low pressure system
"Gradient winds or general winds are named because of the gradient that exists between a high and low pressure system. A high pressure system is a large invisible mountain of air in the atmosphere. A low pressure system is like a sinkhole. Around a low pressure system the air flows in a counterclockwise manner into the area of low pressure. Around a high pressure system the air flows in a clockwise manner. These highs and lows are caused by the differential heating of the earth's surface."
"Such a spinning low pressure system is like a top, subject to erratic movement. It only shifted 90 miles East compared to predicted and it did indeed produce 3 feet of snow in part of Mass. So not such a bad forecast. If it weren't for NYC being so populous and filled with media, it would not be called so bad."
"A low pressure system is like a giant funnel of wind spiralling inwards and upwards forcing warmish air in the centre to rise. As air rises it cools and clouds form."

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