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NWS adjusts curiously low snowfall totals at Central Park

For years now, the meteorological community has been aware that Central Park usually reports snowfall totals lower than its surroundings. For reasons not completely known, surrounding stations at Newark, LaGuardia, and Teterboro Airports almost always seem to report higher snowfall totals. Even local, public reports in Midtown and Lower Manhattan seem to consistently come in higher than the Central Park Zoo. This year, the National Weather Service took to the task and edited the official Central Park reports to better match surrounding data.

Snowfall amounts from three separate storms this winter:

January 6th, 2015: Snowfall total adjusted from 0.5″ to 1.0″ (+0.5″)

January 24th, 2015: Snowfall total adjusted from 2.5″ to 3.6″ (+1.1″)

February 2nd, 2015: Snowfall total adjusted from 3.3″ to 5.0″ (+1.7″)

The total of adjusted accumulations adds 3.3″ of snow to Central Park’s snowfall total, bringing the seasonal snowfall total to 50.3″ in New York City. These adjustments were made by the National Weather Service almost two months (more in some cases) after the snow fell. The National Weather Service, in their official release, says:

THE NATIONAL WEATHER SERVICE PERFORMED AN ANALYSIS OF SNOWFALL 
AMOUNTS THAT FELL AND WERE MEASURED AT CENTRAL PARK EARLIER THIS 
YEAR.

THREE SPECIFIC SNOWFALL AMOUNTS AT CENTRAL PARK WERE LESS THAN 
SURROUNDING OBSERVATIONS. BASED ON THESE FINDINGS...AN ANALYSIS WAS 
PERFORMED THAT MADE USE OF SURROUNDING OBSERVATIONS...SNOW TO LIQUID 
RATIOS AND RADAR DATA FOR ALL THESE EVENTS.

As forecasters, this leaves us with an interesting debate and a bit of an issue at hand. First and foremost, we appreciate the effort by the National Weather Service. This year, it was apparent even as the snowfall observations were coming in and the snowflakes were still falling, that Central Park was registering much lower than surrounding locations. There are several reasons that could be attributing to this, including but not limited to poor observation quality, winter foliage impacts, snowboard temperature. And so, the fact that the National Weather Service took the time to re-analyze the reports against surrounding location data is very encouraging.

That being said, this brings another question to the forefront. While this re-analysis could serve as a beacon for future years accuracy, what exactly does it mean for those future snowfall reports and what does it indicate about the past? If the National Weather Service is acknowledging that snowfall reports from Central Park are lower than surrounding locations, and that they were erroneous, what does that say about years of climate data which featured similar trends? Seasonal snowfall totals, averages, and trends may all be contaminated by this data.

Furthermore, precedent set moving forward comes into question as well. A proverbial “can of worms” may have been opened here, where future snowfall events or local micro-scale snowfall total differences that come into question can be edited as well.

Still, it isn’t the National Weather Service’s fault that this debate is going to arise. There may be a fine line between editing for accuracy and adjusting things to an obsessive degree. We will have to see where that line falls.

The meteorological community, however, certainly appreciates the effort.

Well done.

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