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It’s been a slow start to hurricane season — but it’s still early

This is the first year since 2017 that a hurricane has not developed in the Atlantic by Aug. 1

Hurricane Irma is visible in a satellite image from Sept. 5, 2017. (NOAA and AerisWeather)
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Leading up to this Atlantic hurricane season, numerous signs pointed toward a summer and fall bustling with storms. Forecasters said the broad weather patterns governing the oceans and atmosphere would come together to boost activity; experts with the National Oceanic and Atmospheric Administration and Colorado State University predicted activity above to well above average. Not to mention that climate change has primed oceans for the development of strong tropical systems.

The only thing that seems to be missing from a busy Atlantic hurricane season? The hurricanes.

Just three tropical storms have formed so far this year in the Atlantic basin. While the third named storm doesn’t normally form until Aug. 3 — meaning this year is ahead of average by that metric — the number of storms doesn’t tell the story.

All three systems have been “shorties,” brief low-end tropical storms with limited impacts. Accumulated cyclone energy (ACE), a measurement of the cumulative power of all Atlantic tropical storms, is running at about a third of normal for the date as a result.

The seasonal deficit will only continue to increase unless activity begins to dramatically ramp up through August and September — the historical peak of hurricane season — when longer-tracking, stronger systems typically develop. But there is no immediate sign of that ramp-up starting.

Scientists predict seventh straight above-average hurricane season

Neither the American nor European model ensemble forecast systems — supercomputer simulations, each of more than a dozen slightly different atmospheric scenarios — show much of a signal for tropical activity through the end of the first week of August. Similarly, the National Hurricane Center has not highlighted any regions of expected five-day development.

As of now, there’s no one thing to blame for the lackluster development.

Bouts of strong low-latitude wind and widespread sinking air have stood in the way of development at times, while persistent ocean-bound outbreaks of dry, dusty air blown from the Sahara Desert have helped smother blossoming thunderstorms that can sometimes turn any surviving tropical waves into organized storms.

As a result, the systems that have developed have either been tropical lows that do not strengthen at all or ones that develop so close to land that there isn’t enough time for them to strengthen. So, while the systems may be marginally impactful — Alex, the season’s first named storm, brought flooding rain to southern Florida in early June, for example — they do not contribute much to seasonal ACE.

But this kind of lower-than-expected activity is not unheard of so early in the hurricane season, even in years that go on to become quite active. And there are still signs that the peak season could see a number of hurricanes.

For better forecasts, hurricane hunters probe deep into storms

In an early June news release, leading scientists at Colorado State University continued to forecast a season of well-above-average activity. Despite a lackluster first two months of summer, the release continued to cite many seasonal factors that typically lead to strong tropical development.

First, there is the El Niño/Southern Oscillation, often abbreviated as ENSO. Related to the sloshing of warm and cold water around the Pacific, the oscillation has influences in long-term atmospheric conditions worldwide. Years with a La Niña — the phase of the oscillation currently in effect, per National Oceanic and Atmospheric Administration — tend to see more Atlantic hurricane activity, with conditions unusually favorable for tropical systems to develop and strengthen.

The presence of La Niña, combined with oceanic temperatures in the Atlantic that are currently warmer than average — a testament both to a warming world and to favorable wind patterns — gives forecasters confidence in an above-active hurricane season.

History also tells us to avoid placing too much stock on early-season activity.

This is the first year since 2017 that a hurricane has not developed in the Atlantic by Aug. 1. That year, an uninterrupted stretch of nine consecutive hurricanes formed from late August through mid-October, including the devastating Harvey, Irma and Maria.

In 2015, there were also no hurricanes by Aug. 1; that was the most recent year to end up with below-average Atlantic tropical activity.

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