We’re three days away from the start of hurricane season in the Atlantic Ocean, and we’ve already seen one tropical storm this year. Tropical storms in May aren’t all that rare, but they aren’t exactly an omen, either. Forecasters expect a below-average hurricane season, but it just takes one to make a mess.

Almost all major forecasts released by various organizations over the past couple of weeks have called for a below-average hurricane season in the Atlantic Ocean, with most forecasts predicting eight or nine named storms (tropical storms or hurricanes), four or five of which could become hurricanes, and one or two of those possibly turning into major hurricanes (category three or stronger).

Here’s a chart showing these predictions compared to the 30-year average and last year’s Atlantic hurricane season.

(Since NOAA and WeatherBug create forecast ranges (NOAA predicts a 70% probability of 6-11 named storms), I averaged-out the range and rounded up in the chart above.)

These forecasts generally include Tropical Storm Ana, which formed earlier this May. The storm strengthened to 60 MPH before weakening and making landfall near Myrtle Beach, South Carolina.

The big theme of NOAA’s hurricane preparedness campaign in the days leading up to the beginning of hurricane season—which is next Monday, June 1—is a recurring theme for disasters here on The Vane: “it only takes one.”

The 1992 hurricane season is a great example of a quiet season producing a catastrophic hurricane. We went almost the entire summer without seeing a named storm that year—the first named storm didn’t form until the end of August. That storm was category five Hurricane Andrew, which slammed into southeastern Florida, killing dozens of people and leaving behind tens of billions of dollars in damage in its wake.

Hurricane season forecasts come with a huge caveat that they exist to show trends. Meteorologists can’t predict hurricanes beyond more than a week or so. Forecasters and models can predict long-term large-scale trends (water temperature anomalies, El Niño, general patterns) that can affect whether or not small-scale ingredients can come together in a favorable environment and produce a tropical cyclone. If you’re a month from hurricane season and you see a strengthening El Niño, colder-than-normal ocean temperatures, and you have Saharan dust blowing over the Atlantic, you can be sure that it’s going to be extremely hard for storms to develop.

Last year is a good example of a season both overperforming and underperforming based on what forecasters predicted just before the beginning of the season.

The total number of named storms last year in the Atlantic clocked-in both below average and below what forecasters expected, with only eight named storms (compared to 12 on average and about 10 forecast). However, six of those eight storms became hurricanes—surpassing expectations—several of which made landfall.

The National Hurricane Center (hurricanes.gov) issues five-day forecasts and watches/warnings for tropical systems in both the Atlantic and Eastern Pacific basins. Organizations will update their seasonal hurricane outlooks as we head into hurricane season.

[Images: AP, NOAA | Charts: author | Corrected the first chart to reflect that the averages listed below the forecasts are 30-year averages.]

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