Scatterometer plot of complex low west of Ireland

On 23 April around midnight and west of Ireland a complex low was developing. The red arrows show wind speeds up to 15 m/s and a cyclonic wind direction. One cyclonic centre is located surrounding the group of yellow spots, while another centre is located more to the southwest at the left side of the scatterometer swath. Between both cyclonic centres a line of shear flow is present (where the wind direction turns by 180 degrees) surrounded by wind speeds of 10 m/s strength. The blue arrows in the background represent a 3-hour forecast of the winds by the KNMI High-Resolution Limited Area Model (HiRLAM).

Even on this short forecast range, the HiRLAM model only depicts one cyclonic centre and no shear line at all. As background a METEOSAT Infrared image is shown in black and white. While this shows the supporting cloud structures associated with the ERS scatterometer winds, it does in itself not provide much information on the surface wind conditions. In the next 12 hours after midnight on 23 April, the winds
strengthened and the depression central surface pressure dropped by more than 10 hPa to 974 hPa. In this case the timely available ERS scatterometer winds thus provide guidance on routing conditions to ships at sea.