A 50 percent chance of rain threatens the race for TT glory at the Rio Olympics. And with changing wind also forecast, the weather may play a major role in deciding the medalists.
Held over a distance of 29.9 kilometres, the TT mostly comprises two laps of the Grumari circuit that formed part of the Olympic road race.
From the start, each rider will follow the flat coastal road for 2.5 kilometres before reaching the 24.7-kilometre circuit they complete once before the finish at Copacabana beach.
The first section is largely flat and follows the lumpy coastal road. It also includes a small section of cobbles which created chaos in the road race. But a strip has been paved for the TT so riders can avoid the rough surface.
The course then turns inland up the Grumari climb which averages 9.4 percent over 1.3 kilometres. The first 600m are easy at 3-5 percent but then there’s a very steep section with double-digit gradients, peaking at 24.1 percent before the climb mercifully flattens near the top.
A technical descent then follows, difficult on TT bikes especially on slippery, wet roads.
Once that's over, it’s back onto flat roads before the riders hit the Grota Funda climb which averages 6.8 percent over 2.1 kilometres. More regular than the first climb, it only briefly touches 10% easing off slightly at the midpoint.
Then it's a descent to the coast to complete the circuit before turning back to Copacabana.
Overall, the course has long, flat sections for the powerful riders, a steep, punchy climb as well as a regular, shallower one and some technical sections.
It will be a complete rider that wins the gold medal.
So, who can win?
Anna van der Breggen (Netherlands)
Van der Breggen is the prohibitive favourite for the gold medal after winning the road race. At this point her form is unrivalled and she was the favourite to win the TT even the road race win.
The Dutchwoman has a strong mix of power, technique and climbing ability which suits this varied course.
Probably the best indicator in terms of TT form this season was the 21-kilometre Giro Rosa Stage 7 where van der Breggen finished second. She'll only need to turn around four seconds on Evelyn Stevens to win.
She's the big favourite for the win here and anyone that overcomes the Dutch gold medallist will have earned it.
Evelyn Stevens (USA)
In the later years of her career, Stevens has gone from strength to strength. A superb Giro Rosa has set her in good stead for a crack at a gold medal here.
Three stage wins at the Giro Rosa, including the TT, saw her take second overall at the ‘Grand Tour for women’.
The current World Hour Record holder is a strong all round cyclist who can excel particularly on the climbs and will be one of the few who can match van der Breggen on the ascents.
The 33-year-old will be looking to avenge the lack of a USA medal in the road race, where their strong squad looked almost assured of a medal and came within 150 metres of gold.
Katrin Garfoot (Australia)
Garfoot was one of the main favourites to medal coming into the Olympics after her fourth in the World Championships last year and a dominant win in the Australian nationals.
Continuing her strong early season form with an overall win in the Santos Women's Tour Down Under and a stage win in Qatar, she looked to be on track for Rio when she ramped up her form mid-season.
A chest infection contracted from a training camp has disrupted Garfoot’s preparation significantly and her form is an unknown at this point.
The Orica-AIS rider withdrew from the road race at an odd point just after her hard work covering an attack from Kristin Armstrong (USA) across to a group of dangerous riders.
It would be an impressive comeback to overcome illness to take a medal here but her career is already one of defying expectations. The 34-year-old has broken every supposed barrier since coming to the sport only five years ago.
Linda Villumsen (New Zealand)
Villumsen is generally thought of as a TT rider suited only to the flat roads. But the New Zealander showed versatility on the undulating Richmond course at the World Championships last year, winning by two seconds over van der Breggen.
This course is both harder and easier. The individual climbs are harder, but there’s also a lot more flat road for the reigning World Champion to make use of her power.
She looked in fine form in the road race, riding to 23rd on a course which did not suit her big frame at all.
Villumsen is a good chance if she can limit her losses up the Grumari and Grota Funda climbs.
Winner of the last two gold medals in the Olympic TT, 42-year-old Kristin Armstrong (USA) successfully returned to last year winning the USA national championships and backing up with a fifth at the worlds later in the year.
The evergreen American has raced exclusively in America this season and was beaten in a recent time trial by Tara Whitten and Carmen Small, riders who aren’t really contenders for Rio medals.
But who knows, she certainly has the pedigree and Armstrong wouldn’t have come back to cycling targeting her third Olympics gold medal in the time trial just to make up the numbers.
Elisa Longo Borghini (Italy), Katarzyna Niewiadoma (Poland), Karol-Ann Canuel (Canada) and Alena Amialiusik (Belarus) are all in with a shot of medalling here on a good day and perhaps even finishing with a gold medal.
Women's Time Trial Start List
All times are in AEST and scheduled for broadcast this evening across the channels/platforms of network 7.
9:30pm 25 POL PLICHTA Anna
9:31:30 24 BEL KOPECKY Lotte
9:33:00 23 LUX MAJERUS Christine
9:34:30 22 JPN YONAMINE Eri
9:36:00 21 NOR HEINE Vita
9:37:30 20 FIN LEPISTO Lotta
9:39:00 19 FRA CORDON Audrey
9:40:30 19 CAN WHITTEN Tara
9:42:00 17 POL NIEWIADOMA Katarzyna
9:43:30 16 BLR AMIALIUSIK Alena
9:45:00 15 GBR POOLEY Emma
9:46:30 14 CAN CANUEL Karol-Ann
9:49:00 13 BEL DUYCK Ann-Sophie
9:49:30 12 GER WORRACK Trixi
9:51:00 11 AUS GARFOOT Katrin
9:52:30 10 RSA MOOLMAN-PASIO Ashleigh
9:54:00 9 ITA LONGO BORGHINI Elisa
9:55:30 8 UKR SOLOVEI Ganna
9:57:00 7 NED VAN DIJK Ellen
9:59:30 6 USA STEVENS Evelyn
10:00:00 5 RUS ZABELINSKAYA Olga
10:01:30 4 GER BRENNAUER Lisa
10:03:00 3 NED VAN DER BREGGEN Anna
10:04:30 2 NZL VILLUMSEN Linda
10:06:00 1 USA ARMSTRONG Kristin