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September 29, 2025<\/p>\n
3 min read<\/p>\n
How Hurricane Humberto Is Pulling Tropical Storm Imelda Away from the U.S.<\/p>\n
In a version of the Fujiwhara effect, Hurricane Humberto is pulling Tropical Storm Imelda eastward and away from the U.S.<\/p>\n
By Andrea Thompson edited by Jeanna Bryner<\/span><\/p>\n The U.S. Southeast will likely avoid the worst effects from Tropical Storm Imelda\u2014all thanks to another tropical cyclone.<\/p>\n Imelda and Hurricane Humberto have been churning over the northeastern Caribbean, between the Bahamas and Bermuda, for several days. Last Friday the forecasts were highly uncertain about Imelda\u2019s path and future strength: the possibilities ranged from the storm making landfall in the Carolinas, which would bring torrential rain and floods, to it not making landfall in the U.S. The latter now looks to be the likely scenario. That\u2019s because Imelda dawdled in its development while Humberto quickly exploded into a major hurricane, which has influenced how much the two storms \u201cfeel\u201d each other\u2014essentially a flavor of what is called the Fujiwhara effect. (The East Coast will still feel rip currents from Imelda, though, and the storm could pose a threat to Bermuda as it takes a sharp eastward turn in the coming days.)<\/p>\n READ MORE: Hurricane Science Has a Lot of Jargon\u2014Here\u2019s What It All Means<\/p>\n If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n The higher-than-usual level of forecast uncertainty can be explained partly by the fact that storms in the Atlantic don\u2019t typically form this close to each other. Tropical cyclones are influenced by the larger atmospheric environment, and adding another storm system makes that environment more complex. Meteorologists were also unclear about exactly where the center of Imelda would ultimately form, which made it difficult to know how that center would interact with other features in the atmosphere.<\/p>\n To get a sense of the atmospheric picture last Friday, it\u2019s helpful to remember that the atmosphere is three-dimensional, with various low- or high-pressure areas or wind currents at various altitudes. In this case, there was a low-pressure area higher up in the atmosphere over the Southeast, an area of high pressure that is quasi-permanently centered roughly over Bermuda, and the two storms\u2014Humberto and what would become Imelda, then called Potential Tropical Cyclone Nine. What wasn\u2019t clear was whether Imelda would form quickly enough and in the right place for it to interact with that upper-level low, which would push it more rapidly north and toward a U.S. landfall. \u201cHurricanes are governed by the surrounding wind flow, and the quicker [the storm] gets stronger, the more it gets influenced by winds higher up in the atmosphere,\u201d says Alan Gerard, a retired National Weather Service meteorologist, who runs the consulting company Balanced Weather.<\/p>\n But Imelda was very slow to become organized into a full tropical storm, so it has crept northward slowly, leaving it in the perfect spot to feel the pull of Humberto. \u201cEssentially what happens is: you\u2019ve got [westerly] winds around Humberto from the cyclone, and Imelda just gets caught up in that and follows behind,\u201d Gerard says.*<\/p>\n This is a form of the Fujiwhara effect, says University of Miami hurricane researcher Brian McNoldy. In 1921 Japanese meteorologist Sakuhei Fujiwhara theorized that two vortices spinning through fluid (which is exactly what tropical cyclones are) could come close enough to each other to begin orbiting a common central point. If such storms move even closer, they can eventually merge into one, which happened with Hurricanes Hilary and Irwin in the eastern Pacific in 2017.<\/p>\n READ MORE: How to Decode a Hurricane Forecast<\/p>\n Imelda and Humberto aren\u2019t close enough for that to happen, but the Fujiwhara effect can take other forms once the distance between two storms is within about 800 miles, and each can \u201cfeel\u201d the other, McNoldy says. \u201cThe centers of Imelda and Humberto are now just 600 miles apart, and their outer circulations are already communicating,\u201d McNoldy wrote in an e-mail to Scientific American. \u201cModel forecasts bring them even closer together in the coming couple of days.\u201d<\/p>\n Humberto is weakening the quasi-permanent ridge over Bermuda and opening up a path to pull Imelda behind it. Essentially, \u201cImelda is caught up in Humberto\u2019s wake,\u201d Gerard says.<\/p>\n Though this reduces the risks to the U.S., the interaction could mean that Imelda will pose more of a direct threat to Bermuda than Humberto will; the latter will travel a few hundred miles to the north of the islands.<\/p>\n *Editor\u2019s Note (9\/29\/25): This sentence was edited after posting to correct Alan Gerard\u2019s comment about westerly winds around Humberto.<\/p>\n If you enjoyed this article, I\u2019d like to ask for your support. Scientific American<\/span> has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.<\/p>\n I\u2019ve been a Scientific American<\/span> subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm <\/span>always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.<\/p>\n If you subscribe to Scientific American<\/span>, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.<\/p>\n In return, you get essential news, captivating podcasts, brilliant infographics, can’t-miss newsletters, must-watch videos, challenging games, and the science world’s best writing and reporting. You can even gift someone a subscription.<\/p>\n There has never been a more important time for us to stand up and show why science matters. I hope you\u2019ll support us in that mission.<\/p>\n","protected":false},"excerpt":{"rendered":" September 29, 2025 3 min read How Hurricane Humberto Is Pulling Tropical Storm Imelda Away from the U.S. In a version of the Fujiwhara effect, Hurricane Humberto is pulling Tropical Storm Imelda eastward and away from the U.S. By Andrea Thompson edited by Jeanna Bryner The U.S. Southeast will likely avoid the worst effects from<\/p>\n","protected":false},"author":1,"featured_media":24747,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[50],"tags":[14690,769,14691,13559,7081,8131,811],"class_list":{"0":"post-24746","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-environment","8":"tag-humberto","9":"tag-hurricane","10":"tag-imelda","11":"tag-pulling","12":"tag-storm","13":"tag-tropical","14":"tag-u-s"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/24746","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=24746"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/24746\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/24747"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=24746"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=24746"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=24746"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}On supporting science journalism<\/h2>\n
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