AccuWeather.com

By Jim Andrews, Senior Meteorologist

Apr 19, 2010; 6:11 AM ET

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A satellite image taken Saturday, April 17, 2010 of the ash plume extending from the volcano in Iceland (Photo courtesy of MODIS)

AccuWeather.com meteorologists continue to examine how winds in the upper levels of the atmosphere will be set up between Iceland and continental Europe over the next few days as an indication to how the ash plume from an Icelandic volcano will behave and affect air travel, if the volcano continues to erupt.

It appears the plume could end up shifting farther south Tuesday into Wednesday, potentially becoming more concentrated over the U.K. and possibly even reaching Germany.

Millions of airline passengers will likely continue facing flight delays and cancellations through midweek as a result.

Forecasting the Position of the Main Ash Plume

Most recent observations as of Monday have shown the top of the ash plume extending up to 10,000 feet, on average, above the ground. This height has dropped substantially from the 33,000 feet it was at earlier this past week after the volcano first started erupting.

AccuWeather.com meteorologists are looking at the forecast direction and speed of the winds around 10,000 feet above the ground for clues as to where the ash will continue spreading over the next few days.

While looking at the average trajectory of these winds gives a good indication of where the main ash plume will shift, it is impossible to accurately predict where all the ash emitted from the volcano will spread.

Wind speed and direction vary with height and space. Subtle variations in the wind that stray from the average trajectory will cause some of the ash to spread out from the main plume and get carried in different directions.

This satellite image captured Friday shows an example of how ash can spread out from the main plume. This ash cloud formed over the northern mainland of Europe late last week, well south of the main ash plume.

While no new satellite imagery of the ash plume over Europe has been available since Friday, images from late last week showed the main plume of ash spanning from Iceland over the northern portion of the U.K. into southern Scandinavia.

The overall trajectory of winds at the level of the ash plume is expected to continue steering it from Iceland into the northern U.K. and southern Scandinavia through today.

Tuesday into Wednesday, this trajectory is expected to shift farther south, sending any ash emitted by the volcano farther south through the U.K. and into the northern mainland of Europe. Germany and the Netherlands will be at greater risk during this time.

Winds at the level of the ash plume are also expected to become more aligned Tuesday into Wednesday, which may result in the ash plume becoming more concentrated and posing a greater threat to air travel. This, of course, is assuming the volcano continues to erupt through then.

On a positive note, AccuWeather.com meteorologists expect this greater alignment of the winds to cause the ash plume to become narrower and affect a smaller area.

Details on Separate Ash Cloud That Formed over Europe

Winds across the northern mainland of Europe have been relatively weak for the past few days. With a continued lack of strong winds expected in this location, AccuWeather.com meteorologists anticipate little movement or dissipation through today of the separate ash cloud that formed there.

Winds are expected to increase across this area Tuesday into Wednesday, which may help to stir up and clean out the ash cloud currently in place.

Potentially Beneficial Changes Late This Week

The trajectory of the winds at the level of the ash plume are expected to make a dramatic shift toward the end of this week. Instead of being oriented out of the northwest between Iceland and northern mainland Europe, winds will likely shift to being oriented out of the west-southwest.

This shift should help clean any remaining ash plume out of most of Europe and bring some relief for the aviation crisis, according to AccuWeather.com meteorologists.

Ash Plume's Impacts on Travel

Thousands of flights have been canceled on a daily basis across Europe since Thursday. According to BBC News, only about 30 percent of the normal number of flights would operate in Europe on Monday. Between 8,000 and 9,000 of the 28,000 scheduled flights could take off.

The grounding of flights has been in response to the threat ash has on airplane engines and control systems. Volcanic ash is abrasive and can scratch windshields and accumulate in engines, potentially degrading performance to the point of failure.

As many as two dozen test flights across Europe on Sunday revealed that skies may be safe, but officials are still uncertain of when airspace will reopen.

The virtual shutdown of air travel across Europe is creating nightmares for airline passengers around the world. Many world leaders were prevented from attending the state funeral in Krakow for Poland's President Lech Kaczynski and his wife Maria Sunday.

Conditions have allowed limited flights to resume for a time in parts of Europe, including in Italy, France and Spain. Inter-island travel between Jersey and Guernsey has resumed on Monday and will continue to operate through the evening hours. However, restrictions still remain across much of northern and central Europe.

The Eyjafjallajokull Volcano erupted Tuesday evening (EDT) April 13 under a glacier in southern Iceland. Fears of flooding from the melting glacier immediately prompted the evacuation of up to 800 people.

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Related to the Story:

Why Volcanic Ash Clouds Are a Hazard to Aviation

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