************************************************************************************** MONTHLY WEATHER REPORT DECEMBER 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. ************************************************************************************** Pitsford Hall Weather Station Office: Pitsford Hall Northamptonshire Grammar School Pitsford Northampton NN6 9AX Tel. 01604 880306 (Ext 314) Fax. 01604 882212 Answerphone 07967 438314 (local forecast & readings) E-mail weather@brixworth.demon.co.uk Web site http://www.brixworth.demon.co.uk/weather Registered member of the Climatological Observers Link Corporate Member of the Royal Meteorological Society Station grading: A Climatological Station No: 91012 Station Manager: M J Lewis, BSc(Hons), FRGS Current Officers: Richard Carruthers Charlie Cockrell Michael Franklin Thomas Gutteridge Robert Illingworth Technician: Mrs S West Groundsman: Mr R Green Brief Climatological Summary December started generally mild until the 11th, despite several sharp ground frosts in the first week. However, a noticeably colder spell followed culminating in minima of -4.9C (2m) and -8.8C (grass) on the 20th. Temperatures recovered during the third week as very strong south-westerly winds, gusting to gale force on the 23rd and 24th, brought milder albeit very wet conditions over the Christmas period. The weeks of milder weather generally balanced the cold snap resulting in a mean temperature close to the norm. Rainfall was slightly higher than the norm (123.8%) with some notable falls of snow and sleet contributing much to the daily total on some days. Two spells of particularly wet weather ran from the 10th through to the 13th, and again from the 22nd to the 26th. On 6 occasions during the month surface water was observed in the morning, and the high degree of saturation of the Nene catchment led the Environment Agency to issue an amber alert for the river in the Northampton area on Christmas Eve. On several occasions, overnight rain fell onto frozen surfaces presenting hazardous driving conditions for rush hour traffic. Several accidents were reported on the 30th due to black ice. The absence of hoar frost on this occasion left many drivers unaware of the potential danger. High winds also featured this month. In addition to the strong winds over the Christmas period, gale force gusts resulted in several accidents in the county on the 3rd. Reports were received of a lorry careering out of control down an embankment on the A14 and of power losses and train delays on the Northampton line. Statistical Analysis of Air and Ground Observations - December 1999 Temperatures: Mean Max: 7.2C Mean Min: 1.4C Mean Temp: 4.3C (mean comparison: -0.1C) Highest Max: 12.4C on 24th Lowest Max: 0.9C on 19th Highest Min: 6.4C on 7th Lowest Min: -4.9C on 20th Relative Humidity: Humidities observed at 0830hrs: Max: 99% on 11th Min: 74% on 25th Mean: 87.5% Lowest RH (hygrograph record): 60% on 3rd Rainfall: Total for Month: 79.5mm (mean comparison: 123.8%) Max: 15.0mm on 10th Rain Days: 20 Wet Days: 14 Duration: 45.0 hours Rainfall acidity: Lowest pH: 5.41 on 13th Winds: Max Max Gust: 57mph on 24th Max wind speed at observation: 33mph on 3rd Mean wind speed at observation: 11.6mph Max mean 24 hour wind speed: 16mph on 13th, 25th Mean mean 24 hour wind speed: 8.8mph Directions: north 5, northeast 2, east 0, southeast 0, south 1, southwest 11, west 5, northwest 7, calm 0, variable 0 Pressures: Max: 1028mb on 20th Min: 978mb on 24th Mean: 1007.8mb Sunshine: Total: 34.6 hours Most in a day: 3.6 hours on 29th No of sunless days: 11 Cloud Cover: Mean cloud cover at observation: 62.5% (5.0 oktas) Ground Observations: Lowest Grass Min: -8.8C on 20th Highest Grass Min: 2.4C on 1st Lowest Concrete Min: -7.6C on 19th Highest Concrete Min: 4.4C on 1st Earth Temperatures: Bare Earth mean: 2.8C max: 9.4C on 3rd min: -1.9C on 20th 5cm mean: 2.1C max: 6.4C on 1st min: -0.8C on 20th 10cm mean: 3.0C max: 7.5C on 1st min: 0.1C on 30th 20cm mean: 3.9C max: 7.9C on 1st min: 1.4C on 21st 30cm mean: 4.4C max: 8.0C on 1st min: 2.0C on 21st,22nd 40cm mean: 4.9C max: 8.0C on 1st min: 2.7C on 22nd 50cm mean: 5.6C max: 8.2C on 2nd min: 3.6C on 22nd 100cm mean: 7.2C max: 9.1C on 3rd min: 5.7C on 31st Other observations: Days with fog recorded at 0830 hours: 1 Mean visibility: 7 (good, up to 20km) Days with air frosts: 8 Days with ground frosts: 22 Duration of air frost: 76.5 hrs Days with snow falling: 4 Days with snow lying at observation: 4 Days with hail observed: 0 Days with thunder heard: 0 Days with lightning observed: 0 Gales: 0 Evaporation (tank): Suspended until further notice. Register of Air and Ground Observations - December 1999 1st 2nd 3rd 4th 5th 6th 7th 8th Temperatures Air Max (C) 10.6 10.7 11.6 5.6 10.2 11.5 9 10.6 Air Min (C) 6.1 3.7 4 0.1 -0.6 0.2 6.4 3.1 Dry Bulb (C) 9 4.4 10 3.3 0.4 10.1 7.4 6.9 Wet Bulb (C) 7.6 3.4 8.7 1.9 0 9 6.7 5.9 RH (%) 81 84 83 76 92 86 90 85 Rainfall Total (mm) tr tr 2.5 0.9 _ 4.6 _ 3 Duration (hrs) _ _ 0.4 0.3 _ 2.4 _ 0.6 Acidity (pH) _ _ 6.46 6.41 _ 6.2 _ 6.52 Winds (mph) Direction nw nw sw nw nw w sw sw Speed (0830) 9 10 33 15 5 9 9 12 Speed (24 hrs) 9 11 11 9 8 9 9 15 Max Gust 32 44 53 38 30 30 27 38 Pressure (mb) At 0830hrs 1018 1023 1001 1010 1024 1013 1008 1004 From 0600hrs 1 2 -6 0 3 -0.5 -2 -5 Insolation Cloud types ac cs sc clear ac,sc ac sc ac Cloud cover 6 2 8 0 4 8 7 8 Sunshine (hrs) 1 2.3 0.2 3.1 2.6 0 0.3 0 Visibility 7 7 7 8 7 6 7 7 Other Ppt Snow/sleet falling _ _ _ 1 _ _ _ _ Depth of snow _ _ _ _ _ _ _ _ Hail (<5mm) _ _ _ _ _ _ _ _ Hail (>/=5mm) _ _ _ _ _ _ _ _ Other Obs Thunder heard _ _ _ _ _ _ _ _ Lightning seen _ _ _ _ _ _ _ _ Ground Obs Grass Min (C) 2.4 -1 -0.8 -4.3 -5.4 -3.6 2.1 -1 Concrete Min (C) 4.4 -0.7 -0.9 -3.2 -3.7 -3 3.4 0.5 Bare Earth (C) 5.3 1.5 9.4 1.5 -0.2 9 5.9 5.4 Soil Temps 5cm 6.4 2.2 6.1 1.1 0.5 5.6 5 2.5 10cm 7.5 4.5 6.5 3.1 2.5 5.4 6.1 4.2 20cm 7.9 5.1 6.7 4.4 3.5 5.4 6.5 4.6 30cm 8 6.6 7 5.5 4.5 5.4 6.8 5.4 40cm 8 7.1 7.1 6.5 5.5 5.6 6.9 6 50cm 8 8.2 7.5 6.9 6.6 6.4 7 6.7 100cm 8.4 9 9.1 9 8.8 8.8 8.2 8.1 Slab 1 1 1 0 0 1 1 1 Ground Without snow 1 1 1 4 4 1 1 1 With snow _ _ _ _ _ _ _ _ 9th 10th 11th 12th 13th 14th 15th 16th Temperatures Air Max (C) 7 10.1 10.1 6.4 3.4 1.9 2.7 10.1 Air Min (C) 3.4 3.1 3.2 5.6 1.2 -0.6 -0.6 0 Dry Bulb (C) 4 4 10 6.4 1.7 0 1.4 1.9 Wet Bulb (C) 2.9 3.2 9.9 5.5 1 -0.1 0.7 1.7 RH (%) 81 87 99 86 87 98 87 96 Rainfall Total (mm) tr 15 8.5 3.2 8.6 0.3 tr 0.8 Duration (hrs) 0.1 6.8 3.4 2.3 4.6 0.5 _ 0.5 Acidity (pH) _ 6.4 6.5 6.44 5.41 _ _ 6.41 Winds (mph) Direction sw nw sw n sw nw n nw Speed (0830) 18 3 15 17 16 5 18 8 Speed (24 hrs) 10 8 8 8 6 7 10 10 Max Gust 35 21 38 30 18 32 35 39 Pressure (mb) At 0830hrs 991 1001 988 985 1003 998 1015 1024 From 0600hrs -1 4 -2 1.5 0 0.5 4 2 Insolation Cloud types cu ac,ci sc sc cs cs cc cs Cloud cover 1 2 8 8 6 7 2 2 Sunshine (hrs) 1.7 2.9 0 0 0 1.9 0.8 1.5 Visibility 7 7 5 8 7 6 7 5 Other Ppt Snow/sleet falling _ _ _ _ 1 1 _ _ Depth of snow _ _ _ _ _ 1.5 1 1 Hail (<5mm) _ _ _ _ _ _ _ _ Hail (>/=5mm) _ _ _ _ _ _ _ _ Other Obs Thunder heard _ _ _ _ _ _ _ _ Lightning seen _ _ _ _ _ _ _ _ Ground Obs Grass Min (C) _ 1.5 -0.5 1.2 -2 -4 -5.5 -4.9 Concrete Min (C) 2 0.3 0 3 -0.5 -0.5 -2.5 -3.1 Bare Earth (C) 3 1.6 8.4 5.6 1.1 0.2 0.4 0 Soil Temps 5cm 2.2 2.8 6 4.3 1.4 0.6 0.2 0.2 10cm 3.9 3.9 6.4 5.4 2.2 1.9 1.8 1.4 20cm 4.8 4.2 6 5.7 4.4 3.5 2.6 2.4 30cm 5 5 5.9 6.1 5.4 4 3.4 2.9 40cm 5.6 5.4 5.8 6.4 6.1 4.9 4.4 3.8 50cm 6.1 6.1 6.4 6.7 7.1 5.8 5.3 5 100cm 8.1 7.1 8.1 8 7.9 7.2 7.2 7.4 Slab 1 1 2 2 2 3 3 1 Ground Without snow 1 1 2 2 2 _ _ _ With snow _ _ _ _ _ 2 2 1 17th 18th 19th 20th 21st 22nd 23rd 24th Temperatures Air Max (C) 11.8 3.3 0.9 2.3 5.1 11.5 9.6 12.4 Air Min (C) 1.4 -1.1 -3.3 -4.9 -4.1 0.7 3.7 4.1 Dry Bulb (C) 10 -0.2 -2.7 -4.9 0.9 5.1 4.4 8 Wet Bulb (C) 9.2 -0.7 -3.8 -5.6 0.7 4.1 3.7 7.4 RH (%) 90 90 75 81 96 84 89 92 Rainfall Total (mm) 0.1 _ _ 0.8 0.5 2.2 8.2 5.8 Duration (hrs) 0.1 _ _ 1.5 0.4 4.1 n/a 5.8 Acidity (pH) _ _ _ _ _ 6.34 6.37 6.4 Winds (mph) Direction w ne n w s sw sw sw Speed (0830) 11 1 7 2 20 15 13 15 Speed (24 hrs) 7 3 7 8 14 13 16 15 Max Gust 33 21 23 33 30 38 47 57 Pressure (mb) At 0830hrs 1005 1016 1021 1028 1021 1016 1016 999 From 0600hrs -1.5 1 3 0.5 0 -1 2 1.5 Insolation Cloud types sc cc clear ac sc st clear ci Cloud cover 8 4 0 5 8 8 0 5 Sunshine (hrs) 0 1.2 3.4 1.4 0 0 2.3 0.4 Visibility 7 7 7 7 7 7 7 7 Other Ppt Snow/sleet falling _ _ _ _ 1 _ _ _ Depth of snow _ _ _ _ 1 _ _ _ Hail (<5mm) _ _ _ _ _ _ _ _ Hail (>/=5mm) _ _ _ _ _ _ _ _ Other Obs Thunder heard _ _ _ _ _ _ _ _ Lightning seen _ _ _ _ _ _ _ _ Ground Obs Grass Min (C) -1.5 -6.2 -7.9 -8.8 -7 0 0 1.4 Concrete Min (C) -2 -4.1 -7.6 -7.5 -5.8 0.1 1.3 2.1 Bare Earth (C) 7.5 -0.3 -1.3 -1.9 0.6 3.2 3.1 6.2 Soil Temps 5cm 3.8 0.7 -0.1 -0.8 -0.7 -0.4 1.8 4.8 10cm 3.9 1.5 0.5 0.8 0.7 0.9 1.9 5.3 20cm 3.5 3.4 2.4 1.6 1.4 1.5 3.5 5.3 30cm 3.6 3.9 3 2.3 2 2 3.6 4.8 40cm 4.1 4.5 3.4 3.2 2.9 2.7 3.7 4.5 50cm 4.9 5.1 4.8 4.2 3.9 3.6 4.1 4.9 100cm 7.1 6.9 6.8 6.5 6.4 6.3 6.1 6.1 Slab 1 0 0 0 1 1 1 2 Ground Without snow 1 4 4 4 _ 1 1 2 With snow _ _ _ _ 4 _ _ _ 25th 26th 27th 28th 29th 30th 31st Temperatures Air Max (C) 5.2 5.9 3.6 3.2 4.5 5.4 8.2 Air Min (C) 2.5 2.5 1.4 0.8 -0.7 0.4 2.1 Dry Bulb (C) 4 4.2 2.1 1.8 1.3 2.3 3.9 Wet Bulb (C) 2.4 2.9 1.4 1.4 0.9 2.1 3.8 RH (%) 74 79 87 93 92 96 98 Rainfall Total (mm) 2.2 3.9 0.1 _ 0.6 5.9 1.8 Duration (hrs) 1.1 1.3 _ _ 0.6 7.8 0.4 Acidity (pH) 6.53 6.53 _ _ _ 6.33 6.39 Winds (mph) Direction w w sw n n sw ne Speed (0830) 16 14 9 11 8 11 4 Speed (24 hrs) 10 7 4 5 5 5 6 Max Gust 36 43 22 20 25 25 17 Pressure (mb) At 0830hrs 988 985 992 999 1013 1017 1019 From 0600hrs 3 3 -0.5 3.5 2 -2 1 Insolation Cloud types ac ac cc st cu st st Cloud cover 3 3 5 8 3 8 8 Sunshine (hrs) 0.8 2.6 0 0.6 3.6 0 0 Visibility 7 7 7 5 7 5 4 Other Ppt Snow/sleet falling _ _ _ _ _ _ _ Depth of snow _ _ _ _ _ _ _ Hail (<5mm) _ _ _ _ _ _ _ Hail (>/=5mm) _ _ _ _ _ _ _ Other Obs Thunder heard _ _ _ _ _ _ _ Lightning seen _ _ _ _ _ _ _ Ground Obs Grass Min (C) -0.1 -1.5 -3 -2.3 -6.1 -5 0.2 Concrete Min (C) 1.6 0.1 -0.6 -0.6 -3.5 -3.7 0.4 Bare Earth (C) 2.2 1.6 0.4 1.7 0.6 1.1 3.8 Soil Temps 5cm 2.9 1.2 0.4 0.9 -0.1 -0.1 2.2 10cm 4.5 1.6 0.7 0.9 0.3 0.1 2.8 20cm 5.3 3.5 2.6 2.4 2 1.8 3.1 30cm 5.5 4 3.4 2.9 2.5 2.3 3.1 40cm 5.4 4.6 4.1 3.6 3.4 3 3.4 50cm 5.6 5.2 4.8 4.4 4.1 3.9 3.9 100cm 6.1 6.2 6.2 6.1 5.9 5.8 5.7 Slab 2 2 3 1 0 1 1 Ground Without snow 2 2 4 1 4 4 1 With snow _ _ _ _ _ _ _ Cloud, Visibility and Ground Observation Codes Standard cloud types Cirrus Ci Cirrocumulus Cc Cirrostratus Cs Altocumulus Ac Altostratus As Nimbostratus Ns Stratocumulus Sc Stratus St Cumulus Cu Cumulonimbus Cb Visibility codes X Dense Fog <20m E Dense Fog up to 20m 0 Thick Fog up to 40m 1 Thick Fog up to 100m 2 Fog up to 200m 3 Moderate Fog up to 400m 4 Very poor visibility up to 1000m 5 Poor visibility up to 2km 6 Moderate visibility up to 7km 7 Good visibility up to 20km 8 Very good visibility up to 30km 9 Excellent visibility 40km Ground Observations Without snow Surface dry (without cracks) 0 Surface moist 1 Surface wet (with puddles) 2 Surface flooded 3 Surface frozen 4 Glaze on ground 5 Surface partly covered in dry dust 6 Surface covered in dry dust 7 Thick covering of dry dust 8 Surface very dry with cracks 9 With snow Ground mostly ice covered 0 Wet/compact snow covering < half 1 Wet/compact snow covering half 2 Ground evenly covered by wet/compact snow 3 Ground unevenly covered by wet/compact snow 4 Dry/loose snow covering < half 5 Dry/loose snow covering half 6 Ground evenly covered by dry/loose snow 7 Ground unevenly covered by dry/loose snow 8 Complete snow cover, drifting 9 Observations of the Concrete Slab Dry 0 Moist 1 Wet 2 Icy 3 SYNOP Codes The SYNOP codes listed here are only published in this report once a year in the December issue. The January 2000 issue will contain the complete listing of SYNOP messages released by Pitsford Hall weather station at 0900, 1300 and 1600 hours. A sample of SYNOP messages from December are given at the end of this listing of codes for illustration. Syntax IIiii or IIIII YYGGi 99LLL QLLLL iihVV Nddff 00fff 1sTTT 2sTTT 3PPPP 4PPPP 5appp 6RRRt 7wwWW 8NCCC 9GGgg 222Dv 0sTTT 1PPHH 2PPHH 3dddd 4PPHH 5PPHH 6IEER 70HHH 8aTTT 333 0.... 1sTTT 2sTTT 3Ejjj 4Esss 5jjjj jjjjj 6RRRt 7RRRR 8Nchh 9SSss 000 Group - Identification and Location · IIiii The WMO number of the station. Ship or Buoy Observations: · IIIII The ship or buoy identifier · YYGGi YY -- The day of the month GG -- The hour of the observation (UTC) iw -- Wind type indicator 0 -- m/s (estimated) 1 -- m/s (from anemometer) 2 -- knots (estimated) 3 -- knots (from anemometer) · 99LLL QLLLL LLL -- Latitude of observation to .1 degrees Q -- Quadrant of observation 1 -- North east 3 -- South east 5 -- South west 7 -- North west LLLL -- Longitude of observation to .1 degrees 111 Group - Land Observations · iihVV iR -- Precipitation indicator 0 -- Precipitation in groups 1 and 3 1 -- Precipitation reported in group 1 only 2 -- Precipitation reported in group 3 only 3 -- Precipitation omitted, no precipitation 4 -- Precipitation omitted, no observation ix -- Station type and present and past weather indicator 1 -- manned station -- weather group included 2 -- manned station -- omitted, no significant weather 3 -- manned station -- omitted, no weather observation 4 -- automated station -- weather group included (see automated weather codes 4677 and 4561) 5 -- automated station -- omitted, no significant weather 6 -- automated station -- omitted, no weather observation 7 -- automated station -- weather group included (see automated weather codes 4680 and 4531) h -- Cloud base of lowest cloud seen (meters above ground) 0 -- 0 to 50 m 1 -- 50 to 100 m 2 -- 100 to 200 m 3 -- 200 to 300 m 4 -- 300 to 600 m 5 -- 600 to 1000 m 6 -- 1000 to 1500 m 7 -- 1500 to 2000 m 8 -- 2000 to 2500 m 9 -- above 2500 m / -- unknown VV -- Visibility 00 -- less than 0.1 km 01 -- 0.1 km 02 -- 0.2 km ... 50 -- 5.0 km 56 -- 6 km 57 -- 7 km ... 80 -- 30 km 81 -- 35 km 82 -- 40 km 83 -- 45 km 84 -- 50 km 85 -- 55 km 86 -- 60 km 87 -- 65 km 88 -- 70 km 89 -- greater than 70 km 90 -- less than 0.05 km 91 -- 0.05 km 92 -- 0.2 km 93 -- 0.5 km 94 -- 1 km 95 -- 2 km 96 -- 4 km 97 -- 10 km 98 -- 20 km 99 -- greater than 50 km // -- missing · Nddff N -- Total cloud cover 0 -- 0 eighths (clear) 1 -- 1/8th 2 -- 2/8ths 3 -- 3/8ths 4 -- 4/8ths 5 -- 5/8ths 6 -- 6/8ths 7 -- 7/8ths 8 -- 8/8ths (overcast) 9 -- sky obscured / -- no observation dd -- wind direction in 10s of degrees ff -- wind speed in units determined by wind type indicator (see above) · 00fff (optional) fff -- wind speed if value greater than 100 · 1sTTT -- Temperature s -- sign of temperature (0=positive, 1=negative) TTT -- Temperature in .1 C · 2sTTT -- Dewpoint s -- sign of temperature (0=positive, 1=negative, 9 = RH) TTT -- Dewpoint temperature in .1 C (if sign is 9, TTT is relative humidity) · 3PPPP -- Station pressure in 0.1 mb (thousandths digit omitted, last digit can be slash, then pressure in full mb) · 4PPPP -- Sea level pressure in 0.1 mb (thousandths digit omitted, last digit can be slash, then pressure in full mb) 4ahhh -- Geopotential of nearest mandatory pressure level (use for high altitude stations where sea level pressure reduction is not accurate) a3 -- mandatory pressure level 1 -- 1000 mb 2 -- 925 mb 5 -- 500 mb 7 -- 700 mb 8 -- 850 mb hhh -- geopotential height omitting thousandths digit · 5appp -- Pressure tendency over 3 hours a -- characteristics of pressure tendency 0 -- Increasing, then decreasing -- resultant pressure same or higher 1 -- Increasing, then steady -- resultant pressure higher 2 -- Increasing steadily -- resultant pressure higher 3 -- Decreasing or steady, then increasing -- resultant pressure higher 4 -- Steady -- resultant pressure same 5 -- Decreasing, then increasing -- resultant pressure lower 6 -- Decreasing, then steady -- resultant pressure lower 7 -- Decreasing steadily -- resultant pressure lower 8 -- Increasing or steady, then decreasing -- resultant pressure lower ppp -- 3 hour pressure change in 0.1 mb · 6RRRt -- Liquid precipitation RRR -- Precipitation amount in mm 001 -- 1 mm 002 -- 2 mm ... 988 -- 988 mm 989 -- 989 or more mm 990 -- Trace 991 -- 0.1 mm 992 -- 0.2 mm ... 999 -- 0.9 mm t -- Duration over which precipitation amount measured 1 -- 6 hours 2 -- 12 hours 3 -- 18 hours 4 -- 24 hours 5 -- 1 hour 6 -- 2 hours 7 -- 3 hours 8 -- 9 hours 9 -- 15 hours / -- 24 hours · 7wwWW -- Present and past weather ww -- Present weather 00 -- clear skies 01 -- clouds dissolving 02 -- state of sky unchanged 03 -- clouds developing Haze, smoke, dust or sand 04 -- visibility reduced by smoke 05 -- haze 06 -- widespread dust in suspension not raised by wind 07 -- dust or sand raised by wind 08 -- well developed dust or sand whirls 09 -- dust or sand storm within sight but not at station Non-precipitation events 10 -- mist 11 -- patches of shallow fog 12 -- continuous shallow fog 13 -- lightning visible, no thunder heard 14 -- precipitation within sight but not hitting ground 15 -- distant precipitation but not falling at station 16 -- nearby precipitation but not falling at station 17 -- thunderstorm but no precipitation falling at station 18 -- squalls within sight but no precipitation falling at station 19 -- funnel clouds within sight Precipitation within past hour but not at observation time 20 -- drizzle 21 -- rain 22 -- snow 23 -- rain and snow 24 -- freezing rain 25 -- rain showers 26 -- snow showers 27 -- hail showers 28 -- fog 29 -- thunderstorms Duststorm, sandstorm, drifting or blowing snow 30 -- slight to moderate duststorm, decreasing in intensity 31 -- slight to moderate duststorm, no change 32 -- slight to moderate duststorm, increasing in intensity 33 -- severe duststorm, decreasing in intensity 34 -- severe duststorm, no change 35 -- severe duststorm, increasing in intensity 36 -- slight to moderate drifting snow, below eye level 37 -- heavy drifting snow, below eye level 38 -- slight to moderate drifting snow, above eye level 39 -- heavy drifting snow, above eye level Fog or ice fog 40 -- Fog at a distance 41 -- patches of fog 42 -- fog, sky visible, thinning 43 -- fog, sky not visible, thinning 44 -- fog, sky visible, no change 45 -- fog, sky not visible, no change 46 -- fog, sky visible, becoming thicker 47 -- fog, sky not visible, becoming thicker 48 -- fog, depositing rime, sky visible 49 -- fog, depositing rime, sky not visible Drizzle 50 -- intermittent light drizzle 51 -- continuous light drizzle 52 -- intermittent moderate drizzle 53 -- continuous moderate drizzle 54 -- intermittent heavy drizzle 55 -- continuous heavy drizzle 56 -- light freezing drizzle 57 -- moderate to heavy freezing drizzle 58 -- light drizzle and rain 59 -- moderate to heavy drizzle and rain Rain 60 -- intermittent light rain 61 -- continuous light rain 62 -- intermittent moderate rain 63 -- continuous moderate rain 64 -- intermittent heavy rain 65 -- continuous heavy rain 66 -- light freezing rain 67 -- moderate to heavy freezing rain 68 -- light rain and snow 69 -- moderate to heavy rain and snow Snow 70 -- intermittent light snow 71 -- continuous light snow 72 -- intermittent moderate snow 73 -- continuous moderate snow 74 -- intermittent heavy snow 75 -- continuous heavy snow 76 -- diamond dust 77 -- snow grains 78 -- snow crystals 79 -- ice pellets Showers 80 -- light rain showers 81 -- moderate to heavy rain showers 82 -- violent rain showers 83 -- light rain and snow showers 84 -- moderate to heavy rain and snow showers 85 -- light snow showers 86 -- moderate to heavy snow showers 87 -- light snow/ice pellet showers 88 -- moderate to heavy snow/ice pellet showers 89 -- light hail showers 90 -- moderate to heavy hail showers Thunderstorms 91 -- thunderstorm in past hour, currently only light rain 92 -- thunderstorm in past hour, currently only moderate to heavy rain 93 -- thunderstorm in past hour, currently only light snow or rain/snow mix 94 -- thunderstorm in past hour, currently only moderate to heavy snow or rain/snow mix 95 -- light to moderate thunderstorm 96 -- light to moderate thunderstorm with hail 97 -- heavy thunderstorm 98 -- heavy thunderstorm with duststorm 99 -- heavy thunderstorm with hail W1 -- Past weather (type 1) W2 -- Past weather (type 2) 0 -- cloud covering less than half of sky 1 -- cloud covering more than half of sky during part of period and more than half during part of period 2 -- cloud covering more thna half of sky 3 -- sandstorm, duststorm or blowing snow 4 -- fog, or thick haze 5 -- drizzle 6 -- rain 7 -- snow or mixed rain and snow 8 -- showers 9 -- thunderstorms · 8NCCC -- Cloud type information N -- Amount of low clouds covering sky, if no low clouds, the amount of the middle clouds CL -- Low cloud type 0 -- no low clouds 1 -- cumulus humulis or fractus (no vertical development) 2 -- cumulus mediocris or congestus (moderate vertical development) 3 -- cumulonimbus calvus (no outlines nor anvil) 4 -- stratocumulus cumulogenitus (formed by spreading of cumulus) 5 -- stratocumulus 6 -- stratus nebulosus (continuous sheet) 7 -- stratus or cumulus fractus (bad weather) 8 -- cumulus and stratocumulus (multilevel) 9 -- cumulonimbus with anvil / -- low clouds unobserved due to darkness or obscuration CM -- Middle cloud type 0 -- no middle clouds 1 -- altostratus translucidous (mostly transparent) 2 -- altostratus opacus or nimbostratus 3 -- altocumulus translucidous (mostly transparent) 4 -- patches of altocumulus (irregular, lenticular) 5 -- bands of altocumulus 6 -- altocumulus cumulogenitus (formed by spreading of cumulus) 7 -- altocumulus (multilayers) 8 -- altocumulus castellanus (having cumuliform tufts) 9 -- altocumulus of a chaotic sky / -- middle clouds unobserved due to darkness or obscuration CH -- High cloud type 0 -- no high clouds 1 -- cirrus fibratus (wispy) 2 -- cirrus spissatus (dense in patches) 3 -- cirrus spissatus cumulogenitus (formed out of anvil) 4 -- cirrus unicus or fibratus (progressively invading sky) 5 -- bands of cirrus or cirrostratus invading sky (less than 45 degree above horizon) 6 -- bands of cirrus or cirrostratus invading sky (more than 45 degree above horizon) 7 -- cirrostratus covering whole sky 8 -- cirrostratus not covering sky but not invading 9 -- cirrocumulus / -- high clouds unobserved due to darkness or obscuration · 9GGgg -- Time of observation in hours and minutes 222 Group - Sea Surface Observations · 222Dv D -- direction of ship movement 0 -- calm 1 -- NE 2 -- E 3 -- SE 4 -- S 5 -- SW 6 -- W 7 -- NW 8 -- N 9 -- unknown · v -- ship's average speed 0 -- 0 knots 1 -- 1 to 5 knots 2 -- 6 to 10 knots 3 -- 11 to 15 knots 4 -- 16 to 20 knots 5 -- 21 to 25 knots 6 -- 26 to 30 knots 7 -- 31 to 35 knots 8 -- 36 to 40 knots 9 -- over 40 knots · 0sTTT -- Sea surface temperature s -- sign of temperature (0=positive, 1=negative) TTT -- Temperature in .1 C · 1PPHH -- Wave heights in 0.5 m increments PP -- Period of waves in seconds HH -- Height of waves in 0.5 m increments · 2PPHH -- Wave period and heights (instrumented) · 3dddd -- Direction of swells (up to 2 swells) · 4PPHH -- Period and direction of first set of swells · 5PPHH -- Period and direction of second set of swells · 6IEER -- Ice accretion on ships · 70HHH -- Wave heights to 0.1 m (instrumented) · 8aTTT -- Wet bulb temperature 333 Group - Special / Climatological Data · 0.... -- Regionally developed data · 1sTTT -- Maximum temperature over previous 24 hours s -- sign of temperature (0=positive, 1=negative) TTT -- Temperature in .1 C · 2sTTT -- Minimum temperature over previous 24 hours s -- sign of temperature (0=positive, 1=negative) TTT -- Temperature in .1 C · 3Ejjj -- Regionally developed data · 4Esss -- Snow depth E -- State of ground with snow cover 0 -- predominantly covered with ice 1 -- compact or wet snow covering less than half of ground 2 -- compact or wet snow covering more than half of ground but not completely covered 3 -- even layer of compact or wet snow covering entire ground 4 -- uneven layer of compact or wet snow covering entire ground 5 -- loose dry snow covering less than half of ground 6 -- loose dry snow covering more than half of ground but not completely covered 7 -- even layer of loose dry snow covering entire ground 8 -- uneven layer of loose dry snow covering entire ground 9 -- snow covering ground completely with deep drifts sss -- snow depth in cm · 5jjjj jjjjj -- Additional information (can be multiple groups) · 6RRRt -- Liquid precipitation RRR -- Precipitation amount in mm 001 -- 1 mm 002 -- 2 mm ... 988 -- 988 mm 989 -- 989 or more mm 990 -- Trace 991 -- 0.1 mm 992 -- 0.2 mm ... 999 -- 0.9 mm · t -- Duration over which precipitation amount measured 1 -- 6 hours 2 -- 12 hours 3 -- 18 hours 4 -- 24 hours 5 -- 1 hour 6 -- 2 hours 7 -- 3 hours 8 -- 9 hours 9 -- 15 hours / -- 24 hours · 7RRRR -- 24 hour precipitation in mm · 8NChh -- Cloud layer data N -- cloud coverage of layer C -- genus of cloud 0 -- cirrus (Ci) 1 -- cirrocumulus (Cc) 2 -- cirrostratus (Cs) 3 -- altocumulus (Ac) 4 -- altostratus (As) 5 -- nimbostratus (Ns) 6 -- stratocumulus (Sc) 7 -- stratus (St) 8 -- cumulus (Cu) 9 -- cumulonimbus (Cb) / -- cloud not visible · hh -- height of cloud base 00 -- less than 30 m 01 -- 30 m (100 ft) 02 -- 60 m (200 ft) 03 -- 90 m (300 ft) ... 50 -- 1500 m (5000 ft) 56 -- 1800 m (6000 ft) 57 -- 2100 m (7000 ft) ... 80 -- 9000 m (30000 ft) 81 -- 10500 m 82 -- 12000 m ... 88 -- 21000 m 89 -- greater than 21000 m 90 -- 0 to 50 m 91 -- 50 to 100 m 92 -- 100 to 200 m 93 -- 200 to 300 m 94 -- 300 to 600 m 95 -- 600 to 1000 m 96 -- 1000 to 1500 m 97 -- 1500 to 2000 m 98 -- 2000 to 2500 m 99 -- above 2500 m · 9SSss -- Supplementary information Thunder Report No reports of thunder were received this month. SYNOP Messages - December 1999 (illustration) AAXX 31094 PITSFORD 11010 80403 00022 10039 20037 30030 40185 52010 60064 7106/ 88600 90900 333 10054 20021 31000 88700= AAXX 30094 PITSFORD 11120 82210 00022 10023 20018 30013 40170 57020 69964 75550 88700 90900 333 10045 20004 34105 88702= AAXX 29094 PITSFORD 31270 30007 00017 10013 20003 39971 40128 52021 70120 83100 90900 333 10032 21007 34106 83805= AAXX 28094 PITSFORD 11920 80010 00019 10018 20009 39835 49989 52035 69914 702// 88600 90900 333 10036 20008 31102 88709= United Kingdom Climatological Analysis - December 1999 The rain area finally cleared S England by midday on the 1st, which then was a day of sunny spells and showers. These showers were mainly in W and N parts of the British Isles, and were wintry and blustery over much of Scotland - gusts over 50kn were reported later in the evening from Tiree and Malin Head. Nacreous clouds were again observed, from S Lancashire around 0730GMT. (Thorney Island 15C, Baltasound 0C, Loch Glascarnoch 30mm, Aberdeen 5.6h.) The 2nd began with rain showers over S Scotland and wintry showers over N and W parts of Scotland. More organised rain affected Cent. and S Scotland later in the day, with snow falling on the Southern Uplands. Cloud increased over Ireland from the W with a warm front bringing rain there during the evening, while there was patchy light rain over S England during late afternoon. Gusts to 30kn occurred over parts of S England during the afternoon with gusts to 50kn over exposed parts of Scotland. (Guernsey 14C, Wick 2C max, Lerwick -1C min, Tulloch Bridge 30mm, Eastbourne 6.1h.) A deepening depression crossed S Scotland on the 3rd with gales to its S and N winds and snow following to the N. Gusts to 70 kn were reported across S Scotland and N England, and the pressure fell to 978 mb in the Firth-Clyde Valley around dawn. At Dun Laoghaire there was a 9mb fall in pressure in the three hours to 0000GMT accompanied by damaging gusts SW veering NW. Prestwick recorded a gust of 53 knots and a 6C temperature fall in 1 hour as the cold front passed. Heavy rain fell around the Anglo-Scottish border. The low dragged a cold front across all S areas of the British Isles, the rain finally clearing S England during the evening. Snow showers occurred as far S as N Wales and Shropshire, blocking several roads in the N and causing a spate of accidents. Thunder was reported in the showers from the Northern Isles to Cheshire. Three people died as a tree was blown down in Kings Heath, Birmingham. Strong gusts led to many blocked roads with fallen debris and overturned lorries in Scotland. Road restrictions were imposed in exposed areas as far S as Cheshire and Derbyshire. The A65 was flooded at Settle, and by evening 22cm of lying snow was reported at Aviemore. A gusts of 101mph was measured on the Humber Bridge, with 85mph at Crosby, and 75mp at Leeds (a December record there). (Eastbourne 14C, Aviemore 1C max, Aboyne -1C min, Shap Fell 58mm, Scarborough 3.9h.) Skies largely cleared by dawn on the 4th, although wintry showers continued to fall over some W areas of Scotland and NW Ireland, and thunder was reported over in parts of SW Scotland. At Aviemore, blowing snow was reported at overnight. By dawn there was over a 30cm of lying snow in many parts of N Scotland and a light covering over most of the rest of Scotland, with powdery snow lying as far S as Staffordshire. 10cm was reported lying, unevenly, at Copley. Showers continued to fall throughtout the day, with snow in the N (being widespread as far S as the Midland counties) and rain further S, although skies generally cleared again in the evening. The M8 in Lanarkshire was barely passable due to snow in the morning, and the A635 at Holmfirth and the A6024 Woodhead Pass were closed by snow. One person died in Midlothian as his car skidded on black ice. Snowploughs were used to keep the M74 open, and four Scottish Premier League football games were cancelled due to snow or floods. The ski slopes at the Lecht and Cairngorm operated for the first time this winter. There was only a light covering but that was enough for enthusiastic skiers and snow-boarders. The Christmas tree in Glasgow's George Square was twisted and split by the gale force winds; workmen quickly replaced the original 35foot tree with another one brought from Aberfoyle and quickly redecorated the tree. (Penzance 10C, Spadeadam 0C max, Aviemore -6C min, Lerwick 22mm, Bognor Regis and Hayling Island 6.9h.) The were further snow showers on 5th over N Yorkshire and as far S as Derbyshire before dawn, although by mid-morning warm frontal-rain was starting to spread W across Ireland. By midnight this reached all of Scotland, Wales, N England and SW England. Glasgow had four inches of precipitation this week (roughly equal to a month's average total) and the rain and warmer conditions caused a rapid thaw of lying snow. (Barra and Tiree 11C, Eskdalemuir 1C max, Loch Glascarnoch -8C min, Loch Glascarnoch 22mm, Margate 6.7h.) After a mainly cloudy night the 6th dawned milder than of late. There was some rain and drizzle in S England and S wales for much of the day, before an area of heavier rain and drizzle in Scotland and Ireland moved gradually SE during the day reaching S England and East Anglia by midnight, introducing cooler, showery conditions in its wake. Some of these showers were accompanied by gusts to 50kn in W Scotland and Ireland. Some roads in Cent. Scotland remained flooded for most of the day by the early rain. (Hawarden 14C, Spadeadam 9C max, Fylingdales 2C min, Eskdalemuir 31mm, Kinloss 3.3h.) Early rain over S England cleared by mid-morning on the 7th, to be followed by showers there. Bands of rain and showers affected much of the British Isles during the day, being heaviest in the W. Hail occured over Ireland Scotland, and snow fell on high ground in Scotland; 7mm diamter hail fell in a shower at Llansadrwn, amd almost covered the ground at 1430GMT. There were reports of thunder over parts of S and E England, and gusts to 45kn in places. Roads in Highland and Cumbria were reported to be flooded in places. (Guernsey 14C, Aviemore 1C, Glasgow 17mm, Newcastle 4.5h.) A marked cold front crossed the British Isles on the 8th, part of a frontal system associated with a deep low that gave gales to W and N areas. Radar showed the front to be broken, with some places escaping much in the way of heavy rain. Some Irish Sea ferry services were cancelled earlier in the day, and reported gusts included 62kn Ronaldsway, 68kn Belmullet, 58kn Valentia. Pressure fell to 966mb in W Scotland late in the evening. A ferry from Larne in Northern Ireland was blown off course in gales and high winds as it approached Ardrossan harbour in Ayrshire. It ran aground inside the breakwater, shortly after midnight, being pulled free 11 eleven hours later. Patchy, thin snow cover was mainly restricted to high ground in the W areas of Cumbria, Scotland and Norther Ireland. (Guernsey 13C, Sella Ness 1C, Eskdalemuir 20mm, Belfast 3.7h.) Low pressure crossing Scotland on the 9th brought frequent showers, and heavier spells of rain, over N parts of the British Isles (especially S Scotland and N England), and lighter showers elsewhere. With pressure as low as 966mb before dawn, winds were gale force over S Scotland and N England with gusts to 60kn in places during the morning. A cooler N airflow behind the low brought hail showers to the Northern Isles in the evening, and sleet was observed in a few places in Cent. Scotland. A few of the showers were thundery from SW England to N England. Parts of Kilmarnock town centre were under five feet of water after rivers burst their banks. Shoppers at a supermarket in Glasgow had to be rescued by emergency services using dinghies when flood water trapped them in the store. (Guernsey 11C, Altnaharra -3C, Shap Fell 46mm, Southend 7.0h.) The 10th began with scattered rain and showers mainly over parts of Ireland and Scotland, and with an air frost in many areas of Scotland. During the day more organised cloud and rain spread NE across Ireland and into Wales and SW England by midnight, with some heavy falls in the SW. There wer some sleet and snow in Scotland, and a sharp frost after dark there as temperatures tumbled under clearing skies. (St. Mary's 12C, Loch Glascarnoch -4C, Cardinham 24mm, Folkestone 6.2h.) Clear skies in Scotland early on the 11th soon clouded over except in the extreme N, and the day remained generally cloudy everywhere. Bands of rain, associated with a depression that crossed from N Ireland across S Scotland gave heavy falls in places. Malin Head reported a MSL pressure of 977mb at 1500GMT and there were gusts to 50kn across N Ireland and parts of N Britain. Snow and hail showers occurred early in the morning across N and Cent. Scotland to be followed by rain and sleet as the temperature rose slightly. The first 11 days of the month have brought 189mm to Windermere. (Herne bay 14C, Altnaharra -8C, Capel Curig 52mm, Lerwick 2.3h.) Cloud over much of Britain led to a mild start to 12th except in N Scotland, and by dawn there were reports of flooding from S Scotland, Cleveland, Cumbria, the Midlands and Wales. Strong winds, rain and snow caused difficult driving conditions in N parts of Britain, while in Wales the River Severn burst its banks and thousands of acres were flooded. 10cm of snow was reported to have fallen in Cent. Scotland. Thundery showers occurred in SW England where hail was also observed. (Jersey 10C, Altnaharra 0C max, Altnaharra -6C min, Capel Curig 47mm, Torquay 3.6h.) The 13th started with a band of rain and snow across S Scotland and N England, and a widespread frost in other parts of Scotland; the M74 in Lanarkshire was down to one lane due to snow cover. Fresh snow fell on the mountains of Snowdonia overnight followed by further falls in the morning giving moderate falls on the summits and slight falls as low as 1000ft in places. Cloud and rain began to affect SW Ireland and SW England before dawn (with hail and thunder in Devon), pushing NE into the Midlands and Cent. Ireland. Heavy warm sector rain fell in places, and there was heavy snowfall in Wales and Shropshire (where schoolchildren were sent home early as a result). As the rain moved E, snow fell on the N limits of the warm sector/low in the Midlands, S Pennines and East Anglia, to be followed by wintry showers and cooler conditions over Ireland, Wales and SW England. Parts of Scotland remained below freezing all day, and snow showers fell in N parts of the country. The Snake Pass was closed with 15cm of lying snow reported, while Stornoway reported thunder in the evening. At Coventry Bablake the first air frost of the autumn/winter occurred at 2000GMT - the latest such event since records were first kept in the city in 1892. (Jersey 11C, Biggar -3C max, Tulloch Bridge -7C min, St Athan 24mm, Newcastle 4.6h.) The 14th dawned with showers of snow and hail over Scotland and Northern Ireland, freezing fog over S Scotland and parts of N England, some icy roads in SW England after rain fell on cold surfaces, and a widespread air frost. The Snake Pass in the Pennines was closed. During the areas of wintry weather moved generally S over England and Wales, with hail showers in SW England and sleet and snow reaching the Midlands, SE and Cent. S England by midnight. Thunder was reported in NE England in the evening. 6,000 children in Lanarkshire got an extra day's holiday when 10cm of snow fell in less than four hours. Traffic on the motorway between Glasgow and Edinburgh was badly affected as blizzard conditions affected the road at its highest point. Roads in the north were also badly affected. (Penzance 9C, Buxton (Derbyshire) 0C min, Biggar -10C min, Aviemore 12mm, Hayling Island 7.2h.) Early sleet/snow fell in NE England, Lincolnshire and at Heathrow before dawn on the 15th, with wintry showers in N and NE Scotland also; 0600GMT snow depths included 13cm Aviemore and 8cm at Eskdalemuir, with the A93 closed at the Spittal of Glenshee and the A939 Cockbridge to Tomintoul road also shut. Thunder occurred over Yorkshire around dawn. Much of Ireland, Wales and S England (away from the E coast) had a sunny day, although there were some rain showers in Ireland. Wintry showers fell as far S as the Midlands and Essex, while in Scotland there were rain showers in the W, and sleet or snow in the E and on high ground. In S Wales falls of 10cm resulted in disruption on the higher-level roads. The N wind was fresh at times, with gusts to 40Kn along E England. (St Mary's 9C, Spadeadam 0C max, Biggar -8C min, Leconfield 12mm, Teignmouth 7.2h.) Parts of S England had a brief air frost before pre-dawn cloud on the 16th lifted temperatures; elsewhere there were some snow showers in NE England and rain showers in W Ireland and W Scotland before dawn. During the day, a freshening wind and cloud cover from the W in all areas was followed by rain over Ireland and Scotland. Gusts to 40kn were widespread during the evening, with 56kn reported at Malin Head at 2100GMT; pressure was falling at the rate of over 9mbar in 3 hours over parts of N and W Scotland from 1800 to 2100GMT. (Penzance 10C, Benson -3C, Loch Glascarnoch 18mm, Torquay 5.8h.) Rain over N and W parts of the British Isles moved slowly SE during the 17th, becoming slow-moving over S Ireland and S England during the afternoon and evening. Skies cleared in the N as the rain passed, with wintry showers falling over Scotland. There was also a widespread frost over Scotland and N England by midnight. (Pershore 13C, Redhill -1C, Capel Curig 49mm, Scarborough 6.1h.) The 18th began with clear skies over Scotland (apart from a few wintry showers in places) and a widespread air frost over Scotland and N England. Rain continued to fall in parts S Ireland, S Wales (where there was snow on higher ground), SW and Cent. S England before dawn. During the afternoon heavier rain began to affect S Ireland and S Wales, as a depression tracked E into the English Channel; this turned to snow over the Mendips and high ground in S Wales later in the afternoon before moving E into the Chilterns, Thames Valley, Sussex and W Kent areas (with smaller falls or sleet in neighbouring areas). In Cornwall and Devon the precipitation remained in the form of heavy rain. A band of sleet and snow affected S Scotland and extreme N England for much of the day, while snow showers feel further N. At Cirencester slight rain in the afternoon turned to moderate snow by dusk. Rain turned to sleet and snow around 1500GMT at Bristol Totterdown; temperature fell from 4.5C to just above 1.0C, then at about 1900GMT snow turned back to rain for about 1 hour after which moderate snow fell until 2300GMT. 23mm fell at Uplyme (East Devon) in the 24 hours from 0900GMT, with 50mm at Redruth in 24hours to 1800GMT. (Guernsey 13C, Loch Glascarnoch -2C max, Altnaharra -7C min, Falmouth 50mm, Hunstanton 6.9h.) UK Meteorological Office analysis chart for 0000 GMT on the 19th. The precipitation cleared SE England before dawn on the 19th; the British Isles then had a mainly clear, cold night but with further wintry showers in N and Cent. Scotland. These continued during the day, extending down the E coast of England to Yorkshire. Elsewhere, it was a day of unbroken sunshine, although in many places it remained below freezing in a cold NW airflow. Snow depths included 10cm at Chippenham, 9cm full cover at Cirencester (with a grass minimum (over snow cover) of -11.7C, air minimum was -4.7C), 4cm at 35m altitude in Bristol and 3cm at Chipstead Valley (minimum -10.6C). Other minima included -8C at Topcliffe (N Yorkshire, -14C on the grass). By early morning some Welsh valleys were impassable after over 15cm of snow fell, and 50 vehicles were stranded on the A470. Across much of the S wet lying snow and rain froze during the night as temperatures dropped; 1 person died after a crash on the M4 near Newbury caused by the ice and 2 died in Oxfordshire. 90 homes were flooded in Cornwall (there were flood alerts across Cornwall, Devon and Somerset), while in Sussex the A29 was impassable due to snow at Bury Hill. At Dun Laoghaire, the maximum of 3.6C was the lowest since January 1997. (St. Mary's 8C, Spadeadam -3C max, Biggar -13C min, Falmouth 39mm, Bristol 8.2h.) Showing snow cover at 1400GMT on the 19th. With patchy cloud and a S wind developing over Scotland early on the 20th, the morning was coldest in S England; minimum temperatures included 13C Ross-on-Wye, -12.7C at Hungerford, -8.6C at Drumburgh, -8.3 Wigan, and -9.8C at Stratfield Mortimer (S or Reading) (this is the lowest air minimum in the Mortimer/Stratfield Mortimer area since 12 December 1991). At Cirencester the minimum was -10.4C (-14.5C on the grass), rising to a high of -1.9C. At Weston Coyney (Stoke) -8.5C was the lowest reading since January 1987. Temperatures starting rising rapidly in Cornwall and SW Ireland shortly after dawn, and cloud spread rapidly E to reach much of England by midday. Showers of sleet/snow fell in N scotland during the morning, and rain with gusts to 50kn reached SW Ireland. The rain pushed E for the remainder of the day, falling as snow in parts of W Scotland and Wales by midnight. (St Mary's 8C, Redesdale -5C max, Sennybridge -14C min, Baltasound 4mm, Clacton 6.3h.) The band of precipitation continued to push across the British Isles on the 21st, falling as freezing rain in the Wirral before dawn, as rain in the SW and as sleet and snow in most other places. Snow was measured at 4cm deep in Wigan. Traffic was disrupted from S Scotland to the Midlands, and Glasgow Airport was closed for a while. The precipitation cleared most of England by mid-afternoon, although light rain and drizzle lingered in parts of SW and Cent. S England, leading to fog formation in places. Warmer weather followed the rain and snow, and although some places had a sunny end to the day, fog formed during the evening from NE England to the SW (probably a result of warm air coming in contact with a cold surface). Further rain reached Ireland and W scotland by midnight. (Penzance 13C, Perth and Kinloss 0C max, Aviemore -9C, Penzance 19mm, Prestatyn 5.7h.) The 22nd was unusually cloudy over almost the entire British Isles - possibly the dullest day of 1999. Slow-moving fronts and troughs crossed during the day, with precipitation falling everywhere; clearer, showery air pushed into Ireland during the evening from the W. Gusts to 50kn were reported from Ireland, Scotland, Wales and SW England in S gales. (Chivenor 14C, Redesdale -1C, Tulloch Bridge 49mm, Jersey 0.1h.) Rain cleared E England by dawn on the 23rd, leaving the British Isles in a showery W airflow. These showers fell as sleet or snow over high ground in N Scotland with some hail at lower levels, and thunder was reported from Tiree during the morning. Gusts to 50kn were reported from W districts. Later in the morning an area of cloud and rain reached NW Ireland, and pushed rapidly E and N to affect all but parts of SE England by midnight. Gales were reported from Scotland and N Ireland, with Malin Head reporting a 68kn gust at 1800GMT, later spreading to most coastal areas of England. (Falmouth 13C, Redhill 0C, Loch Glascarnoch 31mm, Clacton 6.2h.) The 24th was windy everywhere with a large and deep area of low pressure close to, or over, N Scotland all day. A deepening low resulted in MSL pressure falling to 948mb at Aberdeen by midnight with very strong winds to the S; gusts of over 100mph were reported to have occurred. At Corsock 951.5mb was recorded, the lowest in 10 years of records, while at Ferryhill a pressure fall of 15.6mb was noted between 1700 and 2000GMT. Bands of precipitation affected most areas from time to time during the day although snow fell only on the higher peaks in Scotland, mostly following the passage of the low. The rain was heavy in parts of S England (including 27mm at Cholesbury on the Chilterns), especially the SW. From Kent to Hampshire S gales, coupled with an unusually short distance between the moon and earth, led to some of the highest tides in living memory. By the end of the day over 50 rivers in Devon and Cornwall were on a yellow flood alert. The River Dart burst its banks and one man died in Galmpton, Devon, and a freak wave in New Brighton swept one man to his death into the River Mersey. In Co Down many coast roads were flooded while in the W part of Northern Ireland lightning strikes led to some power cuts. At Langtoft a thunderstorm occurred at 2130GMT, this being accompanied by a couple of power cuts, and thunder was also heard in the Midlands and Lincolnshire. (Chivenor 14C, Aviemore 2C, Cardinham 59mm, Aberdeen 4.2h.) By dawn on the 25th the sea defences had been breached in several parts of Sussex. 6 people were airlifted off a ship near NE England in force 11 winds, while 400 homes were without power in East Anglia. In Oxfordshire the River Evenlode burst its banks in places. The day began in Scotland with blizzards being reported, as the low near Aberdeen moved N, still deepening. Showers and strong W or SW winds affected most of the British Isles during Christmas day, the showers being thundery in places (with hail at Wigan). In Coventry a thunderstorm with hail around 0040GMT led to lying hail for over 2 hours. Wintry showers were widespread over N and Cent. Scotland (where 50kn gusts occurred during the morning) and a passing trough gave snow showers as far S as Cork and Hampshire. Snow fell on the London Weather Centre, and bookmakers who had been offering 50-1 odds two days earlier against snow stood to lose hundreds of thousands of pounds. During the evening heavy snow was reported in parts of East Scotland, while in Ireland snow lay on hills above 130m outside Dublin. (Guernsey 12C, Lough Fea 0C, Lossiemouth 33mm, Newcastle 4.3h.) Parts of Scotland had a frosty start on the 26th with showers of snow/sleet in places. Showers developed during the day, especially in N and W parts of the British Isles, while there was more extensive rain over parts of S England before dawn. Hail fell as far S as Valentia and Cornwall, with snow observed over N Wales; a light covering of snow occurred in Stoke-on-Trent during the morning. At Copley snow lay 7cm deep at 0900GMT. Thunder was heard over Ireland, the Wirral and S England. In N Somerset, thunderstorms during the day were accompanied by hail, rain and snow. (Torquay and St Mary's Scilly 10C, Aboyne -2C, Eastbourne 41mm, Clacton 4.8h.) The 27th began with a NW airflow over the British Isles, but during the afternoon a deepening low crossed N France and winds in S England became E for a while. After a widespread ground frost, showers again affected mainly W areas with snow falling in Cent. Scotland. Hail and snow fell as far S as Cork, while at 1800GMT Guernsey reported heavy rain after recent snow, and MSL pressure of 987.5mb. Thunder was reported over part of the English Channel, while there was also extensive flooding on Guernsey. (Guernsey 9C, Redhill -2C, Jersey 25mm, Cleethorpes 5.1h.) A NW airstream on the 28th brought an air frost to many places before dawn, although in S England and in some W districts cloud and showers kept temperatures up. Snow fell as far S as the Midlands before dawn, although much of the day was dry in most areas. Road reports at dawn included those of ice on many roads in Scotland, S Wales and SW England. During the evening clearing skies, heralding another widespread air frost. (Torquay 8C, Spadeadam 0C max, Leeming -5C min, Falmouth 17mm, Weymouth 7.1h.) Cloud increased by dawn on the 29th over Scotland and parts of N Ireland with showers of snow in parts of W Scotland. Over England mainy clear skies led to a widespread frost, with some sleet showers in the Midland before dawn and freezing rain at Chalfont St. Giles at 0900GMT. Parts of the A16 in Lincolnshire and the A47 in Norfolk were closed after black ice caused accidents. It remained bright in most places except for N Scotland by day, with further rain showers on some W coasts, although during the evening more organised cloud and rain spread E to W parts of Ireland and Scotland. (Guernsey 10C, Topcliffe -6C, Loch Glascarnoch 15mm, Clacton 7.1h.) Cloud and rain spread across the British Isles on the 30th, although parts of SE England had a sharp frost before the cloud arrived. During the evening fog formed in parts of S Scotland and N England. (Culdrose 11C, Redhill -4C, Llansadrwn 26mm, Stornoway 1.7h.) The 31st dawned damp and mainly cloudy with fog in many parts inland and N England, while frost n Scotland led to some icy roads there. It remained mild, damp and cloudy in most places all day, with further bands of rain spreading across the British Isles and gusts over 40kn in parts of NW Scotland. During the evening skies largely cleared over Ireland and Scotland. (St Mary's 12C, Aboyne -3C, Lusa 12mm, Prestatyn 1.5h.) Information contained in the Climatological Summary 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 3 December High winds gusting up to 53mph and rain lash the county during the morning. Mean wind speed recorded at observation (0830GMT) at Pitsford Hall: 33mph. Pressure trend over the 3 hours prior to 0830GMT: -6mb. Reports received of a lorry careering out of control down an embankment on the A14 and of power losses and train delays on the Northampton line. 13-14 December Significant snowfall. Snow lying until 16th. Depth of lying snow on 14th: 1.5cm, decreasing to 1cm on 15th and 16th. Snow on 13th beginning as sleet and contributing to 8.6mm rainfall equivalent. 20 December Coldest day of the year so far. Air minimum -4.9C. Grass minimum -8.8C. Temperatures at observation (0830GMT): air -4.9C, bare earth -1.9C, earth 5cm -0.8C. Daytime maximum on 19th: 0.9C, on 20th: 2.3C. 21 December Further snow showers, quickly turning to sleet and rain during the morning. 1cm lying snow at 0830GMT. Overnight minimum -4.1C. Air at 0830GMT 0.9C. Widespread traffic disruption around the county as fresh snow falls on gritted roads. Several accidents reported on both minor and major routes. 23-24 December Strong winds and driving rain affect much of the county. Winds gusted up to gale force at Pitsford Hall (47mph on 23rd, 57mph on 24th). A saturated catchment and two days of heavy rain result in an amber alert being issued for the River Nene on Christmas Eve. 30 December Widespread black ice on untreated roads around the county results in several accidents. Despite an air minima of 0.4C, overnight rain had frozen onto freezing surfaces. Grass and concrete minima: -5.0C and -3.7C respectively. An absence of hoar frost in many areas left many drivers unaware of the hazard. Reports from Northants Weather Watchers Reports received from Pitsford Hall weather station's network of weather enthusiasts across Northamptonshire. The weather station is not responsible for any inaccuracy contained in these reports. They are supplied for interest only. From Jeremy Borrett in Wilby : WILBY'S TOTAL MONTHLY & YEARLY RAINFALL (BETWEEN 1994 AND 1999) =============================================================== ______________________________________________________________________ 1994 (mm) 1995 (mm) 1996 (mm) 1997 (mm) 1998 (mm) 1999 (mm) ______________________________________________________________________ January 80 83 44 22 88 109 February 44 76 56.5 66.5 8 21 March 46 55 36.5 11.5 82 37.5 April 54 31 51.5 19 175 76 May 62 36 24.5 92.5 16 68 June 24 95 34.5 149 126 77.5 July 24 19 69 49 19 31.5 August 36 9 70.5 66 62 87 September 122 121 11 42 60 65.5 October 76 28 45.5 81.5 130 59 November 52 82 79 84 45 26.5 December 62 96 55 78 56 88 ______________________________________________________________________ TOTAL (mm) 682 731 577.5 761 867 746.5 ______________________________________________________________________ WILBY'S AVERAGE DAILY TEMPERATURE (1995 TO 1999) ================================================ ___________________________________________________________ 1995 (°C) 1996 (°C) 1997 (°C) 1998 (°C) 1999 (°C) ___________________________________________________________ January 4 3 1 5 6 February 6 5 7 9 6 March 7 4 3 7 8 April 12 12 14 10 15 May 16 12 16 19 19 June 19 19 20 17 19 July 25 21 24 20 21 August 26 21 27 25 19 September 19 18 21 19 19 October 14 13 13 11 13 November 6 4 9 5 9 December 1 2 5 6 5 ___________________________________________________________ WILBY'S AVERAGE AIR PRESSURE (1995 TO 1999) =========================================== ___________________________________________________________ 1995 (mb) 1996 (mb) 1997 (mb) 1998 (mb) 1999 (mb) ___________________________________________________________ January 1008 1010 1024 1011 1014 February 1005 1018 1014 1022 1017 March 1009 1012 1024 1020 1008 April 1016 1016 1023 1001 1011 May 1015 1014 1015 1017 1017 June 1012 1020 1010 1013 1017 July 1013 1017 1021 1013 1019 August 1017 1024 1017 1019 1014 September 1013 1017 1023 1012 1009 October 1016 1014 1017 1011 1014 November 1014 1010 1001 1016 1021 December 1016 1015 1009 1009 1009 ___________________________________________________________ WILBY'S AVERAGE DAILY WIND SPEED (1995 TO 1999) =============================================== ________________________________________________________________ 1995 (mph) 1996 (mph) 1997 (mph) 1998 (mph) 1999 (mph) ________________________________________________________________ January 9 4 1 8 1 February 5 3 7 5 5 March 7 4 3 7 3 April 3 3 4 7 7 May 5 4 7 2 5 June 2 2 13 4 2 July 3 3 7 7 5 August 3 3 9 8 3 September 3 3 6 4 4 October 3 2 6 8 5 November 2 1 4 1 4 December 2 1 6 7 2 ________________________________________________________________ WILBY'S HIGHEST AND LOWEST TEMPERATURES IN 1999 =============================================== __________________________________ Month Highest (°C) Lowest (°C) __________________________________ January February March April May June 25.0 5.0 July August 28.7 7.1 September 26.2 October 17.4 3.8 November 15.3 1.3 December 11.3 -3.6 WILBY'S DECEMBER 1999 MONTHLY WEATHER REPORT ============================================ Report from 1st December 1999 to 31st December 1999. Wind direction -------------- North: 0 days South: 2 dayS East: 0 dayS West: 4 days North-west: 5 days North-east: 0 days South-west: 6 days South-east: 1 day Variable: 1 day Calm winds: 10 days Total: 29 days Wind speed ---------- Average wind speed (mph): 2mph Highest wind speed (mph): 7mph (23rd) Please note that there were some occasions during the month where winds reached gale force but these were not recorded. Temperature ----------- Average temperature: 5.2°C Highest temperature: 11.3°C (22nd) Lowest temperature: -3.6°C (20th) Rainfall -------- Total rainfall (mm): 86mm Highest rainfall (mm): 22mm (11th) Air pressure ------------ Average air pressure: 1009mb Highest air pressure: 1028mb (19th) Lowest air pressure: 985mb (10th) Station Notes During December the weather station began releasing SYNOP messages on a daily basis at 0900 hours and at 1300 and 1600 hours Monday to Friday to report significant weather. The messages are dispatched to Weather Consultancy Services Ltd and released via the Internet. Recently, restrictions imposed on data access via the Internet has seen the disappearance of current SYNOP messages released by Met Office stations. Pitsford Hall is one of a growing number of independent professional climatological stations which are now releasing SYNOP information without restriction. This month's issue of the weather report contains a complete listing of SYNOP codes. The full listing of SYNOP messages will feature in the weather report from January 2000. Also during December, the weather station decided to broaden access to its services by introducing an answerphone service. The local forecast as well as some of the weather readings taken at 0830 hours can be heard on 07967 438314. Furthermore, completion of the telecommunications upgrading in the station office now means that callers can contact the station direct on Northampton (01604) 880306 extension 314. An answerphone has also been placed on this line to take enquiries when the office is unmanned. Additional work has also been undertaken on the weather station's extension from the school IT network. An extra computer has been introduced linked to an ISDN line which greatly increases the rate of data acquisition for compiling forecasts. All the computer systems operated by the weather station appear to have survived the transition into the year 2000 without any problems introduced by the 'Millennium Bug'. The oldest machine simply required adjustment of the date setting. Finally, work is currently underway to repair the clock mechanism of the main hygrograph. Observations of relative humidity are, in the meantime, being made using a back-up Casella-style instrument. Appendix Weather Station Inventory (including equipment in active use as of 3 January 2000) Rooftop Enclosure and Office Standard Stevenson screen containing Mahogany mounted maximum and minimum thermometers (Casel