Foras na Mara

Results of Weather Buoy readings for 8th December weekend

wave pic 9th DecOver the weekend beginning 8th December  the second of two slow moving low pressure systems tracked to the North of Ireland, with strong winds and very large offshore waves, of up to 17.2 metres, living up to the forecasted conditions.

The Marine Institute has for many years been operating the Irish National Weather Buoy Network as a national service on behalf of a number of partners. The information from the buoys, weather reports from Met Eireann and information generated by the Marine Institute from numerical ocean modelling and forecasting allowed a forecast to be prepared that indicated severe wave conditions.

This forecast was broadcast though the normal Met Eireann weather reports on both TV and Radio, alerting commerce and the public alike to what was on the way.   The picture above illustrates wave conditions that were forecast by the Marine Institute-adapted wave model 6 days ahead, prior to the weekend of the December 8th, with significant wave heights of between 14m and 16m (deep red) anticipated off the southwest.  

The figure below shows actual data collected directly by the Weather Buoy Network as the forecasted storm passed across the ocean to the west of the country, over Ireland then onwards over Northern Europe.  

Graph of wave heights on weekend of 8th December

 

 

 

 

 

 

 

 

 

 

 

It shows that, at midnight on 9/12/2007 a record significant wave height was recorded of 17.2m at with a period of 14 seconds.  Wave heights at M3 reached 12.6m which was just below the largest wave recorded at M3 to date (13.2m). Locations of the Weather Bouys and real time reading can be viewed on the Weather Buoy Network Page of the Marine Institute website.

The storms that passed over the country in late November / early December 2007 generated unusually severe offshore conditions that lead directly to very high seas off the entire western seaboard.  

The fact that the tidal heights were not at peak values (see www.irishtides.ie) meant that the large seas did not have the potential to flood that would have been the case had the tidal regime been in the spring part of the cycle. These conditions can be very treacherous as the offshore swell propagates across the continental shelf translating at best to unpredictable conditions at the shore.  

It is continually being demonstrated that the combination of high quality real time (hourly) measurements coming from the deep field buoys and coastal systems, coupled to the mathematical forecasting models, is extending the well proven ability of scientists and engineers to accurately forecast the atmospheric conditions to the ocean.