It’s the mid-September peak of the Atlantic hurricane season, but we are likely to see yet another week pass without any named storm landfalls. According to Michael Lowry’s latest Substack post, the past 18 days without a named storm or tropical depression in the Atlantic is unprecedented: “In the modern satellite era (since 1966), we’ve never seen a shutout during this very active 18-day window of the season, when on average four named storms and two hurricanes form each season. To date the Atlantic basin has recorded the lowest activity since 2014 and, with only one hurricane so far (Category 5 Hurricane Erin), the fewest hurricanes through September 15th since 2002.”
However, recall that in 2024, we also experienced an unusual lull in activity during the first half of September, but the season went on to deliver two punishing major hurricanes: Helene, which was named on September 25, and Milton, which was named on October 6.
Invest 92L in the central Atlantic likely to develop this week
There is one disturbance of interest in the central Atlantic, designated Invest 92L by the National Hurricane Center on Monday morning, that is likely to put an end to this streak later this week. However, the predominant steering currents will likely keep this system out to sea, with the island of Bermuda being the only land area that need be concerned.
On Monday morning, 92L was located in the central tropical Atlantic midway between Africa and the Lesser Antilles Islands, headed west-northwest at 10-15 mph. Satellite images showed that the system was growing more organized, with a moderate amount of heavy thunderstorms that had a pronounced spin. Light wind shear and warm ocean temperatures near 29 degrees Celsius (84°F) were favorable for development, but some dry air was impeding development. With 92L expected to encounter a moister atmosphere later in the week, the models are quite bullish on this system becoming a named storm by this weekend. In their 8 a.m. EDT Tropical Weather Outlook, NHC gave 92L 2-day and 7-day odds of development of 40% and 80%, respectively. The next name on the Atlantic list of storms is Gabrielle.
A remarkably low-impact season thus far
Compared to the fearsome human, financial, and infrastructure tolls wreaked by most of the Atlantic hurricane seasons since 2017, this year’s effects have been strikingly muted. The only named-storm landfalls so far this season occurred more than two months ago.
- Tropical Storm Barry slogged inland near Tampico, Mexico, on June 29 with top sustained winds of 45 mph. Barry led to 8 deaths and an estimated $6 million in damage in Mexico, and the storm’s residual moisture and circulation fed into the intense thunderstorms that produced catastrophic flash flooding in Texas on July 4.
- Tropical Storm Chantal pushed ashore near Litchfield Beach, South Carolina, on July 6 with top winds of 60 mph. Six deaths and at least $56 million in flooding in North Carolina were attributed to Chantal as the storm’s heavy rains pushed across central and eastern parts of that state. Some rainfall totals exceeded 10 inches, and several rivers hit major flood stage, according to the North Carolina State Climate Office, which noted the similarity of state impacts from 2024’s Tropical Storm Debby and 2025’s Chantal.
Out of six named Atlantic storms thus far, the only hurricane of the bunch — Category 5 Erin — wove its way through the northwest Atlantic without reaching any coastlines. The most direct impacts from Erin occurred before it was even designated as a tropical cyclone. After moving off the African coast, Erin’s seed disturbance passed over the Cabo Verde Islands on August 9, dropping torrential rains and triggering flooding that caused nine deaths and left two people missing. Days later, one man drowned in the rough surf produced by Hurricane Erin along the north coast of the Dominican Republic. Erin’s enormous circulation brought widespread coastal flooding and beach erosion to the U.S. East Coast.
Mario gets a new lease on tropical life
Tropical Storm Mario seemed to have fizzled beyond repair on Saturday night, September 13. Spinning off the Pacific Mexican coast about 80 miles southwest of Manzanillo, Mario was well below tropical storm strength, its top winds a mere 30 mph, at 2 a.m. EDT Sunday. That’s when the National Hurricane Center classified the storm as post-tropical and declared, “This is the final NHC advisory.” But just nine hours after writing that epitaph, the center had the rare task of reviving bulletins on a storm declared dead, as showers and thunderstorms had reconsolidated around Mario and satellite imagery indicated that tropical-storm-force winds had returned.
As of 11 a.m. EDT Monday, Mario was located about 290 miles (470 km) southwest of Cabo San Lucas, Mexico, heading west-northwest at 12 mph (19 km/h) . Mario’s top sustained winds were up to 60 mph (95 km/h), as the storm takes advantage of light wind shear below 10 knots, a moist atmosphere (mid-level relative humidity around 70%), and sea surface temperatures around 29 degrees Celsius (84 degrees Fahrenheit), which is around 1°C (1.8°F) above average for mid-September. Much cooler waters lie just ahead for Mario, dropping below 26 degrees Celsius by late Tuesday, and wind shear will increase markedly, so the storm is predicted to peak today and become a post-tropical remnant low (again) by Wednesday.
Deep moisture from Mario, carried northeast by summer monsoonal flow, will push into southern California and southwestern Arizona later this week, with the details still uncertain. Showers and thunderstorms may deliver a bit of much-needed moisture, but some of the storms could produce gusty winds with little rain, especially on the leading edge of the moist push. Lightning from these “dry thunderstorms” will raise the risk of fire starts in the drought-stricken mountains and foothills.
Another disturbance well southeast of Mario could develop on its heels, likely taking a similar track parallel to Mexico’s Pacific coast. In its Tropical Weather Outlook issued at 8 a.m. EDT Monday, NHC set the 2- and 7-day odds of development of this system at 20 and 60 percent, respectively.
Unusually quiet in the Western Pacific as well
As of Monday, there were no named storms in the Northwest Pacific Ocean. Typhoon season has been strikingly tepid there, where accumulated cyclone energy (ACE) is a mere 34% of average for the season thus far. Not a single typhoon has yet reached the equivalent of Category 3 strength; on average, five typhoons that strong have occurred by now.
According to data going back to 1945, 2025 is in second place for the latest point in the season for a major Category 3 or stronger typhoon to form. The record was on Sep. 21, 1974, when Typhoon Agnes became a Cat 3 with 120 mph winds (thanks go to Sim Aberson for this stat). Recent runs of the GFS and European model show the potential for a major typhoon to spin up in the waters a few hundred miles south of Japan early next week, so we may come very close to breaking the record for the latest Cat 3 in the basin.
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Great Job Jeff Masters and Bob Henson & the Team @ Yale Climate Connections Source link for sharing this story.
