This morning, U.S. forecasters are predicting a convergence of Hurricane Sandy, an early winter storm in the west and cold arctic blast from north which would make for some very messy and expensive weather over the Northeast US and Atlantic provinces for the first half of next week.

"It'll be a rough couple days from Hatteras up to Cape Cod," said Jim Cisco, a forecaster with the National Oceanic and Atmospheric Administration (NOAA). "We don't have many modern precedents for what the models are suggesting."

Forecasting the weather 4 or 5 days before it happens is difficult because so much can change in that time. However, it's also difficult to dismiss the results when every piece of guidance you use starts pointing towards the same thing, with even greater certainty, each time you update your forecast.

That's what's happening right now.

The computer models forecasters use for guidance in making their forecasts showed the first indications of the merger of these weather systems, and the results of each subsequent model have made it more and more likely.

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As of Tuesday, Jeff Masters, Director of Meteorology for Weather Underground, was only giving Sandy about a 40 per cent chance of hitting the East Coast, but by Wednesday he had increased that to 70 per cent. Cisco was a bit more optimistic about Sandy to start, giving it a 60 per cent chance, but he also increased the chance to 70 per cent on Wednesday.

Even computer models that didn't show the merger to start began to fall in line with the ones that did.

To make matters worse, the full moon occurs on Monday, which will make tides near their peak, due to the combined tidal forces of the Moon and the Sun. This will increase the severity of any flooding the coast experiences due to Sandy.

It still remains to be seen exactly how things develop, as there are still some uncertainty about the storms and the timing of the entire event. Sandy is set to make landfall very late on Monday night or early on Tuesday morning, but it could make landfall anywhere between Delaware and Maine, which will be a big factor in where the majority of the precipitation ends up. It's also still uncertain if the hybrid storm will see the injection of cold air from the north, which, along with the exact track of Sandy, will determine exactly how much snow will be seen.

However, with the kind of chances they're seeing for this hybrid storm, and the potential damage it could do, sounding the warning bell a little bit earlier than usual isn't a bad thing. According to the Associated Press article, Cisco said that there could be several inches of snow or rain in the mid-Atlantic states, depending on where Sandy makes landfall, and up in the mountains the snowfall amounts could be measured in feet instead of inches. Also, with the powerful winds from Sandy combined with this potential for snow, and the trees still leafy at this time of year (with tree branches being able to hold more snow), there is a greater chance of power lines being snapped by overloaded branches, and some forecasters are saying that power outages could last well into the following week.

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There has been some comparison to the so-called 'Perfect Storm' that hit New England in 1991, but according to Cisco that storm is not comparable to what this hybrid storm could do.

Masters agreed, saying: "The Perfect Storm only did $200 million of damage and I'm thinking a billion. Yeah, it will be worse."

With all these projections for what could happen along the U.S. Atlantic coast and New England, residents of Canada's East Coast should be keeping an eye on this as well. If the forecasts for this hybrid storm turn out to be correct, and it turns into a major snowstorm that buries New England, it's not likely to spare the Atlantic provinces a similar dose of winter weather as it passes through.

The Canadian Hurricane Centre isn't reporting on Hurricane Sandy yet, because it's still too far away, however, you can be sure that the forecasters there are keeping a watch on it.

Don't get caught in the rain.

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