Humber Bay Current Weather readings: From the Etobicoke Yacht Club Weather Station
Weather Analysis
A typical September Race day between noon and 3 PM has:
· A 92.4% chance of No Precipitation,
· An 80% chance of winds exceeding 6 Knots,
· A 75% likelihood of sunny or partly cloudy conditions.
Although Lake Ontario is the smallest (surface area of 18,960 km2) of the Great Lakes, boating activity in Canadian waters is heavier than oh the other lakes. Not only are there several sizable population centres on its shores, heavy industrialization adds to traffic and environmental problems.
The most highly variable weather on Lake Ontario occurs in the spring and autumn. In the spring and early summer alternating warm and cool air masses move through quickly, causing cloudiness and frequent thunderstorms.
Waves on Lake Ontario are generally only up to 1m (3 feet) high, but in rare cases may exceed 5m (15 feet). Lake Ontario has some of the deepest waters in the Great Lakes. Its average heat of summer, upwelling of water from the frigid depths does occur, particularly along the north shore, from Burlington to Oshawa, after two or three days of west to northwest winds.
Weather Patterns
Tropical air masses moving up from the Gulf of Mexico are a major influence on summer weather, and occasionally a temperature inversion occurs (especially around the Golden Horseshoe). The cooler air near the lake surface is trapped under a layer of warmer Gulf air above, allowing for the creation of smug and humidity to build up, and creating calm but very unpleasant, muggy conditions.
The effects of lake breezes are noteworthy on Lake Ontario, particularly in the Greater Toronto Area (GTA) where the difference in temperatures over the warmer land and cooler water are amplified by the miles of concrete (buildings and highways) along the lakeshore. The resulting lake breeze is enhanced by channeling (and with east northeast winds, by convergence), making winds between Mississauga and Oshawa particularly brisk and pleasant for sailing.
Toronto Harbour and approaches
The lake breeze is enhanced by the heat of this large urban area - winds near Toronto Island are often easterly during summer because of the lake breeze and channeling. Approaching the harbour from the east, there can be confused seas due to shoaling 1 1/2 km offshore from the Eastern Gap to Frenchman's Bay. The Leslie Street Spit shelters the water of Toronto Harbour and eastern portion of the island limiting wave heights. The inner harbour has variable winds with some gustiness due to the city and tall buildings.
The western approach to the inner harbour can have confused seas due to the reflection of waves off sea walls, but inside the harbour passage is calm. There is noteworthy current along the south side of Toronto Island. Its direction varies an it is surpassingly strong. Humber Bay is sheltered with southeasterlies, but souhtwesterlies can cause waves to reflect off the sea walls. There is probably wave/current interaction at the mouths of the Humber and Rouge Rivers, and some funneling of winds down the Humber Valley.