The storm that walloped the U.S. east coast and parts of Central Canada Monday night is not your run-of-the-mill hurricane. While the term "Frankenstorm" may sound sensationalistic, it's fairly apt: Sandy's an amalgam of weird weather events. This hurricane/tropical storm/Nor'easter makes for a researcher's dream and emergency planner's worst nightmare: It's messy, complex and unpredictable. And we can expect to see more like it.
Warming oceans, wilder storms
September temperatures off the mid-Atlantic coast were the second-warmest on record. Like typical tropical storms, Sandy was born in the southwest Carribean Sea as a powerful thunderstorm, with latent heat driving rainclouds almost 15 kilometres high. Most hurricanes draw energy from warm ocean currents but lose some of their oomph once they reach the northeast and the water gets too cold for them to sustain that power. Not Sandy. It maintained hurricane status until it hit land Monday evening, thanks to Gulf Stream temperatures that were as much as three degrees warmer than normal, as well as interactions with atmospheric disturbances coming from shore. "Everything came together to allow this thing to rev up in a very unusual way," said University of Washington atmospheric scientist Cliff Mass. Just as unusual is that it remained revved up until it hit land.
Hurricanes this big usually get messier after they reach shore. This is especially true for Sandy, which smacked into another, low-pressure weather system shortly after it hit land. The resulting stacked storm caused snow instead of rain in the Appalachians. The hybrid weather system could be called a "Nor'easter." If that sounds too prosaic, "you could still call it 'Superstorm Sandy,' " said Jeff Masters, meteorologist and Weather Underground co-founder. But "it's not a hurricane." The stacked storm is expected to head northeast toward New Brunswick, but slowly. It is being held up by a super-high pressure system over Greenland – think clear skies, dry weather – that might be exacerbated by Arctic ice melt. Interactions with other systems, especially that low-pressure winter storm Sandy hit, makes life more complicated for anyone in the predictions game.
Weather forecasting has become far more sophisticated in recent years. But the weather systems they're dealing with are becoming much tougher to forecast. "Hurricanes are always hard to predict. This one was especially so because it was so close to another low-pressure system," Prof. Masters said. "Our understanding of that [transition] process is poor." But if warmer water extends hurricane season into winter storm season, that could mean more collisions. "This sort of ocean temperature is going to be the normal by, say, 50 years from now," Prof. Masters said. "It's going to be much easier … to get major hurricanes impacting the northern U.S. and Canada."
Predicting the future and getting it right gets expensive. And meteorologists argue public funding for their research isn't keeping pace with changing weather patterns. U.S. atmospheric expertise has fallen behind that of the United Kingdom. The U.S. National Oceanic and Atmospheric Administration is slated to lose $182-million from its satellite program next year. "It's like taking your car out for a drive into the biggest storm you've ever seen, and you go with a dirty windshield," Prof. Masters said. "You don't see what's coming." This year, the first accurate forecasts for Sandy came from the United Kingdom. U.S. meteorologists are using data from a satellite launched from India, Prof. Masters said. Uncertain forecasts mean governments widen evacuation zones as a precaution. This is pricey, but could also prove fatal if people ignore evacuation orders, Prof. Masters said, because "now you're crying wolf more often."
Wind velocity in kilometres an hour at 11 p.m. EST Monday.
Minimum pressure, in millibars. The lower the pressure, the more powerful the storm. This is one of the lowest-pressure hurricanes the east coast has seen.
Wind diameter in kilometres – the storm's full reach in all directions.
Degrees above normal for Atlantic ocean temperature off U.S. east coast.
Number of Septembers since 1900 when the Gulf Stream's been as warm as this year's.