© Jim Galvin
Newcastle, County Down, Northern Ireland, United Kingdom of Great Britain and Northern Ireland
Latitude: 54° 10' 46'' N
Longitude: 5° 52' 29'' W
09 August 2015 1206 (Local Time)
Camera direction: towards E
Image P/S code: P.7.3
Image I.D.: 5488
CL = 5, CM = 3, CH = 1
The photo shows an unusual view of Stratocumulus (species lenticularis), looking downwind of the wind flow. Viewed from the side, lenticularis often forms a series of waves in the shape of lenses or almonds, usually with well-defined outlines and generally of orographic origin. In this image, the photographer was within 5 km of the peaks of the Mountains of Mourne, Northern Ireland, UK, which exceed 600 m. A strong boundary layer wind forced the airflow up the windward side of the mountain range, with this view showing the compensating downward flow on the leeward side; immediately in front of the photographer, the cloud is dispersing to leave a clear slot. In the distance, the next in a series of waves can be seen. Small amounts of Cirrus and Altocumulus cloud are also visible through the gap.
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The synoptic pattern at 0000 UTC on 10 August 2015 was similar to that at the time of the photograph. Low pressure was centred near Iceland, with a front trailing down the North Sea to southern Ireland. An occluded front was approaching western Ireland. The image location was in a stable boundary layer region between the fronts.
The sounding from nearby Castor Bay, Northern Ireland (WMO 03918) shows 25-kt (12.9 m/s) winds and a saturated layer from about 890 to 940 hPa. The flow on the windward side of the mountains was capped by a temperature inversion, creating conditions for wave cloud development below approximately 1 000 m.
The time lapse shows the formation of lenticular clouds over Table Mountain, South Africa on 8 November 2015 from about 1450 to 1930 hours local time. A number of species and varieties are illustrated in this time-lapse video. The formation of Altocumulus lenticularis (standing wave) is seen approximately 20 seconds into the video. There is also an extensive layer of stratiformis enveloping the sky from around 30 seconds, and orographic clouds can be seen moving over the windward slopes of the mountain.
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This stationary wave cloud has formed in a strong, stable and relatively moist airflow over the double peaks of Mt. Elbrus, Russia's highest mountain. It has the appearance of an extended flag, pennant or banner downwind from the mountain summits, and from the point of observation is classed as Stratocumulus lenticularis. An Altocumulus cloud above also exhibits a wave pattern initiated by airflow over the mountain.
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The patch of orographic Stratocumulus at 1 - 2 has its base at 600 m and its upper surface at 1000 m. Cumuliform bulges emerging from this patch indicate some instability. Note that on the windward side the base is particularly sharp and the bulges are not present, in contrast to the leeward side, where the bulges are conspicuous. Fibrous patches of lenticular Stratocumulus and Altocumulus are also present.
The picture was taken on the southern edge of an anticyclone centred over the 30th parallel. North-westerly surface winds brought somewhat unstable modified cold air over the island.
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