Okay, got some quotes here:
JAMA, Vol. 118, No. 9, Feb. 28, 1942. "Surgical Experience at Pearl Harbor", by John J. Moorhead, M.D.
"I had arrived in Honolulu on December 3 at the invitation of the Honolulu Medical Society to give a course on "Traumatic Surgery." By a strange coincidence the second lecture was entitled "Treatment of Wounds, Civil and Military," and this was given on Friday night, December 5, approximately 36 hours before the attack. ..."
So, we know Dr. Moorhead was there, and was giving a course on traumatic surgery. Now, I'm not sure everybody has organized a medical convention, but, having been in too close proximity to someone who was doing so once, I can assure you they are not slap-together affairs. Typically they are scheduled 6 months to a year in advance.
The Hawaiian Medical Journal website has an article that recapitulates this info.
Okay, but why was the lecture series being held, and why at Hawaii?
Journal of Military History, Vol. 53, No. 1, January, 1989, pp. 65-78, "The US Army Medical Department and the Attack on Pearl Harbor":
Before defense arrangements commenced in 1940, army medical facilities consisted of two large hospitals on the island of Oahu-- Tipler Hospital at Fort Shafter and the Station Hospital of Schofield Barracks, which together had a normal capacity of 650-- and a smaller medical facility of 10 beds at Kilawea Military Camp on Hawaii Island. Supplementing those facilities were a few dispensaries scattered about the various military stations in the islands. Tripler also contained the major medical supply depot.
When in 1940 it became known that the Hawaiian garrison would be greatly augmented in strength, expansion of the hospitals became a pressing need. King ordered temporary wards set in barracks and on deep hospital porches, as well as construction of a new hospital at Hickam Field in the South Sector of Oahu. His actions increased the number of beds, including emergency beds, to more than 1,449. With this increase went changes designed to improve the ability of the hospital to function rapidly in events of war, including specific measures for treatment of gas casualties.
Impressive! FDR knew in 1940 that the Japanese were going to attack, so he ordered a bunch of hospital space so that he could treat the wounded so they wouldn't die and increase the death toll which he wanted as large as possible to get America behind the war in Europe after the war in the Pacific started without the Germans. Whew.
A quick note on the "huge number of Red Cross parcels" supposedly sent to the island before the attack. The above article notes that these were produced by ladies on the island, over a course of months.