Will Hurricane Sandy hit the east coast?

Overview
Hurricane Sandy will move north and eventually become what is called a hybrid storm. Storms that are tropical in origin are called tropical storms. Storms that originate in colder climates are called cold core storms. Tropical storms, as they move into colder water, often transition into a cold core storm. Sometimes, as will be the case with Sandy, the storm resembles bits of both types and we call this a hybrid. The semantics of what type of storm Sandy becomes when and if it impacts the Mid-Atlantic or New England region isn't important. Meteorologists will, if the storm becomes a blockbuster, debate what type of storm it was for years. We still debate the "perfect storm" from 1991 and whether that should have been named a hurricane. There is also the possibility Sandy remains purely tropical.

The track
You might wonder why the heck the track is so tough to predict. The answer is that the atmosphere, regardless of Sandy, is undergoing a major shift of sorts. This transition is occurring at the same time Sandy is moving northward. When you get a major storm happening during one of these shifts the models meteorologists use are less reliable. The other reason is that the impact of the storm is still 5 days away. By tomorrow and early this weekend we will have a much better idea of what will happen with the storm. One of the larger patterns that we look at to affect east coast storms is the North Atlantic Oscillation (NAO). This pattern recently became negative and is forecast to peak in the negative phase in the next few days. Some of our largest storms have occurred when the NAO is negative.

The models
Until the storm hits you will hear a lot and see maps that show something called the 'spaghetti' plots. These plots show a map, like the one below with several different lines on it. Each line is a different model or prediction. You want to notice where most of the lines converge or trend over time to make a forecast. I explain the plots to my students like this. It's like asking who will win the world series in April, August and October. The closer you get to the actual event the more the lines converge on one solution. The closer we get to Sunday and Monday the more these plots are going to show one consensus forecast.

Here in the United States, one of our models, the Global Forecasting System or GFS is run nearly two dozen different ways to get even more tracks. This is called ensemble forecasting when you basically use one model tweaked several different ways. In some ways this is what Cooks Magazine does when they test a recipe for something like brownies. They make slight variations in temperature, type of butter etc. and see how it all turns out.

Jet Stream
In the end, it's the jet stream that will carry the storm. The map below shows the forecast position of the jet Monday. Notice the block up over the northern part of the Atlantic. This is like a traffic jam preventing the storm from moving eastward like normal. While this block is in place the jet stream is coming along and may capture the storm and move it northward. The exact configuration of the jet will determine exactly how the storm moves. It could go into the mid-Atlantic region or come into New England. It still also may move under the block and curve away. That scenario is looking less likely as of this writing.

Past History
We can get some idea of how Sandy will move by looking at some past storms that have developed in that region. There are two storms that come to mind that affected our area that formed in the Cuba/Jamaica corridor. The great gale of 1878 and hurricane Hazel in 1954 both impacted New England and caused significant damage. Sandy will take its own path but it is worth noting where other storms have gone this time of year.

Impacts
At the very least New England is going to clouds increase Sunday and then drizzle and light rain will ensue. Monday into Tuesday will be the peak of the storm before we clear out Wednesday. Worst case scenario is that the coast experiences winds gusting to hurricane force, inland areas have 3-6" of rain causing some flooding and power outages become widespread. Coastal beach erosion and even damage could be a problem as well. For now, if you have a boat still in the water it might be prudent to get it out of the water and I would spend time this weekend cleaning out the gutters. Remember, if you lose power it could be out for days, don't spend money stocking up on perishables.

Gardening this week
There are many plants that bloom in the fall. Toad lily, asters, mums, joe pye weed, roses and many others wait or continue blooming into late fall. It's a good idea to have a garden with plants that bloom in all different season. When I design my gardens I select plants that bloom from February to November here in the northeast. Additionally, but adding some special evergreens, I can bring color to the garden all year long.


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