Super El Niño will determine which parts of US get rain and snow this winter

This winter is set to feature numerous strong storms affecting the West Coast and southern half of the country, according to the official winter outlook released Thursday by the National Oceanic and Atmospheric Administration. The outlook is dominated by the influence of the near-record strong El Niño event.

El Niño, which is characterized by above-average ocean temperatures in the tropical Pacific that lead to a domino effect of shifts in weather patterns around the globe, is likely to peak in intensity in December but make its mark throughout the winter months across the Lower 48 states.

Given the influence of El Niño this winter, much of the country is expected to be milder and wetter than average, though not necessarily less snowy than is typical, according to NOAA forecasters.

Given the near-record intensity of the current El Niño and record-warm ocean temperatures globally , there is the potential for any winter storms to bring unusually heavy rains and mountain snows to the regions that lie in their path.

Warmer waters enable greater evaporation, and warmer air can carry more moisture, thereby providing storms with added moisture to work with as they strike land and move across the country.

While no two strong El Niño winters are the same, most have temperature and precipitation trends in common. That’s because El Niño typically points the jet stream — the west-to-east flowing, cross-country river of air that steers storms — at the southern tier of the US.

The result tends to be more storms and wetter and cooler weather in southern portions of the country, while northern states turn drier and milder than average, according to NOAA . (Yes, snow-loving Northeasterners, that typically means less snow on average during strong El Niño winters, especially in inland areas.)

However, NOAA meteorologist Jon Gottschalck said that some of the storms along the southern tier may turn northeast along the East Coast, potentially bringing heavy rain and snow to the big cities of the Mid-Atlantic and Northeast, depending on the availability of cold air. “These storms could be very strong,” Gottschalck said.

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In addition to above-average precipitation projected for the West Coast and across the southern states, precipitation along the eastern seaboard is also expected to be above average.

Across the Southeast and parts of the southern Plains, where El Nino’s cooler trend and increased precipitation set the table for snow, sleet and freezing rain. Exactly how much frozen precipitation these areas see will depend on how cold it gets, and whether the cold air coincides with storms.

Although El Niño is likely to be the dominant player influencing winter weather, it is not the only game in town. Other players, such as the polar vortex, will also influence how much cold air and snow falls, especially along the northern tier of the country.

California could be hit hard by this El Niño, as reliable seasonal computer model projections are showing the state could see far above-average precipitation for the winter.

Democratic Governor Gavin Newsom has already declared a state of emergency in the run-up to the El Niño winter, given the potential for significant inland flooding, high winds, heavy mountain snow and coastal flooding from waves riding on top of unusually high tides during any major storms.

History has shown that strong El Niños are no guarantee of an unusually wet California winter, but that they do tilt the odds in favor of such an outcome. And El Niño events can be particularly damaging there. A super El Niño in 1997 to 1998 set seasonal rainfall records across the Golden State and caused widespread flooding and mudslides.

“While higher chances of rain and snow may bring relief to drought-afflicted areas, too much precipitation on dry soil can fuel destructive flash floods and mudslides. Now is the time for communities and individuals to plan ahead for the upcoming winter,” Ken Graham, director of the National Weather Service, said in a statement.

El Niño also has an influence on severe thunderstorms, which after peaking in spring, normally pick up steam again near and along the Gulf Coast from late fall to early winter.

El Niño puts Florida at a particularly higher risk of them during the winter. The script flips in other parts of the Gulf Coast, which are less active than normal, according to Michael Tippett, a climate scientist at Columbia University.

Notably, warmer-than-normal temperatures are possible over more than half of the Lower 48. El Niño can’t be blamed for everything — a world warming due to fossil fuel pollution is always playing a role. Winter is the fastest-warming season for most of the US, according to an analysis from the non-profit research group Climate Central .

The areas forecast to be drier than normal aren’t quite perfectly in sync with El Niño, but they are confined to the northern tier, where it is also expected to be milder than average. And unusually warm and dry is not the combination that will produce snow.

As with winter temperatures, research shows a warming climate has also impacted snowfall over the decades. Annual snow amounts have dropped in nearly two-thirds of the US since 1970, according to Climate Central .

Only time will tell just how wintry this winter will be, but El Niño will almost certainly be a main player alongside our warming climate.

根据美国国家海洋和大气管理局周四发布的官方冬季展望，今年冬季美国西海岸和南部地区将出现多场强风暴。此次展望主要受到接近历史最高强度的厄尔尼诺现象的影响。

厄尔尼诺现象的特征是热带太平洋海域温度高于平均水平，从而引发全球天气模式的连锁反应。厄尔尼诺现象的强度可能在 12 月达到顶峰，但其影响将持续整个冬季，波及美国本土 48 个州。

据美国国家海洋和大气管理局 (NOAA) 预报员称，受今年冬季厄尔尼诺现象的影响，预计美国大部分地区的气温将比往年更温和、更潮湿，但降雪量不一定会比往年少。

鉴于当前厄尔尼诺现象的强度接近历史最高水平，以及全球海洋温度创历史新高，任何冬季风暴都有可能给沿途地区带来异常强降雨和山区降雪。

较温暖的海水能促进蒸发，较温暖的空气能携带更多水分，从而为风暴登陆和横扫全国提供更多水分。

虽然没有两个强厄尔尼诺冬季是完全相同的，但大多数冬季的气温和降水趋势都有共同之处。这是因为厄尔尼诺现象通常会将喷射气流——这股自西向东流动、横跨美国大陆、引导风暴的气流——导向美国南部地区。

据美国国家海洋和大气管理局（NOAA）称，其结果往往是南部地区风暴增多、天气更加潮湿凉爽，而北部各州则比平均水平更加干燥温和。（是的，热爱下雪的东北部居民们，这意味着在强厄尔尼诺现象影响下的冬季，平均降雪量通常会减少，尤其是在内陆地区。）

然而，美国国家海洋和大气管理局（NOAA）气象学家乔恩·戈特沙尔克表示，南部沿海地区的一些风暴可能会转向东北方向，沿东海岸移动，并可能给大西洋中部和东北部各大城市带来强降雨和降雪，具体情况取决于冷空气的供应情况。“这些风暴可能会非常强烈，”戈特沙尔克说。

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除了预计西海岸和南部各州降水量将高于平均水平外，预计东海岸沿线的降水量也将高于平均水平。

在美国东南部和南部平原部分地区，厄尔尼诺现象带来的降温趋势和降水增加，为降雪、雨夹雪和冻雨的出现创造了条件。这些地区究竟会有多少冻雨，取决于气温的低低以及冷空气是否伴随风暴。

虽然厄尔尼诺现象可能是影响冬季天气的主要因素，但它并非唯一因素。其他因素，例如极地涡旋，也会影响冷空气和降雪量，尤其是在该国北部地区。

加州可能会受到厄尔尼诺现象的严重影响，可靠的季节性计算机模型预测显示，该州冬季降水量可能会远高于平均水平。

鉴于厄尔尼诺现象可能导致严重的内陆洪水、强风、山区大雪以及在特大风暴期间，海浪叠加异常高的潮汐而引发的沿海洪水，民主党籍州长加文·纽森已在厄尔尼诺冬季来临前宣布进入紧急状态。

历史表明，强厄尔尼诺现象并不能保证加州冬季一定会异常潮湿，但确实会增加这种结果发生的概率。而且，厄尔尼诺现象对加州的破坏性尤其大。1997年至1998年的超级厄尔尼诺现象打破了加州冬季降雨量的纪录，并引发了大范围的洪水和泥石流。

“虽然降雨和降雪概率的增加可能会缓解干旱地区的旱情，但过多的降水落在干燥的土壤上会引发破坏性的山洪暴发和泥石流。现在正是社区和个人为即将到来的冬季做好准备的时候，”美国国家气象局局长肯·格雷厄姆在一份声明中表示。

厄尔尼诺现象也会对强雷暴产生影响，强雷暴通常在春季达到高峰后，从深秋到初冬，在墨西哥湾沿岸地区再次活跃起来。

厄尔尼诺现象使佛罗里达州在冬季面临更高的热带风暴风险。哥伦比亚大学气候科学家迈克尔·蒂佩特表示，墨西哥湾沿岸其他地区的情况则恰恰相反，这些地区的热带风暴活动低于往年。

值得注意的是，美国本土48州中超过一半的地区气温可能高于往年同期水平。厄尔尼诺现象并非造成所有现象的原因——化石燃料污染导致的全球变暖始终发挥着重要作用。非营利研究机构气候中心（Climate Central）的分析显示，冬季是美国大部分地区升温速度最快的季节。

预计降水量低于往常的地区与厄尔尼诺现象并非完全同步，但这些地区主要集中在北部，预计北部地区的气温也将高于平均水平。而异常温暖干燥的天气组合并不会带来降雪。

与冬季气温一样，研究表明，气候变暖也对近几十年的降雪量产生了影响。据气候中心（Climate Central）的数据显示，自1970年以来，美国近三分之二地区的年降雪量有所下降。

今年冬天究竟会有多冷，只有时间才能证明，但厄尔尼诺现象几乎肯定会与气候变暖一起成为主要因素。