Status:Finalized Material from: Ivan, Linus
Discussed in the following Daily reports:
Picture
1. Impact
An outbreak of severe convection occurred on 5th May 2015 (the first such outbreak of 2015 over Europe). It affected mainly The Netherlands and Germany, but to some extent also Austria and the Czech Republic. Severe thunderstorms developed from the Netherlands into North Germany yesterday afternoon into evening. Those produced very large hail, severe convective wind gusts and a number of tornadoes in NE Germany. One of these was pretty strong of category F2 or even F3 according to the damage it caused near Schwerin. There is a YouTube video of one of those tornadoes showing a spectacular supercell with nice visible rotation and a tornado forming (see ). The lightning map shows lightning activity accoding to different time frames. Approaching the end of the day severe storms started developing in northern Austria where there is a severe weather report of 20mm of rain in 40min from 1:40 a.m. on the 6 May. These severe thunderstorms occurred over an area of high instability (high CAPE) and high wind shear. These conditions favour development of supercells and long-living storms.
2. Description of the event
The plots below shows short forecasts of MSLP and precipiation.
MSLP and precipiation (short forecasts)
The plots below show short forecasts of z500 and t850.
z500 and t850 (short forecasts)
The large-scale development shows advection of warm air from short-west in front of a cyclone that developed north of the Azores.
The plot below (a) shows Z500 and lightning density for Europe, using the UK Met Office lightning database. Lightning activity over the Netherlands and northern Germany is quite high. A number of severe weather reports (b; source: ESSL severe weather database) has been collected from the region of the highest lightning activity, including 4 tornado reports over NE Germany. One of the observed tornadoes over Butzow, Germany, has been categorised as F3 tornado with 30 injured people.
a)
b)
Precipitation totals over Europe from 05 May 06UTC to 06 May 06UTC (data: GTS and EFAS):
Maximum wind gusts on 5 May:
Meteosat IR enhanced (symbols and numbers represent stations where upper level observations are available at 12UTC, 5May 2015) and tephigrams from selected locations:
CAPE and 925-500hPa wind shear, ECMWF analysis at 12UTC, 5 May 2015:
3. Predictability
3.1 Data assimilation
3.2 HRES
(HRES forecast for wind gusts)
3.3 ENS
Convective EFIs (experimental products) highlighted Central Europe as prone to severe convection up to 5 days in advance with a tendency to give stronger signal to the south ( Austria, southern Germany, the Czech Republic) instead of northern Germany and the Netherlands in the medium range (days 4 and 5).
EFI for CAPE:
EFI for the composite parameter SHEAR*sqrt(CAPE):
EFI for total precipitation:
(EFI for precipitation, wind gusts, CAPE and CAPESHEAR)
3.4 Monthly forecasts
3.5 Comparison with other centres
4. Experience from general performance/other cases