Okay, hold up. What’s a bomb cyclone? We heard about these in years past but maybe you still don’t completely understand what this is. Sounds scary, right?

A Bomb cyclone is also known as Bombogenesis. “Bombogenesis is a popular term used by meteorologists when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars in 24 hours. A millibar measures the atmospheric pressure. This phenomenon can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters.” (Definition from NOAA)

Bombogenesis is expected with a mid-latitude cyclone posed to impact the Northeast on Thursday. While this does sound scary, just like every other weather event that is forecast, as long as you prepare, you’ll be fine!

Will we actually see bombogenesis occur? 
Let’s take a look at the NAM (North American Model) at the time when a low pressure forms.

19Z on Wednesday we see a pressure of 999 mb

This particular model has an area of low pressure forming near the Chesapeake Bay this afternoon.

09Z on Thursday morning we see a pressure of 972 mb

This is a look at that same low pressure at its strongest point according to the NAM model. The pressure has now dropped to 972 mb. That’s a change of 27 mb in 14 hours! So, yes, we will likely see bombogenesis happen.

So, what are the impacts? 
Heavy rain, strong winds, coastal flooding and some higher elevation snow is expected with this storm.

Rain showers have already begun across the Mid-Atlantic states and that will continue to intensify as this storm strengthens. Most areas across the northeast are bracing for 1-3″ of rain with some locally higher amounts anticipated closer to the coast.

Total Liquid Precipitation Expected through Saturday morning. 

You can see that much of Upstate New York, Massachusetts, Rhode Island, Connecticut, Vermont, New Hampshire and southern Maine will see the bulk of the moisture associated with this system. Now, 1-3″ of rain is enough to cause some flooding issues depending on how fast it falls but I wouldn’t think that there would be widespread *freshwater* flooding with this storm.

Winds are an important parameter to look at when talking about coastal storms and Nor’Easters (which this is technically an early-season Nor’Easter). A Nor’Easter is defined as “a storm along the East Coast of North America, so-called because the winds over the coastal area are typically from the northeast. These storms may occur at any time of the year but are most frequent and most violent between September and April” (definition from the NWS).

Wind Gusts from Wednesday to Saturday.

Winds are definitely going to be howling the next few days. Where you see oranges and reds, those are where the strongest winds will be. So, coastal areas and of New England will see wind gusts approach 80+ mph! Of note, the darker blues and greens and where winds will gust upwards of tropical storm force. Also of note is the fact that even after the strongest of the storm moves away, those in the Northeast will still see gusty winds continue through Saturday with winds gusting between 20-40 mph.

I bring up the threat of coastal flooding because, with tropical storm and hurricane force winds out there, there will absolutely be big swells. Strong winds over the ocean mean big waves and big swells.

Wave Heights and Direction on Thursday Afternoon

So, here we look at the Wave Watch 3 model. This shows large waves offshore as big as 25 feet. Along the coast, wave energy will be elevated. Areas from Long Island to Coastal Maine could expect waves of 10 feet possible with higher waves on more remote or more secluded island locations. These types of waves make it possible to see coastal flooding. If you typically have issues with coastal flooding during times like these, you’ll likely face a few issues with this storm. 

While this is a pretty early time for a Nor’Easter to hit, there will be pockets of cold enough air to make snow a possibility, if not a likelihood in some areas. 
Snowfall expected through Friday 
Here we see snowfall totals as we head closer to Saturday. There are several areas to watch. First, the Appalachain mountain of West Virginia. these areas could see up to 12″ of snow! Seems hefty, right? It is, but you’ll have to account for a good bit of melting as this is the first snow for this area of the year. Pocahontas county where Snowshoe Ski Area is in West Virginia will likely have some fresh snow to excite those ready for ski season. 
We also are looking at northern New York State and the mountains fo New Hampshire and Vermont. Those areas will likely see several inches of snow. There are some favored slopes here so the possibility of seeing 1-2 feet of snow is also there but again, this is an early season storm so we have to think about temperatures and melting. 
Don’t freak out over the term ‘bomb cyclone’. Yes, meteorologically, it will be impressive to see but 1-3″ of rain accompanied by strong winds is handleable. If you’re along the coast, prepare for more impacts but mostly this will be a rain event with gusty winds. 
~Rain or shine
  I’m Andy Stein 

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