Tonight meteorologists and weather enthusiasts are quite excited to watch the upcoming development of the big ocean storm which will form tomorrow.   You may be wondering what the big deal is about a storm that is more of a miss than a hit and you are certainly justified in that thinking.  However, let me put the size of the storm in perspective. 

When we evaluate storms, one of the ways we note the strength of a low pressure center is by its pressure.   Storms exist to balance the atmosphere.  Their purpose is to mix cold and warm air and try to achieve equilibrium.  When a large difference in temperature exists and energy from the jet stream rides over this contrast storms often develop.

Air rises in storms, and as the air leaves the planet the pressure lowers.  Wind is the air rushing into the storm trying to fill the void being created by its formation.  If the storm is really large the air can’t fill the void fast enough and the pressure continues to fall.  The faster the pressure drops the more wind we experience as those winds are attempting to balance the rising air.  

Normally, on an average day, the pressure of the air above you exerts about 1013 millibars of pressure.   In a typical strong storm this pressure can fall to 980 millibars.  At that level of pressure a storm would generate a considerable amount of wind and precipitation.   The faster the pressure falls each hour during a storms development the greater the intensity. 

When a storm loses 24 millibars of pressure in a day the storm is said to have undergone bombogenisis.   In layman’s terms, this is akin to the atmosphere exploding a storm in a very short period of time.  During the upcoming storm the pressure is forecast to drop 30 millibars in one day.   This will create a storm in the ocean with a pressure typically seen in a category three hurricane. 

Low pressure isn’t the only factor in why a storm produces a lot of wind.  If there is a big high pressure area a few hundred miles away this generates even more wind.  In the upcoming situation there will be a high with a pressure of 1030 millibars in Canada.

The reason I spent so much time with that explanation is because I want you to understand the scope of this storm.   While the heaviest precipitation will fall over the outer part of Cape Cod, far eastern Maine and Nova Scotia the wind field is enormous and has the potential to be damaging.

What if?

I don’t like what if scenarios because they bring nothing to the table.  That said, some of you might be thinking what if the storm came closer to the coastline?  The reality is the storm would have to move nearly 200 miles further west than predicted and this isn’t likely at this point.  IF however it did, we would be looking at a damaging nor’easter with 1 to 2 feet of snow, widespread power outages and an all around bad situation.

The reality

The main threat from this storm is the wind.  This is especially true over eastern Maine where the blizzard watch is posted.  To punctuate the strength of the storm, note the hurricane force wind warning just off our coastline.

Timing

The Tuesday evening commute won’t be an issue, but the one Wednesday morning may be a bit slow.  Early Wednesday, over the immediate coastline, there is likely a period of light snow.

The storm will move quickly and therefore any snow will end early across area before the commute is over and continue over Down East Maine much of Wednesday.  These times will be tweaked a bit during the day Tuesday.

Wind

As I wrote, the wind is the big issue from this storm.  While some parts of eastern Maine will exceed 6 inches or more of snow, it’s the near hurricane force gusts just offshore that are the big story.  Even in Portland, winds will be strong enough to cause scattered power outages.  However, winds do not appear to be forecast at a level to cause widespread power issues for most of us. 

If you live east of Penobscot bay I recommend preparing for power loss.  If it doesn’t happen, consider it a good thing.

Once the storm passes, it remains chilly and windy Thursday before we turn milder for the end of the week and the start of the weekend. I’ll have much later Tuesday and during the evening as the snow develops.