News•July 2, 2014

New Storm Surge Maps Debut With TS Arthur

Tropical Storm Arthur, the first named storm of the 2014 Atlantic hurricane season, is slowly churning its way up the East Coast. Expected to become a hurricane before Thursday, Arthur could make landfall in North Carolina, bringing with it a surge of seawater.

The GOES West satellite snapped this image of a somewhat ragged-looking Tropical Storm Arthur at 8 a.m. ET on July 2, 2014. Despite its appearance, Arthur is expected to strengthen over the next 24 hours.
Click image to enlarge. Credit: NOAA

The threat has prompted the National Hurricane Center (NHC) to roll out for the first time its experimental storm surge maps, in an effort to help coastal residents better appreciate the dangers of such a sudden influx of water.

As Hurricane Sandy made clear, the damage caused by tropical cyclones, the generic term for tropical storms, hurricanes and typhoons, comes largely from their storm surge, not their winds. After several storms that produced large storm surges and wreaked havoc on coastal areas — particularly Hurricane Ike, which hit Galveston, Texas, on Sept. 13, 2008 — made it clear that these surges were an underappreciated threat by the public, the NHC developed maps that would show exactly how a given storm’s surge was expected to affect a particular area.

“This is a really desperately needed update,” Jamie Rhome, a storm surge specialist with the NHC who is heading the mapping effort, told Climate Central at the beginning of the hurricane season (which started on June 1).RELATEDFirst Tropical Storm Looms, As Does a Wet July 4th
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Storm surge has also become an increasing threat as coastal populations have climbed and global warming has caused sea levels to rise.

In determining how much areas might flood, mappers take into account a storm’s size, its intensity and its expected path. The maps also factor in the topography of the potentially inundated area and the astronomical tides. They show the expected levels of flooding on a color-coded scale that denotes how much water will rise above ground level.

Potential storm surge flooding from Tropical Storm Arthur along the East Coast from 5 a.m. ET July 2 to 10 a.m. ET July 5. The map is an experimental feature rolled out by the National Hurricane Center for the 2014 Atlantic hurricane season.
Click image to enlarge. Credit: NHC/NOAA

With Tropical Storm Arthur, currently about 100 miles east-northeast of Cape Canaveral, Fla., and moving northward at 6 mph, the NHC has issued an inundation map for a swath of the East Coast stretching from northern Florida to the Virginia-North Carolina border. Most areas under a flood threat there are expected to see surge up to 3 feet above the ground (the lowest level shown on the maps), with some pockets that could see greater than 3 feet, particularly in North Carolina. The full map can be see at the NHC website.

The NHC emphasizes that while the maps are intended to give residents a better picture of flood risk, the public should always follow local evacuation orders.

Arthur strengthened overnight from Tuesday to Wednesday, and currently has maximum sustained winds of 60 mph. As it continues to move over warm waters, which help fuel the convection that drives tropical cyclones, Arthur is expected to become the first hurricane of the 2014 season by Thursday.

A zoomed-in view of potential storm surge flooding in the Wilmington, N.C., area from Tropical Storm Arthur.
Click image to enlarge. Credit: NHC/NOAA

A tropical storm warning has been issued for the area of the coast from Little River Inlet, N.C., to the North Carolina-Virginia border. Warnings are issued when tropical storm conditions are expected in the area within 36 hours. A hurricane watch is currently in place for the coast of North Carolina from Bogue Inlet to Oregon Inlet and Pamlico Sound. The watch means that hurricane conditions are possible in the area in 48 hours. Hurricane hunter aircraft are currently keeping a close eye on the storms’ development.

The current expected track of the storm puts it brushing North Carolina’s Outer Banks, but the uncertainty in the track ranges from a more direct hit on the area to the storm bending out to sea.

The storm surge map effort the NHC is inaugurating with Arthur is slated for a two-year experimental run while Rhome and his colleagues evaluate its performance. They’re also asking the public to provide feedback, and have a survey set up on their site for users to weigh in.