Some weather forecasters are claiming that we are set to be hit by months of snow and freezing temperatures this winter.
How will Derry be affected?
Various media outlets have reported that this winter could be even worse than the Beast from the East, which blanketed much of the country earlier this year.
Headlines suggested it could be "the coldest for 10 years" and that the country is facing "four months of snow."
The cold snap prediction stems from forecasts from Exacta which link it to an El Niño climate event in the Pacific Ocean.
This can trigger more extreme conditions in other parts of the world and is linked to cold weather in the UK.
Exacta forecasters also suggest the weather will deteriorate in December because low-pressure storm systems clashing with much colder air over the country could potentially bring snow and ice storms.
How El Nino affects our weather
A Met Office blog published yesterday explains that El Nino is the warm phase of the so-called El Niño Southern Oscillation (ENSO) – the largest natural fluctuation in the earth’s climate system – which stretches along the equator across the Pacific Ocean.
During more extreme El Niño events, such as the event beginning in late 2015, the surface ocean temperature rose almost 3C above the long-term average. However, the rise in temperature in this winter’s anticipated event is expected to be far less, around 0.5-1C above normal.
Professor Adam Scaife, head of long-term to decadal climate prediction at the Met Office Hadley Centre, says the "most likely" outcome is a "weak to moderate strength El Niño event.
“This event, however, is expected to be much less intense than the joint record El Niño of 2015-16."
Prof Scaife says that the influence of the ENSO cycle can be a useful tool for long range weather forecasting but that it's important to understand that it's not the only factor which determines UK weather, adding: "For example, the Quasi-Biennial Oscillation (QBO) with its 14-month pattern of alternating easterly and westerly winds along the equator can weaken or strengthen the jet stream."
What the Met Office says
Met Office forecaster Bonnie Diamond says any long-term computer models being used to make these predictions are not accurate.
Ms Diamond stressed that a truly accurate weather forecast can only really be done up to seven days in advance:
"The Met Office and other meteorological forecasters are saying there is a slight chance of weak El Nino conditions this year, but this is unlikely to have a significant impact on weather in the UK."
She also referred to Met Office calculations which say the likelihood of a colder than average Autumn is about 5 per cent, and that the probability it will fall into the warmest of their categories is 40 per cent.
The same calculations were also highlighted this week by Met Office forecaster Helen Robertson, who also said: “We can also expect below-average precipitation in the period up to December, predicted by the UK’s official forecasters as falling into the driest of our five categories, with 20 per cent likelihood - and slightly less likely to be wetter than average.”