Weather topic: Massive rains in Greece

In the last few days unimaginable amounts of rain have come together in Greece. The storm Daniel had caused persistent and heavy rainfall in Greece since Monday.

In the east of the country in particular, as much rain has been recorded locally as would fall in a year in some places here. The dimensions are catastrophic. Flooding and flash flooding have been widespread and several deaths have been reported so far.

Storm lows and strong thunderstorms are also common in the Mediterranean region, but such gigantic amounts of rain have never been measured in Greece in such a short time. Several factors are responsible for the current weather situation: On the one hand, a stable omega weather situation has set in over the past few days, with a distinctive high-pressure area settling over Central Europe and flanked by a low in the south-west and a low in the south-east. The Greek letter Omega can then be seen on the pressure map – hence the name.

This weather situation is very stable and brings Central Europe a very dry weather section on the one hand and changeable and wet weather to the Mediterranean countries affected. The low-pressure areas are also relatively stationary, rotating their precipitation areas counter-clockwise over and over again over the same areas.

The very warm temperatures of the Mediterranean Sea come into play as the next important factor in this storm constellation. The water temperatures are currently on average about 2 to 3 degrees warmer than usual. This allows more water to evaporate and offers more precipitable water to the atmosphere.

Finally, the orography of Greece in combination with the trajectory of the low plays a decisive role. The rainy areas were repeatedly pushed against the mountains on the east coast of Greece by a south-easterly current, causing long-lasting and heavy rainfall.

In Zagora on the east coast of Greece, 754 liters of rain per square meter were measured within 24 hours on Tuesday alone. This roughly corresponds to the annual amount of precipitation for Düsseldorf. However, the station in Zagora did not continue the measurements on Tuesday afternoon due to disturbances. In the meantime, the station seems to be running again and amounts of rain have been reported. As of 10 a.m. on Thursday, around 909 liters per square meter were measured for the whole of September. It’s still raining in the region right now, so these numbers are only going to increase.

Starting tomorrow, however, the storm will move further south and the precipitation in Greece will decrease. The omega situation will then also weaken here in the next week and new low pressure areas have a chance to reach Central Europe again. But they won’t bring us such enormous amounts of rain. The precipitation record was reached on August 12, 2002 in Zinnwald-Georgenfeld in the Ore Mountains. Almost 353 liters per square meter fell within 24 hours.

Some examples of other stations that were particularly affected by the Daniel storm are as follows as of 10 a.m. on Thursday, September 7th: