David Epstein: Why did forecasters get this nor’easter wrong?

The forecasting industry gets it right a lot, but, sometimes, it gets it really wrong. And we definitely got it really wrong today.

Pembroke- 03/22/18- It doesn't look spring-like on Spring Street in Pembroke as the snow continued to fall in the morning, but was not as bad as originally forecast. There was about an inch of snow in the area.  Photo by John Tlumacki/Globe Staff(metro)
Spring Street in Pembroke on Thursday. –John Tlumacki / The Boston Globe

If you weren’t following the latest changes to the forecast Wednesday afternoon and evening, you were probably surprised to find almost no additional snow on the ground this morning.

The forecasting industry gets it right a lot, but, sometimes, it gets it really wrong. And we definitely got it really wrong today.

I can tell you with a lot of certainty that it’s very frustrating for any meteorologist to miss a forecast, but it’s also humbling. It’s just a fact of the matter: The atmosphere is incredibly complicated and always will be.

Meteorologically, the storm never really got its act together because too much dry air ate away at the precipitation shield on the northern and western flank.

Advertisement

However, there was significant snow not too far away. In New York City, for example, some spots got more than a foot of snow.

That was the potential here in Southern New England if the axis of heavy precipitation had tilted more toward the northwest.

Forecasting models

Of course, there are always computer models that we all use to guide us, but, frankly, their performance hasn’t been as good in the past few weeks.

Although the models successfully understood a storm would form, they did a poor job of placing the precipitation within the storm. I suspect the unusual blocking pattern that we are in is throwing the models for a loop.

While the European model did a better job forecasting this system than other models, it also was way overdone. But in other recent storms, other models have outperformed the Euro, so it’s dangerous to just follow one.

For example, if we had believed the NAM model on Wednesday morning, we would have forecast 10 to 15 inches of snow in Boston. This model accurately predicted the amount of snow seen in New York, but it arced the precipitation band way too far to the northwest.

via GIPHY

Good forecasting means using the models as a tool, rather than following them directly.

Advertisement

When I started pulling back on accumulation Wednesday afternoon and evening, my forecast was still going against the guidance.

There’s a saying that “the trend is your friend,’’ and, to me, the trend started becoming quite clear with the information that came in Wednesday afternoon.

Some storms are just handled by the models worse than others.

Case in point, even as late as early Thursday morning, the European model was still insisting a lot of snow would fall over southeastern Massachusetts — up to 9 inches. This is why you can’t look at these maps and just make a forecast.

European snowfall prediction from early Thursday. —WeatherBell

No one likes to be wrong in any industry.

Part of forecasting the weather is accepting you can’t always get it right, and sometimes, you’re going to get it really wrong.

Now it’s on to the next challenge. Frankly, I’d like to start forecasting some sunshine and warm weather.

Weather
Yes, April snow is coming
March 31, 2018 | 8:47 PM