Ominous steering currents for Florida may be on horizon as quiet hurricane season persists | WeatherTiger

·4 min read

From the heart (and no, I am not referring to Hard Equations And Rational Thinking), I believe August to be the worst month of the year.

Heckish heat and sauna humidity continues, despite the good part of summer, in which creating small, colorful explosions in the sky is socially acceptable, being long past.

Kids are making grim countdown calendars for the 288 days until summer vacation; the rest of us reckon with a dispiriting 112 days left in hurricane season.

Still threat-free, but a slow start to storm season doesn't mean much as September peak nears

From the tropical perspective, August is not the absolute worst, but it certainly is the on-ramp to the most dangerous portion of the season.

About 25% of continental U.S. landfall activity occurs in August, second to the 45% or so that takes place in September. So far, the U.S. has been unscathed, and there are no threats over the next seven to 10 days.

The only tropical disturbance worth noting is a tropical wave in the eastern Atlantic struggling mightily against a bone-dry airmass. Even on the off chance this wave slowly develops, steering currents will hustle it out to sea early next week.

That slow start doesn’t mean much.

Florida major hurricane landfalls in September, 1900-2021
Florida major hurricane landfalls in September, 1900-2021

Of the historical hurricane seasons best matching 2022’s leisurely pace, half of them finished above and half below the normal level of U.S. landfalls for the full year.

Much more meaningful are the predictors like La Niña and Tropical Atlantic ocean temperatures that I discussed in WeatherTiger’s updated season outlook last week, which continue to point to net Atlantic hurricane activity about 50% higher than the average since 1970.

More from the desk of WeatherTiger:

Are dangerous steering currents setting up?

Of course, where those hurricanes develop and track is important, as similarly active years can have wildly divergent impacts.

In 2004, nine Atlantic hurricanes led to six U.S. hurricane landfalls and $60 billion in damage. In 2010, twelve Atlantic hurricanes caused zero U.S. landfalls and less than $250 million in losses. In other words, no one sits around the campfire and recounts the legends of the 2010 hurricane season.

What makes for a dangerous steering current regime? For Florida’s two busiest months, the average locations of high-pressure ridges and low-pressure troughs for years in which major hurricanes struck the state tell the tale.

Florida major hurricane landfalls in October, 1900-2021
Florida major hurricane landfalls in October, 1900-2021

In the 16 Septembers since 1900 with a major hurricane landfall in Florida, there is an increased tendency for strong, persistent high-pressure systems aloft set up over the Great Lakes and Eastern Seaboard.

The clockwise windflow around this “blocking” high-pressure ridge steers hurricanes developing in the Atlantic’s Main Development Region west across the state and prevents northward turns east of Florida.

In October, the favorable pattern is just the opposite. The 12 Octobers since 1900 with major hurricanes in Florida have a tendency for more high-pressure blocks in eastern Canada, the southwestern U.S., and the north-central Atlantic, favoring upper level troughs over the Midwest and eastern U.S. that steer hurricanes north out of the Caribbean and toward the Gulf Coast.

Some analog and long-range modeling indicates that blocking may start to develop over the western Atlantic in the last week of August, and blossom over the Great Lakes through the first half of September. This would be a worrisome steering pattern for the historically most active weeks of hurricane season, should it indeed develop.

Hang in there and enjoy the hurricane hiatus

Of course, steering patterns are literally capricious zephyrs, and landfall risk outlooks have very modest historical skill. WeatherTiger’s predictive algorithm projects around an additional 6 units of Accumulated Cyclone Energy (ACE) to occur over the continental U.S. during the remainder of the season. A normal year would have about 4 more units of ACE after mid-August.

That means landfall risks are above normal for Florida over the next few months, and there are some shadows on the cave wall favoring a worrisome steering regime in September. As ever, it would be surprising to get through the next 10 weeks without at least some major tropical intrigue for Florida or the rest of the continental U.S.

So, don’t be shocked if August plays to its demotivational strengths by the end of the month. However, there’s nothing tropical to worry about in the near future, so like a cat clinging to a laundry line, hang in there, baby, and keep watching the skies.

Ryan Truchelut, WeatherTiger
Ryan Truchelut, WeatherTiger

Dr. Ryan Truchelut is chief meteorologist at WeatherTiger, a Tallahassee start-up providing forensic meteorology and expert witness consulting services, and agricultural and hurricane forecasting subscriptions. Get in touch at ryan@weathertiger.com, and visit weathertiger.com for an enhanced, real-time version of our seasonal outlook.

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This article originally appeared on Tallahassee Democrat: Florida hurricane season forecast for August and September