PARIS (Reuters) - Ash from an erupting Icelandic volcano could reach northern Scotland by Tuesday and parts of Britain, France and Spain by Thursday or Friday if the eruption continues at the same intensity, airlines were warned Sunday.
The warning is based on the latest 5-day weather forecasts, but is being treated cautiously because of uncertainties over the way the volcano will behave and interact with the weather.
Iceland's airports were closed Sunday due to fears that ash from the Grimsvotn volcano, which began erupting on Saturday, could threaten the safety of passenger aircraft.
With winds currently blowing the ash northwards, authorities said there was little risk of any further disruption to European or transatlantic airspace over the next 24 hours.
But as low-pressure weather systems move into Europe and Scandinavia, there are concerns that northwesterly winds capable of dispersing ash toward the rest of Europe will pick up.
Airlines were told to brace for the possible further spread of ash later in the week during a conference call with weather experts and officials responsible for European airspace.
Ash could reach northern Scotland by midday Tuesday and other parts of Britain, western France and northern Spain by Thursday or Friday if nothing changes, weather officials said.
A spokeswoman for Eurocontrol, which coordinates air traffic flows, declined to comment, referring to the latest published updates which ruled out major problems in the next 24 hours.
The new warning assumes the volcano will continue to spew ash at the same rate and there is no change in forecasts over a period of five days, both of which are uncertain.
Saturday's disruption took place amid mobile, low-pressure air in the north Atlantic whose movement is not easy to predict.
That contrasts with a stable high-pressure weather pattern during a crisis a year ago when a pervasive and slow-moving cloud of ash forced a six-day shutdown of European airspace, stranded tens of thousands of people and damaging economies.
Sunday, Britain was considering whether to send up a special aircraft capable of monitoring the concentration of ash, but a decision had been taken, officials said.
(Reporting by Tim Hepher; editing by Daniel Flynn and Mark Heinrich)