This week marks the 50th anniversary of the historic, deadly flooding spawned by Hurricane Agnes and its remnants in June 1972 across the eastern U.S., including the hardest-hit states of Pennsylvania and New York.
Agnes was one of the largest June hurricanes to ever roam the Atlantic Basin. According to the National Hurricane Center, its circulation spanned about 1,150 miles in diameter.
The storm's origins can be traced back to Mexico and the Caribbean.
A large disturbance was first detected over the Yucatán Peninsula of Mexico on June 14, 1972. This system drifted eastward and organized into a tropical depression later that day after emerging over the northwestern Caribbean Sea.
Feeding off the warm waters of the Caribbean, the depression reached tropical storm strength (winds of at least 39 mph) early on June 16.
The newly formed tropical storm turned northward on June 17 and continued to intensify. Agnes became a Category 1 hurricane over the southeastern Gulf of Mexico on June 18 when NOAA reconnaissance aircraft detected sustained winds of 85 mph.
Hurricane Agnes continued on its northward trajectory, which sent it in the direction of the Florida Panhandle, where it made landfall on June 19 with maximum sustained winds of 75 mph, barely at Category 1 strength. According to the NHC, the highest wind gust reported on land was 55 mph in Apalachicola, Florida.
Agnes turned northeastward after landfall and quickly weakened to a tropical depression over Georgia by June 20.
However, after Agnes merged with a secondary non-tropical low-pressure system situated to its west, it was able to regain tropical storm strength over eastern North Carolina on June 21. The center of the storm moved offshore near Norfolk, Virginia, that evening, and it continued to regain strength over the western Atlantic Ocean.
Agnes then made a northwestward turn and was on a collision course with the Northeast and mid-Atlantic coasts, setting the stage for the torrential rainfall that would result in historic flooding across the eastern U.S. over the coming days.
Agnes' main circulation center dissipated over Connecticut that night, with the secondary low-pressure system then taking over as the dominant circulation as it moved into northeastern Pennsylvania.
These remnants of Agnes stalled over the region and continued to drench the eastern U.S. until June 25.
The worst impacts were felt in the Northeast and mid-Atlantic states, where widespread rainfall totals greater than 10 inches were recorded from northern Virginia to the Finger Lakes of New York. Localized areas picked up 14 to 19 inches of rain.
According to NOAA's Weather Prediction Center, the highest total of 19 inches was measured in western Schuylkill County in eastern Pennsylvania's Coal Region.
The torrential rainfall produced widespread severe flooding from Virginia northward to New York state. Additional flooding also occurred in the western Carolinas.
Several rivers rose to all-time record crests because of the heavy rains, which led to the inundation of homes, businesses, factories, bridges and other infrastructure, resulting in very significant damage.
Some of the most extensive flooding was observed along the Susquehanna River in Elmira, New York, and Wilkes-Barre, Pennsylvania.
In Elmira, 20,000 people were forced to evacuate their homes as the river overflowed its banks and flooded the city, according to the University of Rhode Island. As that water rushed downstream, the flooding caused a dike to be breached in Wilkes-Barre, resulting in the near destruction of the entire city.The University of Rhode Island also noted the rising Susquehanna River flooded the Pennsylvania capital of Harrisburg, where the governor's mansion was submerged in floodwaters.
"It is difficult, if not impossible, to determine how much of the rainfall might have occurred separately from the baroclinic system had Agnes not been located to the east," the NHC wrote in its tropical cyclone report for Hurricane Agnes. "Regardless of the energy sources and circulation dynamics that caused the floods, however, this devastation could not have occurred without the extreme importations of moisture to the area by the depression that had been Hurricane Agnes."
Agnes and its remnants were responsible for 122 deaths, of which 113 were associated with the flooding in the eastern U.S. The other nine deaths were caused by severe thunderstorms and tornadoes spawned by Agnes in Florida. Seven additional deaths were also blamed on Agnes in western Cuba.
Agnes was responsible for $2.1 billion in damage in the U.S., mostly as a result of the historic flooding.
At the time, Agnes was the nation's costliest natural disaster on record, far exceeding the combined losses from Hurricane Betsy in 1965 and Hurricane Camille in 1969, which had previously been the nation's two most destructive storms, according to the NHC.
It should come as no surprise that the World Meteorological Organization voted to retire the name "Agnes" from being used again for a future Atlantic Basin tropical storm or hurricane, joining a list of 94 total retirees through 2021.