Donaldson was able to see Mount Taranaki from his kayak yesterday but a strong easterly wind and predicted gales has pushed him further offshore.
It's hoped he will make landfall by the end of this week.
Donaldson lived in Rotorua for 12 years before he and his family moved to Auckland two-and-a-half years ago to be nearer to his boatbuilder and the ocean.
"Our son is heavily asthmatic and he has been in A&E many times," said Mrs Donaldson.
"Like anything, you can restrict what you do or you can get up and set goals.
"This proves that asthma isn't a barrier. He's very much focused on promoting correct asthma management and the importance of physical exercise, such as swimming. One New Zealander every week dies from asthma, so it's really important that the message is out there."
Last year, the Donaldsons moved to Australia for the first attempt at crossing the Tasman. This was pulled within a few days due to problems with the boat.
In April, Donaldson set off on his second attempt and, as of yesterday, he was 60km offshore but with strong easterly winds working against him.
"It's gut-wrenching for him," Mrs Donaldson said.
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"At first he was texting me once a week, but he's had so many trials and tribulations that he's phoned a few times this past couple of weeks. She said people have been sending messages via his website, which she had been passing on.
"We've had people compare him to people who have done massive feats, like Hillary. People can't visualise what he's going through but he has had waves two storeys high coming at him. This is a mental and physical feat."
Supporters from Rotorua are eagerly waiting for Donaldson to complete the challenge. He has coached a number of people in the city for races such as Ironman. One of his former athletes is Jamie Campbell, who has completed two Ironman races back to back and cycled eight times around Lake Taupo.
"He's an excellent coach," said Mr Campbell. "We've all achieved stuff and he's been in the background pushing us. It's good to see him out there. He tried out for the transatlantic race many years ago but didn't make the final team. I think it has been at the back of his mind for a very long time to do something great."
Donaldson and his support crew have been helped by weather aficionado Bob McDavitt, who has been providing daily weather and sea condition forecasts to the kayaker.
He expects the forthcoming storm will bring gale force winds to the general location of Donaldson, who this morning was 70km west of New Plymouth. He has drifted 12km in the last 24 hours.
His support crew anticipate he will continue to drift south west at a similar rate despite having a drogue in the water in an attempt to reduce the effects of the north east winds.
Sea conditions are such that he is currently unable to paddle until the storm passes, and is confined to the inside of the kayak.
"As you can imagine this is less than pleasant in expected four to five metre swells with gale force winds," said supporter John Funnell, who has supplied air support.
Donaldson's Control Centre deployed the MV Reef Spirit, from New Plymouth to shadow him. The MV Reef Spirit reached Scott at 4.15pm yesterday and the intention is MV Reef Spirit will remain to shadow him to the finish line.
He has adequate food, water and battery power for communications and operation of his bilge pump to last to at least to the weekend.
"It is fair to say Scott has had more than his share of challengers over the last 79 days at sea," Mr Funnell said.
¦Messages of support and contributions to the crossing can be made at www.doubleditch.co.nz.
