Thirteen inches in northern New Jersey. Seventeen in Upstate New York. White-out blizzard conditions in Worcester, Mass., and snow falling at a rate of three inches per hour in southern New England. An avalanche closed down a highway in Pennsylvania and knee-deep water surged onto the shore in Delaware and New Jersey.
Sounds like a pretty major storm for the Northeast, right? Wrong — because in Central Park meteorologists were forecasting 18 to 24 inches, and only a fraction of that fell.
This isn’t a problem with the storm, obviously, it’s a problem with the forecast. People were bummed on Tuesday morning when they woke up and saw Central Park had only reported four inches as of 8 a.m.
Twitter took over from there.
Turns out, people like their snow! Especially when it’s in the forecast and they spend 48 hours preparing for it. I can’t blame them — I would be bummed, too.
Unfortunately, weather forecast models are not excellent right now. They didn’t pick up on the small shifts that would make all the difference in Winter Storm “Stella.” Another problem is that meteorologists rely too heavily on these models — which have made incredible strides in accuracy over the past decade — and not enough on instinct.
In fact, there were even hints that things were shifting on Monday, but the vast majority of forecasters stuck to their maps. They did not convey (loudly) the uncertainty in this storm, treating it with the same apparent confidence as the Blizzard of 2016. Snowzilla this storm was not.
And to be fair, as my friend Andrew Freedman at Mashable said, it’s hard to communicate that things might not pan out as planned when you’re also under a blizzard warning:
… millions of people were outraged this morning that their much-advertised blizzard was not to be. This was despite the fact that the forecast was always highly uncertain for New York City, Philadelphia, coastal Connecticut and western Long Island.
Part of the problem may have been that blizzard warnings were issued, and National Weather Service (NWS) maps showing the “most likely” amount of snow were plastered across social media, and these consistently showed at least a foot of snow or more for New York.
Meanwhile, the atmosphere was always going to do what the atmosphere was going to do. As is the case with every nor’easter, the track matters. A lot.
The biggest East Coast snows are caused by nor’easters. They feed on moisture and heat from the warm Gulf Stream. If the storm takes the right track up the East Coast, it can dump a boatload of snow from D.C. to Boston. If the track is too far to the west — like Tuesday’s — the big winter storm will turn into a gross, sleety mess.
It’s all because of where the cold air is. In order for it to snow, the air needs to be below 32 degrees, which is on the northwest side of the storm. The rain happens on the southeast side of the storm. What’s left in between is the dreaded “wintry mix” of snow, sleet, freezing rain and rain.
This is a really rudimentary GIF to illustrate the forecast challenge.
Now take a look at the difference between what the forecast models were predicting and what actually happened. The difference between the center of the storm in the forecast and the center of the storm in reality is not that far, but it was more than far enough to burst New York’s snow bubble.
To sum up: Forecasting is hard, meteorologists need to do better with uncertainty and hopefully we all enjoyed this “faux day” in a basically snowless winter.