Hurricane Arthur promises to deliver a harsh blow to the North Carolina Outer Banks. But other than some tropical rains indirectly related to this storm, it will veer well away from Washington, D.C.
So just how vulnerable are we in the D.C. region to these systems? And, if we are, where do they come from?
First let’s look at the overall spread of tropical systems across the record.
Out of the gate, the answer to how vulnerable we are depends on the kind of tropical weather system you want to know about. If you’re asking if we’re vulnerable to direct hits off the ocean, then the answer is no, we’re not. Of the 151 storms off the ocean that have passed within 200 miles of the District, only 6 have made landfall in Virginia.
Looking at the map above, numerous storms have passed just offshore the region. Sixty or more storms passed near the North Carolina coast, like Arthur, before hooking back out to sea. Storms tracks tend to run parallel to the Gulf Stream and the winds around the Bermuda High, the semi-permanent clockwise steering current off the Southeast coast. That’s why direct hits close to D.C. are uncommon.
It turns out our hurricane impacts arise mostly from the remnants of tropical systems that pass through after weakening. These remnant systems can be very dangerous though, contributing to major flooding, wind storms, or as in the case of Hurricane Ivan’s remnants in 2004, tornado outbreaks.
But let’s look at the named storms that have passed within a 200-mile radius of Washington which, as mentioned earlier, adds up to 151 storms.
Storms that tracked through the 200 mile radius originated throughout the tropical Atlantic with more generating in the Atlantic than the Caribbean or Gulf. The vast majority of them tracked up through the Southeast, especially North Carolina.
Of the bigger (high impact) storms (see below), most originated in and tracked across the ocean. This makes sense. If a storm originates in the Gulf, then it has to track over land for a long distance before reaching our area, and it may weaken altogether before reaching our location. Whereas a storm coming off the ocean can tap that ocean energy for a longer duration and be stronger when it reaches our area, as shown in the map below.
If we examine the 64 that tracked within 100 miles of DC, the majority made landfall in North Carolina or northern Florida (near or in the panhandle). Most of these came through in September, near the height of the season
So, to answer the three questions asked at the beginning:
How vulnerable are we? Vulnerable to direct hits? No. They’re exceedingly rare. Most impacts come from remnant systems.
Where do they come from? All over the tropics, but the higher impact storms come from the central Atlantic.
When? The middle to latter parts of hurricane season, peaking in September as the season does too. The chances of a tropical visitor exist throughout the season (Example: Andrea, 2013), but they peak in September.
(The author, Jordan Tessler, is a Capital Weather Gang summer intern)
NCDC/WMO IBTrACS global data was filtered to include just North Atlantic systems. Those lines where then merged to create single-system tracks which a line density function was applied to to calculate density.
For the other maps, a 200 mile buffer was defined around the District then the track data was filtered to select only those tracks that crossed into the radius. Origin points were calculated and landfall data was acquired by finding the points of intersection with a shapefile of the states, points were tabulated by state.