Lee’s impacts and hurricane season dynamics

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Lee’s impacts and hurricane season dynamics

Post-tropical storm Lee made landfall in western Nova Scotia on Saturday, causing widespread damage, including downed trees and power outages along the North Atlantic coast. On top of strong winds, Lee brought coastal flooding and heavy rains to Atlantic Canada.

Animation of Lee, transitioning from a Category 1 Hurricane to a Post-Tropical Cyclone over Nova Scotia on September 16. Source: GOES-16 Air Mass RGB images.

In Nova Scotia, approximately 277,000 people were without power due to fallen trees and downed power lines. In neighbouring New Brunswick, nearly 90,000 people experienced power outages. Winds exceeded 100 km/h in some areas and reached 117 km/h in Halifax, leading to the closure of the Halifax airport.

Large waves hit Nova Scotia’s coast, flooding roads along the shore and cluttering them with debris. While some coastal areas, including the region around Peggy’s Cove lighthouse, required significant cleanup, others were largely spared.

It marks the second year in a row that a powerful storm has reached Canada after Hurricane Fiona ripped into eastern Canada a year ago.

Hurricane seasons tend to peak in early fall

As we have noticed, tropical cyclone activity has been ramping up across the Atlantic Basin in recent weeks. This is because hurricane season tends to peak after the Northern Hemisphere summer, as it takes time for the necessary conditions to be in place for hurricanes to fully form. These conditions include:

  • Warm ocean waters of at least 26.5°C to a depth of at least 50 metres;
  • Deep moisture and an absence of dry air throughout the atmosphere;
  • A lack of strong winds aloft that could shear storms apart; and
  • A tropical disturbance that serves as the “seed” for initial system development.

While the June solstice brings maximum solar radiation, oceans usually reach their warmest temperatures in late summer and early fall. This warmth is crucial for fuelling hurricanes by evaporating moisture into the atmosphere.

The lack of strong temperature contrasts and weaker jet streams (high-altitude, fast-flowing air currents) over warmer water also reduce wind shear (change in wind speed or direction), which is needed for allowing tropical cyclones to form and develop. Together, these factors create a favourable environment for hurricanes to thrive later in the summer season.

Hurricane season peaks in September in the Atlantic Ocean. Credit: NOAA.

The Atlantic hurricane season runs from June 1 to November 30, with the peak of the season typically coming in September. Once ocean temperatures begin to decrease and the jet streams begin to increase in strength, we tend to see hurricane season begin to wind down toward the end of fall.

For more information, visit: Current hurricane conditions.


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