The first telecon over the S2S weather extreme subproject took place on Monday 29 April 2013. Were present at this meeting:

• Yuhei Takaya
• Arun Kumar
• Hai Lin
• Frederic Vitart
• David Anderson

The goal of this meeting was to discuss a first case study of an extreme weather event. It was agreed that the cold March over Europe would a good test case study for the S2S extreme weather subproject.

The following figures show an evolution of 2-metre temperature anomalies and geopotential height at 500 mb averaged over weekly periods over February and March 2013 from the ECMWF reanalysis

March2013.pdf

These figures show that the onset of the event took place in the first week of March. Therefore forecasts starting from mid February would be interesting to analyse for their skill to predict the onset and the persistence of the cold spell over Europe.

It was agreed to exchange forecast data between NCEP, EC, JMA, ECMWF and UKMO (to be confirmed by Alberto)

We agreed on the following points:

• Starting dates: all forecasts between 14th February and 4th March- (daily frequency for NCEP and UKMO; weekly for ECMWF, JMA and EC)
• Forecast length: depends on each centre but not more than 60 days.
• Variables: near surface temperature (2mtm for most of us) as a start. We may later extend the study to Z500
• Output frequency: Daily averages: mean of 0, 6, 12 and 18Z
• Anomalies relative to each model climate
• Grid definition: 1.5x1.5 grid (2.5x2.5 for JMA), starting at 90N and 0E (North to South)- 240x121 grid points
• Format GRIB
• Time frame: 1 month for the data to be available (end of May) - Analysis first half of June - telecon to be arranged shortly after
• The data should be put on a local ftp server and Frederic will pull the data to ECMWF.