Storm Forecast
Valid: Sat 11 Apr 2020 06:00 to Sun 12 Apr 2020 06:00 UTC
Issued: Sat 11 Apr 2020 07:20
Forecaster: GATZEN

No threat levels have been issued.

SYNOPSIS

A polar trough is still placed across northern Europe and extends into eastern Europe, where dry and cool air persists. At the southern flank of this trough, the mid-level trough across Turkey progresses east and leaves the forecast area. The strong jet ahead of this trough will also not affect the forecast area today.

Across Central Europe, the mid-level ridge will continue. It will weaken at its western flank due weak mid-level troughs that slowly progress east into western Europe. At lower levels, weak boundaries have formed across western Europe that are associated with increased low-level moisture. At the same time, lapse rates of the air mass have improved further.

DISCUSSION

Spain and southern Portugal, Pyrenees

A mid-level trough has entered the region from the west. Rather cold mid-level air and diurnal heating results in increasing lapse rates during the day. Low-level moisture is slightly higher compared to latest days, and the air mass has already proved to be supportive for convective storms. Therefore, we expect new storms to form in the afternoon, especially across mountains with upslope circulations. Main limiting factor for initiation is actual cloud coverage indicated by latest satellite imaginary. However, models predict that these clouds will dissolve during the day and CAPE can build. Storms that form will be mostly non-severe given weak CAPE and shear. Locally, excessive precipitation is not ruled out due to the slow storm motion. Some marginal hail is also possible due to the low wet bulb freezing level.

Southern British Isles

Some storms have formed in the last hours over Wales and northern England. These storms where mostly elevated and formed ahead of a weak trough and currently move across the North Sea. Today, lapse rates will continue to improve across England. A frontal boundary will strengthen across northern England in response to diabatic frontogenesis, and latest models indicate increasing moisture along the frontal boundary that partly overlaps with steep lapse rates. Limiting factor for convection initiation is the lack of forcing, also compared to yesterdays storms. However, some frontogenetical forcing is expected over northern England and topographic forcing can be again expected over Wales. We therefore issued a low probability for some storms that will move north-east in the evening, before decaying. Weak vertical wind shear will limit any severe threat. Steep low-level lapse rates across parts of England may support some severe wind gust threat, though.

Northern Syria, northern Iraq, northern Iran

Thunderstorms are again predicted across the area. With sufficient low-level moisture, partly due to outflow boundaries of yesterdays storms, and strongly increasing low-level lapse rates in the coming hours will result in surface-based CAPE of some 100s J/kg. Weak vertical wind shear will limit any storm organization, however, the deep boundary layer supports a high wind gust threat.