HOUSTON - There's been a rumor that Hurricane Ophelia will hit Ireland as a hurricane. This is not true. Currently at the latitude of North Carolina, it'll make a bee-line for Ireland (which sits at the same northern latitude of Canada) but before it gets there it will lose its tropical characteristics. Simple as that. Rumors that Ireland will be hit, "by a hurricane" are false. It may have the intensity of a nontropical equivalent (similar effects) but it will be categorically (no pun intended) different. I came across an article today and have heard it suggested elsewhere, that this 'hurricane' will represent the first strike to the British Isles in history. Since the 19th century, there have been nearly a dozen post-tropical systems like this which approached as a hurricane, but then lost the tropical characteristics needed to define it as such, well before tracking over that region. It's unusual to have a cone heading for Europe, but not unheard of. (While the aforementioned areas are under the NHC cone, it doesn't mean Ophelia will reach those areas as a tropical system: It's just the National Hurricane Center identifying where the discrete remnant center will go. The cone ends where it's expected to become absorbed into a frontal boundary and become non-identifyable as the remnant low.)
When Ophelia makes it up there early next week, it'll have become, "post tropical", also known as, "extra tropical." This means it'll just be a big, ocean gale. Big waves, heavy rain, gusts past 70mph. It'll have very little difference to other big North Atlantic storms -- something Europe endures from time to time. Ireland has seen this type of tempest before, and they will see it again. They'll have strong gusts and heavy rain, but it's not going to be a Katrina for Dublin. It could knock out power like other big North Atlantic systems. On the other side of the world, Alaska often sees the remnants of typhoons (the same thing as a hurricane), and they can wreak havok on the Bering Sea (ala the, "Deadliest Catch" TV show), but they too are no longer, "tropical".
How and why will it lose its classification as a hurricane? When it reaches Ireland, it'll have long been pulling its energy from the atmosphere, rather than from heat of the ocean water. That's because (like Alaska), the water is too cold. Tropical systems need water temps in the low 80s to maintain and survive. Waters off Europe are running in the 50s and 60s. Ophelia's remnants will lose the eye and become a frontal system, with warm air to the southeast and cold air to the northwest. Notable differences with a non-tropical system also include an end to any potential for rapid intensification. It also means a wider, more diffuse wind-field (instead of being concentrated at the center with potentially devastating winds). There will also be potential for winter precipitation at the higher elevations of wherever this tracks... Yes, not exactly, "a hurricane."
I think it's important to identify fact from fiction, even if it's kind of a subtle technical classification with similar effects. It is the difference between real news and ... not. When policy-making often results from events, it's critical to properly identify what caused the event.
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