Lead photo above of Corning, NY is courtesy of the NWS.
As the calendar turns to June, warm temperatures and the prospects of severe weather take center stage in the Northeast. However, we are also reminded that it is time for the tropics to awaken as hurricane season begins.
June is not necessarily known for being an active month in the tropics for the Atlantic and Caribbean. In fact, there have not been many notable tropical systems in the history of the region for either June or July, as it is typically not until August that the tropics really begin to heat up.
Favored tropical cyclone tracks by month. Courtesy NOAA.
It certainly does not mean that tropical systems cannot form in these early stages of the hurricane season. In 1972, a system forming out of a group of thunderstorms along the Yucatan Peninsula developed into a tropical depression on the 14th. As the storm escaped the throws of the high terrain and turned through the Yucatan Channel and into the Gulf of Mexico, it was able to gain tropical storm status and was named Agnes on the 15th.
Given the early season, conditions were not necessarily optimal for strengthening. Still, Agnes achieved hurricane status over the warmer waters of the Gulf on the 18th. Agnes held its strength as a category 1 hurricane with 85 mph winds, until its landfall over the Florida Panhandle on the 19th. The storm then weakened to a tropical depression as it tracked over land for a day or two in the Southeastern US. While it dumped a few inches of rain in the region, impacts were generally minor overall, though a few fatalities were reported in Florida.
Unfortunately, the worst impacts from Agnes were yet to come. From the Southeast states, the storm tracked offshore of Cape Hatteras, which typically is the beginning of an out-to-sea track for most tropical systems. This was not the case with Agnes, as the combination of a low pressure over the Great Lakes and a blocking high pressure to the northeast forced the storm to make a northwest turn. Agnes regained tropical storm strength over the warmer Gulf Stream waters and made a second landfall directly over New York City.
Map A) Surface map (NOAA) showing Agnes as a tropical storm just off the coast of New Jersey a few hours before its second landfall.
Map B) Upper level map at the 500 mb level (about 18,000 feet, NOAA). The blue "H" shows the blocking high pressure which kept Agnes from going out to sea. The red "L" depicts the upper level low over the Great Lakes, which helped pull the cyclone into the coast.
The results were far more destructive for the Mid-Atlantic and parts of the Northeast. Though the track largely spared the Delaware and New Jersey from the most significant issues, the same could not be said for other surrounding inland areas. Agnes dumped upwards of 10 - 15” of rain over inland areas along the spine of the Appalachians from Virginia to New York. The excessive rainfall was courtesy of orographic lift, which was enhanced by the storm’s east to west oriented path. This rainfall, combined with a wet pattern leading up to the storm, overwhelmed river systems, which crested at historical levels. The result was devastating flooding, with many towns virtually washed away and city centers turning into rivers with several feet of water.
Flooding in Wilkes-Barre, PA from Agnes. There were many other towns across the Appalachians which endured similar impacts. Courtesy NWS.
The large-scale impacts up and down the I-95 corridor from Agnes left a lasting memory, but it's quite amazing it occurred in June. In fact, the National Weather Service, dubbed it “was one of the largest June hurricanes on record.”