Even as the devastation wrought by Hurricane Helene across the U.S. Southeast becomes ever more vivid, the North Atlantic – now at record-warm levels for late September, topping even 2023 – has been ginning up other tropical systems of interest, one of which may be a named storm that would bear watching in the Gulf of Mexico within the next week.
Helene itself has produced more than enough trouble. At least 91 deaths have been attributed to Helene as of midday Monday, according to the Associated Press. Most of those who died were in the Appalachians of western North Carolina and adjoining South Carolina and Tennessee, where Helene swung across late Thursday and Friday one day after a predecessor rain event (PRE) had dumped torrential rain across the region. With highways, electricity, and communications all still tenuous on Monday, and the region’s rugged terrain keeping some areas inaccessible, officials and rescuers – and family members – were struggling to gain a full scope of the disaster and to help those in need.
It’s already clear that Helene will end up being the deadliest and costliest U.S. storm since at least Hurricane Ian in 2022. The sheer isolation and destruction in the hardest-hit areas – which is eerily reminiscent of Hurricane Katrina, though playing out in a far different physical landscape – suggests it could take days more to bring immediate relief to those suffering, much less to assess the full toll of this horrific storm.
Fortunately, most of the Atlantic’s tropical activity this week will remain safely out to sea, and forecast models have ramped down somewhat on the potential Gulf system (though not enough to put it aside and out of mind, given the location and the time of year).
Kirk, the latest Atlantic storm, is predicted to become a large, long-lived major hurricane
Tropical Storm Kirk – the third Atlantic system to gain a name in the last six days – was christened at 9:35 a.m. EDT Monday after wind data from a satellite-borne scatterometer showed that sustained winds were up to 45 mph. The average date of the eleventh named Atlantic storm (based on 1991-2020 data) is October 2, so the Atlantic’s pace of named-storm production is now ahead of climatology for the first time since late August.
As of 11 a.m. EDT Monday, Kirk was centered almost midway between the Caribbean and Africa in the central tropical Atlantic, about 690 miles west of the Cabo Verde Islands, with top sustained winds up to 50 mph. All signs point to Kirk becoming a potent hurricane as it follows a classic recurving track well out to sea across warmer-than-average waters. Kirk should remain over sea surface temperatures of around 29 degrees Celsius (84°F) for the next five or six days, with light to moderate wind shear of 5 to 10 knots and a very moist environment (relative humidity 65 to 70 percent). The SHIPS rapid intensification model on Monday morning gave a 47% chance that Kirk’s sustained winds would reach 100 knots (putting it over the Category 3 threshold) by Thursday morning, similar to output from the HMON, HAFS-A, and HAFS-B intensify models and to the National Hurricane Center’s prediction of a Cat 3 Kirk by late Wednesday. It’s possible Kirk will be roiling the open North Atlantic as a major hurricane even into next week.
Isaac and Joyce on the way out
Isaac, which peaked as a Category 2 hurricane in the mid-latitude North Atlantic on Saturday, was declared post-tropical at 11 a.m. EDT Monday. Though still packing sustained winds of 60 mph, Isaac was moving over increasingly chilly waters, and ferocious wind shear was pushing its deeper showers and thunderstorms (convection) well northeast of its low-level center (see Fig. 2 above). Isaac will slowly weaken as it enters a chain of mid-latitude storms and fronts and is predicted to dissipate before reaching Ireland.
Meanwhile, short-lived Joyce was hanging on as a tropical depression at 11 a.m. EDT Monday with 35 mph winds. Plagued by wind shear pushing dry air into its circulation, Joyce was predicted to become a post-tropical cyclone by Monday evening as it drifts northward into the central subtropical Atlantic.
Yet another disturbance, this one in the far eastern tropical Atlantic, has potential to become a named storm, especially by later this week. In its Tropical Weather Discussion issued at 8 a.m. EDT Monday, NHC gave this system 30 and 80 percent odds of development in the 2- and 7-day periods, respectively, as it moves slowly west to west-northwest. Ensemble models suggest that rather than following in Kirk’s foosteps, this system will track further to the south, potentially making it farther across the Main Development Region of the tropical Atlantic over the next 1 to 2 weeks, so residents of the Lesser Antilles will want to monitor its progress (and will have plenty of time to do so).
Watching the western Caribbean and Gulf of Mexico (again)
Much as Helene did, an area of circulation may emerge late this week or even early next week over the western Caribbean and move into the Gulf of Mexico. However, as shown in Figs. 3 and 4 above, ensemble forecast models are giving very mixed signals on how strong this system might become and where it might track. An ultimate motion toward the north is plausible, given the early-October timing, and the waters of the western Caribbean and Gulf are certainly more than warm enough to sustain another powerful hurricane.
It remains to be seen whether upper-level conditions will be as supportive as they were during Helene, as the dramatic configuration of a cut-off upper low in the Mississippi Valley and a strong ridge near the East Coast isn’t expected to materialize this time. As evident in Figs. 3 and 4, most of the ensemble solutions through next Monday keep whatever might develop on the weaker side, another positive nugget (although these models are not designed for explicit guidance on storm intensity).
As of 8 a.m. EDT Monday, NHC was giving this potential system near-zero and 40% odds of development into at least a tropical depression over the next two and seven days, respectively.