Nearly a week after Hurricane Sandy struck the Mid-Atlantic coast of the United States, the affected region is still reeling from the shock. This really was an unprecedented storm in the truest sense of that word.
Among the amazing aspects of the event was the extraordinarily accurate and early forecasting of the storm. Numerical forecast models were latching on to the correct scenario, including the unusual and rapid leftward turn off the Mid-Atlantic coast, as early as five to seven days before the event (depending on the particular model in question).
This kind of forecast accuracy was a pipe dream, even for run-of-the-mill storms, just 20 years ago. We are all living through a quiet revolution in weather forecasting and high-profile events such as Sandy make it very clear. The advance warning offered by these accurate medium-range forecasts undoubtedly saved dozens, perhaps hundreds of lives, and literally billions of dollars in damage in New York City alone.
From what we know in its immediate aftermath, the storm itself was the result of an unusually strong interaction between a late-season tropical cyclone (the original Hurricane Sandy) and a mid-level extratropical disturbance that grew in intensity as it approached the coast. Such interaction is a common feature of the transition seasons — fall or spring.
There are reasons to believe that in a warming climate the frequency of these kinds of interactions may increase potentially leading to an increase in strong examples, like Sandy, of this kind of severe weather.