It’s too early to predict hurricane season

Talk on social media in recent weeks has focused on the upcoming hurricane season, which starts June 1. Weatherbell, an analytics company that helps us build the weather maps we use in our daily forecasts, published a web article in December warning of a “hurricane season from hell” this year.

But Matthew Rosencrans, the National Oceanic and Atmospheric Administration’s lead forecaster for the seasonal hurricane outlook, says predicting a busy hurricane season this far out can be perilous. Here are five good reasons why, even two months later, it’s way too early to make that call.

1. El Niño-southern Oscillation changes

We’re in the midst of an El Niño phase, which means equatorial waters in the eastern Pacific Ocean off the coast of South America are warmer than what’s typical. During La Niña, those same tropical waters are cooler than average. These two phases are part of a larger system called the El Niño-southern Oscillation.

Rosencrans says many changes in the ENSO status can occur between winter and May, when the seasonal tropical cyclone outlook is published.

“Some of our forecasts have us going into La Niña by the summertime … Do we actually emerge through that April and May period when we’ve had very low skill for years?” Rosencrans says, referring to ENSO forecast uncertainty during the spring months.

Many factors during the spring can sway the ENSO status and, historically, forecasting those changes have been incredibly difficult for seasonal forecasters because of a phenomenon called the “spring barrier.”

2. Getting through the spring barrier

According to the NOAA, the spring barrier isn’t a physical wall. Instead, we should think of it as a low spot in ENSO forecasting accuracy. Why is forecasting the ENSO state so treacherous during the spring months?

“Forecasters think it has something to do with the transition into the monsoon season in western and eastern Asia,” Rosencrans says. Adding clout to this notion is how, especially in the spring, dynamical models that use realtime data perform better than statistical models.

3. Dynamical models vs. statistical models

Dynamical models, like what forecasters use to predict thunderstorm development in the span of two to three days, are run more frequently and use the most recent observation data as input. Statistical models, on the other hand, often build on monthly or seasonal data averages. The fact that dynamical models are able to ingest real-time data, like subsurface ocean temperatures, could partly explain why these types of models perform better at determining the future ENSO state.

4. Unreliable data

Making predictions on what a hurricane season may hold is tricky enough in May when NOAA releases its official outlook. It would be even more precarious to release an outlook in January or February.

“If you use data from February to correlate that with tropical cyclone activity later in the year, those correlations are going to be much lower … By waiting until May, we can get correlations that are much higher, so our predictions are able to be more accurate,” Rosencrans says.

How much error is reduced by waiting until May to publish the official hurricane season outlooks? Rosencrans says forecasts issued in May tend to be about 50% more accurate than those published in April.

5. Impossible predictions

According to Rosencrans, it makes more sense to do probabilistic landfall forecasts.

For instance, if 10 hurricanes have made landfall in a given area in the past 100 years, that area has a 10% chance of a landfall in any given year. Rosencrans says the Gulf of Mexico is particularly prone.

“Almost every year we get at least one landfall along the Gulf coastline … there’s almost nowhere for cyclones in the Gulf to go besides hitting a coastline,” he adds.

Rosencrans says he doesn’t “want to put out a forecast and have it be inaccurate more often than it’s accurate.”

“There’s still a lot of science work on that end to make forecasts earlier in the season more reliable,” he says.

Even if it’s too early to make predictions on the coming hurricane season, Rosencrans says it’s not too early to buy extra nonperishable foods and other hurricane supplies, so you’re not scrambling just before a storm arrives.

“Reviewing plans and practicing evacuation with your family … Get a little more prepared, as prepared families are safe families.”