Wednesday, January 20, 2016

Big Snows Not The Biggest Threat From Upcoming Stormal

I seriously doubt coastal flooding will be as
bad as in Superstorm Sandy in New Jersey, shown
here, but there is a threat of coastal damage
with this upcoming nor'easter. 
The East Coast is still gearing up for one of those blockbuster nor'easters that tend to get us weather geeks excited, the populace panicked and snow lovers rejoicing, or cursing if the snow misses.

Of course, the forecast is still tricky, and everybody is trying to pin down exactly who gets the most snow, the most wind, the most tidal flooding, that sort of thing.

I think forecasts for the nature of the storm will get a little more precise, accurate and certain later today. That's because the main initial weather disturbance that will cause this storm is coming ashore over the United States West Coast.

That will enable weather instruments and meteorologists to get a more detailed and complete assessment of what's going on in the atmosphere. It's easier to measure such things overhead on land, than it is when things are still over the remote Pacific Ocean.

The forecast for the storm will still end up being imperfect, as they always are for nor'easters, but at least by the end of the day we'll have higher confidence as to what's going on.

Already, winter storm warnings were up this morning for parts of Kentucky and Tennessee due to a smaller, initial storm rolling through ahead of the main action coming in Friday.

A wide area from the Ohio Valley to much of the Appalachians and East Coast are indeed due for a pretty big dump. Some areas in the central Appalachians and parts of the Middle Atlantic states could end up measuring the snow in feet, not inches.

While up to three feet of snow is certainly a big deal, if it materializes, this isn't the only threat from this likely upcoming storm. In fact, the snow isn't even the most serious threat, though it's the aspect of the expected nor'easter that's getting the most attention.

Much more worrisome is the good chance this storm will bring on some serious coastal flooding and coastal erosion. Secondary threats also include damaging icing, the threat of severe weather and possibly tornadoes, flooding, and of course, the snow.  
Forecast maps are still showing a strong nor'easter
on the East Coast Saturday.

Let's break it down:


This storm might ultimately be remembered more for its coastal flooding and damage than the snow it will probably dump.

The storm will come along this weekend when the moon is full, which means tides will already be higher than usual.

The barometric pressure in this storm, when it's off the Mid-Atlantic coast, is forecast to be quite low. Such low pressure means the air isn't pressing down on the ocean so much, so the water can expand upward. That would contribute to higher tides, too.

The counterclockwise flow, from the east, will mean strong winds will blow over large expanses of the western Atlantic Ocean and push the water toward the East Coast, further increasing tides.

Add to that the fact that sea levels have risen a bit due to global warming, so the starting point from which the ocean water will rise and potentially cause flooding is that much higher.

While it's still uncertain how bad the coastal flooding might end up being, forecasters are getting concerned.

Yesterday, the National Weather Service office in Mount Holly, in southern New Jersey said this storm might bring one of the Top Five highest tides on record, and suggested people with coastal property prepare now.

In New York City, some forecasters feared the tide might become as high as it was during Hurricane Irene in August, 2011. Irene wasn't as bad as Superstorm Sandy a year later, but Irene still flooded parts of Lower Manhattan.

Again, nobody is sure how bad any coastal flooding might be, but it's definitely something to watch


As the storm begins to get it's act together near and north of the Gulf Coast Thursday some severe thunderstorms and possibly even tornadoes could break out. If that happens, the best chance is in Louisiana, western Mississippi and maybe southern Arkansas.

As the storm moves east, there's an uncertain chance of more severe weather in Florida. That prospect is iffy since they'e already had enough with the tornadoes and severe thunderstorms and damaging winds over the past week or so.


There will be a transition zone between the heavy snow to the north and rain to the south and east as this storm gets going along or off the Carolina coast.

It looks like there could well be a zone of freezing rain -- maybe a lot of it -- in the Southeast. I'm not sure yet, but the best bet looks to be in much of North Carolina. Maybe southern Virginia, too. There is a chance that enough freezing rain will accumulate in some areas to bring down lots of trees and power lines.

Forecasting ice storms this far in advance is particularly tricky. This IS something to keep an eye on though.


As it's developing the storm will dip down toward the Gulf of Mexico (as I noted in the severe weather section above) When it does that, it will pick up boatloads of moisture from the Gulf of Mexico.

Nor'easters tend to also draw a LOT of moisture from the Atlantic Ocean as they develop. Waters just off the Eastern Seaboard are much warmer than normal. That means the storm will be able to draw even more moisture into its system than normal, since warmer water is more easily drawn into weather systems.

That opens up the possibility of flooding in southeastern North Carolina, South Carolina and Georgia.

It's been an incredibly wet winter in that section of the country, so it wouldn't take much to set off some flooding.

That said, although flooding is always dangerous, this will fall well short of a mega flood disaster, like the one that struck South Carolina last fall. 


Yes, we have to talk about the snow. Remember how I said in the flooding section that the water off the East Coast is unusually warm, and the storm can thusly draw in more moisture than usual.

When that big moisture load hits the cold air north and west of the storm, the snow would become particularly heavy. That's why everyone is so excited and panicky over this potential storm. Because the snow could come down harder than it does in a "normal" nor'easter.

The first winter storm watch for heavy snow with this storm was issued for much of West Virginia. You'll see those watches and alerts spreading a lot during the day today and tomorrow.

I wouldn't be surprised to see isolated snow totals of up to three feet in the mountains of West Virginia, western Virginia and maybe North Carolina.

The National Weather Service office in Washington/Baltimore appeared ready as of mid-morning to issue a blizzard watch for later Friday and Saturday. 

In some areas, the snow will be wet and heavy. And possibly mixed with freezing rain. That would cause widespread power failures in the most affected areas. Again, it's too soon to pin down precisely who gets the most snow, who gets the dry, powdery snow, and who gets the more dangerous wet and heavy stuff that knocks down trees and power lines.
Sorry, northern New England snow enthusiasts.
It's still looking you''re going to miss out on
the upcoming nor'easter, but you did get a bit of
snow yesterday, as seen in this photo taken
Tuesday morning in Colchester, Vermont. 

There are snow lovers here where I live in northern New England. Miracles can happen, but it still looks like northern New York, Vermont, New Hampshire and western Maine are going to sit this storm out

Southern New England is going to be living on the edge. I'd hate to be a meteorologist in places like Massachusetts and Connecticut right now. The northern edge of the precipitation is going to have a sharp cut off between heavy and light.

If the storm goes literally just 20 miles north or south of where it is forecast to go, areas in southern New England that are forecast to get light snow could get dumped on, or areas that are forecast to be buried could get next to nothing.

By the way, if, on the day before a nor'easter, you forecasted it to go 50 miles west or east of where it actually goes, you've still done an excellent forecasting job with these notoriously fickle storms. It's nearly impossible to get the path right within a margin of 20 miles.

There's still going to be a lot of updates on this storm as forecasts become more refined.

As I noted yesterday, there's a lot of hype out there. And a lot of information to digest, just in this blog post alone.

If it looks like you're going to get hit with this storm, just relax, chill, make whatever preparations local forecasters tell you to make. And then ride it out at home where you're safe and warm - unless you're right along the coast.

A few places might end up getting a truly memorable storm, we'll have to wait and see. But it's winter, not the end of the world. So enjoy the ride.

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