning and early afternoon over most of the British Isles, with 968 mb being reported at Shannon at 0300 GMT. Further bands of blustery rain and showers affected the British Isles during the day with gusts to 40 kn being widespread as the wind gradually veered to the SW. The evening footbal match at Swansea City was postponed due to a waterlogged pitch. (Gravesend 16C, Loch Glascarnoch 3C, Capel Curig 32mm, Margate 9.6h.) 

Rain over Scotland continued to move N during the night, to be followed by showers over the British Isles on the 22nd. These showers were often heavy and blustery, with hail and thunder in places. Shortly before midnight, another area of rain began pushing into Cornwall from the S. According to a report in the Dublin Evening Herald, a tornado in Ballygawley (Co. Sligo) around 1410 GMT caused several thousands of pounds worth of damage with trees being uprooted and objects being carried for several hundred metres. (Great Malvern 16C, Spadeadam 6C, Shap Fell 24mm, Guernsey 10.8h.) 

A slow-moving area of heavy rain over SW England during the night moved into N England by the end of the 23rd, with falls being large in the SW. Wells reported 24.3mm of rainfall and there was local flooding of roads, eg. the A3102 in Wiltshire. There was a ground frost in some northern areas before dawn, but cloud and rain soon spread to W Scotland. It remained sunny, however, in between these two rain areas, with rain showers over Ireland. (Coltishall 16C, Aviemore 0C, Exmouth 27mm, Isle of Man 12.1h.) 

The 24th was a cloudy day over much of Scotland, S and E England and the Midlands. Rain in W Scotland largely cleared by midday, and overnight rain in NE England gave way to showers there; there were further showers in E districts of England (some heavy and with thunder, e.g. at Chedburgh). W England, Wales and Ireland had sunny spells. (London 17C, Aboyne 0C, Chedburgh 33mm, Tenby 11.8h.) 

Frontal rain pushed into S Ireland, SW England and S Wales by dawn on the 25th. This slow-moving area of, at times heavy, rain continued to push NE during the day, extending to SE England, the Midlands and Wales by the evening. Parts of East Anglia had a sunny day until the frontal cloud arrived, while it remained rather cloudy in Scotland. Mist and fog formed over parts of NE England and SE Scotland by midnight. (Aspatria 18C, Shap Fell 2C, Cardinham 50mm, Clacton 11.1h.) 


With an easterly wind off the North Sea, early morning fog on the 26th was dense in places in NE England and SE Scotland; although it cleared from most places, it did persist for most of the day in parts of NE England, resulting in some low maxima (e.g. 8C maximum at Loftus). Scotland and N Ireland has a mainly dry and sunny day, but rain over S Ireland, Wales, the Midlands and W England was slow to move, being heavy in places with thunderstorms reported. Later in the day rain and drizzle also fell in East Anglia. (Herstmonceux 19C, Loch Glascarnoch 2C, Barbourne 41mm, Stornoway 11.6h.) 


The 27th was much drier than in previous days, due to an anticyclone centred just W of Scotland; pressure rose to 1035.3 mb at 2100 GMT at Malin Head. Mist and fog over NE England and E Scotland persisted in places until about midday; most other areas were clear overnight, although early cloud in S England, the Midlands and Wales gradually disappeared during the day. Once early fog and cloud had gone, it was mainly dry and sunny in most places, and quite warm in parts of NW England and W Scotland (21.8C at Kyle of Sutherland and 21.5C at Windermere) where the E wind was light. A notable exception was the Outer Hebrides, where fog lingered all day in places, while cloud remained all day in the Northern Isles. At Cirencester, a heavy thunderstorm from 1529 GMT to 1552 GMT resulted in 11.7mm of rain, with half the carriageway of the ring road under water on the W side of the town. (Dalmally 22C, Tulloch Bridge 1C, Cirencester 12mm, Tiree 13.9h.) 

Most of the British Isles has a warm and sunny day on the 28th. The exceptions to this were N and central Scotland where there was extensive low cloud with some light rain, and some coastal areas of E and NE England where early morning cloud did not clear in the E wind and temperatures remained low. Later in the evening this low cloud started to push W over East Anglia and SE England. 22.6C was reported from Windermere (unofficial site) and 21C from Llanbedr (official site), while in Ireland 19.8C was measured at Cork. (Tynemouth 8C max, Leeming 2C min, Wick 2mm, Manchester 14.2h.) 

It was again largely warm and sunny over much S Ireland, Wales and the S half of England on the 29th once early morning low cloud and drizzle in E and Cent S England had dispersed, with 20.6C at Shannon. In N and W Scotland it was cloudy with some light rain, while N England, N Ireland and S Scotland had sunny spells with warm conditions in SE Scotland. (Charterhall (Borders) 22C, Eskdalemuir 3C, Kirkwall 4mm, Newquay 13.6h.) 

After a clear night with ground frost in places, Wales, S and central England had a warm and sunny day on the 30th away from the coasts where an E wind kept temperatures lower. There was some cloud over N areas and over much of Ireland; where this persisted all day, as well as along the E coast, temperatures remained low. The unofficial station at Bristol Totterdown reported a maximum of 23.1C. (Northolt 22C, Benson -0C, South Uist 2mm, Bognor Regis 13.9h.) 


Information supplied courtesy of Roger Brugge, Climatological Observers Link.

 
Notable Weather Events in Northamptonshire

The following report is taken from the weather station's web site

1 April 
Warmest day of the year so far. Daytime maximum 18.5C. Previous high was 17 March (18.2C). Also sunniest day of the year so far, 9.3 hours recorded.

20-23 April 
Heavy rains affect much of the county. Total on 20th: 9.6mm over 11 hours; total on 23rd: 10.5mm over 8.5 hours.

27 April 
Sunniest day of the year so far: 11.1 hours recorded.

30 April 
Warmest day of the year so far. Daytime maximum 21.3C. Previous highs: 18.5C on 1 April, 18.2C on 17 March.


Station Notes

Ground Enclosure
The weather station commissioned its new ground enclosure at the end of April. Work on the site had been delayed for several months owing to waterlogging. However, the site now provides the station with an accurate record of grass and concrete minimum temperatures, soil temperatures at 5cm, 10cm, 20cm and 30cm depths, and state of the ground observations (bare earth plot and concrete slab). The station anticipates introducing additional thermometers at 50cm and 100cm depth, and a Hook-type evaporimeter within the next few weeks. Once these instruments are in place, Pitsford Hall will become one of the very few school-based climatological stations in the United Kingdom with a complete inventory of Met Office approved instrumentation.

Ground observations are made at the same time as the main set of air observations at the rooftop enclosure at 0830 hours. The readings are then delivered to the statIon office for addition to the weather report released via e-mail, fax and world wide web at 0900 hours. 
The grass and concrete minimum thermometers are re-set at 0830 hours and remain in situ during the day. Both instruments are protected against condensation by means of blackened radiation shields. As part of the environmental project, Acid Rain 2000, soil acidity is also determined at six-monthly intervals (December and June). Adjacent to the enclosure a small area of mixed woodland is monitored for ecological change in response to acid rain and other atmospheric pollutants.

Both the underlying geology and soil of the ground enclosure are representative of the Northamptonshire Uplands. The rocks are Northamptonshire sands (Inferior Oolite) overlying clays (Middle Lias). The sands act as a natural aquifer above the impermeable clays resulting in soils which are badly drained and frequently waterlogged. A large number of springs mark the junction between the Lias clays and sands, and in Pitsford alone there are reckoned to be around 800. The heavy saturation of the soils results in a small diurnal temperature variation. This typically gives rise to persistent mists and patchy fog during the winter months and late ground frosts during the spring. The soil type is an acid brown earth.






Met Office Focus Group Meeting
Northamptonshire Grammar School's involvement in climatological education has been recognised by the Royal Meteorological Society and the UK Met Office. The station manager recently attended a focus group meeting at University College, Northampton on 28 April, aimed 
at advising the Met Office on ways of improving its provision of materials for meteorology education in schools. The minutes of the meeting will be presented to the Met Office by Malcolm Walker, education officer of the Royal Meteorological Society.  Top of the agenda was the potential of the world wide web in the dissemination of meteorological information. The work of Pitsford Hall weather station is this respect was commended. The weather station has recently applied for corporate membership of the Royal Meteorological Society.

Visitors from Finland
At the time of going to press, we can report that the weather station is currently hosting some visiting students from Finland. The school, Kyrkslatts Gymnasium, have become actively involved in the weather station's ecological project, Acid Rain 2000. The school has been anxious to establish its own weather station and monthly data from Finland provides an interesting comparative exercise for the students at Pitsford Hall. Weather data from Finland can be downloaded from the Acid Rain 2000 web site, http://www.brixworth.demon.co.uk/acidrain2000/.

Publication of Data
The weather station has also won a contract to provide bi-monthly climatological data for publication in a local community newspaper. The Brixworth Bugle is circulated to the villages of Brixworth, Lamport, Hanging Houghton, Pitsford and Scaldwell reaching approximately 5000 people. The station also supplies data for publication in Weather Front, the bulletin of the East Midlands Branch of the Royal Meteorological Society. This is in addition to the main publication of data which is via the bulletin of the Climatological Observers Link and the global climate summaries of the University of Reading Meteorological Department.







 
Appendix

Weather Station Inventory 

(including equipment in active use as of 30 April 1999)

Rooftop Enclosure and Office

Standard Stevenson screen containing
	Mahogany mounted maximum and minimum thermometers (Casella type)
	Wet and dry bulb hygrometer

Large pattern Stevenson screen containing
	Sheathed pattern maximum and minimum thermometers (UK Met Office with calibration
	certificates)
	Sheathed pattern wet and dry bulb thermometers (UK Met Office with calibration certificates)
	Thermograph (UK Met Office)
	Hair Hygrograph (UK Met Office)

Campbell-Stokes Sunshine Recorder (UK Met Office MKII)

Snowdon-type pattern raingauge (UK Met Office)

British Association pattern raingauge (for recording rainfall acidity)

Tilting syphon rainfall recorder (UK Met Office MKI)

Wind vane (UK Met Office)

Totalising Cup-Counter Anemometer (UK Met Office, mounted on 5m mast)

Digital wind direction system (Digitar, for determination of maximum gust)

Fortin-pattern mercury barometer (currently being serviced)

Open-scale micro-barograph (UK Met Office)

High resolution digital pH meter (Hanna)

Two PC's with modem links and dedicated fax/phone line


Ground Enclosure 

Soil thermometers (5cm, 10cm, 20cm, 30cm) (UK Met Office and Casella types)

Grass and concrete minimum thermometers (UK Met Office with calibration certificates)

Bare Earth Plot

Concrete Slab