* Middle East-Japan rates climb by $21,000 a day from 6-1/2-year low
* Unipec fixes 20 of the 50 supertankers chartered in last week -Reuters data
* VLCC market to be "hot" in Q4 -VLCC broker
By Keith Wallis
SINGAPORE, Sept 4 (Reuters) - Freight rates for very large crude carriers (VLCCs) face a roller-coaster ride on uncertain cargo volumes and vessel supply ahead of a fourth-quarter boom, brokers said.
Charter rates, which have rebounded sharply, could fall as more supertankers become available for charter in the last 10 days of this month, a Singapore-based VLCC ship broker said on Friday.
Rates from the Middle East to Japan have climbed 17 points on the Worldscale measure after hitting a six-and-a-half year low on Aug. 26. That is equivalent in average earnings of almost $21,000 per day.
Supertanker rates from West Africa to China have also recovered.
That followed a surge in chartering activity with around 50 eastbound cargoes fixed from the Middle East and West Africa by operators and traders, including the National Shipping Company of Saudi Arabia (Bahri), and Morgan Stanley, Reuters chartering data showed.
Unipec, the trading and shipping arm of China Petroleum & Chemical Corporation (Sinopec), fixed 20 of these cargoes from the Middle East and West Africa to Asia, mainly China.
Many of the early fixtures were older vessels or supertankers chartered straight from dry dock at cheaper rates by owners because otherwise the ships would have to wait for cargo, the broker said.
Rates climbed as this supply of prompt tonnage disappeared, although the market may face a similar situation in the next week or so.
Whether rates rise or fall "depends on who blinks first," the broker told Reuters.
"Charterers could sit still (withholding cargoes) to force rates down. If they start getting nervous (and release cargo) owners will be in control (to push rates higher)," the broker said.
"The VLCC market in general remains very volatile," Norwegian ship broker Fearnley said in a note on Wednesday.
"The fourth quarter is still going to be hot, but we're not there yet," the Singapore broker said.
VLCC rates for the benchmark route from the Middle East to Japan rose close to W46 on Thursday, up from W29.75 a week earlier, and the highest since Aug. 6.
Supertanker rates from West Africa to China climbed to around W46 on Thursday, against W40 the same day last week, and the highest since Aug. 14.
Rates for an 80,000-dwt Aframax tanker from Southeast Asia to East Coast Australia were stable at around W97 on Thursday, one point higher than last week.
Clean tanker rates from Singapore to Japan fell to near W156.5 on Thursday, from around W162.75 the previous Thursday, on ample tonnage, a Singapore clean tanker broker said on Friday. (Reporting by Keith Wallis; Editing by Biju Dwarakanath)