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Weathercam "image of the day" Bergen, Norway
Student maps & analysis for 23 March, 2000 |
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Today, there was a deep slow-moving depression over the Atlantic. At 0000 UTC, its depth was 988 mb and its centre was at 54°N 24°W. By 0600 UTC, it had deepened to 980 mb and its centre moved to 57°N 23°W. By 1200 UTC, it had deepened a little more, to 976 mb, and was still centred at 57°N 23°W. This depression was mentioned in yesterday's CloudWatch report. It developed as a wave on the cold front that extended yesterday from western Russia to the western Atlantic south of the Newfoundland Grand Banks. The front was still largely intact today, though considerably more distorted than yesterday.
A shallow area of low pressure brought rain to the north-western tip of France, the Channel Islands and many parts of the British Isles. This Low moved northwards in the southerly flow ahead of the Atlantic depression. At 0600 UTC, it had a centre of 1006 mb over the middle of the Bay of Biscay and a centre of 1005 mb over the Celtic Sea (between Land's End and the south-western tip of Ireland). At 1200 UTC, it was evident merely as a trough extending south-eastwards from the Atlantic Low.
Pressure was still low over northern Norway. The central pressure of the depression was 977 mb at 0600 UTC and 980 mb at 1200 UTC. As was the case yesterday and the day before, an occlusion wrapped right round this Low, from the north of Norway, across the Barents Sea and round the northern and eastern flanks of the Low to western Russia. At 0600 UTC, the (weak) cold front of this now well-decayed Low extended across northern Poland and southern Denmark to the north-eastern tip of England. From there, the front continued as the warm front of the Atlantic Low.
Radar images show that a band of rain moved northwards across north-west France and the British Isles during the day. The northern edge of this rain had reached south-west Scotland by 0800 UTC, the Glasgow area by 1100 UTC, the southern part of the Great Glen by 1400 UTC and the northern part by 1500. Over Wales, it was wet almost all day. Over eastern England, there was hardly any rain until the evening.
Pressure was higher than of late over southern Iberia (1018 mb at 0600 UTC, 1016 mb at 1200 UTC) but there was still a lot of cloud over Spain and Portugal today. A deep Low (1002 mb) centred near Cyprus brought cloud and rain to the eastern Mediterranean. To the west and north-west, over much of Italy, the Plain of Hungary and central Europe, skies were largely clear of cloud. The anticyclone that had been so dominant over western and central Europe on previous days was now but a weak ridge of high pressure. Over south-eastern France and the far north-west of Italy, cloud was extensive, associated with weak areas of low pressure. This cloud sheet moved south-eastwards into northern Italy during the afternoon.
The winds over Scandinavia were from a westerly point (mainly from the north-west over central and northern Norway and Sweden). They were from the east or south-east overthe British Isles and the Low Country and from the south over much of France. Elsewhere in the CloudWatch world, they tended to be rather light and variable.
Since the days of the ancient Romans, if not before, Britain has been known as a land of mist, fog and rain! England lived up to its reputation for producing fog earlier in the week. Today, many parts of the British Isles had some rain, which was, in fact, something of a novelty, because March has been rather dry in many parts of Britain this year. Today seems to have been a miserable day at Wells, judging by the report from the CloudWatch school there. At other CloudWatch locations, however, the rain, though widespread, was light or no more than moderately heavy. Reports of medium-intensity rain came only from the schools in Liverpool, Wolverhampton, Holywell and Roose. Elsewhere, the rain was very light. The rain spread to Lincolnshire and Yorkshire during the evening. Probably the best place to be in the British Isles today to escape thick layer cloud was the north of Scotland, where cumulus and cumulonimbus were the main cloud types.
Elsewhere, very few CloudWatch participants reported precipitation. Both stations in Spain reported nimbostratus cloud and rain and the Eagle's Nest reported slight drizzle. The observers at this station were above the cloud (8/8 stratus) at 0825 UTC but found themselves in it later on, when the cloud base rose. [Eagle's Nest: how much of your cloud today was orographic?]
At the CloudWatch schools in Scandinavia, the day was quite sunny, as the reports from Kolbotn, Bor's School, Rantakylan and the schools in the Stockholm area show. For a view of today's cumulus activity over Finland and parts of Sweden, visit the Dundee satellite website, looking particularly at the 1250 UTC Channel 1 image. The cumulus activity over the sea to the west of Norway shows up clearly, too, on this image. The reason for the convective activity is that the winds here were blowing from the north-west, and these winds were cold. The air was heated from beneath as it passed across the warmer sea. Thus, the air became unstable.
There was some fog today in northern Italy (as the report from Bozen indicates). Generally, however, the weather was sunny for the first half of the day, though Torino was on the edge of an extensive bank of cloud, as the 1330 UTC Meteosat C2D image shows. This is a 'visible image', showing the clouds as an observer inside the satellite would see them if looking in black and white. The bank of cloud moved south-eastwards, bringing cloud to Bozen during the afternoon.
As the 1330 UTC Meteosat image and the images from Dundee show (see, particularly, the 1429 UTC image), St George's School (Switzerland) had quite a lot of cloud today. Krakow, however, had a lot of sunshine, though a few showers did develop over northern Poland today. Both at Bozen and Torino, contrails were persistent this morning, indicating that the upper troposphere was moist. For upper-air soundings at stations across Europe, click here.
To finish, we return to the rain over the British Isles. At Reading, there was light intermittent rain for about two hours during the afternoon. Cars were covered with dirty spots, on both the bodywork and the windows. This suggests that dust from the south, possibly Saharan dust, was brought down by the rain. The winds in the troposphere have in recent days been consistent with this suggestion. Perhaps a CloudWatch school will feel moved to investigate. If, for such a project, you need any help over finding upper-air charts on the web, please contact Malcolm Walker. The upper-air soundings that are archived on the web provide temperatures, dew points, wind speeds and wind directions from the bottom of the troposphere to the top and upwards from there into the lower stratosphere.
On the chart for your region, you should find a weather station fairly near to you or even very close to you. On the chart for Italy, for example, there is an observation for Malta, and on the chart for Scandinavia you can find observations for Bergen, Oslo and Stockholm. On the chart for Spain, observations for Madrid and Valencia can be seen.
Here is a selection to choose from (click on the name):
Helsinki-Vantaa | Stockholm/Arlanda | Bergen/Flesland | Krakow | Berlin-Tempelhof | Koeln/Bonn
Bolzano (Bozen) | Torino/Caselle | Torino/Bric Della Croce | Madrid/Barajas | Valencia/Aeropuerta
Bristol/Lulsgate | Manchester Airport | London/Heathrow | Birmingham Airport
For other stations in Great Britain, click here.
Austria | Belgium | Czech Republic | Denmark | Finland | France | Germany | Hungary
Italy | Jersey | Latvia | Lithuania | Netherlands | Norway | Poland | Portugal | Russia
Spain | Sweden | Switzerland | United Kingdom
From: education@royal-met-soc.org.uk Subject: World Meteorological Day Date: Thu, 23 Mar 2000 12:11:50 -0000 Dear CloudWatch friends Today is World Meteorological Day. What is the significance of 23 March 2000? Well, 23 March is World Meteorological Day every year, but it's especially significant this year because the Convention of the World Meteorological Organization (WMO) came into force on 23 March 1950, so this year WMO celebrates its 50th anniversary. See: http://www.wmo.ch/wmo50/ and http://www.wmo.ch/web/Press/WMD2000.html There's a theme for World Meteorological Day every year. This year, it's "WMO - 50 years of service". WMO is a Specialized Agency of the United Nations. It is based in Geneva and has 185 members (179 Member States and six Member Territories). It's a very important body in meteorology. For details of WMO's work, visit: http://www.wmo.ch/ Best wishes Malcolm Walker
