Mammatus Clouds (a Special Form of the Cumulonimbus Anvil) Appear at Dusk in the Cold Final Part of a Severe TS, Illuminated by the Trieste Lights, Behind the “Punta Sottile” Promontory; Muggia, Trieste, FVG, Italia
26-July-2023
Mammati (plural of Mammatus in Latin and meaning udder in English) are not often visible in this area, probably because the strongest thunderstorms pass mainly during the night hours.
In this case the twilight and above all the artificial light of the city, above which they extend, allow their precarious and partial observation, but still worthy beyond the poor quality of an image taken by hand with a long time..
Mammatus cloud is a tormented and thick part of the Incus of a Cumulonimbus capillatus and the result of rounded cloudy pockets convex downwards, generated by ice crystals connected to the descending cold air and interspersed by the ascent of water droplets, creating a rather regular pattern, in general…, less so in this case the "udders" of which are larger than average and more irregular.
Mammati are described as signs of an imminent worsening of the weather with probable hail and wind, but…
In my experience, on the contrary, certainly limited only to "my area" of observation and photography, this cloud, being placed in the cold part of the Tstorm (outflow/downdraft), generally the final one, almost always indicates an improvement in the weather with cold and transparend air at all altitudes.
Only on a couple of occasions, with cold fronts from the north-east, but between late autumn and winter, I noticed some small mammatus preceding the storm front (generally weak or moderate), but in in that case the semi-retrograde motion could explain its fake position "in front of the storm".
In the summer I have never seen mammatus before a thunderstorm, as the rising warm air preceding the storm (inflow/updraft) prevents the formation of these coid descending pockets, and this seems quite obvious, while the Whale’s Mouth cloud can be deduced, which looks a bit like the mammatus, but is actually the exact opposite, that is with pockets, much more tormented indeed, facing upwards and therefore concave as seen by the observer.
I think it could happen to have mammatus before the storm when it suddenly changes direction, therefore going back to areas that were previously placed behind or flanking the storm cell and which are then reached, but it is certainly not a frequent case in these parts.
With this I don’t want to change the rules, on the contrary, I just say that my observations (and they are many and careful) suggest that, for some reason (…), in this area the mammatus clouds almost always appear when the thunderstorm is running out.
Posted by stefano zerauschek on 2023-08-26 11:10:34
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