Status:Ongoing analysis Material from: Linus
1. Impact
TC formed on 1 November over northern-central Atlantic and underwent extra-tropical transition around 3-4 November south of Greenland and slowly propagated eastward. Along a front on 6 November heavy rainfall was produced over southern England and the North Sea. On 7 November the main low pressure system reached Ireland bringing more rainfall to the British Isles.
2. Description of the event
The plot below shows the 24-hour precipitation 6 November 00UTC to 7 November 00UTC (from ogimet.com).
The plots below show analyses of MSLP (contour) and 6-hour precipitation forecast (shade) from 4 November 00UTC to 9 November 00UTC, every 12th hour.
3. Predictability
3.1 Data assimilation
3.2 HRES
3.3 ENS
The figures below shows Extreme Forecast Index (EFI) and Shift of Tails (SOT) for 24-day precipitation on 6 November.
The plot below shows the forecast evolution plot for 24-hour precipitation valid 6 November 00UTC - 7 November 00UTC for the box over southern North Sea. Mean of observations - green hourglass, concatenated 6-hour forecasts - green dot, HRES –red, ENS blue box-and-whisker, Model climate – red box-and-whisker. Triangle marks the maximum in the model climate based on 1200 forecasts.
The plots below show the tropical cyclone track for the operational ECMWF forecasts from 3 November 00UTC (first plot) to 29 October 00UTC (last plot). The symbols shows the position on 3 November 18UTC. HRES (red), ENS CF (blue), ENS PF (grey) and BestTrack (black). The cyclone was dropped as a TC after 3 November 18UTC but continued to intensity. The evolution of the cyclone path was well captured from 1 November 00UTC, although the forecast suffered a bit from a slow propagation error. Before 31 October there was not much sign of a genesis in the forecast.
The plots below show TC activity for 1-2 November from BestTrack (first plot) and ensemble forecasts with the shortest lead time first. As noted above, there was not much of signs for genesis before 30 October.
The plots below show evolution of diagnostics for extra-tropical transition for TC Martin in forecast from 2 November 00UTC. One can note that some members drop the cyclone on 3 November, but for the members that keeps the cyclone it intensifies and becomes more symmetric (negative B values).
3.4 Monthly forecasts
3.5 Comparison with other centres
4. Experience from general performance/other cases
5. Good and bad aspects of the forecasts for the event
- Genesis not captured well in the medium-range
- Rainfall prediction over western Europe from 2 October onwards, when the extra-tropical transition was predicted well