Knabb hopes to reduce the shock level in the future by expanding and improving the center’s communication skills.

After two years at the Weather Channel, he honed his skills at getting his message across on television, learning to project above his normal soft-spoken voice and to rein in jargon.

“I think of myself talking to a friend or family member,’’ he said. “They know I know the science but that’s not what they want or need to know.”

Bill Read, Knabb’s predecessor, was the first hurricane center director to use Twitter but Knabb has embraced it in an experimental run, tweeting up to 20 messages a day as Isaac skirted South Florida. As of Friday, he had accumulated 12,657 followers and the next storm to near the mainland United States will almost certainly add to the total.

Separate warnings from storm surge, tornadoes and flooding might help the public better prepare for storms. But after decades of study by social scientists and emergency managers, it remains baffling why some chunk of a population in the danger zone invariably rejects evacuation orders — no matter what category of hurricane threatens.

Post-storm surveys after Andrew, a catastrophic Category 5 hurricane, suggest nearly 30 percent of residents in Miami-Dade County refused to leave the most vulnerable coastal areas. Knabb believes past experience plays some role, with residents figuring that if they did well in one storm, they’ll be fine in another one. But each storm is different, bringing with it a different mix of trouble,

Consistent messages from NHC forecasters, the media and emergency managers are critical to getting people to move to safety, Knabb said, but persuading some people to seek safer shelter is “so much more complicated than any of us actually want to admit.”

“Does the number of feet of surge we’re saying tip the scale and get them to go? Does the category of storm make them go? Does the TV meteorologist get them to go? It’s not a simple answer,” he said. “I think that is what everyone is searching for after the fact. What is it that people are not hearing?’’