Status:Ongoing analysis Material Status: Finalised Material from: Linus, Esti
...
, Tim
| Show If | ||
|---|---|---|
| ||
Discussed in the following Daily reports: |
...
2. Description of the event
2.1 Broadscale
The plot below shows an animation of MSLP and precipitation from HRES, with a small-scale cyclone developing over northern Germany.
Following a period in the developmental upper jet right entrance region, the most rapid cyclogenesis occurred as the upper level jet axis was crossed, . The plots below of 300mb isotachs and mslp, from the Met Office global model, illustrate this process. Rapid development during jet-crossing is quite common.
The plot below shows the warnings on Meteoalarm from 5 October, with a red warning for wind gusts over northern Germany.
2.2 Mesoscale
Satellite and radar sequences around the time that the maximum gusts hit Berlin both suggest, via filamentation in the cloud head region, that the gusts could well have been due to the "Sting Jet" phenomena. The fact that the gusts inland were so high is also believed to be a characteristic of sting jets, because of the top-down destabilisation mechanism that is believed to be involved (as on the "3D visualisation" poster below).
The following plots place short range max gust predictions from HRES into the context of the vertical profiles of wind, T and Td. 13UTC was chosen from this run as the time with the maximum over-land gusts. Although this time does not coincide exactly with the time of maximum gusts over Berlin, the data are believed to be indicative of the atmospheric characteristics over Berlin (and indeed other areas in N Germany) when the peak gusts were occurring. Correctly pinpointing details in these finely balanced situations is always difficult for models.
Maximum instantaneous gusts in short range HRES run, at T+13=VT 13Z on 5 October 2017, right panel has HRES Tephigram locations added
HRES soundings at T+13=13Z within the strong wind area
The following poster (presented at the EGU conference in April 2018) discusses this case in the context of using 3-D visualisation to trace out, in 3-dimensions, the jet cores.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show the 24-hour maximum wind gusts from HRES for 5 October and MSLP valid 5 October 12z. The first plot shows 24-hour maximum wind gusts from observations.
...
4. Experience from general performance/other cases
...
5. Good and bad aspects of the forecasts for the event
...