Tracking the Bay's Biggest Hurricanes
STORM TRACKS TELL A STORY. Hurricanes and tropical storms that create the most dramatic storm surges in the Chesapeake have one thing in common: they sweep northwards along the west side of the Bay's mainstem. Official records and human memories report strong surges and heavy flooding from these monster storms: the August Hurricane in 1933, Hurricane Hazel in 1954, and, most recently, Hurricane Isabel in 2003. In each case the eye of the storm stayed west of the Chesapeake Bay.
Hurricanes are tropical cyclones that spin with a counterclockwise rotation. According to oceanographer Bill Boicourt, cyclones moving up along the Eastern Shore of the Chesapeake drive water out of the Bay, but cyclones moving along the west side do the opposite: they drive water up the Bay. These "wrongside hurricanes" send their winds arcing out over the mainstem where their south winds can turn the long narrow fetch of the Bay into a funnel, driving a huge surge north against small coastal towns and islands and flooding downtown Annapolis and Baltimore.
Western shore rivers are especially vulnerable during these storms. Winds curving around from the southeast can align with the long fetch of the James and the Potomac, turning these rivers into funnels and driving flood waters into cities like Richmond, Colonial Beach, Alexandria, and Washington, D.C. During the August Storm of 1933 and Hurricane Hazel in 1954, the storm surges coincided with astronomical high tides, driving water levels even higher.
The track for Tropical Storm Agnes tells a different story. Agnes was a "backdoor hurricane" that came ashore along the Gulf of Mexico, then weakened to a tropical depression as it traveled north overland. Just south of the Chesapeake, the storm passed offshore and began regathering strength as a tropical storm. When it curved ashore again north of the Bay, it combined with another low pressure storm to pour heavy rains into the Chesapeake watershed. The massive flooding and resulting runoff brought surges of sediment flowing down the bay, covering seagrasses, burying oyster beds, and lowering salinity levels dramatically. Agnes, though less dramatic, may have done more damage to the Bay's ecology than any other storm in recent history.