Tropical storm warnings in Florida as flooding threat grows
A tropical weather system forecast to become Tropical Storm Alex will bring heavy, flooding rainfall and strong winds to the Florida Keys and South Florida, including metro Miami, Fort Lauderdale and West Palm Beach, through Saturday.
Why it matters: The heavy rains, which will also extend up the west coast of the state into Fort Myers and possibly Tampa, are likely to lead to widespread, life-threatening flash flooding. This will be the case regardless of whether the storm earns the name Tropical Storm Alex.
What's happening: The storm is just the first in what is expected to be an unusually active Atlantic hurricane season and comes just after the season's official start on Wednesday.
Context: Due to climate change, tropical storms and hurricanes are producing heavier rains than just a few decades ago, thanks to warming sea and air temperatures. The air holds about 7% more water vapor for each 1°C increase in temperature.
Threat level: The storm's rains began affecting the peninsula Friday, with the heaviest rains falling through Saturday.
- Some areas, including the Florida Keys and southern Florida, could see up to a foot of rain in this storm, with rainfall rates of 2 to 3 inches per hour at times. This could cause "considerable flash and urban flooding," the Hurricane Center warns.
- The National Weather Service forecast office in Miami is warning of "major rainfall flooding [that] may prompt many evacuations and rescues." This office and the forecast office in Tampa are also signaling the potential for many structures to be flooded, and escape routes to be rendered impassible due to floodwaters.
Of note: Flooding may be particularly acute in low-lying coastal areas where incoming storm surge waters from the storm's relatively modest tropical storm-force winds will help prevent draining from the land into the sea.
- Miami, for example, has been coping with a sharp increase in so-called "sunny day flooding" from astronomical high tides as sea levels rise and render drainage systems ineffective.
The intrigue: The storm has one of the key ingredients needed to be classified as a tropical storm — sustained winds at 39 mph or greater, mainly occurring on the east side of the storm's approximate center.
- However, as of Friday morning, the storm lacked a well-defined center of circulation but is forecast to develop one as the day goes on. Once this occurs, it will earn the name Tropical Storm Alex.