Riots in southeast Helen leave at least 52 dead » Yale Climate Relations

Helen, the fourth hurricane to make landfall on the U.S. Gulf Coast in 2024 and the worst to date, has killed dozens of people and likely caused billions of dollars in damage. Helene crashed into the Big Bend crescent along Florida's Gulf Coast on Thursday evening, September 26, as a Category 4 storm with estimated maximum sustained winds of 140 mph. Helen's devastation extended far beyond landfall, as the fast-moving storm swept through eastern Georgia and then westward into the Tennessee Valley, bringing record rainfall and triggering flash floods in the southern Appalachians. Flash floods and mudslides. At least 3 million U.S. customers were still without power as of noon Saturday, according to poweroutage.us.

As it accelerated inland, Helen soon merged with a cut-off upper low in the Mississippi Valley. By Saturday, Kentucky had become a post-tropical cyclone, which was expected to persist through much of the weekend while weakening and producing less rainfall.

According to the Associated Press, as of noon on Saturday, September 28, at least 52 Helen-related deaths had been confirmed in six states. According to the Tampa Tribune, at least 11 people have died in Pinellas County, Florida, all in mandatory evacuation zones, mostly due to storm surge entering homes.

Helen's other deaths included inland flash flooding, downed trees, car crashes and a late-night tornado near Jordan, Georgia, that killed two people. Helen did not produce a large number of tornadoes, but preliminary filtered data from the NWS/NOAA Storm Prediction Center shows at least 21 tornadoes were reported between September 25 and 27. Some of these were produced by widespread showers and thunderstorms that formed in a classic precursor rain event (PRE) that preceded Helen.

Helen's worst flooding occurred in western North Carolina. The full scope of damage in the mountainous region remained difficult to assess Saturday, as Interstate 40 and numerous smaller roads were either closed or washed out, leaving many residents without power and/or cell phone service. The French Broad River in Asheville crested at 24.67 feet Friday afternoon and the Swannanoa River in nearby Biltmore crested at 26.10 feet; both Each crest broke the records of 23.1 feet and 20.7 feet set by the devastating Gulf Coast hurricane in July 1916.

As Dr. Jeff Masters discussed in his September 27 post, the massive storm surge and catastrophic rainfall that Helen produced, as well as Helen’s jaw-dropping rapid intensification before landfall, revealed Some possible traces of human-caused climate change. Helen’s records include:

—Highest storm surge ever recorded Three of six long-term tide gauges on the west coast of Florida. Cedar Key, Clearwater Beach and St. Petersburg all recorded high water levels near midnight Thursday night, about 2 to 2.5 feet higher than all previous data from 50 to 110 years ago.

—Highest daily rainfall on record Asheville, 9.89 inches between September 26 and 27 (7.94 inches recorded before Helen on October 24 and 25, 1918), 13.98 inches between September 25 and 27 (October 24 to 27) The record before Helen on the 25th was 8.49 inches) (24-26, 1918). Atlanta recorded its second-wettest three-day period on record, with 11.12 inches of rain falling between September 25 and 27, trailing only the 11.75 inches that fell between December 7 and 9, 1919.

Hurricane Isaac intensifies in mid-Atlantic latitudes

Especially at non-tropical latitudes (39.3 degrees north latitude), Hurricane Isaac displayed impressive power. On Friday morning, Isaac became the sixth hurricane of the 2024 Atlantic season, and by Saturday morning it had become a super-powerful Category 2 storm with maximum sustained winds of 105 mph.

As of 11 a.m. ET Saturday, Isaac was about 700 miles west-northwest of the Azores, with sea surface temperatures relatively cold at about 24 degrees Celsius (75°F). Very cold air aloft creates enough instability in the environment to create an impressive (convection) barrier to showers and thunderstorms around the clear eye. Isaac is expected to weaken starting Saturday night as it is absorbed by mid-latitude high-altitude storms and loses its tropical characteristics.

Joyce roams the open Atlantic; another named storm could follow

After becoming the tenth named storm of the season on Friday, Tropical Storm Joyce remained unimpressive and non-threatening on Saturday, heading northwest through the remote mid-Atlantic about 10 miles east of the northern Leeward Islands. 1150 miles. Joyce's maximum sustained winds remained at 50 mph at 11 a.m. ET Saturday. Strong southerly shear pushed much of Joyce's convection north of its center. This shear is expected to continue despite sea surface temperatures warming to around 29°C (84°F), pushing dry air into the storm and hampering further development. As the storm weakens, Joyce's west-northwest motion should gradually slow down over the weekend and could become a tropical depression on Monday.

The remnants of Joyce may eventually be absorbed by a strong Cape Verde disturbance, which is expected to strengthen over the eastern and central tropical Atlantic early next week. Initially, this system should move west-northwest along the Joyce Line; eventual relapse will be a common outcome at this location, although it is too early for any confident forecasting. In its Tropical Weather Outlook, released at 2 p.m. EDT on Saturday, the National Hurricane Center gave a 30 percent chance of the disturbance developing within two days and a 70 percent chance of developing within seven days. The next name on Atlantic's list is Kirk.

Another Gulf threat could emerge within next week to ten days

It's too early to make any specific forecasts of timing, location or intensity, but persistent signals in forecast models suggest another tropical cyclone could emerge in the Caribbean and move into the Gulf of Mexico in the first few days of October. The pattern emerging from several operating models, notably GFS, is that a low pressure center detaches from the Central American Gyre (the same phenomenon that produced Helen) over the western Caribbean and then moves north into the Gulf, potentially intensifying a tropical storm or hurricane . Some, but not all, members of the GFS ensemble model, as well as a handful of European ensemble members, pictured such a scene during Friday night's run. Both GFS and Euro operating models predict an upper-level pattern will develop late next week, which may support development in the Gulf, with the main jet stream moving northward in early October.

In its Tropical Weather Outlook, released at 2 p.m. ET on Saturday, the National Hurricane Center said there was at least a 50 percent chance that such a system would develop within two days, but the chance was close to zero within two days. A tropical depression from the northwestern part of the ocean entering the southern Gulf of Mexico. The next name on the Atlantic list after Kirk is Leslie.

Jeff Masters contributed to this article.