As Michael churned toward the coast last October, forecasters feared the compact hurricane would blossom into a fierce storm far worse than their projections.
But what they weren't able to predict were Michael's three rapid explosions of power that ultimately made it the first Cat 5 hurricane to make landfall since 1992's lethal Hurricane Andrew and one of only four to ever hit the U.S. While track forecasts have vastly improved, predicting intensity remains a challenge.
"The rapid intensification is such a tough forecast for us," National Hurricane Center Director Ken Graham said this week during the state's annual hurricane conference. "There's some things we don't know."
Fast-changing storms also pose the biggest threat for catching residents off-guard. Just three days before landfall, Graham said, all four Cat 5 storms were still tropical storms.
This coming season, meteorologists with Colorado State University, who issue a preseason statistical prediction in April, are calling for a below-average season based on the ongoing weak El Niño weather pattern in the Pacific that helps tamp down hurricane winds. The official preseason forecast from the National Oceanic and Atmospheric Administration is scheduled to be released May 23.
The difficulty in forecasting the swift change comes from the complex structure of hurricanes and what conditions help create it. Meteorologists know warm water acts as fuel, but only the ocean's surface temperature are measured, Graham explained. Deeper ocean temperatures may also intensify hurricanes but are not well modeled or understood. A government shutdown in January also slowed progress during the offseason.
"It's trying to understand the parameters of the ocean," he said. "It's the actual heat content of the ocean. We need to get that modeled."
As the planet grows warmer, understanding those temperature changes will become more critical. Atmospheric scientists say it not yet clear if the climate is producing more intense storms, but they suspect that will happen in the future.
While intensity forecasting remains complex, forecasting hazards has improved dramatically. Storm surge warnings that were issued for the first time along the mainland coast last year will extend to Haiti, Puerto Rico and the Dominican Republic in the coming season, Graham said.
"The biggest thing was mapping the coast," he said. "You have to have tons of data before you can even think about any sort of inundation mapping."
Forecasters are still testing the expansion of the five-day forecast to seven, giving the public and emergency managers more days to prepare.
"It's one of the bigger requests we get," he said. "People want more time on the timeline."