Rare September nor’easter could bring coastal flooding, gusty winds to the Northeast

A potent storm could develop into a rare September nor’easter later this week, raising concerns for coastal flooding, wind damage and rain in parts of the Northeast.

A quick refresher: A nor’easter is a strong coastal storm that gets its name from the direction its punishing winds come from — northeast. Nor’easters typically develop off the East Coast between Georgia and southern New England and are most common from mid-fall to mid-spring. The storms are typically major snowmakers in the winter, but that’s not a factor this time.

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Right now, the potential nor’easter is just a twinkle in the atmosphere’s eye. It’s forecast to form off the coast of the Carolinas or Virginia sometime Wednesday or Thursday.

It will likely strengthen from that point and peak in strength this weekend. But where exactly the storm tracks as it heads north is still in question.

Regardless of its track, some coastal flooding issues are guaranteed, even when the storm is in its early stages. More widespread impacts depend heavily upon how closely it hugs the East Coast.

There are two main scenarios we’re monitoring now.

Some weather forecast models are depicting a storm that beefs up very quickly from mid-to-late week as it slides up the East Coast to linger near the coasts of New Jersey and New York’s Long Island this weekend.

A stronger storm closer to the coast means powerful, gusty winds would hit nearby areas, including Boston and the rest of southern New England, New York City and even parts of the Mid-Atlantic.

It’s too early to say exactly how strong these gusts could become, but some up to 50 mph are possible, especially Friday into Saturday. These winds will also rough up seas considerably and intensify coastal flooding, pushing tides 2 to 3 feet higher than normal.

Rain is likely, but it’s difficult to pinpoint if there will be any flooding concerns. Some areas may not be able to soak up even moderate rain as readily as normal. Parts of the Northeast and Mid-Atlantic have been soaked in recent weeks and dangerous flooding struck earlier this month in New Jersey and Connecticut.

The storm could then loiter just off the coast into next week. The longer it’s out there, the longer impacts will linger.

The nor’easter would also hover over warmer than normal water off the coast for an extended time in this scenario. Nor’easters are not warm-water fueled tropical systems like hurricanes, but if they hang out over warm water long enough, they can become hybrid systems — fed by both the ocean heat and energy in the atmosphere — or fully tropical.

This nor’easter is unlikely to become tropical, but it’s not impossible. If it did, the impacts wouldn’t change much; the National Hurricane Center would just have to keep an eye on it.

Other forecast models predict a potent storm, but keep it farther off the East Coast.

Rough seas and similar levels of coastal flooding are still likely with this scenario, but the wind and rain threats would not be as intense as in scenario one.

The timing of the storm’s development and its generally northeast track is similar in this scenario, but where it could linger is different.

The most noticeable impacts along the coast south of New England would likely occur through Friday.

The storm could remain off the coast of southern New England through at least Sunday, meaning coastal flooding issues could persist there, especially around the Massachusetts Cape.

Coastal flooding is a lock this week, even if the nor’easter stays farther offshore, with two other factors driving the threat.

The first is a strong area of high pressure set up over eastern Canada, sending crisp and chilly air to the Northeast. High temperatures in the region are forecast to only climb into the 60s into the weekend as a result.

As the nor’easter takes shape off the Mid-Atlantic coast on Wednesday or Thursday, air will be squeezed between the fledgling storm and that high pressure farther north, increasing wind speeds along the East Coast.

The second factor at play: a full moon. Tide levels will climb higher each day until they hit their monthly peak around Saturday’s full moon. Higher water levels and stronger winds are the exact combination for serious coastal flooding.

Coastal areas from Virginia to New Jersey could start seeing some flooding at high tide as early as Tuesday evening, and some gauges could push into major flood stage by Thursday morning.

Flooding issues will likely peak late this week or early this weekend for many spots, and could be slow to ease next week if the nor’easter lingers close to the coast.

本周晚些时候，一场强劲的风暴可能会发展成罕见的九月东北风暴，引发人们对东北部分地区沿海洪水、风灾和降雨的担忧。

简单回顾一下：东北风暴是一种强烈的沿海风暴，因其强劲的风向——东北风——而得名。东北风暴通常在佐治亚州和新英格兰南部之间的东海岸形成，最常见于仲秋至仲春期间。这种风暴在冬季通常会带来大量降雪，但这次不会。

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目前，这场潜在的东北风暴还只是大气中一个模糊的迹象。预计它将在周三或周四的某个时候在卡罗来纳州或弗吉尼亚州沿海形成。

风暴很可能在此基础上继续增强，并于本周末达到强度峰值。但风暴北上的具体路径仍存在不确定性。

无论风暴路径如何，即使在风暴初期，一些沿海地区也必然会遭遇洪水问题。更广泛的影响则很大程度上取决于风暴与东海岸的接近程度。

我们目前正在关注两种主要情况。

一些天气预报模型显示，这场风暴将在本周中后期迅速增强，并沿东海岸北上，本周末在新泽西州和纽约长岛沿海地区徘徊。

更强烈的风暴靠近海岸意味着强劲的阵风将袭击附近地区，包括波士顿和新英格兰南部其他地区、纽约市，甚至大西洋中部部分地区。

现在判断这些阵风的强度还为时尚早，但部分地区风速可能高达每小时 50 英里，尤其是在周五到周六这段时间。这些强风还会显著掀起巨浪，加剧沿海洪灾，使潮位比正常水平高出 2 到 3 英尺。

降雨的可能性很大，但很难确定是否会引发洪水。一些地区可能无法像往常一样迅速吸收中等强度的降雨。近几周来，美国东北部和大西洋中部部分地区持续降雨，本月初新泽西州和康涅狄格州也遭受了严重的洪灾。

风暴随后可能会在近海徘徊至下周。它停留的时间越长，其影响也会持续越久。

在这种情况下，东北风暴也会在近海温度高于正常水平的海域上空盘旋很长时间。东北风暴并非像飓风那样由暖水驱动的热带气旋，但如果它们在暖水上空停留足够长的时间，就可能演变成混合型气旋——既受海洋热量的影响，也受大气能量的影响——或者完全转变为热带气旋。

这场东北风暴不太可能发展成热带风暴，但也不是完全不可能。即便发展成热带风暴，影响也不会有太大变化；国家飓风中心只需密切关注其动向即可。

其他预测模型预测会有一场强劲的风暴，但会使其远离东海岸。

在这种情况下，海况恶劣和沿海洪水程度相似的可能性仍然存在，但风雨威胁不会像第一种情况那么强烈。

在这种情况下，风暴的发展时间和大致向东北方向的路径与之前类似，但它可能停留的地方则有所不同。

新英格兰以南沿海地区受到的影响最明显，可能会持续到周五。

这场风暴至少在周日之前可能会一直停留在新英格兰南部沿海地区，这意味着沿海洪灾问题可能会持续存在，尤其是在马萨诸塞州海角附近。

即使东北风暴停留在更远的海域，本周沿海地区仍将发生洪水，还有两个因素加剧了这一威胁。

首先，加拿大东部上空形成了一个强烈的高压区，将清爽的冷空气输送到东北部。受此影响，预计该地区周末最高气温仅会攀升至60华氏度左右。

周三或周四，随着东北风暴在大西洋中部沿岸形成，空气将在新生风暴和更北部的高压之间受到挤压，从而增加东海岸的风速。

第二个影响因素是：满月。潮位将逐日升高，直至周六满月前后达到月度峰值。水位上涨加上强风，正是引发严重沿海洪灾的罪魁祸首。

从弗吉尼亚州到新泽西州的沿海地区最早可能在周二晚上涨潮时开始出现洪水，到周四早上，一些地区的水位可能会达到严重洪水警戒线。

许多地区的洪水问题可能会在本周晚些时候或本周末早些时候达到高峰，如果东北风暴持续在沿海地区附近徘徊，下周洪水可能难以缓解。