Hurricane Isaias is bearing down on the U.S. Gulf Coast and is expected to make a dangerous landfall tonight, according to FOX Weather. The storm is projected to strengthen into a major hurricane as it approaches the coast, prompting evacuations in parts of Alabama and Florida.
As of Friday, Isaias was a Category 2 storm that forecasters expected to keep intensifying, Yahoo reported. CNN described evacuations as already underway while the hurricane neared Category 3 strength. AP News reported that Isaias is expected to reach major hurricane status before it reaches land.
Why it matters
A hurricane becomes "major" when it crosses into Category 3 on the Saffir-Simpson Hurricane Wind Scale. That scale sorts tropical cyclones by their maximum sustained wind speeds alone, and Category 3 covers winds of 111 to 129 mph.
The threshold is more than a label. Damage potential grows exponentially rather than in a straight line as winds speed up, which means a major hurricane can cause harm far out of proportion to a modest increase in wind speed. Storms with Category 3 winds are capable of stripping roofs from well-constructed homes, breaking or uprooting most trees, and taking down power grids and municipal water systems for days or even weeks after the storm moves through.
What the forecast calls for
The official forecast has Isaias beginning to weaken this afternoon, according to the reporting. Even so, the hurricane is still expected to arrive as a dangerous Category 1 or Category 2 storm at landfall.
That projected weakening does not remove the threat. A Category 1 or 2 hurricane at landfall still carries damaging winds, and the hazards around a landfalling storm — including flooding and infrastructure damage — persist regardless of the final category.
Evacuation orders are in place in parts of Alabama and Florida, according to Yahoo and CNN. Residents in those areas are being moved out ahead of the storm's arrival tonight.
Effects reaching inland
The storm's reach is not limited to the coastline. WZTV reported that a flood watch has been issued for Middle Tennessee, with rain and wind expected to arrive earlier on Saturday morning.
That inland flood watch illustrates how a Gulf landfall can push hazardous weather well beyond the immediate coast, with rainfall and wind affecting communities as the system moves north.
What to watch
The key thing to watch is whether Isaias completes its expected strengthening into a major hurricane before landfall tonight, and how much it weakens in the hours before it comes ashore.
