From today's Wall Street Journal in an article about oil and gas
production issues in the Gulf resulting from hurricane Ivan:

Chris Oynes, regional director for the MMS, said preliminary data from
the government's National Oceanic and Atmospheric Administration show
that central Gulf of Mexico was hit by mammoth waves -- including
perhaps the tallest ever recorded in the Gulf -- that exceeded the
design requirements of the area's infrastructure. "There were some
extremely large waves," he said. "There is some evidence that there
was one rogue wave, the largest ever seen in the Gulf of Mexico, some
90 feet high."