He initially pursued a career in architecture and briefly worked as an apprentice architect for a housing developer in San Antonio, but the onset of the Great Depression soon brought an end to that pursuit.

[3] After a stint as a hurricane forecaster in Miami under Grady Norton, he was assigned to help create the Army Air Force weather school in Panama.

After the war, he persuaded Air Force Hurricane Hunters to allow him to fly along on what he called 'piggy back missions', where he would take scientific observations using the primitive instruments.

He continually urged Weather Bureau management to fund modest levels of hurricane research, but budgets during the early 1950s didn't allow this.

Once NHRP was assured longevity in 1959, Simpson left the project to finish his doctorate in meteorology at the University of Chicago, studying under his friend Dr. Herbert Riehl.

The encouraging results led the Weather Bureau and the Navy to start Project Stormfury in 1962, with Simpson as director.

[12] Simpson was an Honorary Member of the American Meteorological Society (AMS) and a Fellow of the Explorers Club of New York.

[13][14][15] He is interred, along with his wife Joanne (who died in 2010), in Rock Creek Cemetery in Washington, D.C.[16][17] Their shared headstone features an engraving of the NHRP logo.

A February 19, 2015, memorial service held in Simpson's honor featured AMS past presidents Louis Uccellini (also a former National Weather Service director) and Richard Anthes, as well as meteorologist Greg Holland of the National Center for Atmospheric Research (NCAR).