201402 - Windstorm - British Isles (12 Feb)

Status: Finalized Material from: Linus

Discussed in the following Daily reports:

http://intra.ecmwf.int/daily/d/dreport/2014/02/10/sc/

http://intra.ecmwf.int/daily/d/dreport/2014/02/12/sc/

 1. Impact

http://www.bbc.co.uk/news/uk-26166796

For the event, red warnings were issued for high wind speeds on Ireland, Wales and western England (see figure above from meteoalarm.eu).

2. Description of the event

The figures above shows satellite images from yr.no. The first figure is for 12 February 00UTC and the following are with 3 hours apart. The maximum reported gust was 108 mph (48 m/s) according to BBC.

The figures above shows maximum observed wind gusts during 12 February (24-hour period). Several stations on Ireland and Wales/England reported wind gusts above 40 m/s.

3. Predictability

3.1 Data assimilation

3.2 HRES

The series of figures above shows HRES forecasts of the maximum wind gust during the 12 February and the MSLP valid 12 UTC. The colour scale is the same as for the observations in the previous section. The first forecast is from 12 february 00 UTC and the following is 11 February 00UTC and so on (with 1 day apart).

3.3 ENS

Dalmatian plots for maximum wind speed at ~1km around a cyclonic feature. The first plot is from 12 February 00 UTC, valid 12 hours later. The following plots are with one day apart. All forecasts had a lot of cyclonic features with high wind speeds over the western Atlantic for this day. 4 days before the event the ensemble seems to converge to a position west of Ireland. One issue for this case is the phase speed of the cyclone, which seems to be too low. Some of the longer forecasts had a deep cyclone one day before that did not materialised.

Extreme index forecasts for maximum wind gusts valid on the 12 February, from 1 (12 Nov 00UTC), 2, 3, 4, 5 days before the event. The figures also includes the values for the 99th percentile. All lead times have relatively high EFI is present in the area.

3.4 Monthly forecasts

3.5 Comparison with other centres

4. Experience from general performance/other cases

• Two days later, another storm hit the British Isles, see 201402 - Windstorm - British Isles (Valentine's day)

5. Good and bad aspects of the forecasts for the event

• This week had a strong potential for intensive cyclones. Some forecasts had another system just one day before that did not happened. The details for the present storm was well captured 4 days before the event.
• The phase speed seem too low.