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Sources: BBC, National Weather Services, Intellicast, Space Science and Engineering Center, the Met Office, Yahoo! Weather
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TODAY’S HEADLINES
TODAY’S EXTREMES
Hottest: Two Boats School, Ascension, 38°C
Coldest: Rantakylan Koulu, Mikkeli, Finland, -17.9°C
Windiest: 44 km/h at several places: Richard Lander School, Truro, UK; Milford Haven School, Pembrokeshire, UK; St Patrick’s Primary School, Preston, Lancashire, UK; and Portgordon Primary School, Morayshire, UK
Driest: Pasadena City College, California, relative humidity 16%
Wettest: Jakarta International School (Indonesia), 27 mm of rain
FEATURES OF THE DAY
To find these features, click here. Feature 1 is intended for secondary schools, Feature 2 for primary schools.
TODAY’S REVIEW OF METLINK OBSERVATIONS
Have you looked at today’s weathercams? If not, click here.
To view today’s observations in the database, click here.
To find out how your observations compare with the average for January, click here.
EASTERN AND SOUTHERN ASIA
"Rain finally stopped", said the students of the Jakarta International School. Only 27 mm of rain measured today! Still quite cloudy at Jakarta, though, with 7 oktas of cloud (stratocumulus and altocumulus) observed at 7 am Local Time today (00:00 GMT). Temperature then 23°C, with wind calm and relative humidity 95%. Maximum temperature 29°C, minimum 22°C; about average for the time of year. "Humid, sunny and fine" said the students of the Medan International School, Sumatra. Temperature at 8 am Local Time (00:00 GMT) 25.0°C and the cloud cover 7 oktas of cumulus. Maximum temperature 35.0°C, which is 5°C above average for the time of year. Minimum temperature 22.0°C.
Another chilly morning with mist and fog at New Delhi but sunny again by noon. Only one okta (of cirrus cloud) at 12.35 pm Local Time (07:05 GMT). The wind then north-easterly Force 1 and the temperature 20°C. Maximum temperature 21.2°C, minimum 6.5°C; both figures close to the average for the time of year.
AFRICA AND ASCENSION
"Cloudy and warm" on Ascension today, with 6 oktas of cumulus and cumulonimbus cloud at 12.38 pm Local Time (12:38 GMT). Temperature then 27°C and the wind 15 km/h from the west. Maximum temperature 38°C. Also warm at the Banani International school in Lusaka (Zambia), where the maximum temperature was 35°C. Temperature 29°C at 10 am Local Time (08:00 GMT) and the cloud cover then 6 oktas of altocumulus. Wind south-easterly Force 1.
Quite warm, too, at Kgaswe Primary School in Botswana today, with a maximum temperature of 32°C. Seven oktas of cumulonimbus cloud at 10 am Local Time (08:00 GMT), with rain of medium intensity falling. "Getting more humid by the day; rain on the way", said the students of Peterhouse at Marondera in Zimbabwe. Calm with a temperature of 22.6°C at 8 am Local Time (06:00 GMT). Cloud cover then only 3 oktas (of cumulus). Maximum temperature 27.3°C, minimum 20.1°C.
"Fairly hot" in Kampala, with the temperature 24°C at 11 am Local Time (08:00 GMT). Sunny at the time (3 oktas of cirrus cloud) but quite windy, too (24 km/h from the south-east). Temperature near average at Highbury Preparatory School in Hillcrest, South Africa. Maximum 27°C, minimum 19°C. Wind south-easterly Force 4 and the temperature 21°C at 7 am Local Time (05:00 GMT).
EUROPE
Colder in some parts of Finland than at Edmonton in Alberta today. Temperature at Mikkeli -13.9°C at 10 am Local Time (08:00 GMT). Minimum temperature -17.9°C, maximum -12.1°C. A "clear, sunny, calm winter day, with glittering snow and white scenery", the students reported. To see what Mikkeli looks like in these conditions, click here and scroll down the page to the picture that is labelled "snowy schoolyard and ice rink in Mikkeli, Finland". Almost as cold at Vörå and Vasa as at Mikkeli. Temperature at Vörå -13.4°C at 1 10 pm (11:10 GMT). Only one okta of cloud (cirrus) and the day "crisp and cold". Minimum temperature -15.9°C, maximum -7.2°C. Temperature at Vasa -12.6°C at 12.57 pm Local Time. Minimum temperature -14.2°C, maximum -6.3°C. Considerably warmer in southern Sweden than in Finland. Temperature at Bor School near Värnamo +4.3°C at 8 am Local Time (07:00 GMT). Rain of medium intensity falling. Weather described as "calm, dismal, fog, mild, overcast, warm for January". Maximum temperature 5.6°C, minimum +0.4°C. Temperature above 0°C in southern Norway, too. Even so, snow falling at Oslo at 12.15 pm Local Time (11:15 GMT). Sky then overcast and the temperature +2.5°C. Wind calm. Maximum temperature 2.5°C, minimum -4.0°C. For a webcam view of Oslo today, click here. For excellent webcam views of snowy Finland’s roads today, click here.
Another beautiful day in Constanta, Romania, where the cloud cover was at no time today more than a small amount of cirrus (one okta at 8 am and 12 noon Local Time, 3 oktas at 3 pm and 2 oktas at 6 pm). Much warmer than average for the time of year. Average maximum temperature 3°C. Maximum today 12.7°C. Maximum yesterday 15.0°C. A light breeze blew from a northerly point all day. A lovely sunny day on Malta, with only a small amount of cirrus cloud (one okta). Temperature 15°C at 10 am Local Time (09:00 GMT) and the wind Force 3 from the south-west. Maximum temperature 20°C, which is 5°C above average for the time of year. The students reported that a maremoto occurred last night, this being "like an earthquake in the sea".
"Mild and dry" in Madrid, where there were small amounts of cirrus cloud today (one okta at 9.15 am Local Time, 4 oktas at 3.20 pm). Temperature 8°C at 9.15 am (08:15 GMT), 12°C at 3.20 pm. Winds light, from the north Force 1 in the morning, the west Force 2 in the afternoon. Madrid another place that was warmer than average. Maximum temperature 14°C yesterday, 12°C today. Average for the time of year 10°C. Minimum temperature last night 6°C. Average for the time of year 0°C. Dull but mild in Strasbourg, France. Temperature reached 12.0°C today, which was 9°C above average. Minimum temperature 6°C last night, compared with the average of —1°C.
The report from Dublin’s Malahide Community School summed up the weather of the British Isles today: "another Atlantic frontal system approaches; wind and rain forecast". Slight rain falling at 9 am and the pressure falling, as is the case when a depression is approaching. Sky completely overcast.
"Grey, dull and windy" at Truro in Cornwall, the wind direction being south-westerly. Cloud type altostratus. Pressure falling there, too. Overcast with nimbostratus and pressure falling at Milford Haven in Pembrokeshire. Overcast, too, at several other places: Preston in Lancashire, Stone in Staffordshire, Pinewood School at Bourton near Swindon, St Oswald’s School in Sheffield and Bedales School at Petersfield in Hampshire. The cloud types at all of these places suggestive of an approaching Atlantic weather system.
A halo seen at Reading in England at 10 am (observation at the Royal Meteorological Society). For information about haloes, click here. Four oktas of cumulus cloud at Belvue School in Northolt near London at 12 noon. Six oktas of altostratus at Westbourne House School near Chichester in West Sussex at 10.30 am. "Clouds now coming over and wind picking up", the students reported. Sky "pinky purple in the east this morning" and pressure falling at Delabole in Cornwall. One okta of cirrus at Chaldon in Surrey. Cirrocumulus at Pitsford Hall Weather Station in Northampton and Lawford in Essex. One okta of cirrus at Radley College in Oxfordshire at 8.30 am, with the remark: "long-lasting contrails". These observations also indicative of an approaching frontal system. For further details, see Today’s Analysis.
A "bright sunny day with clear blue skies and a light winds" at Farr High School, northern Scotland, but a "severe weather warning ahead!". Dry and sunny at Portgordon in Morayshire at 1.37 pm, but raining farther south in Scotland at 1.30 pm, at George Watson’s College in Edinburgh.
NORTH AMERICA
"Winter storm causes problems from California to New England" was the title of a feature on the NOAA website today. To read it, click here. Low temperatures, snow, freezing rain and thunderstorms have already occurred across the USA and more severe weather is expected. Malibu in California has had its first snow in ten years. Raleigh in North Carolina was today well to the east of the boundary between warm and very cold air. The temperature there was 16°C at 7.52 am Local Time (12:52 GMT) with 7 oktas of cirrostratus cloud. Fog and a heavy dew reported. The weather was very different at Aurora in Illinois, where the temperature at 12 noon Local Time was only +1°C and snow was falling. A north-easterly wind of Force 6 was blowing and the sky was completely overcast. "Ten inches of snow fell during the night", the students reported. "School was called off due to the snow", they added! As predicted, the weather was warmer than of late at Edmonton in Alberta. It was still very cold, though, with a temperature of —15°C at 9.30 am Local Time (16:30 GMT). The maximum temperature of —5.0°C was considerably higher than of late but was still only 2°C above average for the time of year.
The weather was "overcast, breezy and cool" at Moses Lake in Washington State, with a temperature of 5°C at 11 am Local Time (19:00 GMT). The weather was therefore a little warmer than average, for the average maximum temperature at this time of year is only +0.9°C. At Katy in Texas, rain of medium intensity was falling and the sky was covered with nimbostratus cloud. The temperature at 2.05 pm Local Time (20:05 GMT) was 14°C. "This morning it was warm and now it’s cold", the students reported. Maximum temperature 27°C, which is more than 10°C above average for the time of year.
"Sunny and cool; warmer than yesterday" was reported from Reseda in California, where the temperature was 10.9°C at 1041 am Local Time, after a minimum of —1.7°C. A "clear day in Pasadena", the students of Pasadena City College reported. No cloud at all at 12.37 pm Local Time (20:37 GMT). Temperature 15°C. Maximum temperature 16°C, minimum 4°C. Thus colder than average for the time of year. Sunny, too, at Livermore in California, where the temperature at 1 pm Local Time (21:00 GMT) was 11°C, the highest of the day. The minimum temperature was —3.9°C. Thus, Livermore was another place colder than average for the time of year.
TODAY’S ANALYSIS
For today’s Features of the Day, click here.
On the so-called ‘visible images’ from satellites, what you see is more or less what you would see with your own eyes if you were in the satellite and looking in black and white. On the so-called ‘infra-red images’, the whitest areas are the coldest and the blackest the hottest. Thus, high clouds show as white areas. Medium-level clouds and very cold land areas show as grey. For information on how to obtain satellite images of the highest quality, see the notes section below.
For the history of the Beaufort Scale of Wind Force and guidance on how to interpret weather charts, go also to the Notes section.
AUSTRALASIA AND SOUTHERN ASIA
It is evident from the visible satellite image for 03:00 GMT today that cold air was then flowing across the Sea of Japan from eastern Asia and becoming unstable when heated and moistened from below as it passed over the sea. There was a strip of cloud-free air off Russia and Korea but cumulus clouds were present over most of the Sea of Japan. There appears to have been orographic lifting over the western (windward) slopes of Japan, for there was more cloud over these slopes than over the sea. In contrast, the eastern (lee) side of Japan was comparatively free of cloud. Off the eastern coasts of Japan, air remained cloud-free for a while, but passage of the eastward-moving air over the sea soon produced clouds again.
Today’s 06:00 GMT satellite image from Wisconsin shows that the ITCZ was again active over the eastern half of the Indian Ocean, Indonesia and the western part of the Pacific. As is usual at this time of year, the axis of the ITCZ lay a few degrees south of the equator in most parts of the eastern hemisphere, but the ITCZ was not as active today over Jakarta as it was yesterday and the day before (when 200 mm of rain fell on Jakarta, i.e. 60% of the month’s average rainfall). January and February are the wettest months of the year in Jakarta. Which are the wettest in Singapore and Medan (and why)? To find the climatic data you need to answer this question, click here for Medan and here for Singapore.
Today’s 08:00 GMT visible satellite image shows that skies were cloudless or near-cloudless over much of the Indian subcontinent and a large part of the Arabian Sea. The Indus Valley can be seen clearly. So, too, can the snow-covered Himalayas. Throughout much of the troposphere, air sinks over southern Asia at this time of year, keeping skies largely free of cloud. The sinking air is part of the Hadley Circulation. The small amount of cirrus cloud reported at New Delhi today may well have been formed by aircraft (contrails). A tropical depression today brought cloud to Sri Lanka and southern parts of the Bay of Bengal. Much of this cloud was cumulonimbus. The ITCZ can be seen near the foot of the satellite image, its axis several degrees south of the equator.
Today’s 06:00 GMT weather chart for Australia and adjacent regions shows that barometric pressure was again low over most parts of Australia and the Coral Sea, with pressure high to the west of New Zealand’s North Island (1021 mb), the south of Tasmania (1025 mb) and the south-west of Perth (1033 mb). The cold fronts near New Zealand’s South Island and to the south of Australia can be seen clearly on today’s infra-red satellite image for 05:32 GMT, with an extensive area of cumulus and cumulonimbus activity visible south-west of the cold front that lay to the south of Australia. This image shows a few scattered cumulonimbus clouds over Queensland and the far north of Australia, but the Australian monsoon appears to have been weak today.
AFRICA
Today’s 06:00 GMT weather chart for southern Africa and adjacent oceans shows that pressure was low near Durban (1011 mb) and over the Mozambique Channel (also 1011 mb). Low, too, over north-eastern Namibia, this being a so-called ‘heat low’, which is a feature that appears on charts of sea-level isobars over elevated plateaux when air temperatures are high (see note in green below). Rain over south-eastern South Africa associated with the Low near Durban and its associated fronts. Pressure high off Cape Town (1025 mb) and near Kerguelen (1030 mb). Once again, there were many vigorous depressions over the Southern Ocean in the so-called ‘Roaring Forties’ and ‘Furious Fifties’. As on previous days, a ridge of high pressure extended northwards over the South Atlantic as far as Ascension Island. The satellite image for 06:00 GMT shows that the ITCZ was not as active over Africa as it has been of late, but it must be noted that the satellite image shows cloud formations quite early in the day (only 8 am in southern Africa). As a result of strong surface heating, this being the time of year when the sun is overhead at mid-day south of the equator, convective clouds tend to build up during the day. The sun was overhead at 17°30’S today. Sinking air in the Hadley Circulation again maintained clear skies over most parts of North Africa.
Students might like to consider what meaning sea-level isobars have in regions which lie well above sea level! Much of southern Africa lies more than 1000 metres above sea level.
EUROPE
To return to the weather report for the British Isles, click here.
The weather chart for 00:00 GMT for Europe and the eastern North Atlantic shows a deep depression (966 mb) west of Ireland (near 52°N27’W). This depression moved rapidly eastwards. This morning, easternmost parts of England were under the ridge of high pressure ahead of the Low. The halo at Reading indicated cirrostratus cloud, as this is the only cloud that displays a complete halo. Several stations farther west reported altostratus cloud. The classic sequence of clouds associated with a warm front was observed.
Satellite images showed the cloud patterns of the depression and its fronts very clearly. For an 06:00 GMT image, click here. For a 12:00 GMT image, click here. To return to the weather report for the British Isles, click here.
Today’s 06:00 GMT chart of isobars, temperatures and significant weather shows the low temperatures over Finland (and western Russia), mist and fog over southern Europe and snow and rain over Norway, Sweden, Latvia, Lithuania, Denmark and the Low Countries. The plotted observations over Scandinavia also show the low temperatures over Finland and the precipitation over Norway and Sweden. The fog over southern Europe was most likely radiation fog, which occurs when skies are clear at night and winds light. As the 00:00 GMT weather chart shows, pressure was high over the southern half of Europe and winds generally light. For a feature which focuses upon radiation fog and steam fog, click here.
Stormy weather is forecast for the British Isles tomorrow. For information about one of the most damaging storms to strike the United Kingdom in recent times, namely The Great Storm of 1987, click here. For a feature on the storms that brought havoc to the British Isles in October 2000, click here. This feature contains exercises that are intended for school use.
NORTH AMERICA
For a chart showing temperatures (in degrees Fahrenheit) over North America at 10:00 GMT today, click here. This shows the huge contrast in temperature between the mild south-east and the bitterly cold air over central, western and south-western parts of the USA. Notice how low temperatures were over central Canada: below —35°F (-36°C) in some places. For a chart showing temperatures over the USA at 11:00 GMT today, click here. For a chart showing isobars over North America at 11:00 GMT today, click here. For a chart that shows fronts and significant weather at the same time, click here. For a detailed plot of observations and isobars over North America at 00:00 GMT today, click here. These charts show that high pressure was the dominant influence over western parts of the USA, whilst low pressure was centred south of the Great Lakes.
FEATURES OF THE DAY
For Today’s Review of MetLink Observations, click here.
For Today’s Analysis, click here.
To return to the analysis for Europe, click here.
To go to the Notes section, click here.
FEATURE 1
To go to Feature 2, on WEATHER HOUSES, click here.
RADIATION FOG AND STEAM FOG
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The picture on the left shows fog over Bute Park in Cardiff, South Wales, UK. The picture on the right shows fog over the St Lawrence at Quebec in Canada. The kind of fog that occurred at Cardiff is called radiation fog. The kind that occurred at Quebec is called steam fog.
RADIATION FOG forms when the sky is clear and the wind speed no more than Force 1. Typically, it forms at night and dissipates during the day. In mid-winter, however, particularly in latitudes where the sun is low in the sky (e.g. north-west Europe), it may linger all day.
When the sky is clear at night, land surfaces radiate heat to space and therefore cool. Sea and lake surfaces do not, however, cool by more than a small amount overnight (much less than 1°C). If the air in contact with a surface is cooled to its dew-point temperature, small water droplets form (condensation). If there is no wind, droplets of dew form - on, for example, grass. If there is a very gentle breeze, the tiny water droplets are stirred upwards to form a shallow layer of radiation fog, as in the picture of fog at Cardiff. This type of fog does not form over the sea because the temperature of the sea’s surface stays much the same day and night. If the dew-point temperature lies below minus 0.5°C, hoar-frost forms instead of dew. It does not form between 0°C and minus 0.5°C because latent heat is released when condensation occurs and this heat is sufficient to melt the tiny ice crystals that make up hoar frost as they form. During the day, the sun’s rays heat the ground beneath the fog. Most of the rays are actually reflected from the top of the fog but some reach the surface, otherwise it would not be daylight in the fog! The ground is gradually heated until the dew-point temperature is exceeded. The fog then dissipates, often very quickly.
STEAM FOG forms when cold air flows over water that is more than 9° or 10°C warmer than the air. Over sea water, steam fog is called sea smoke. Condensation results mainly from the cold air mixing with the air that is in contact with the water surface. However, convection also occurs, because the water is so much warmer than the overlying air. This convection causes the mixed air to rise a metre or more, thus enhancing the process of fog formation. Because of the convection, the water appears to ‘steam’. At Quebec on the occasion the photograph was taken, the air temperature was minus 20°C and the cold air was flowing over water behind the ship from which the photograph was taken. The temperature of the water could not have been lower than about 0°C, otherwise the water would have been frozen! In the St Lawrence at Quebec, the water’s salinity is close to zero, so the water’s freezing point is close to 0°C.
Radiation fog may be as much as 100 metres deep, and it tends to lie in valleys, because that is where katabatic drainage takes cold air. Moreover, valleys are moist if, as is often the case, they contain streams and/or marshy ground. Steam fog and sea smoke are rarely more than a metre or two deep. Steam fog may be seen on a small scale over a bowl of hot water, especially if the water is out-of-doors on a cold morning.
For Today’s Review of MetLink Observations, click here.
For Today’s Analysis, click here.
FEATURE 2
To return to the feature on RADIATION FOG AND STEAM FOG (Feature 1), click here.
Weather houses like those shown above used to be very popular. They are devices that show changes in humidity. When the air is moist, the man with an umbrella comes out of the house. When the air is dry, the woman comes out. The principle behind this device is that the man and woman are attached to a support that is hung on a twist of humidity-sensitive material such as hair or catgut. The material stretches when moist and shrinks when dry.
It is quite easy to make a weather house. You can use Lego to make the house itself, a thick piece of card to make the support and thinner card to make the figures of the man and woman. You can suspend the support from a cork. The tricky bit is getting the support to hang in exactly the right place, so that the man isn’t always in the house or always out of it!
If your weather house is in a lounge, classroom or anywhere else indoors, it responds to humidity changes in the room where it is located, rather than to changes out of doors.
Source of the line diagram: ‘The Weather Book for Primary Teachers’ by Steve Harrison and Frank Havard (Simon & Schuster, 1991).
Source of the picture not known. For pictures of weather houses, click here or here. These are both commercial websites.
To go back to the feature on RADIATION FOG AND STEAM FOG (Feature 1), click here.
For Today’s Review of MetLink Observations, click here.
For Today’s Analysis, click here.
To return to the analysis for Europe, click here.
NOTES
SATELLITE IMAGES FROM DUNDEE
You can obtain satellite images of the highest quality from the Dundee Satellite Receiving Station, Dundee University, Scotland. For further information, see the ‘Notes’ sections of the MetLink weather reports for 22 and 23 January.
To return to Today’s Analysis, click here.
To go to Features of the Day, click here.
THE BEAUFORT SCALE OF WIND FORCE
If you want to learn about the history of the Beaufort Scale of Wind Force, click here. If you don’t know where on the web to find the scale for land observers, click here.
To return to Today’s Analysis, click here.
INTERPRETATION OF WEATHER CHARTS
For guidance on how to interpret weather charts, click here.
To return to Today’s Analysis, click here.