The blocking weather situation continues: In the morning the sun shines everywhere, during the course of the day cumulus clouds form over the mountains and as a result isolat showers or thunderstorms develop. Among meteorologists this type of weather is generally known as diurnal weather.
But today, Thursday, there was something slightly different from the previous days: early in the morning, mium-high, partly tower-shap clouds, so-call altocumulus castellanus, pass through temporarily. On the northern ge of Switzerland and in the Black Forest, there were even isolat showers. This morning convection can be observ again and again during the summer days, usually towards the end of a high pressure period. Already on
last Sunday
Some early risers got wet in such morning showers
morning thermals
Showers or thunderstorms that occur early in the morning, in conditions of low winds near the ground and without clear fronts, are known as “morning thermals” in the ballooning community. However, the phenomenon itself has nothing to do with the
classic thermals
Rather, it is normal convection, which is detach from the atmospheric boundary layer near the ground and is therefore not primarily dependent on the time of day.
The requirements
As always with showers and thunderstorms, a strong drop in temperature with increasing altitude and sufficient humidity are requir beforehand. If both parameters are present, the atmosphere is in a potentially unstable state. Unlike with “normal” showers and thunderstorms, which occur during the day, these conditions are only present for morning convection above a certain altitude. Close to the ground, the air is stably layer due to nighttime radiation.
imaging of radiosounding
The radio sounding from Payerne shows the vertical course of the saudi arabia phone number library temperature (r) and the humidity (dew point, blue). The strong night-time inversion can be
seen near the ground. (MeteoSwiss)
The lifting mechanism
In order to convert the potential energy contain within the unstable layering of the atmosphere, an initial trigger is ne. Unlike during the day, the thermal bubbles that rise from the hills and mountains and subsequently trigger the formation of cumulus clouds are absent in the early morning hours. Wind convergences trigger by topography are also not an issue at night due to the stable boundary layer.
The triggering must therefore occur in the middle how to handle the most common sales layers (keyword: “elevat convection”). Today, a weak convergence zone was responsible for the triggering or lifting of the moist, awb directory unstable air mass. At the southern ge of a low pressure system, westerly winds carri moist air towards the northern ge of Switzerland. At the same time, there was little wind over the Central Plateau at this level, and towards the west, the model data even show a weak southerly wind tendency.
During the day, the weather was back to normal: thanks to the low pressure just north of Switzerland and the slightly more humid air, convection got going faster than yesterday, for example. The first lightning strikes were register in the Jura at midday and the showers and thunderstorms were generally somewhat more numerous than in the previous days.
