-Kees Willemse is professor of off-shore engineering, Delft University.  The opinions expressed are his own.-

The news that a huge metal cap has been successfully placed over several of the leaking oil vents at the Deepwater Horizon site marks a potential turning point in the Gulf of Mexico crisis.

It is already estimated that each day some 10-15,000 barrels of the oil that are spilling out into the ocean are being captured and diverted to ships on the sea surface.

Despite this engineering success, a complete end to the oil leakage is unlikely until new relief oil wells are completed -- a drilling process that could take most of the summer, and potentially into the autumn.  This is because the newly installed metal cap is unlikely, even in the best case scenario, to stop all of the oil spilling out.

In advance of the completion of the relief wells, a potentially major new complicating factor is the arrival of the hurricane season last week.