Synoptic Situation: February, 8th 2010
To describe the weather situation, which caused extreme snowfall in the south of Austria, the synoptic situation some days earlier has to be examined.
The ECMWF analysis gives an overview of the weather situation on Feb, 8th 2010 at 18 UTC (initial position: February 8th 2010 00UTC).
Europe was dominated by a blocking situation, so-called omega block. A ridge over the Atlantic, with the centre over Iceland, was flanked to two well developed troughs. The system on the westside lay over the Atlantic Ocean, with two centres of deep pressure. The trough on the eastside, where several depression centres - over Scandinavia, France and northeast of Russia- were embedded, extended over almost whole Europe. Because of a small ridge of high pressure in Austria and ensuing strong atmospheric cooling during the night, fog/low stratus was generated in the lower levels, which lasted the next days. On the mountains there were sunny weather conditions. Due to cold air advection from the northwest and warm air advection from the south a surface low developed over Spain. The corresponding front system caused in this area partly heavy snowfall. This surface low, with the associated front system, marked the weather on February, 10th - 12th in Austria.
Figure 2.1: ECMWF chart 8 February 2010 1800UTC
Figure 2.2: Meteosat 9 Airmass RGB: 8 February 2010 1800UTC
Due to cold air rearward of the low (blueish area) from the north, intrusion of dry stratospheric air, which provided high Potential Vorticity (reddish area) over the Iberian Peninsula and warm airmass from the sea, the possibility of further cyclogenesis was given.
Figure 2.3: Meteosat 9 IR10.8; overlay ECMWF Temperature Advection 700 hPa: 8 February 2010 1800UTC
The dipole in the Mediterranean Sea of cold air advection (blue lines) and warm air advection (red lines) is a sign of the ongoing cyclogenesis.
Figure 2.4: Meteosat 9 IR10.8; overlay ECMWF Geopotential height 1000 hPa (violet) and 500 hPa (green) and PVA500 (yellow): 8 February 2010 1800UTC
Additional to the previous mentioned temperature advection PVA at the east coast of Spain indicated further development of the depression. Another criterion for cyclogenesis was that the surface low and the upper low was not situated in the same geographical area.
Figure 2.5: Meteosat 9 Microphysics RGB: 8 February 2010 1800UTC
The yellowish areas over Central Europe, especially in Austria, and some parts in the north indicate fog/low stratus, which is charcteristic for still calm weather. The temperature were below 0°C in Austria. The reddish areas indicate thick ice clouds of the frontal system.