Weather for the Olympics

The 2012 Summer Olympics (the Games of the XXX Olympiad) are planned to take place between 27 July 2012 and 12 August 2012 in London.

Although Londoners don't let weather spoil a sporting event, recent bad summer weather does not bode well for sales of tickets for outdoor events.

After a wet June and July already off to a wet start, United Kingdom's national weather forecasters are predicting more of the same for the coming month especially as rain is fairly common in London around this time of year.

This summer the problem has been heat wave temperatures in Central Europe causing more than usual evaporation, which results in rain within a few days within a few hundred miles.

Thunderstorms and flooding have resulted across Europe and when upper level winds carry rain-laden clouds north to the cooler UK, heavy rain events are created there also.

If heat wave air continues to bring convective showers across the Channel, the London Olympics may be affected. It will depend on wind direction.

Damp conditions would favour athletes from western countries who are used to rain, disadvantaging Caribbean rivals who train on warm and dry tracks.

Because the sun's heat is less determinable we cannot gauge rain amounts, but studying moon's orbits can determine the potential timing of weather events with 80% accuracy.

Taking lunar factors alone into account it is looking unlikely that the whole Games event will be entirely dry, yet half of the 17 days may stay clear.

The all-important opening ceremony could be in more settled weather but the closing ceremony is likely to be wet.

Starting just after a 1st Quarter phase on the 26th the moon progresses through a weak perigee on the 29th and southern declination, then through a full moon on 2 August and lunar equinox on 5 August.

The southern declination is when the moon is furthest south for the month and it typically brings warmer summer temperatures to the northern hemisphere, magnified by the moon in perigee.

The reverse will probably happen in the southern hemisphere, bringing a brutal cold snap to the South island around the 30th..

Southern declination may mean more humid conditions for the first few days of the Games until the full moon on 2 August.

Summer full moon days are typically very warm and this could bring heat exhaustion to some rowers. Because equestrian events also cover the full moon day, hotter conditions may affect performances of the horses.

The lunar equinox creates turbulence and around 5th-7th rogue breezes may affect the sailing.

Many events will be oblivious to the weather. Swimming, diving, basketball and gymnastics all happen in covered venues.

Beach volleyball could be impacted by the weather around the 6th- 8th, as water hardens sand, making it easier to move around on and creating a faster game.

Events that are weather-dependent are archery, athletics, beach volleyball, canoe slalom, canoe sprint, BMX, road and mountain bike cycling, equestrian, modern pentathlon, rowing, sailing, shooting, and the triathlon.

So what do the regular forecasters say? The UK Meteorological Office has predicted that dry weather in London is very unlikely during the Olympic Games this month.

Radar cameras in weather satellites only scan what is happening now so next-day forecasting is their specialty. This far from the opening ceremony satellite radar cannot indicate much.

Using the moon method for each day's events my opinion would be that from 27 July - 4 August could be mostly dry, with occasional breezy winds.

The full moon in perigee between 29 July - 9 August may bring about four days of high daytime temperatures.

In the last week of the Games rain is likely to be intermittent, including possible falls around lunchtime of the day of the closing ceremony.

Uncovered athletic events may possibly be threatened in the last half of the Games, and on the day of the marathon, slippery roads may bring congestion to public transport.

But despite the odd heavy fall about two days after the full moon, not many heavy rain days are anticipated.

Ken Ring of www.predictweather.com is a longrange weather consultant for Australia's Channel Seven.