Hurricane Sandy has lurched westward as it heads toward landfall late Monday. It's also swapping energy sources as it becomes extratropical. The process sometimes gives storms a boost of power.
Even as it makes a left turn to head toward the coast, it also is swapping energy sources to become an extratropical cyclone.
"But to have it occur over the western Atlantic and then to recurve inland with such a major effect is extraordinary," Dr. Mass adds.
The shift from tropical to extratropical tends to intensify the storm for a period, as well as redistribute winds and rainfall in ways that can shift the regions most heavily affected by wind and rain.
Indeed the hurricane's vast size – tropical-storm-force winds extend up to 420 nautical miles from Sandy's center – has prompted federal officials to warn people not to focus on where the storm makes landfall because the areas affected by coastal surges, heavy rains, and high wind remain extensive.