2010 Lake Ontario 300 Challenge

The Forecast
It was a typical start to a summer day as participants made their final preparations on the morning of the June 17th.  At 8 am, the Toronto Airport observed a temperature of 79F, a dew point of 66F, slightly overcast skies and a modest westerly wind around 10 knots. On a broader scale, a cold front associated with an occluded low pressure system centered over James Bay was draped across northern Lake Huron and the Georgian Bay. The forecast issued by the Hydrometeorological Prediction Center (HPC) predicted that this frontal boundary would continue to move south, reaching Lake Ontario by 8:00 pm on Saturday evening and southern New York by Sunday morning (forecast graphic).

HPC's 24-hour forecast of fronts, pressure and weather valid at 00Z on Sunday, July 18, 2010 (8 pm on July 17, 2010). (larger image)

The passage of a cold front during summer is often accompanied by thunderstorms and severe weather. The National Weather Service (NWS) office at Buffalo, NY (KBUF) recognized this possibility, along with a forecast for southwest winds, in the Lake Ontario marine forecast issued at 3:55 am on July 17:

National Weather Service Buffalo NY
Lake Ontario Open Waters from the Niagara River to Hamlin Beach

Discussion: A 30.1 high centered over Pennsylvania will move slowly to the east today while a cold front drops south toward Lake Ontario during the afternoon. The front will cross Lake Ontario this evening, then stall south of New York State tonight.

This Afternoon...Southwest winds 10 to 20 knots becoming west. Scattered showers and thunderstorms. Waves 2 to 4 feet.
Tonight...West winds 5 to 15 becoming northwest. Scattered showers and thunderstorms in the evening. Waves 2 to 4 subsiding to 2 feet or less.

The forecasters at KBUF also published an Area Forecast Discussion (AFD) at 7:26 am on July 17 which provided a detailed analysis of the current weather pattern and their reasoning for the various public forecasts that would be issued during the morning hours. The AFD included references to a pair of pending Small Craft Advisories, the first for Lake Erie beginning at 9:00 am in response to strong southwest winds and wave heights approaching four feet. The second applied to the central and eastern portions of Lake Ontario regarding increasing winds, and was to be effective at 2:00 pm.

The AFD also provided additional details regarding the potential for thunderstorms and the area where their development was anticipated: “instability and convergence will increase between the lakes over the Niagara Peninsula with some convection breaking out early-mid afternoon.”  The marine section of the AFD stated: “thunderstorm development is expected along and just south of the Lake Ontario shoreline later this afternoon.”

The forecast information above, the weather briefing provided to the participants on Friday evening, and the Day One Convective Outlook produced by NOAA’s Storm Prediction Center (SPC) all reached the same conclusion — thunderstorms were possible over Lake Ontario, but an organized outbreak of severe thunderstorms was not expected. Although the forecast wasn’t particularly threatening, the combination of the approaching cold front, strong southwest winds, and the mention of thunderstorms should have raised concerns among participants about the potential for challenging weather conditions.

There are several hazards associated with thunderstorms. The most significant threat to a sailboat is the wind associated with the storm’s downdraft, either from the large waves it is capable of producing or from its destructive impact upon the boat’s sails, rigging or other mechanical systems. Even a modest thunderstorm is capable of producing sudden downburst winds in excess of 50 knots. A wind of this magnitude striking a boat carrying 500 square feet of sail area delivers over 5,000 pounds of force. Sails can be ruined, fittings broken and people injured very quickly in such a scenario.

For a primer on thunderstorms and downdrafts, click here.