Mason Scientists Attribute Quiet Hurricane Season to El Niño, Dust Storms

Posted: January 5, 2007 at 1:00 am, Last Updated: November 30, -0001 at 12:00 am

By Tara Laskowski

Now that the 2006 hurricane season has ended with thankfully little activity, Mason scientists at the Center for Earth Observing and Space Research (CEOSR) attribute the quiet 2006 hurricane season to the current El Niño year.

El Niño and La Niña events tend to develop from April to June, reach the maximum strength from December to February and typically persist 9 to12 months. They recur approximately every 2 to 7 years. An El Niño year means that the sea surface temperature is abnormally high throughout much of the equatorial Pacific, exceeding 1.5 degrees Celsius in the central Pacific and far eastern equatorial Pacific. The opposite is true for a La Niña year. The last major El Niño event occurred in 1997-98.

“During an El Niño year, although the sea surface temperature over the Atlantic Ocean is usually higher, the vertical wind shear is also stronger, which inhibits the formation of hurricanes,” says Menas Kafatos, co-dean of the College of Science and director of CEOSR.

“However, there are recent indications that perhaps even more important, dust storms off Africa, which tend to inhibit the formation of hurricanes, were numerous this year.”

CEOSR has been studying the hurricanes using satellite data from NASA and the National Oceanic and Atmospheric Administration platforms and by conducting sophisticated model runs. CEOSR combines statistical analysis with numerical models by using satellite observations of sea surface temperature and numerical analysis of vertical winds.

Over a long term, monitoring of sea surface temperature and vertical wind shear can tell scientists if these two indicators are higher or lower than the long-term average. Higher than normal sea surface temperatures assist in the formation of tropical cyclones, yet strong vertical wind shear inhibits hurricane development by ventilating its warm core.

As for the next hurricane season, Kafatos and his team are still working to determine if conditions will make it a quiet or active season. Current observations and forecasts suggest El Niño conditions are likely to persist at least through the early part of 2007, says Kafatos.

Out of a large set of dynamical and statistical forecast models, nearly all predicted an El Niño through the end of 2006. But whether this will lead to fewer hurricanes in summer 2007 is unknown at this time, says Kafatos. The global conditions will be monitored at CEOSR.

Write to at