Clouds Part 1 (From Worcester News)

Clouds Part 1

3:44pm Thursday 10th September 2009 in News By Paul Damari

Clouds that form at high altitude have names beginning with "cirr" or "cirro". Cirrocumulus, Cirrostratus, Cirrus. These are high level clouds ranging between 5 and 14 km (16,500-45,000 ft), and often at lower level in high latitudes than in the tropics, because the tropopause is higher in the tropical regions of our globe. All high level clouds beginning "cirr" because of their resemblance to hair, they are as thin and wispy as they look and are made by the changing of water vapour into ice crystals at very high altitude due to temperatures which are well below the freezing level.

Patchy cirrus can been seen in otherwise cloudless skies in fine anticyclonic conditions, but they are also seen ahead of approaching warm fronts. If cirrus increases across the sky as a uniform layer, which we in the trade call cirrostratus, wind and precipitation will soon follow. Often a halo can be seen around the sun or moon, and the saying goes "the bigger the ring the nearer the rain".

Cirrus cloud is made from falling ice crystals drawn out be the wind and often resembles a mares tail. The longer the filaments, the stronger the upper wind. Sailors at sea once used cirrus as a "wind warning", gales can also be expected especially in the autumn and winter months.

Next Week Clouds Part 2

Glossary -

Halo: A bright circle of light around the Sun or Moon. It is white with a touch of red on the inside, and violet on the outside when it appears around the Sun. It is caused by the refraction of light through ice crystals at high altitude and may be followed by rain as part of a depression or low pressure system.

Weather for Coming Week
Monday 7th September-11th September
High pressure influencing our weather through the coming week into next weekend bringing with it fair pleasantly warm weather. Winds mainly light to moderate from the south-west then north-east to east from mid week onwards. Mist and fog may form early each morning-tide.

Maximum temperature 20-22c 68-72f.

Minimum temperature 13-15c 55-59f but cooler later in week.

Last Week's Observations (Monday-Sunday)

Highest day temperature............21.0c on Monday 31st August

Lowest night temperature............9.2c on Thursday 3rd September

Wettest day...............................11.2 mm on Wednesday 2nd September