Gulf Coast faces hurricane threat as Tropical Depression Nine is forecast to strengthen

CIRA/CSU & NOAA | Rendered by Dakota Smith

A strengthening tropical depression is primed to become Hurricane Isaias and batter parts of the southern US this week with heavy rain and strong winds.

Tropical Depression Nine has sustained winds of 35 mph and was located about 600 miles south of the mouth of the Mississippi River as of Tuesday evening.

The system is expected to push east above the Yucatan Peninsula and then turn sharply north toward the northern Gulf Coast. It’s forecast to strengthen quickly and become a Category 2 hurricane with 100 mph winds by Friday.

Isaias will likely usher in flooding rain, powerful winds and storm surge, to areas from southern Louisiana to the Florida Panhandle beginning on Friday. The storm could also spin up several tornadoes as its rainbands lash the coast.

This will be the first hurricane of the year in the Atlantic basin, ending a record-long wait tied to the effects of a likely record-strong El Niño .

Exactly where the storm could track or how strong it will be when it approaches land are still not set in stone, but anyone along the Gulf Coast from Louisiana to Florida’s Big Bend should monitor the forecast closely.

Florida Gov. Ron DeSantis declared a state of emergency for 25 counties Tuesday ahead of the storm, urging residents to prepare disaster plans and stock hurricane supply kits. State emergency teams are staging generators, fuel, food, water and flood barriers in the Tallahassee and Santa Rosa areas to support the response.

Oil companies are also taking precautions in the Gulf. Shell is evacuating nonessential personnel from six offshore platforms, while BP is removing nonessential workers and securing its offshore facilities, the companies said Tuesday.

This storm is making a run through El Niño-influenced atmospheric conditions that have largely stymied tropical systems throughout the Atlantic hurricane season so far. Gulf waters are record warm for this time of year, providing plenty of fuel, but that’s only part of the equation.

The bane of Atlantic tropical systems this season has been wind shear. This refers to winds blowing at different speeds and from different directions at several levels of the atmosphere. Wind shear can tear tropical storms and hurricanes apart.

This new system is benefitting from low wind shear in the southern Gulf, but it’ll find higher wind shear guarding the Gulf Coast to the north, threatening to shred the storm as it makes its approach.

But the system is also forecast to move quickly, so its exposure to the higher wind shear may be limited. If the storm were to move slower, it could weaken quickly as it meanders in hostile conditions.

The storm’s strength and path are also intertwined. A stronger storm’s circulation extends higher into the atmosphere, allowing winds at those heights to steer it differently than a weaker system. That path, in turn, will determine how long it spends over warm water and how much hostile wind shear it encounters, shaping how strong it is when it reaches the coast.

No matter its final fate, heavy rain is a concern on the Gulf Coast and in other parts of the South by late this week. The storm could bring 3 to 6 inches of rain, with localized rainfall up to 10 inches in spots, from southern Louisiana to the Florida Panhandle and Big Bend. The downpours could start to ramp up along the coast as soon as Friday and then continue to soak the region while creeping farther inland through the weekend.

As this year has already shown, it doesn’t take a hurricane-strength system to cause significant impacts, particularly in a warming world that’s making tropical systems wetter.

Tropical storms Arthur and Edouard didn’t last long, but their heavy rain resulted in significant flash flooding and water rescues. Parts of Louisiana and Mississippi took the brunt of Arthur’s flooding while Edouard dropped over 20 inches of rain in eastern Texas.

Pinning down the location and severity of any storm surge flooding, strong winds and tornadoes along the northern Gulf Coast is even more difficult this far out in time because we need to know how strong the storm will be and exactly where it will track. The earliest those impacts could arrive is late Friday or Saturday.

Four named storms — that’s tropical storm strength or greater — typically form in October and November, but some hurricane seasons can have a stronger finish while others quiet down.

The last few years illustrate this year-to-year ebb and flow. Seven storms formed during October and November in 2024, but just two formed during the same time in 2023.

Late-season storms tend to form closer to the United States, including in the Gulf, Caribbean and off the Southeast coast, which makes them more likely to impact land.

While there are usually fewer storms, they can still be destructive.

Last year, Category 5 Hurricane Melissa devastated Jamaica in October’s final week.

Hurricane Michael roared into the Florida Panhandle on October 10, 2018, becoming the latest landfalling Category 5 on record in the US. And Hurricane Sandy may be the most notorious of all: It morphed into a hybrid superstorm in late-October 2012 and walloped the East Coast.

Super El Niño’s grip on the Atlantic basin means a repeat of notorious late-season hurricanes is less likely this year. Its storm-killing wind is the main reason this season could go hurricane-free for the first time in reliable records .

CIRA/CSU 和 NOAA | 由 Dakota Smith 绘制

一个不断增强的热带低气压即将发展成飓风伊萨亚斯，并于本周给美国南部部分地区带来暴雨和大风。

截至周二晚间，热带低气压九号的持续风速为每小时 35 英里，位于密西西比河口以南约 600 英里处。

预计该系统将向东移动，经过尤卡坦半岛上空，然后急转北上，朝墨西哥湾北部沿岸移动。预计该系统将迅速增强，并在周五达到二级飓风强度，风速可达每小时100英里。

预计从周五开始，伊萨亚斯飓风将给从路易斯安那州南部到佛罗里达州狭长地带的地区带来强降雨、狂风和风暴潮。风暴的雨带袭击海岸线时，也可能引发多场龙卷风。

这将是今年大西洋盆地出现的第一个飓风，结束了与可能出现的强厄尔尼诺现象影响相关的漫长等待。

风暴的确切路径以及登陆时的强度目前尚未确定，但从路易斯安那州到佛罗里达州大弯区沿墨西哥湾沿岸的居民都应该密切关注天气预报。

佛罗里达州州长罗恩·德桑蒂斯周二宣布该州25个县进入紧急状态，以应对即将到来的风暴，并敦促居民制定灾难应对计划，储备飓风应急物资。州应急小组正在塔拉哈西和圣罗莎地区部署发电机、燃料、食品、饮用水和防洪设施，以支持救援工作。

石油公司也在墨西哥湾采取预防措施。壳牌公司周二表示，该公司正在从六个海上平台撤离非必要人员，而英国石油公司则正在撤离非必要工作人员并加强其海上设施的安保。

这场风暴正穿越受厄尔尼诺现象影响的大气环境，而这种大气环境在迄今为止的大西洋飓风季中大多阻碍了热带系统的形成。墨西哥湾海水温度创下同期历史新高，为风暴提供了充足的能量，但这只是影响风暴强度的因素之一。

本季大西洋热带气旋的最大敌人是风切变。风切变指的是大气层不同高度上风速和风向的差异。风切变会使热带风暴和飓风迅速瓦解。

这个新系统受益于墨西哥湾南部较低的风切变，但它将发现北部墨西哥湾沿岸存在较高的风切变，这可能会在风暴接近时将其撕裂。

但据预测，该系统移动速度很快，因此其受强风切变影响的时间可能有限。如果风暴移动速度较慢，则可能在恶劣环境下缓慢移动并迅速减弱。

风暴的强度和路径也密切相关。较强的风暴环流延伸到更高的大气层，使得高空风对其的引导作用与较弱的风暴截然不同。而风暴的路径反过来又决定了它在温暖海域停留的时间以及遭遇的恶劣风切变程度，最终影响其登陆时的强度。

无论最终结果如何，本周晚些时候，墨西哥湾沿岸和南部其他地区都将面临强降雨的威胁。这场风暴可能带来3到6英寸的降雨，局部地区降雨量甚至可能高达10英寸，影响范围从路易斯安那州南部一直延伸到佛罗里达州狭长地带和大弯区。沿海地区的降雨最早可能从周五开始增强，并在周末持续侵袭该地区，同时向内陆蔓延。

正如今年已经表明的那样，即使不是飓风级别的系统，也会造成重大影响，尤其是在全球变暖导致热带系统降雨量增加的情况下。

热带风暴亚瑟和爱德华持续时间虽短，但带来的强降雨引发了严重的突发性洪水，并导致多起水上救援行动。路易斯安那州和密西西比州部分地区受亚瑟洪水的影响最为严重，而爱德华则在德克萨斯州东部降下了超过20英寸的降雨量。

由于我们需要提前知道风暴的强度和确切路径，因此现在预测墨西哥湾北部沿岸风暴潮、强风和龙卷风的具体位置和严重程度更加困难。这些影响最早可能在周五晚些时候或周六到来。

10 月和 11 月通常会形成四个命名风暴——即热带风暴强度或更高——但有些飓风季的尾声可能会更猛烈，而有些飓风季则会平静下来。

过去几年的数据体现了这种逐年波动的趋势。2024年10月和11月形成了7场风暴，而2023年同期只形成了2场。

季末风暴往往在美国附近形成，包括墨西哥湾、加勒比海和东南沿海地区，这使得它们更有可能影响陆地。

虽然风暴通常较少，但仍然会造成破坏。

去年十月的最后一周，五级飓风梅丽莎重创牙买加。

2018年10月10日，飓风迈克尔席卷佛罗里达州狭长地带，成为美国有记录以来登陆时间最晚的五级飓风。而飓风桑迪或许是最臭名昭著的：它在2012年10月下旬演变成混合型超级风暴，重创了美国东海岸。

超级厄尔尼诺现象对大西洋盆地的控制意味着今年再次出现臭名昭著的季末飓风的可能性较小。其带来的足以摧毁风暴的强风是​​今年飓风季可能在可靠记录中首次无飓风发生的主要原因。