Tracking hurricane Sandy: As storm 'zigs', it's also changing dramatically

Pete Spotts in the Christian Science Monitor: With hurricane Sandy on final approach to formally making landfall near the southern tip of New Jersey late Monday evening, the storm is on the verge of an unusual shift. Even as it makes a left turn to head toward the coast, it also is swapping energy sources to become an extratropical cyclone.

Such transitions occur several times a year to typhoons in the western Pacific, notes Clifford Mass, an atmospheric scientist at the University of Washington at Seattle, in an e-mail exchange. "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. In Sandy's case, such changes already have been factored into forecasts from the National Hurricane Center and local National Weather Service forecast offices in the eastern US.

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...

5-day forecast track for Tropical Depression Eighteen of the 2012 Atlantic hurricane season, from the National Hurricane Center