San Diego under rare tropical storm watch with Rachel set to bring coastal flooding, heavy rain and strong winds

San Diego is under a tropical storm watch for only the second time on record as Tropical Storm Rachel is forecast to make landfall in Mexico’s northern Baja California Peninsula early Sunday morning, bringing coastal flooding , high winds and inland flash flooding from Southern California to the Desert Southwest.

A Level 3 of 4 threat of flooding rainfall has been issued for Saturday night through Sunday from parts of Southern California to southern Nevada, southwest Utah and northwest Arizona, including San Diego and Las Vegas. This means numerous flash flood events are expected, with significant impacts possible.

San Diego and Las Vegas could see an inch or more of rainfall from this storm. That is about double the rainfall they usually see in all of October in San Diego, and triple that in Las Vegas. This raises the likelihood for flash flooding in desert areas, which cannot rapidly absorb intense bursts of rainfall.

Peak wind gusts in and around San Diego are expected early Sunday morning, and will most likely range from 25 to 40 mph in lower elevations to 50 to 70 mph in the mountains. Stronger gusts are possible if Rachel takes a more northerly track or they could trend weaker if Rachel shifts farther south, according to the National Weather Service.

The only other time that San Diego was under a tropical storm watch was for Hurricane Hilary in 2023 , the first year that such forecast alerts began to be issued for this region.

There were infrequent and tropical weather systems that affected Southern California before 2023, according to the NWS forecast office in San Diego, but they did not trigger such watches or warnings.

Wind gusts between 45 to 55 mph are expected inland across the Desert Southwest in parts of Arizona, southern Nevada and Utah on Sunday.

Coastal flooding is a significant concern with Rachel, particularly in areas that have already been damaged by high waves and unusually high tides in recent months. Southern California’s coastline is expected to see coastal flooding as Rachel’s waves move toward the coast on top of pre-existing high-water levels.

This could flood roads and damage structures along the coast, especially around times of high tide both Saturday and Sunday. The morning high tide is between 9 to 10 a.m. PT and the evening one peaks around 10 p.m. PT.

A coastal flood warning is in effect from the Malibu coast and Los Angeles County beaches to coastal San Diego County until Sunday afternoon.

According to the National Hurricane Center, “ life-threatening surf and rip current conditions” are likely along the coasts of Southern California and northern Baja California.

Coastal water levels have already been running unusually high in California due in part to the near-record strong super El Niño event in the tropical Pacific, which results in higher-than-average water levels and coastal flooding along the West Coast. In some areas, homes have already been lost to the sea. Waves from powerful offshore hurricanes in the eastern Pacific have worsened the coastal flooding situation in Southern California in particular.

“Major coastal flooding has already been occurring in some areas, with observed water levels running as much as 1.5 feet above predictions,” the Hurricane Center stated. The NHC warned that hazardous coastal conditions are expected to continue next week, even as Tropical Storm Rachel dissipates over the southwestern states.

圣地亚哥有记录以来第二次处于热带风暴警报之下，热带风暴瑞秋预计将于周日清晨在墨西哥北部的下加利福尼亚半岛登陆，给从南加州到西南部沙漠地区的沿海地区带来洪水、强风和内陆山洪。

周六晚至周日，从南加州部分地区到内华达州南部、犹他州西南部和亚利桑那州西北部，包括圣地亚哥和拉斯维加斯，已发布3级（共4级）强降雨洪水威胁预警。这意味着预计将发生多起突发性洪水，并可能造成严重影响。

这场风暴可能会给圣地亚哥和拉斯维加斯带来一英寸或更多的降雨。这大约是圣地亚哥十月份通常降雨量的两倍，拉斯维加斯则是三倍。这增加了沙漠地区发生突发性洪水的可能性，因为沙漠地区无法迅速吸收如此强烈的降雨。

预计圣地亚哥及其周边地区将于周日清晨迎来强风，低海拔地区风速可能在每小时25至40英里之间，山区风速可能在每小时50至70英里之间。据美国国家气象局称，如果“瑞秋”飓风向北移动，风速可能会更强；如果向南移动，风速可能会减弱。

圣地亚哥此前唯一一次受到热带风暴预警是在 2023 年的飓风希拉里期间，那也是该地区首次发布此类预报警报。

据圣地亚哥国家气象局预报办公室称，2023 年之前，南加州曾出现过一些不常见的热带天气系统，但这些系统并未引发此类预警或警报。

预计周日，亚利桑那州、内华达州南部和犹他州部分地区，以及美国西南部沙漠内陆地区，将出现时速 45 至 55 英里的阵风。

瑞秋飓风带来的沿海洪灾令人担忧，尤其是在近几个月来已经遭受巨浪和异常高潮破坏的地区。预计随着瑞秋飓风的巨浪在原有高水位之上涌向海岸，南加州海岸线将出现沿海洪灾。

这可能会导致沿海道路被淹，建筑物受损，尤其是在周六和周日的高潮时段。上午的高潮时间为太平洋时间上午9点至10点，晚上的高潮时间约为太平洋时间晚上10点。

从马里布海岸和洛杉矶县海滩到圣地亚哥县沿海地区，沿海洪水预警将持续到周日下午。

据美国国家飓风中心称，南加州和下加利福尼亚北部沿海地区可能出现“危及生命的海浪和离岸流”。

加州沿海水位已经异常高涨，部分原因是热带太平洋地区出现了接近历史最高强度的超级厄尔尼诺现象，导致西海岸沿线水位高于平均水平，并引发沿海洪灾。在一些地区，房屋已被海水吞噬。来自东太平洋近海强劲飓风的巨浪，尤其加剧了南加州沿海洪灾的严重程度。

飓风中心表示：“部分地区已出现严重沿海洪灾，观测到的水位比预测值高出1.5英尺。” 飓风中心警告称，即使热带风暴“瑞秋”在西南部各州逐渐消散，危险的沿海状况预计下周仍将持续。