Jordan Spieth (R) of the U.S. carries an umbrella as he walks down the sixth hole during a practice round ahead of the British Open golf championship on the Old Course in St. Andrews, Scotland, July 15, 2015. (Russell Cheyne-Reuters)

On the British Open’s opening day at the Old Course in St. Andrew’s, the world’s top golfers were treated to gentle winds and comfortable temperatures well into the 60s.  These nearly ideal playing conditions have allowed the field of pros to tame the historic course, the majority remaining at or under par.

But the weather will change dramatically Friday, truly testing the players’ games and ability to adapt to very difficult conditions. Rain is expected early Friday, a likely nuisance for players with early tee times.  While the rain should taper around late morning, howling winds from the south – sustained at 20-25 mph and gusting to 35 mph will pose a major challenge throughout the day.

GFS model simulation Friday afternoon local time showing low pressure over the Atlantic just west of northern Scotland on Friday, driving strong winds inland, their sustained intensity portrayed by the different colors, in knots. (

“When you have that type of wind, equipment doesn’t help you a whole hell of a lot,” Tom Watson, five-time British Open Champion, told the Wall Street Journal in an article on the hazards of weather at The Open.

On Saturday, conditions are likely to turn even more inclement. The UK Met Office forecasts sustained winds from the southwest of 22-26 mph gusting over 40 mph combined with “heavy, sometimes thundery showers.”

It’s not just the intensity of the wind but also changes in its direction that will make the course extremely difficult Friday and Saturday. Between Friday and Saturday, the prevailing wind direction will veer about 90 degrees from southeasterly to southwesterly.

“A five-degree wind change here changes the whole golf course completely. I’ve always found that very fascinating,” Tiger Woods told the Wall Street Journal.

A vigorous area of low pressure originating from the Atlantic and crossing extreme northern Scotland is responsible for the anticipated burst of windy conditions.

By Sunday, as the low pressure area scoots away, winds are forecast to ease and shower chances are low, perhaps allowing players to make a move up the leaderboard less deterred by the weather. However, it will be a tad cool, with highs only in the upper 50s to around 60 (14-15 Celsius).

Here’s a great primer on British Open golf weather by Jon Nese, professor of meteorology at Penn State: