In the meantime, another trip across the run off area at turn one would drop Rea down to fourth behind Sylvain Guintoli, who was making swift progress up the order as the only rider capable of challenging Haga's lap times.
With the weather seemingly stabilising, Guintoli gradually caught Sykes ahead of him to be on his tail by lap twelve, the Kawasaki rider now more than ten seconds behind a relentless Haga.
However, Guintoli's charge would coincide with a sudden deterioration in the weather conditions over the first, third and fourth sectors of the lap, prompting a chaotic spell as the unassuming riders struggled to adapt to the changes.
Guintoli was the first to make a mistake, running wide at the first corner as he attempted to overtake Sykes, but he fared better than Rea just behind them, the Ulsterman dropping the Honda at high-speed, sending both man and machine skating down the track and into the barriers.
Leon Camier and Makoto Tamada were also victims of the shower before the weather claimed its highest-profile victim in Haga, who fell at the high-speed Schumacher –S. Though unharmed, it was a bitter retirement for both himself and the satellite PATA team.
With Haga out and Guintoli losing four seconds in his trip off the circuit, Sykes suddenly found himself in the lead, the Kawasaki man gesticulating over the finish line to suggest the race should have been stopped.
He got his wish on lap 14 when, as the race reached the two-thirds marker – thus enabling organisers to declare the result -, the red flag was dropped.
With the result counted back to the 13th lap, it meant Sykes would be declared a stunned winner, a result that sees Kawasaki make a welcome return to the top step of the podium after five years. Indeed, it even marks Kawasaki's first WSBK podium since 2007, as well as Sykes's first victory.
The chaotic final two laps had done its job of shaking up the order behind, with Guintoli and Jakub Smrz completing the podium for the Effenbert-Liberty Ducati team.
A new personal best for Guintoli, it is the second time the Czech team has gotten both of its riders on the podium having previously achieved the feat at Miller Motorsports Park.