Using modern computerized weather simulations, scientists with the National Oceanic and Atmospheric Administration (NOAA) have taken another look at Lake Superior weather conditions during the 1975 wreck of the freighter Edmund Fitzgerald, and have concluded that the ship was in a vulnerable position during a crucial six-hour period when weather conditions during the storm were at their most extreme.

A reanalysis of the weather conditions during the November 1975 gale when the Edmund Fitzgerald went down, killing all 29 aboard, shows in addition to high winds and waves, the freighter was caught in waves traveling west to east. This can result in a hazardous rolling motion for vessels traveling southward, the direction that the Edmund Fitzgerald was heading as it tried to reach the safety of Whitefish Bay, about 15 miles from where it sank, say the NOAA scientists who conducted the review.

"During the late afternoon and early evening of November 10, conditions deteriorated rapidly, with winds in excess of 69 miles per hour, hurricane-force gusts, and waves more than 25 feet high," said lead author Thomas Hultquist, science and operations officer at NOAA's National Weather Service (NWS) Forecast Office in Negaunee.

"This shows how quickly conditions can worsen and become life threatening on the Great Lakes," wrote Mr. Hultquist and his coauthors, Michael Dutter from the NWS Forecast Office in Cleveland and David Schwab, from NOAA's Great Lakes Environmental Research Laboratory (GLERL) in Ann Arbor.

The NOAA authors combined meteorological observations from the storm with hindcasts - forecasts run in retrospect - of conditions throughout the storm. The hindcasts indicated the critical sixhour window that proved fatal to the ship and its crew. Hindcasts help meteorologists better understand historical events, which could also improve forecasts.

A lack of surface weather observations made it difficult for researchers to determine the actual conditions of the 1975 storm. However, using high resolution numerical computer models, the three researchers were able to simulate a more complete picture of wind and wave conditions during the storm. One of the models used was the NOAAWind-Wave Model.

"While high winds on Lake Superior are not rare, it is unusual for the waves to get that high on the lake," said Mr. Schwab. "It's unlikely that Captain Ernest McSorley, the skipper of the Edmund Fitzgerald, had ever seen anything like that in his career."

The authors note that storms of the magnitude of the November 1975 storm occur every two to six years on average. Lake Superior is the largest of the Great Lakes. The size of the lake, the low number of vessels traveling the lake, and the infrequency of the high wave conditions makes the tragedy of the Edmund Fitzgerald a rare event.

"Modern observation and forecast systems have substantially improved forecasts for the Great Lakes over the past 30 years, allowing for greater advance notice of storms, which allows most ships to avoid such severe conditions," the authors wrote. "But the tragic events of 10 November 1975 should continue to serve as a reminder of the hazards one can encounter when traveling on the Great Lakes."

The findings are the cover article in the May issue of the Bulletin of the American Meteorological Society (BAMS).