It’s been vewy, vewy, quiet out there – still, it only takes one Cat 5 to ruin your whole damn day.
Michael Lowry in Eye on the Tropics:
It’s been an unusually quiet stretch during what is traditionally one of the busier parts of the hurricane season.
The Atlantic hasn’t produced a named storm since Ernesto, which formed way back on August 12th. As Dr. Phil Klotzbach – senior research scientist at Colorado State University who heads up the gold standard of seasonal outlooks – posted to social media this morning, this is the first time since 1968 the Atlantic hasn’t notched any new formations between August 12th and September 3rd.
Not to mention, the disturbances with any development potential since Ernesto have largely underperformed. We see those struggles in the system we’re following through the Caribbean today.
So is it time to raise the white flag and surrender to/celebrate what appears to be a big seasonal bust?
What the past tells us
There’s no denying the past few weeks have been unusual and unexpected. But a funky period sandwiched in the ramp up period to the traditional seasonal peak isn’t without precedent.
Consider 1961, which saw Category 2 Hurricane Anna in July then went 46 days before Betsy formed in September, a Category 4 hurricane immediately followed by Category 4 Carla and Category 5 Esther. It was a year scraping the bottom of the ACE barrel (Accumulated Cyclone Energy or ACE is used as a scorecard for seasonal hurricane activity) at the turn of September that even to this day remains a top 10 ACE producer.
Or more recently 2022 that went an astounding 61 days between Colin on July 1st and Danielle on September 1st, a season with a third the activity through September 2nd as this season, but which ended above average, with a catastrophic hurricane hit (Ian) and the latest hurricane strike on record for the Florida peninsula (Nicole).
Why we shouldn’t bet against the back part of the hurricane season
The Main Development Region of the tropical Atlantic is egregiously warm – amazingly still rivaling 2024’s unprecedented levels – and vertical wind shear has been well below average across the bellwether Caribbean. These are two important factors – the two biggest factors identified by researchers – for hurricane season activity but not the only factors at play.
Seasonal forecasts have busted before, most famously in 2013 which saw the lowest activity in 30 years despite calls for above average hurricane activity.
Could 2024 become another 2013? While it’s certainly possible the seasonal outlooks get it wrong this year, the issues we’ve identified so far shouldn’t be a showstopper. If part of the issue has been a northward displaced monsoon trough – a breeding ground for tropical saplings that’s lately become entangled in dry and dusty air – it should naturally correct as the monsoon trough shifts southward this month. As we’ve discussed in previous newsletters the Central American Gyre also becomes a bigger player again in September and October, which would presumably pick up any slack left from anemic tropical waves.
Lately there’s also been chatter of very warm upper levels in the troposphere (at around 50,000 or 60,000 feet) – a byproduct of global warming – that could be making the Atlantic more stable than normal and capping thunderstorm growth despite record warm sea surface temperatures. If this is indeed the case, the upper levels naturally cool during the fall, and at a much faster rate than the ocean, so the cooling in the air above would naturally make the atmosphere less stable for the back part of the hurricane season.
We’ve also written that the emerging La Niña in the eastern Pacific gives credence to a backloaded hurricane season, something researchers have shown during previous La Niña episodes.
With 65% of tropical activity typically happening after September 3rd, including some of the strongest hurricanes on record, and without a smoking gun to explain why the struggles should persist, it’s premature to call the season a bust, especially after a catastrophic Category 5 hurricane and two U.S. hurricane landfalls.
None of us will complain if the current struggles continue but we also know better than to presume they will.
NOAA National Center for Environmental Information points out that some pretty big years got off to slow starts. Also, worth pointing out that although big CAT 5 storms get a lot of attention, we’ve seen several big tropical systems, one that was not even a hurricane, create major havoc in Florida this year.
Hurricane Debby damages were still being tallied at the time the charts below were being created.
2024 in Progress…
In 2024 (as of August 8), there have been 19 confirmed weather/climate disaster events with losses exceeding $1 billion each to affect United States. These events included 15 severe storm events, 1 tropical cyclone event, 1 wildfire event, and 2 winter storm events. Overall, these events resulted in the deaths of 149 people and had significant economic effects on the areas impacted. The 1980–2023 annual average is 8.5 events (CPI-adjusted); the annual average for the most recent 5 years (2019–2023) is 20.4 events (CPI-adjusted).
Potential Billion-Dollar Events
The following is a compilation of events in which damage costs potentially exceed the $1 billion-threshold. This is only a preliminary list as calculations are not yet finalized and total costs have not been determined (as of August 8, 2024).
- Central Severe Weather: Hail storms, high wind and tornadoes impact several central states on June 12-13.
- Midwest Flooding: Damaging floods impact several Midwestern states in late-June.
- Hurricane Debbie: Category 1 Hurricane Debbie made landfall in Florida on August 5.
UPDATE: Tropical report from Houston Station.