Monday, November 5, 2012

A Nor'easter for the Northeast

Monday, November 5, 2012
2:39 P.M.

Let me first start out by saying that this storm will be nowhere near as strong as Sandy. I was looking at some of the statistics from Sandy... 185 fatalities and at least 52.4 billion dollars in damage (the second costliest hurricane in the history of the U.S.), and I was shocked. I knew the storm was going to be bad, but I had no idea it would cause as much devastation as it did. I underestimated the destructive potential of Sandy.

This upcoming Nor'easter is, however, a strong storm, and should be taken seriously, especially since it is hitting areas that have already been ravaged by Sandy.

The biggest differences between this storm and Sandy is that this storm is much weaker and is not a hurricane. Remember how I talked about hurricanes being "warm core" storms and extratropical cyclones being "cold core" storms? This shows up very clearly on the models. I took another look at the 850 mb temperatures forecast by the European model and was struck by how different the temperatures at the storms' core were. Below is Sandy. Again, it is from the Monday, October 29 12z HWRF model at 850 mb, and these charts show the geopotential heights (contours, 30m interval), temperatures (color fill, 2 degrees Celsius interval), and the wind vectors (m/s)

6 hour forecast (from 12z October 29)

And here's the chart for the upcoming storm.

75 hour forecast (from 12z November 5)

You can clearly see that the upcoming storm has much more cold air at its center than Sandy, and you can also see that it is considerably weaker than Sandy. However, comparing your typical Nor'easter to Sandy is like comparing a Toyota Prius to a Mack Truck.

This Nor'easter is expected to bottom out at around 984 millibars, which isn't historically strong but still qualifies as a major storm. The Hanukkah Eve Storm of 2006 bottomed out at 970 millibars offshore and weakened to 976 millibars by the time it crossed southern Vancouver Island, and the Hanukkah Eve Storm knocked out power to nearly 1.5 million people. This storm will pack a punch, and it needs to be taken seriously.

57 hour forecast

The chart above shows the 10 meter wind speed in knots, with the direction given by the streamlines. There is a swath of 50 knot winds offshore, and it looks like the strongest winds are ahead of the storm's warm front and bent-back occlusion. Places like Cape Cod and Long Island will get hammered with winds, and these winds are strong enough to push a weak storm surge into these areas, which brings the danger of re-flooding low-lying areas that were pummeled by the surge from Sandy.

81 hour forecast

This storm will also be extremely slow-moving, and 24 hours later, it has only moved ~ 350 miles at an average of 14.5 miles per hour, which is pretty slow for an extratropical storm. This is not a good thing; it means that the Northeast will get battered by wind and snow (yes, snow) for an extended period of time. The snow is predicted to start Wednesday afternoon, and the map below (which is 6 hours after the snow is predicted to start according to this model, which is the Euro) shows the three-hour snowfall over the area for Thursday November 8 at 03:00 UTC. I looked for a 24-hour snowfall map, but this was all I could find. 

 Thu, 08 Nov, 03:00 GMT

Forecast hour 63

Six hours later, the snow has moved northward into Maine. 

Forecast hour 69

These model charts show snowfall all the way down to the coast, but I seriously doubt the coast will see snow. Instead, it will see 1-3 inches of rain, which is enough rain to cause some serious problems, and places inland could see several inches of heavy, wet snow. We'll have a better idea of the predicted snow totals as we get closer to the event.

This storm has the possibility to bring flooding due to higher-than-normal water levels and waves to coastal regions and the potential to damage trees and structures that were weakened by Sandy. The bottom line is that this will not be a historic storm, but it will be strong, and it couldn't come at a worse time. My thoughts are with the people on the East Coast, and I hope this storm doesn't make things too much worse.

Thanks for reading.

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