Before exploring the data, review these accounts of the conditions encountered by the Polarstern as it passed through a cold front in the South African region on 23 and 24 November 2013. The accounts will give you a better understanding of the impacts of cold fronts and the types of decisions that research and other vessels make based on them.
Said Dr. Vera Schlindwein, Chief Scientist on the Polarstern: “Until Friday evening (22 November), we spent every minute of ship time on research. But afterwards, we had to escape southwards to avoid a storm in our survey area. We found calm conditions in the centre of the storm, which allowed us to sample and image the seafloor. Back in the survey area, though, we only had 24 hours of suitable weather (until 23 November) before we were forced to go for shelter, this time northward.”
According to the weather forecasters on the ship, the storm was a record system with a central pressure near 940 hPa, which reached its peak on 23 November. The forecasters realized that the ship wouldn’t be able to escape the broad storm field but there weren’t good options for avoiding it. Going north would cost the scientists severals days of research time, while going south would move the ship close to the ice edge, a risky proposition. The captain and crew chose a path that they hoped would let them avoid the worst of the storm. But the weather got worse on 24 November and the ship never reached its desired position. It was exposed to bad weather, with wind gusts up to 64kt and waves up to 10 metres. Individual rogue waves reached the ship’s bridge level (about 17m high) before the weather finally calmed down around midnight on 24 November.
Now we’ll explore the weather events more closely. We’ll start by looking at observational data for the weather and sea state, and compare the data to the model output to assess its accuracy. If the model output is consistent with the observations, we will use it to forecast the weather and sea state for the next 24 hours.