Evolution of instability in the southwest of Romania May 19-20 2020

The next period, more precisely, the days of May 19 and 20, 2020, will be characterized by a high degree of atmospheric instability over the entire southwestern half of Romania. The situation in question will be associated with the action of a low pressure field generated in the central basin of the Mediterranean Sea (fig.1).

Associated with significant amounts of water, frequent electrical discharges, hail and wind that can take on the appearance of a gale during showers.

Figure 1. Synoptic context Europe May 19, 2020, 12 UTC

From the current estimates (May 18, 2020, GFS forecast model, 00 UTC), throughout the south-western part of Romania, amounts of water are estimated to exceed 30-40 l/m2, this on the first day (May 19, 2020) .

The next day will bring even greater amounts of water, up to 60-80 l/m2, mainly in the southern area of ​​Oltenia and, possibly, in the Getic Subcarpathians and Southern Carpathians.

An important aspect in this episode with unstable weather will be the effective evolution of convective processes in the south-western part of Romania, where there are also Hail Combat Groups, such as those from Drăgășani, Segarcea, Vânju Mare and Group South.

According to the most recent atmospheric models, for the southern regions, but especially for the southwestern ones, the hail will reach quite high dimensions, which is also illustrated on the two forecast products of the convective parameters on the vertical section of the troposphere (Fig. 2A and B).

Figure 2. Analysis of cloud hail and convective parameters: A. north-east Serbia, 50-60 km from south-west Romania
Figure 2.1 Analysis of convective parameters and cloud hail: B. in the Vânju Mare protected area

In association with the high values ​​of atmospheric instability in the western Balkans and southwestern Romania, the convective cloud developments will be extensive, exceeding, on average, 10.5-11 km and their base will be at 1.25-1.80 km .

The convective processes from the east of Serbia, especially, are of increased interest, because the conductive flow is oriented from the southwest to the northeast, on azimuth 220-230°, with a travel speed of 50-70 km/h.

The profile in fig. 2A was made in NE Serbia for May 19, 2020 at 15 UTC, at approx. 55 km from southwest Romania. According to it, convective cloud formations are possible that generate cloud hail with average sizes of 4-5 cm.

The following profile (fig. 2B) was made for May 20, 2020, 9 UTC on the Vânju Mare protected area.

According to the latter, there are prerequisites for convective cloud systems to generate hail with dimensions of 3.5-4.5 cm in the cloud.

On the ground, due to the height of the isotherm of 0°C (3.35-3.75 km), the qualification of medium and even large sizes.

Disclaimer: for official information, consider only the official forecasts of the National Meteorological Administration (A.N.M.)