Early fears Typhoon Fitow would wreak havoc over the Korean peninsula with torrential rain and winds of up to 100mph are subsiding.
The suggestion now is the periphery of the typhoon will at least make for a wet race around the Korean International Circuit.
That could ultimately level out the playing field for Alonso and lead to a mistake from Vettel, who has a healthy 60-point cushion over the Spaniard with six races remaining.
Alonso, however, appreciates that whether dry or wet on Sunday, Red Bull and Vettel will still take some stopping.
"You never know in wet races who will be the lucky one," said the Ferrari driver.
"If they are very fast, as they should be, and we have an off weekend then they will be in pole position and will win the race.
"If there are mixed conditions, then maybe we are lucky, maybe we are unlucky, and if the latter then we say bye-bye to the championship.
"It's hard to predict, but even in the wet they should be the maximum favourite. With the downforce they have in wet conditions they should be even stronger.
"If it is wet we'll see if it changes things, but it's something we cannot control."
In his quest for an improbable success, Alonso is drawing inspiration from Team Oracle USA's stunning America's Cup triumph recently.
Trailing Team New Zealand 8-1 at one stage, Oracle - who drafted in Sir Ben Ainslie to help overturn the deficit - produced one of sport's greatest comebacks to win 9-8.
"The president (Luca Di Montezemolo) and I think anything can happen," added Alonso.
"Like the America's Cup, we saw the American team was 1-8 down and they won 9-8.
"We know it is difficult, but if you have two lucky races things can change very quickly, but we need a lot of luck. We know that.
"We need to be realistic because we don't have the pace to beat them (Red Bull) in normal conditions, so we need luck in all six races.
"If we have luck, everybody can be sure we will be there to take advantage. We will not give up until it's mathematically impossible."