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Chris Bedford
Scuttlebutt News:

Weather synopsis for 2016 Olympics

by Chris Bedford, Sailing Weather Services

Chris Bedford owns Sailing Weather Services, which provides complete meteorological services for competitive sailors and adventurers worldwide. Bedford's company provided weather services for Ericsson 4 during their winning 2008-9 Volvo Ocean Race campaign, and is the meteorologist for the BMW Oracle Racing team.
(September 30, 2009) The Olympic bidding process has narrowed the field to four major cities located in 4 rather different climates and, therefore, 4 different prevailing weather patterns. The four finalists are Chicago (USA), Madrid (Spain), Rio de Janeiro (Brazil), and Tokyo (Japan).

With the exception of Madrid, all cities are coastal with access to harbor facilities and waters suitable for holding the sailing competitions in relatively close proximity to the Olympic city - certainly much less than the 1-hour plane flight like in 2008 when the Beijing Olympic events were held in the coastal city of Qingdao. The exception is Madrid, where sailing events will be held on the Mediterranean Sea off Valencia, making use of its recently updated marina facilities courtesy of the city's status as host of the 32nd America's Cup.

Before providing a brief summary of the prevailing wind and weather conditions at each sailing venue under consideration, I will first off discuss sensible weather. The warmest venue is Tokyo with an average temperature of 79F (26C). Valencia is a close second at 77F (25C). Rio de Janeiro is coolest with an average of 72F (22C) - remember, its winter in the southern hemisphere. In terms of extreme heat, all the venues stack up similarly with approximately 1 out of every 5 days exceeding 90F (32C), though Tokyo has a slight edge here with up to 1/3 of the days 90F (32C) or higher in the warmest month - August.

Tokyo also wins the Gold in terms of rainfall, averaging over 5 inches in the month of August with rain on over 20 days of the month. Valencia is driest with rain on less than 5 days, though Rio is a very close second (winter is the dry season in Rio).

The prevailing winds at each candidate city offer reasonably favorable prospects for sailing. In particular, extreme wind events - like that experienced at a recent event hosted in Weymouth at the site of the 2012 Games - are not expected. While not impossible, gale force winds at all the candidate sailing venues are certainly rare.

Chicago (USA)
Located on Lake Michigan, sailing in Chicago is largely dependent on either an afternoon thermally generated lake breeze, or a moderate to fresh gradient wind - typically from the W or SW. Much of the sailing will take place in close to the lake front and that can be challenging - particularly in offshore winds rumbling through the urban canyons of the city. There is suitable sailing breeze nearly every day, though some racing could take place in very light airs when the lake breeze is fighting the prevailing offshore westerly gradient.

Light morning land breeze winds often change to a NE/ENE wind which veers to the right through the afternoon giving rise to a ESE lake breeze. The most challenging days will be when gradient winds blow from the southwest. These hot winds can battle it out with the lake breeze to create completely different winds between courses in the north and those in the south.

The average daytime wind speed is 8-9 knots, but sailing in winds closer to 5 knots and sometimes over 20 knots is not uncommon.

The randomizer in Chicago could be the sometimes fierce thunderstorms which move off the lake front from time to time. These are most common in the early morning (pre-sailing) or afternoon (mid-race) and upset the wind field for several hours each time. Thunderstorms occur about 6 days per month.

Proposed event dates:
Olympics: July 22-Aug 7
Paralympics: Aug 12-Aug 28

Madrid (Spain) - Valencia
Winds in Valencia are dominated by the daily sea breeze. June and July are often the windiest months in Valencia thanks to the peak of strong thermal component at the end of spring and start of summer. By August, winds start to ease off. Normally, light offshore winds in the early morning die quickly to a period of light and variable conditions. Sea breezes often start at mid-day or shortly after noon, building from 5-8 to 10-13 knots, though stronger sea breezes are often experienced to the south of the marina area.

Anyone who has sailed in Valencia will tell you that itís more complicated than it would seem and there can be significant changes in the wind conditions day-to-day. Still the weather pattern is relatively stable and winds are reliable enough to make sure that sailing events will be completed.

Like Chicago, thunderstorms can sometimes move off the coast and cause problems for the wind. After all, it is the summer monsoon season over the Iberian Peninsula. Normally, this is only a problem about 4 days in a month.

Proposed event dates:
Olympics: Aug 5-Aug 21
Paralympics: Sept 9-20

Rio de Janeiro (Brazil)
Most of the sailing will take place in Guanabara Bay, though the possibility to hold events outside on the Atlantic off Copacabana Beach also exists. Being winter in Rio, winds can be a little fickle at times. There is still a sea breeze, but there can also be some stronger and more persistent offshore winds from the N - especially ahead of the more powerful cold fronts that make their way up the Brazilian coast that time of year.

Because sea breezes are weaker and the wind is more variable, average wind speeds are the lightest of the four cities at around 7 knots. This is not necessarily a bad thing. The wind is fairly predictable and it is often obvious in the morning whether an offshore wind will likely tamp out any chances of a sea breeze or if a light sea breeze be able to blow up into the sailing area.

There can be occasional strong wind events in Rio. The strong southern Atlantic fronts and lows developing offs the coast can push wind and swell north on to Rio's south-facing beaches. The effects of these storms are often mitigated within Guanabara Bay, but moderate to fresh winds are not out of the question for 2 or 3 day periods a couple times in the month.

Proposed event dates:
Olympics: Aug 5-Aug 21
Paralympics: Sept 7-18

Tokyo (Japan)
Sea breezes are the main source of winds in Tokyo. The sea breeze is a reliable, almost daily feature on Tokyo Bay. Winds sometimes do blow in from the E/NE when there is low pressure or a tropical system to the southeast of Japan, but these episodic events are far less prominent in the historical wind record than the sea breeze.

Average daytime wind speed on Tokyo Bay is expected to be around 11-12 knots. I would be inclined to call Tokyo the windiest of the four venues according to average wind speed and persistence of the wind. Of course the frequency of rain can be a problem, with showers on the bay causing the variable winds. Fortunately, the sea breeze manages to keep much of the rain inland, allowing steady breezes to last longer on the bay.

The main weather concern in Tokyo would be from an ex-Typhoon moving east of the country. Itís a little early in the season for such things during the Olympic schedule, but not out of the realm of possibility. The tropical cyclone risk to the Paralympics nearly one month later is more of a concern. In any case, the effects of such systems are normally short-lived at 1-2 days.

Proposed event dates:
Olympics: July 29-Aug 14
Paralympics: Aug 31-Sept 11

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Note: Sailing Weather Services was contracted by the USA for the 2008 Olympics, but other work prevented them from making the commitment to the effort they wanted for the 2012 quad.

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