The deep blue sky that changed history on September 11
The lack of weather was noteworthy on the morning of the U.S. attacks
Weather is the unassuming backdrop of our daily lives. We rarely remember the conditions on any given day unless a sudden storm throws a wrench into our routines.
The morning of Sept. 11, 2001, stands alone in opposition to that rule. The deep blue sky and near-perfect temperatures feature prominently in almost every personal story recounting the attacks in the U.S. on that early autumn day.
Clear, blue skies are such a cornerstone of that day's memory that a large exhibit in the 9/11 Memorial & Museum, called "Trying to Remember the Color of the Sky on That September Morning," serves as a remembrance of those lost both that morning and during the previous attack in 1993.
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One cold front very nearly changed the course of world history.
A potent low-pressure system over far northern Quebec brought much of eastern North America their first taste of autumn after a long, hot summer.
This front swept from the Great Lakes toward the East Coast late on Monday, Sept. 10, sparking showers and thunderstorms along its leading edge. One of those evening thunderstorms swept over New York City.
High pressure dominated the setup the following morning. Cool, crisp air stretched from Calgary to New York, where the temperature at 9:00 a.m. was 18°C.
A strong high combined with dry air aloft to paint a vividly, memorably blue sky that stretched from one horizon to the other for many regions throughout the eastern halves of the U.S. and Canada.
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The same cold front responsible for those fall-like conditions also helped to keep a hurricane from threatening both the U.S. Northeast and the Atlantic provinces. Hurricane Erin was a once-powerful storm that grazed Bermuda on a general northwestward track.
Blocked from hitting land by the cold front, the storm loomed not far from the coast as satellite imagery and astronaut photographs captured smoke rising from Lower Manhattan.
The cold front’s slow passage also allowed thousands of international travellers to find safe harbour on Canadian shores. Gander, Nfld., alone hosted more than 30 of the hundreds of international flights that were prohibited from entering U.S. airspace.
Central Newfoundland saw hazy skies and gentle winds for much of that morning. Conditions remained favourable for incoming flights despite the front’s arrival around the lunch hour, and the community reported no rainfall as those flights departed over the next couple of days.
Header image courtesy of NOAA/NASA.