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50-50 Low

50-50 Low.

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50-50 Low

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  1. 50-50 Low The 50-50 low is put in place by a negative NAO. This low is called such due to its location about 50 longitude and 50 latitude. This low is important because it blocks coastal storms along the East coast against a wedge of arctic high pressure to the storms’ north This high pressure is usually located south and/or west of the 50-50 low.

  2. 50-50 Low According to Dave Tolleris, the “50-50 Low” affects the overall pattern across eastern North America in several ways. Enhances the intensity or amplitude of the negative NAO in general and the Greenland Block negative NAO in particular. Keeps cold air source (high pressure) in place. Trap and lock example. Thus, more precipitation falls as snow due to the prevailing NW, N, or NE wind. 3. Prevents systems in Plains/Midwest from passing west of the Appalachian Mountains.

  3. High (Greenland Block), Low (50-50 Low), High (Arctic High) Configuration

  4. February 2003 Presidents Day Storm (50-50 Low, PV, and High Pressure)

  5. Blizzard of 1996 (January 6-8, 1996): 50-50 Low, PV, and High Pressure

  6. Polar Vortex, 50-50 Low, and the NAO As stated on my last two posts this snowstorm threat comes about because the West Coast Ridge is fracturing  as it gets  battered by energy coming in from the Pacific. The northern end of the Ridge over northwestern Canada breaks off as a bubble of positive height anomalies -- high pressure in the jet stream-- which moves into north central Canada. This forces the huge PV   to move into southeastern Canada  and  to stays in place. The PV which typically is situated over Hudson's Bay is now displaced to the south. Because the vortex is displaced over southeastern Canada   it   acts  JUST as the   50/50 Low would  in setting   up  a strong confluence zone in the PJ. It is the confluence zone which allows the cold High pressure over Eastern and Central Canada to build.

  7. Polar Vortex, 50-50 Low, and the NAO Without the blocking features somewhere over Greenland or eastern Canada--- such as a - NAO or 50/50 Low -the cold HIGH pressure area over the Great Lakes or southeastern Canada will often slide out to sea during the East coast storm which is one reasons why in the big cities of the Northeast snow changes to rain. BUT in major snowstorms however the blocking does exist over eastern Canada and High pressure is trapped so the cold air is held in place and mostly precipitation over the Northeast even the big cities falls the snow.

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