Status:Ongoing analysis Material from: Ivan, Linus, DMI
Discussed in the following Daily reports:
http://intra.ecmwf.int/daily/d/dreport/2015/04/22/sc/
1. Impact
An episode of extremely warm conditions were observed over the North Pole in mid April. The analysis suggests that the warmest period was between 15 and 17 April, when a southerly flow brought warm air. After that quite cold weather came back over the Pole.
2. Description of the event
For the warmest period from 15 to 17 April significant anomalies could be seen over the North Pole in the figure above. They seem more pronounced for the 2-metre temperature compared to T at 850 hPa. Significant positive anomaly can be noticed over Europe form the Mediterranean up to England and Germany caused by warm advection from North Africa. It also appears to be quite cold for the season over Africa. All the anomalies displayed are calculated from ECMWF analysis versus ERA-Interim.
3. Predictability
3.1 Data assimilation
3.2 HRES
3.3 ENS
The 17 April seems the warmest day over the Pole with daily mean temperature anomalies of the order of 20C (top panel in the figure below). The plot below shows the the EFI and SOT for 2-metre temperature for a 1-day forecast (bottom-left) and 7-day foecast (bottom-right)The predictability of this extremes is quite high. EFI for D+7 show a strong signal with positive SOT denoting a chance of temperatures to go beyond the climate.
With the cycle 41r1 we are extending the EFI for certain parameters in the far medium range to highlight anomalous weather from day 10 to day 15 (see figure below). The EFI forecast for 2-metre mean temperature highlights the warm anomaly from the Pole to Siberia, warm anomaly over France and England and the cold anomaly over Africa.
3.4 Monthly forecasts
3.5 Comparison with other centres
4. Experience from general performance/other cases