The shortest distance from San Francisco to Tokyo (4,536 Nautical Miles) is the "Great Circle," which arcs far to the north near the Aleutian Islands. This course is against the prevailing Westerlies bringing chances of gale winds.
I will take the longer (approximately 5200 miles) "Trade Winds" route, sailing mostly between 25 and 30 degrees North Latitude most of the trip. I anticipate rough sailing while beating and close reaching in the strong coastal North-Westerlies during the first 600 - 800 miles. The middle 3,000 to 3,500 miles should be running with the Northeast Trade Winds and passing just north of Hawaii. The final stretch of 800 - 1,000 miles will bring NAI'A heading Northwest toward Tokyo in variable winds, fog, currents, and shipping.
NAI'A will have to average 7.2 knots to finish the course in under 30 days, breaking the record of 34 days!! She is very capable of this speed, having averaged 8.6 knots in the 2100 mile 1996 Transpac - San Francisco to Hawaii.
Expert weather router, Bob Rice, will advise me of the weather window for the start day in April and the exact course to sail for optimum sea and wind conditions. I plan to call Bob on SSB (single sideband radio) about every other day. NAI'A also carries a weatherfax which prints out weather maps of the Pacific for studying on board. (check out all of NAI'A's specs.)