Milano Event • 8 July 2021
(European weather patterns, 3D perspective)
A lot of extreme factors came together in the 8 July 2021 weather event in northern Italy, e.g. Milano but also in other regions near by.
Chilly air over France 15-21°C
[59-70°F] due to a deepening trough there, while at the same time we have very high temperatures on the east side (Italy, Austria, Slovenia, Balkan countries, Central Italy) up to 35-40°C
[95-104°F], and on top also very high due point temperatures around 20-23°C /
68-73.4°F which means a highly unstable airmass with lots of energy (2000-3000 J/kg MLCAPE) - plus a local surface low which over Piedmont (Turin area), early morning of 8 July initiated already the first big mega thunderstorms. It all together created the perfect recipe for disaster over Northern Italy, but also neighboring areas east of it.
All this "autumn like pattern" which strangely established over West Europe - mainly UK and France - where chilly air is pumped in from the west - clashes with hot, especially humid air over central Europe, forcing it upwards.
That means huge thunderstorm clusters as well mesoscale thunderstorms along the thresholds which separates cold from hot - the kind of brew, which gives birth to all kinds of extreme weather. This also happened later in the evening, over East Northern Italy, Austria and one center over Czech Republic growing into Poland.
This map shows lightning strikes for the past 48 hours; so from 7 July 09:49 UTC to 9 July 09:49 UTC.
Here you can also spot that the earlier tornado over/outside of Barcelona which was an isolated area of lightning strikes right outside the city, over the sea.
This is a map from 8 July 2021, at 12.00 UTC - which shows the potential energy embedded within air masses. As you can see, the purple area, is located over Genoa and Turin into Northern Italy, showing extreme high levels of CAPE up to 2500 J/kg - which, when it coincidences in an unstable weather environment (forced/rapidly rising air), is a recipe for extreme weather ! That condition more then fulfilled over Northern Italy on 8 July 2021.
This map shows the surface temperatures in °C - where you can see that the temperature differences between France (15-21°C) and Northern Italy (35°C), where very large.
Dew Point Temperatures
When i see dew point temperatures going up to
20°C or even higher - that is almost always a direct messenger for intense thunderstorm development.
Observing clouds
At local level, when you observe the sky, there are some type of clouds which can give you a hunch of what to come in terms of thunderstorm development: There is one cloud type, called
Altocumulus Castellanus, which is a middle high, puffy cloud but with special characteristic; many little towers growing on it, often appearing in longer rows.
The other is
Altocumulus floccus - middle high, puffy "unstable" looking clouds, kind of "tropical" look, with eager vertical growth. (Not to mix up with bigger clouds). Sometimes you can see the same "floccus" clouds around sunrise, but those are often innocent; they simply dissipate after the sun dries out the morning moisture - and usually don't point at thunderstorm development.
Then there are these clouds which on their lower side look like "creamy 'Jupiter' clouds" (
Stratocumulus undulatus or even the more strange looking
asperitas version), a puffy-creamy low level cloud, which has an interesting, at times even really ominous look and feel - like the calm before the storm. Then it's pretty close to weather action.
Mammatus clouds, breast like shaped formations from a cloud "hanging" or growing downwards, are often sign of imminent strong rain or even hail. They are most common below the anvil of a Thunderstorm cloud.
Oh... did i mention... I love weather & clouds ? 
