Three main factors came together to cause Hurricane Sandy:
1. A huge storm with winds gusting up to 90 mph (145 kph) was set to make landfall somewhere on the East Coast that Monday night.
2. But a storm like Sandy would normally be losing steam by now as it moved into colder, less energetic waters. In this case, however, a trough of low pressure dipping down from the Arctic was feeding the hurricane, actually strengthening its intensity as it moves northward. (Higher tides because of a full moon may also increase flooding from the storm.)
3. The third weather factor feeding Sandy, a high-pressure system, was pushing the hurricane onshore.
There is some debate about whether climate change had anything to do with Hurricane Sandy and those like it that have behaved unusually but the research is inconclusive.
Hope this helps.
