That was quite a storm which rolled through Maine overnight and this morning as we went from almost no wind Sunday morning to winds gusting near 70 miles an hour early Monday in some places. Most areas had winds between 40 and 50 miles per hour with a gust just before 5 a.m. of 60 miles per hour in Portland.
That caused tree damage and numerous power outages. As of mid-morning Monday more than 300,000 homes were without power.
So what caused the wild weather and why did it move in and out so quickly? Let’s take a look:
In order to understand last night’s weather we need to think about low-pressure systems and why they develop. A low pressure system, or what most people call a storm, is an area where there is less air than in spots around it. The reason why there’s less air is because the air in a low-pressure system is going up. We can’t take all the air off the planet so air rushes in to replace the rising air.
Highs and lows develop in different parts of the jet stream.
When the air leaving above the low pressure system is greater than the air coming in at the surface, the pressure rapidly decreases. The lower the pressure gets the stronger the storm becomes. Another way to think about this is that if you have a big leak in a swimming pool the water level will go down even if you have a garden hose replacing the water. Air was rushing into the low pressure giving us all that wind here on the ground, but air was being evacuated over the top of the system even faster by a powerful jet stream with even stronger winds. Mount Washington’s winds were gusting over 130 miles per hour early Monday.
THE JET STREAM IS CRITICAL
The jet stream has been in a meridional configuration over the past week, which means it has a lot of loopiness to it. When the jet stream has large dips, known as troughs, this helps create something called divergence and diffluence in the upper levels of the atmosphere. This then aids to storm development. Basically, these two phenomena aid in helping to lift the air off the ground and make storms more powerful..
The jet stream winds were blowing particularly strong over the northeast the past 24 hours.
As the storm developed off the coast of the Mid-Atlantic on Sunday evening, the jet stream going over the top of this low pressure system lifted so much air off the surface that the pressure began to fall rapidly. As this was occurring, all the air rushing in to replace that rising air became the wind we all experienced overnight.
Notice the air rushing towards the low pressure area over upstate New York Monday morning.
As the low continues to move up into Canada, the pressure will start to rise and we will experience the winds rushing toward that low pressure system as it continues to move further away. Winds will finally relax Tuesday night as the storm’s influence will have moved too far away from New England.
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