Transition months can be deadly! For those who suffer from weathermania, the months of October and March are of particular interest as it is during this period that we typically transition from autumn to winter and winter to spring respectively. One such transition period, October of 1991, saw trick-or-treaters in Minnesota slog through 8 inches of snow, while those in the northeast experienced the “perfect storm”. As light flurries begin to fly in southern Minnesota today (sadly, no record snow is on the way), the east coast is once again preparing for what might well turn out to be another “perfect storm”.
On October 28th, 1991, a cold front off the eastern seaboard produced an extra-tropical low near Nova Scotia, while a very strong high pressure system in eastern Canada provided the catalyst for a steep pressure gradient (70mb) between the two systems, creating 100 foot waves in the process. The high pressure system formed a blocking ridge that forced the extra-tropical low to the southeast where it absorbed Hurricane Grace and its associated energy and moisture. This “perfect storm,” as journalist and author Sebastian Junger defined it, eventually resulted in over $200 million (1991 dollars) in damages along the east coast, and 13 fatalities, including all six hands of the Andrea Gail, a commercial fishing vessel made famous by George Clooney and Mark Wahlberg.
Meanwhile, a powerful low pressure system (984mb) brought moist air to the Midwest that collided with Arctic air from the north and resulted in the “Great Halloween Megastorm.” I was a sophomore in high school in 1991, and all I can recall from the Halloween blizzard is that my good friend Brent and I shoveled his parents driveway repeatedly throughout the night and well into the following morning as 28.4 inches of snow fell in the Twin Cities. To our south where warm air remained aloft, the same system deposited 2-3 inches of ice across southern Minnesota and northern Iowa that closed Interstate 35, damaged up to fifteen percent of the corn crop that was still in the fields, and resulted in the loss of power to 80,000 homes for nearly a week.
As I sit in my living room this morning, the Weather Channel, a small upstart in 1991, is once again broadcasting the potential for a “perfect storm” heading towards the eastern seaboard. Hurricane Sandy is currently moving into the Bahamas as a Category 2 storm, and a strong high pressure system exists over the Northeast creating a blocking ridge that has the potential to push the storm to the west. While numerous computer models disagree about the exact trajectory of the storm, most agree that it will eventually make landfall along the eastern U.S. early next week.
October is a unique period in our annual pilgrimage around the sun. Autumn is fading rapidly in the Midwest, warm temperatures and ample moisture exists in the south, and winter is nearly established in the Arctic. The idea of a “perfect storm” should not come as a surprise to anyone given these realities, but as the 24-hour coverage of Hurricane Sandy on the Weather Channel and news outlets across the western hemisphere can attest, the public as a whole often needs reminding that October is a transition month, and transition months can be deadly.
Source: Ostro, S. 2009. Meteorological Perfection. The Weather Channel. (www.weather.com/blog/weather/8_20575.html).