January 25–28, 2015 Winter Storm/Blizzard

Winter Weather Discussion

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wxman57
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Re: January 25–28, 2015 Winter Storm/Blizzard

#41 Postby wxman57 » Tue Jan 27, 2015 3:29 pm

cycloneye wrote:NYC was a bust as totals are under what was expected.Kudos to GFS.


The GFS tends to move all storm systems farther off the East Coast than other models. It's kind of like the Canadian getting the development of a TC right. If it forecasts everything to develop then eventually it will be right. In this case, the low formed 50-100 miles farther offshore than the Euro was forecasting, thus the bust for NYC. Not a bust for areas east of there, though.
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RL3AO
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#42 Postby RL3AO » Tue Jan 27, 2015 4:27 pm

It is impossible to make a single correct snowfall forecast. There are too many unknowns and snowfall gradients can be absurdly tight (see NYC and northern NJ). People who give snowforecasts do a TERRIBLE job at expressing the uncertainty when it is high.

From the WPC forecasts from the 26th at 0z

25th percentile (means a 75% chance of getting AT LEAST this much snow...also means a 25% chance you get less)

Image

There is a lot of uncertainty with snowfall. The western side (Philly/NYC/Albany) ended in the 10 to 25th percentile. Is this a bust? It was an unlikely outcome but a 20% chance of rain still means it might rain. The most likely outcome for NYC was gonna be 16 to 24" but it was not explained well enough that it was not the ONLY possible outcome.

(Note: WPC graphic from WeatherBell using the WPC Grids)
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Re: January 25–28, 2015 Winter Storm/Blizzard

#43 Postby ronjon » Wed Jan 28, 2015 6:14 am

Heres actual versus predicted. Not bad except for Philly and NYC.

http://www.huffingtonpost.com/huff-wires/20150128/us-winter-weather-snowfall-totals/
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