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Click on today's infra-red satellite images below for full size version (source: Nottingham University)
Click here for today's whole-earth Intellicast image
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In south-east England this afternoon and evening, it has been cloudy and rainy, with winds from the west or south-west and temperatures above 10°C. In southern Scotland today, it has been very wet, with over 30 mm of rain in 12 hours in some places. In the north of Scotland, blustery showers have replaced earlier wet weather, and Stavanger, too, in the south-west of Norway, has experienced unsettled, mild, weather with showers of rain. What is causing the unsettled weather in the British Isles and southern Scandinavia?
The principal sources of cloud, poor visibility, rain and strong winds in middle and high latitudes are weather features called depressions, which are highly mobile low-pressure systems several hundred to a few thousand kilometres in diameter. Their general direction of movement is towards the east, but they may move in any direction. Over the oceans, they tend to be at their most intense when their centres of low pressure lie between the parallels (latitudes) of 50° and 70°.
Today's weather chart for north-west Europe and adjacent parts of the North Atlantic Ocean shows a large depression centred near Iceland (60-65°N), with strong westerly winds on its southern flanks. In the northern hemisphere, winds blow counter-clockwise around depressions. Much of the rain has been associated with fronts crossing the British Isles, though blustery showers have occurred south and south-east of Iceland, as can be seen on satellite images available from Dundee. Clusters of shower clouds (cumulonimbus clouds) show up on satellite images as speckled areas. Fronts are boundaries between air currents of contrasting temperature and humidity. A cold front has today been moving southwards across Scotland and northern England, with cool air to its north replacing warmer air to its south. It reached southern parts of the British Isles this afternoon. On the eastern flanks of the depression, fronts have brought precipitation to southern Norway. In northern Finland, north-westerly winds associated with a depression north of Norway have brought temperatures lower than yesterday's, as the weather report from our school near Vaasa indicates.
Today's weather chart for the oceans south and west of southern Africa shows several depressions centred near 50°S, one of them a very intense system with a central pressure as low as 960 mb. Between 40° and 50°S, in the so-called 'Roaring Forties', there were strong winds from the west. Between 50°S and the Antarctic continent, there were strong easterly winds. In the southern hemisphere, winds blow clockwise around low-pressure systems. To study weather systems over the Southern Ocean, you can use weather charts available from the South African Weather Bureau or the Australian Bureau of Meteorology.
The tropical cyclone that was off southern Madagascar yesterday has continued to travel southwards and is now well away from land. The cyclone off western Australia has also ceased to be a problem.
The MetLink schools in Australia, where it is summer, have reported fine weather and high temperatures. With high pressure east of Tasmania, northerly winds have brought hot air from the interior of Australia to our schools in Victoria. What will tomorrow bring, though? Weather charts and satellite images indicate that a cold front is approaching Tasmania and Victoria from the west.
As MetLink weather reports from southern Africa, Ethiopia, Uganda, Oman and Ascension show, and satellite images confirm, the weather has been fine, hot and generally sunny in the subtropics. At Bombay, too, the weather has been hot and sunny, but today's hourly weather reports from Bombay (Santa Cruz) Airport mentioned smoke. What was the reason for this? Bombay: can you tell us more about this observation?
Visitors to Spain, Portugal and Mediterranean locations expect warm, sunny weather for their summer holidays but may not be aware that the weather can be very changeable in winter. There was fog at the MetLink school in Spain this morning (Vidal), rain in Portugal (Gabriel Pereira) and quite a lot of cloud around Malta.
Fnally today, we visit Edmonton, Alberta, where it was still quite mild for the time of year. The temperature at James Gibbons School reached -2.5°C by day and did not fall below -11°C at night! As their weather report shows, winds were from a southerly point. Even where winds were from the north, though, in Quebec Province, temperatures were not especially low for this time of year.
To visit the website of your national weather service, click here, but please note that some countries do not yet have websites.
Again, like yesterday, the weather in the MetLink world has not been much out of the ordinary for the time of year. As today's DTOT Meteosat image shows, the Intertropical Convergence Zone (ITCZ), the band of near-equatorial convective systems that produce cumulus and cumulonimbus clouds, thunderstorms and heavy bursts of rain, lay, as usual at this time of year, a little to the south of the equator, with generally clear skies to the north and south of it (the dominant influences there being subtropical anticyclones). The zone was, however, a little more extensive than yesterday. The weather reports from MetLink schools in southern, central and North Africa show that the weather in those places was again warm and generally sunny, with temperatures reaching the upper 20s and in some places 30°C. Weather charts and satellite images show that vigorous depressions were again present over the Southern Ocean well to the south of South Africa and Australia, but this occurrence is normal, for these latitudes have been nicknamed the 'Roaring Forties' and 'Furious Fifties. The dominant weather influence at Ascension was again the South Atlantic subtropical anticyclone.
In Oman and south-east Australia and at Bombay, the weather was also warm and sunny, with temperatures up to 30°C. The JMA/GMS satellite image of Australia shows a few clouds over Victoria, where our MetLink schools are located. It also shows that skies over the desert regions of Australia were a little cloudier than yesterday, though the cloud appears to have been at medium and cirrus levels. With high pressure east of Tasmania, northerly winds have brought hot air from the interior of Australia toVictoria. What will tomorrow bring, though? Weather charts and satellite images indicate that a cold front is approaching Tasmania and Victoria from the west.
There was again warm, dry, sunny weather at Bombay, but the hourly observations made at Bombay (Santa Cruz) Airport mentioned smoke. Where did this smoke come from? Bombay: can you tell us why smoke was reported?
Over southern Europe, as our schools in Spain, Portugal and Malta reported, the weather was apparently not as pleasant as yesterday. There was rain in Portugal, fog at Tarragona and cloud around Malta. In Cyprus, though, the weather was sunny and clear.
In northern Europe, depressions have again brought strong winds, rain and mild weather. In south-east England this afternoon and evening, it has been cloudy and rainy, with winds from the west or south-west and temperatures above 10°C. In southern Scotland today, it has been very wet, with over 30 mm of rain in 12 hours in some places. In the north of Scotland, blustery showers have replaced earlier wet weather, and Stavanger, too, in the south-west of Norway, has experienced unsettled, mild, weather with showers of rain.
Today's weather chart for north-west Europe and adjacent parts of the North Atlantic Ocean shows a large depression centred near Iceland (60-65°N), with strong westerly winds on its southern flanks. Much of the rain has been associated with fronts crossing the British Isles, though blustery showers have occurred south and south-east of Iceland, as can be seen on satellite images available from Dundee. Clusters of shower clouds (cumulonimbus clouds) show up on satellite images as speckled areas. A cold front has today been moving southwards across Scotland and northern England, with cool air to its north replacing warmer air to its south. It reached southern parts of the British Isles this afternoon. On the eastern flanks of this area of low pressure, fronts have brought precipitation to southern Norway. In northern Finland, north-westerly winds associated with a depression north of Norway have brought temperatures lower than yesterday's, as the weather report from our school near Vaasa indicates.
The UK Met.Office's forecast chart for 1200 UTC tomorrow indicates that winds over the British Isles will be from the north-west, with high pressure south-west of Ireland and low pressure over Scandinavia. Showers can again be expected over Scotland and Northern Ireland.
Fnally today, we visit Edmonton, Alberta, where it was still quite mild for the time of year. The temperature at James Gibbons School reached -2.5°C by day and did not fall below -11°C at night! As their weather report shows, winds were from a southerly point. Even where winds were from the north, though, in Quebec Province, temperatures were not especially low for this time of year. Charts from the Canadian Meteorological Service show an area of low pressure just to the west of Vancouver, a ridge of high pressure over central Canada and a depression just to the west of Newfoundland.
How different is your weather from average? To try and find out, you might like to visit the Royal Meteorological Society's website, where you will find a facility called Climate on the Web. Go, in particular, to Buttle and Tuttle's WorldClimate.com and The Washington Post's site.
To visit the website of your national weather service, click here, but please note that some countries do not yet have websites.
