Monthly review September 2021

The month of September was 1.6 degrees too warm compared to the reference period 1961-
1990 at the weather station Dresden-Klotzsche. With a monthly mean of 15.9 °C, it was one
of the warmest September months since 1961 (61 years). It is still in 11th place in the
ranking.

169 hours of sunshine were recorded, an increase of 21 hours compared to the official
reference period 1961-1990. The record is still held unreservedly by September 2006 with
233 hours.

The sum of all single measurements of precipitation reached 23.5 mm in September at our
measuring station in Coswig. Thus, the monthly sum corresponded to 51 % of the normal
value for this month. Thus, we registered a very dry first autumn month with regard to the
total amount of precipitation. By a hair we would have reached only about 30 % at the
Intercultural Garden Coswig (IKG), as for instance in the nearer surroundings, because on
29.09. by chance an extremely small-scale heavy rain cluster developed directly near the IKG,
moved northward and later dissolved. This area received nearly 10 mm of rain in a very short
period of time. Only a few 100 m away to the west and east it remained mostly dry.


Weather characteristics:
From the beginning, the month of September was predominantly characterized by omega
weather conditions, with high pressure influence predominating over our area. This is also
reflected in the overall dry weather. At the beginning of the 3rd decade of September, a
largely zonally oriented jet stream, typical for autumn, developed temporarily over the
North Atlantic and Northern Europe, which also briefly affected Northern Germany. But
already after 23.09. the "old" meridional flow patterns reappeared. Long-wave high-altitude
troughs dominated the flow conditions over the eastern North Atlantic and over Eastern
Europe, while a high-altitude wedge extended in between from Central Europe to
Scandinavia (Fig. 1). Omega weather patterns now again prevented the spread of
disturbances that affected the weather. The drought thus continued into October.

sep2021_edited.jpg

Fig.1: Omega stuation over Europe (the typical omega shape of the high over Scandinavia is
clearly visible) on 28.09.2021 (source: Berlin weather map).

Autor: Wilfried Küchler