Seminole, Okla. ? Days before deadly tornadoes raked the Plains, forecasters warned people big storms were on the way and that they would be large and powerful. Scientists even predicted almost to the hour when the twisters might strike.

They were almost right on the money.

Standing in the middle of her tornado-destroyed home, Shelley Heston Bolles gets a hug from a family member Tuesday in Little Axe, Okla.

Technological advances, particularly the use of supercomputers that can crunch vast amounts of atmospheric data, have given meteorologists powerful new tools to warn of oncoming storms long before they strike.

The line of storms may have spawned as many as 19 tornadoes as it marched through central Kansas and into Oklahoma Monday evening, leveling houses, flipping cars and dropping hail as big as softballs. Two people were killed and dozens more injured.

State officials revised Monday’s death toll from five to two after discovering three critically injured Cleveland County children had survived.

“What is disheartening is to tell people for a week that something is going to happen, get warnings out and still have people lose their lives,” said Dick Elder, chief meteorologist with the National Weather Service in Wichita.

In the early 1980s, computer models forecast storms two days in advance. But meteorologists still had to rely heavily on radar and storm spotters to confirm the location, size and strength of tornadoes.

“Comparing 20 years ago to today it is different as daylight and dark,” Elder said. “We still use spotters to verify what we are seeing, but our warnings are so much more.”

Computer models can now forecast threatening storms a week or more in advance — and do so more accurately than ever.

Supercomputers at the National Oceanic and Atmospheric Administration in Camp Springs, Md., provide information that is sent to the Storm Prediction Center in Norman, Okla., and on to National Weather Service field offices, where warnings are issued for local areas.