El Niño and Saharan Dust Silence Atlantic Hurricane Season

厄尔尼诺现象与撒哈拉沙尘令大西洋飓风季陷入沉寂

It’s the middle of Atlantic hurricane season, but you’d be forgiven for forgetting that it’s even happening. 现在正值大西洋飓风季的中期，但如果你忘了这件事，也是情有可原的。

The basin has only seen three named storms since the start of hurricane season in June, a trio of weak and largely disheveled tropical storms. One or two additional tropical storms are possible through the middle of August as the season struggles against a bevy of unfavorable conditions. 自六月飓风季开始以来，该海域仅出现了三个被命名的风暴，且这三个热带风暴都较为微弱且结构松散。由于本季正面临一系列不利条件，预计到八月中旬可能还会出现一到两个热带风暴。

They include this year’s El Niño, which is on its way to making history as sea surface temperatures soar to unprecedented heights across a critical swath of the Pacific Ocean, as well as persistent puffs of dry, dusty air that are blowing off the coast of Africa. 这些不利条件包括今年的厄尔尼诺现象——随着太平洋关键海域的海面温度飙升至前所未有的高度，该现象正走向历史性高点；此外，还有从非洲海岸吹来的持续不断的干燥沙尘气流。

Together, these distant forces are working to stifle any opportunity for tropical storms to develop across the Atlantic basin. Forecasters now expect one of the quietest hurricane seasons in years, with fewer than 10 named storms likely to sneak through the unfavorable conditions. 这些遥远的力量共同作用，抑制了大西洋盆地热带风暴发展的任何机会。气象预报员目前预计，这将是近年来最平静的飓风季之一，可能只有不到10个被命名的风暴能够突破这些不利条件。

Experts have been stunned by how fast El Niño has intensified this summer. This pattern of warmer-than-normal waters around the equator in the eastern and central Pacific significantly alters global weather patterns. 专家们对今年夏天厄尔尼诺现象增强的速度感到震惊。这种赤道东太平洋和中太平洋海域水温异常偏暖的模式，显著改变了全球的天气格局。

El Niño requires water temperatures in a key region around the equator to run at least 0.5 degrees Celsius (0.9 degrees Fahrenheit) above normal for several consecutive months. Measurements show that this swath of the Pacific is at least 1.5 degrees Celsius above average for this time of year, with portions of the region seeing astonishing anomalies of as much as 4 degrees Celsius above normal. 厄尔尼诺现象的形成要求赤道附近关键区域的水温连续数月比正常水平高出至少0.5摄氏度（0.9华氏度）。测量数据显示，该太平洋海域的水温比往年同期平均水平高出至少1.5摄氏度，部分地区甚至出现了比正常水平高出4摄氏度的惊人异常。

Abnormally warm waters in the Pacific Ocean lead to widespread pockets of rising air in the region, which alter the upper-level wind patterns. Increased convection over the Pacific, combined with the readjusted upper-level wind patterns, work together to send stronger-than-usual winds blowing east over the Atlantic basin—a phenomenon known as wind shear. 太平洋异常温暖的海水导致该地区大范围空气上升，从而改变了高层风向模式。太平洋上空增强的对流，加上调整后的高层风向模式，共同作用使得比往常更强的风吹向大西洋盆地——这种现象被称为风切变。

Thunderstorms are the seeds from which a tropical system grows. Strong winds aloft disrupt the structure of a budding thunderstorm, which ultimately prevents individual storms from organizing into a tropical system. 雷暴是热带气旋形成的种子。高空强风会破坏正在形成的雷暴结构，最终阻止单个风暴组织成热带气旋系统。

These same conditions are having the opposite impact on tropical cyclone activity across the steamy Pacific Ocean. The western Pacific typhoon season was busier by the beginning of August than any season in almost 50 years. Four storms across the region reached the equivalent strength of a Category 5 storm, including Sinlaku in April and Bavi, Dolphin, and Genevieve in July. The central and eastern Pacific are also hopping, with the US National Hurricane Center expecting above-average activity in this region through autumn. 同样的条件对炎热的太平洋地区的热带气旋活动却产生了相反的影响。到八月初，西太平洋台风季的活跃程度已创下近50年来的新高。该地区有四个风暴达到了相当于5级飓风的强度，包括四月的“森拉克”，以及七月的“巴威”、“多拉”和“吉纳维芙”。中太平洋和东太平洋也同样活跃，美国国家飓风中心预计该地区在秋季之前的活动将高于平均水平。

But El Niño isn’t the only factor putting a crimp in this year’s Atlantic hurricane season this year. The West African monsoon is usually a key player in sending thunderstorms streaming over the Atlantic that can later turn into tropical systems. But this year’s monsoon has been a bit lackluster this year, with below-average rainfall in places like Sierra Leone and Guinea signaling that we’re seeing weaker disturbances than usual. 但厄尔尼诺现象并不是今年阻碍大西洋飓风季的唯一因素。西非季风通常是向大西洋输送雷暴的关键因素，这些雷暴随后可能演变成热带气旋。但今年的季风表现有些乏力，塞拉利昂和几内亚等地的降雨量低于平均水平，这预示着我们所观测到的扰动比往常更弱。

The Sahara Desert is also limiting this hurricane season’s already meager potential. Intrusions of dry, dusty air keep blowing east to west across the Atlantic, acting like a lid on the atmosphere that’s suppressing most opportunities for thunderstorm development. 撒哈拉沙漠也在限制本就微弱的飓风季潜力。干燥的沙尘气流不断从东向西横穿大西洋，就像给大气层盖上了一层盖子，抑制了雷暴发展的大部分机会。

Together, these factors are working together to produce the least active Atlantic hurricane season since at least 2013. Forecasters use a metric known as Accumulated Cyclone Energy (ACE) to quantify a season based on the intensity and longevity of its storms. An average Atlantic hurricane season produces an overall ACE of 122.5. This season has so far produced an ACE of 3.1, which is just 23 percent of average for the middle of August. 这些因素共同作用，导致大西洋飓风季的活跃程度降至至少2013年以来的最低水平。气象预报员使用“累积气旋能量”（ACE）这一指标，根据风暴的强度和持续时间来量化飓风季。一个普通的大西洋飓风季总ACE值为122.5。而本季目前的ACE值仅为3.1，仅为八月中旬平均水平的23%。

Fewer storms doesn’t mean zero storms, though, and El Niño years have a history of producing intense and devastating hurricanes despite unfavorable conditions overall. Despite its struggle, this year’s Tropical Storm Arthur still may have broken Louisiana’s 24-hour rainfall record with more than 29 inches of rain reported near the community of Cottonport. And in the past, Hurricanes Camille, Ivan, Charley, Michael, Idalia, and Lee all occurred with El Niño conditions present. That means coastal residents should continue monitoring forecasts and have plans in place in case a storm does threaten land. 然而，风暴较少并不意味着没有风暴。尽管整体条件不利，但厄尔尼诺年份历史上也曾出现过强烈且具有破坏性的飓风。尽管今年热带风暴“亚瑟”发展受阻，但它在路易斯安那州科顿波特社区附近带来的降雨量超过29英寸，可能打破了该州24小时降雨记录。此外，历史上“卡米尔”、“伊万”、“查理”、“迈克尔”、“伊达利亚”和“李”等飓风都是在厄尔尼诺条件下发生的。这意味着沿海居民仍应持续关注天气预报，并做好应对风暴威胁的准备。