Under water: Rain keeps coming

Rainfall through 5 p.m. Sunday: 42.1 inches

Normal rainfall to date: 29.3 inches

August-October precipitation prediction: Above normal

Sources: National Weather Service/Charleston International Airport, Charleston; National Climate Prediction Center

The ground is so sopping that an afternoon thunderstorm leaves sheets of water on the streets. More rain than normal is forecast for the Lowcountry for the next three months. And we’re moving into the height of hurricane season.

That combination could spell trouble, if a tropical system brings big winds and a heavy downpour.

A few inches of rain can flood a stretch of roadway; a lot of inches could leave a lot more streets underwater. When the ground is soaked, storm winds are more likely to topple trees, and topple them farther inland than would be expected for a coastal storm.

“Any time the ground is so saturated, the roots don’t hold,” said Russell Hubright, S.C. Forestry Commission forestry management director.

“We’re seeing flash flooding in the pattern of (current) rainfall. There’s just nowhere for the water to go,” said Hope Mizzell, state climatologist.

Emergency managers say the ground conditions don’t change how they prepare for tropical-season storms: Disaster response and recovery plans are developed looking at worst case scenarios, said Sean Smetana, Charleston County media relations coordinator. But the county’s public works department already is working to clear up a backlog of work caused by the excessive rainfall.

And state and local emergency officials have been discussing the rainfall, said Derrec Becker, S.C. Emergency Management Division public information coordinator.

The Cape Verde season, named for the islands off west Africa, usually runs from mid-August into October. The period is the heart of the hurricane year, when tropical cyclones tend to form off the African coast and turn into powerful hurricanes as they cross the Atlantic. Those storms pose the greatest threat to the Southeast.

Hurricane guru William Gray’s Tropical Meteorology Project at Colorado State University continued to call for an active year in its mid-season update Friday.

The rain-sodden ground can even worsen the impact of storm surge from a land-falling hurricane, said Scott Harris, College of Charleston geology professor.

Looking for a silver lining? Here’s a couple of threads. Charleston area was statistically the driest location in the state for July, despite more than 5 inches of rain dropping at the official weather gauge at Charleston International Airport. That’s a pretty deceptive total, though. Nearby locations had a lot more rain. Meanwhile, a storm front could bring possibly heavy showers through the early week.

But the tropics are quiet, for the moment at least. Storm waves coming off Africa, the waves that can become Cape Verde hurricanes, are getting snarled in a dust plume off the Sahara Desert. The dust and dry air tend to tamp down the storms and are expected to last at least through the week.

Reach Bo Petersen at 937-5744, @bopete on twitter or Bo Petersen Reporting on Facebook.