|
Weathercam "image of the day" Krakow, Poland
Student maps & analysis for 20 March, 2000 CloudWatch data for 20 March, 2000 |
|
|
Weathercam "image of the day" Krakow, Poland
Student maps & analysis for 20 March, 2000 CloudWatch data for 20 March, 2000 |
|
Pressure was high over the British Isles. At 0000 UTC today, a High of 1037 mb was centred just off south-west Ireland. By 0600 UTC, it had moved very little and its central pressure had changed little (to 1036 mb). By 1800 UTC, it had declined to 1030 mb but still extended across the British Isles to northern Germany.
The UK Met.Office's 0000 UTC chart shows a cold front extending north-eastwards from mid-Atlantic past Shetland to the coast of Norway just north of Trondheim and onwards to a Low of 969 mb centred near Tromsø. This front moved south-eastwards during the day and waves developed on it. By 1800 UTC, the front lay across the northernmost part of Scotland and ran across southern Sweden and southern Finland. The Low from which this front extended moved north-eastwards and was centred to the east of Svalbard by 1800 UTC. A warm front associated with this Low brought cloud to Poland, northern Germany and the southern Baltic [exercise for students: what type of cloud?].
Pressure was low today over Portugal, Spain and the southernmost part of France. At 0000 UTC, a Low of 1013 mb was centred off south-west Portugal. By 0600 UTC, it had deepened to 1011 mb. By 1800 UTC, it had deepened still further to 1008 mb. Pressure was low, too, over western Russia.
There was rain in eastern Spain and snow over many parts of Bulgaria, Romania and Ukraine. Snow showers occurred over northern parts of Scandinavia and the far north-west of Russia. In association with the front that moved into the north of Scotland today, drizzle and light rain occurred over the northernmost parts of the British Isles. Elsewhere, the anticyclone brought generally dry weather, but many parts of England were foggy early in the day.
The winds over Scotland and Scandinavia were from the west. Over the rest of the British Isles and over much of France, Germany and the Low Countries, they were light and variable.
32 schools and individuals had entered observations in the database by 2300 UTC today. Of these, only Farr High School in the north of Scotland, CEAM at Valencia in Spain and The Eagle's Nest in France reported precipitation. There was rain at Valencia, where nimbostratus cloud was reported at 0800 UTC. Satellite images show that cloud covered much of eastern Spain all day today. Slight to medium snow was reported from The Eagle's Nest, which is located at an altitude of 1350 metres on the south face of Mont Lozere (1699 m), the highest peak in the Cevennes National Park. The cause appears to have been a weak trough of low pressure from a Low centred just off the south coast of France. Slight to medium drizzle was reported from Farr High School. In the early morning, fog occurred in parts of England, as the reports from Northampton, Abingdon and the Royal Meteorological Society show. This fog soon cleared.
Satellite images from Dundee show that wave clouds were widespread over southern Norway and central Sweden. These clouds are clearly evident on the satellite images (see, particularly, the 1324 UTC and 1601 UTC Channel 1 and Channel 4 images). They show up as parallel bands of cloud at right angles to the wind, which blew from the west. They did not reach Kolbotn, Bor or the Stockholm area, where skies were generally free of all but cirrus cloud. Indeed, the moisture in the upper troposphere was evident in the reports of persistent contrails over Bor and the Stockholm area. The Channel 1 images are what are called 'visible images', i.e. they show what your eye would see if you were looking in black and white. The Channel 4 images are infra-red. On these, the coldest areas are the whitest, the hottest the blackest.
Persistent contrails were also observed at Bonn (Germany), Bozen (northern Italy), Conyers (north of England), Hautlieu (Jersey) and Clarens (Switzerland). They were also observed at Strasbourg, where the observer noted that the trails had formed a near-perfect cross. He also suggested that the light cirrus that could be seen may have originated as earlier aircraft trails. Upper-air soundings show that the upper troposphere was moist in all of the places where persistent contrails occurred.
At Clarens, there appears to have been a lovely sunny day, but cloud was not far away. As Dundee and Meteosat satellite images show, a band of cloud covered much of Austria and southern Germany for part of the day. The clear skies over Switzerland, northern Italy and south-east France allowed excellent satellite views of the Alps (see Dundee Channel 1 images for 1504 UTC and 1601 UTC). See also the Meteosat C2D images, which are 'visible images'.
Lastly today, we note the observations from Holywell, North Wales, which is near a power station that generated a small amount of cloud this morning. Other CloudWatch participants are near power stations. Look out for clouds associated with these power stations (enhanced cumulus growth, for example, over warm plumes).
Subject: Interesting clouds Date: Sun, 19 Mar 2000 20:21:34 -0000 Dear CloudWatch friends Below you will find sections of two satellite images which I think you will find interesting. The images were obtained from the Dundee satellite receiving station http://www.sat.dundee.ac.uk/ on 19 March, 2000. The 0634 UTC (GMT) image, an infra-red 'Channel 4' image, appears to show three parallel aircraft condensation trails over the Atlantic north- west of Ireland. I say "appears" because I can't think what else the clouds in question might be. Humidity conditions in the upper troposphere were such that contrails could be expected to persist. The alignment of the clouds marked with arrows on the attached file (WNW- ESE) is not consistent with the wind direction (WSW) at trans-Atlantic jet airliner levels (11-11.5 km) but is consistent with the flight paths of planes crossing the Atlantic from Canada to the UK. The 1623 UTC image shows a cloudy wake downwind of the Faroe Islands. The wind direction at the surface over the ocean near the Faroes is shown on the diagram in the attached file. The image is a visible 'Channel 1' image. The clouds you see on the picture are what you would see if you were in the satellite and viewing in black and white. If you are not already a registered user of the Dundee University satellite facility and wish to become one, you should visit: http://www.sat.dundee.ac.uk When connected, click on "Register for free images" and then follow the instructions to gain FREE access to images. You need to choose a password when registering and use it to gain access to the images. If anyone disagrees with my comments on the two images in the attached file, please let me know. Best wishes Malcolm Walker
