The European Centre for Medium-Range Weather Forecasts, “the best weather-modelling service in the world”, as far back as last Friday week flagged the extent of the potential threat of Lorenzo.
Despite the criticisms of weather forecasters from some online, the warning warranted sitting up, taking notice and responding accordingly, according to Prof Peter Thorne of Maynooth University.
In recent days Met Éireann issued status-orange wind warnings for the western seaboard as gusts of up to 130km/h were expected, combined with storm surges likely to cause coastal flooding and damage.
It held off issuing status-red warnings – its highest warning level.
In the end gusts were weaker than predicted and warnings were regularly adjusted and scaled back, says Prof Thorne, an expert in storm patterns. “These are always forecasts, until they occur.”
His comments came amid some recrimination online about no major storm coming to pass, even if it had always been made clear it was the leavings of a category-five hurricane that was going to hit Ireland and that it would have petered out into a storm at that stage.
“I don’t think it was over-hyped by Met Éireann. Whether with the media and others it was over-hyped is an interesting question,” observed Prof Thorne.
Given recent extreme weather events and climate trends, Ireland has to always expect the worst from extra-tropical storms that are remnants of hurricanes. A category-five hurricane so far east in the Atlantic is “hugely exceptional and potentially worrying” for Ireland, he added.
UCC climatologist Dr Kieran Hickey is uncompromising about those now suggesting concerns were unduly whipped up and asking what all the fuss was about.
“It’s puerile to be coming out with that kind of thing. It’s in the category of internet trolling nonsense,” he believes. With the unpredictability of weather, the precautionary principle must apply; “better to be overprepared and wrong than underprepared and wrong”.
Lorenzo started out as a category-five hurricane that was heading for Ireland with a risk it could be more destructive than Storm Ophelia. It began disintegrating over Tuesday night and into Wednesday morning some 1,000km out in the Atlantic. But it still represented a substantial threat if it hit land over Ireland.
At the last minute, it turned west off Ireland rather than turning back over the country, Dr Hickey notes. “Because Ireland is located in a dynamic weather environment, we should never be surprised as to what this could throw at us.”
Moreover, the latest trends show more intense hurricanes and extra-tropical cyclones are likely – though not necessarily more frequent. The “Night of the Big Wind” dating back to January 1839 is still the worst recorded storm ever to hit Ireland, but in current circumstances he would not be surprised “if that’s surpassed soon”.
Likewise, “Ireland has yet to experience a hurricane, which brings both exceptional high wind speed and rainfall” – here again, it’s probably only a matter of time.
Prof Thorne says the continuing warming of ocean surfaces, exacerbated by global heating, means oceans are more likely to reach the 26.2 degrees required “to build and maintain tropical cyclones” that will in turn move closer to Ireland.
Ophelia had unique characteristics, he recalls, especially in the way it interacted with the fast-flowing jet stream over the Atlantic and transitioned closer to Ireland; Lorenzo was far more typical and transitioned much further out to sea.
Wet and warm winter
As for the coming winter, it cannot be said we are facing into a stormy period. The latest seasonal forecasts produced by the Copernicus Climate Change Service in Reading suggests we are facing a similar winter to 2015, which means it is probably going to be wetter and warmer.
This is a probability; “not nailed on certainty,” he stresses, but is backed by indications from the “north Atlantic oscillation”, the balance of atmospheric pressure between north and south over the ocean. The service uses computer models to analyse forecast variables (air and sea-surface temperature, atmospheric circulation and precipitation) with view to the following six-month window.
With so much land already flooded or saturated due to heavy rainfall in recent weeks, especially along the western seaboard and in the midlands, the risk of flooding events is, however, heightened. This will impact most on farmers, and those living in flood plains or in urban areas known to flood more frequently.