Hawaii's zone is now UTC-10, it was UTC-10.30 in 1941. So 8.00 am Hawaiian time in 1941 is the same as 8.30 am today when it comes to things like the amount of daylight present but obviously not the affairs of humans which go by the clock. When the IJN strike took off around 6am, there was enough light for Akagi to use signal flags to order the launch to start, and since the Akagi was north of Pearl Harbor dawn was slightly later for it, given it was December.
From Day of Infamy by Walter Lord, 7 December Hawaii,
Air Plotting centre, only 1 officer present Lt Tyler, fighter pilot, second time on duty, without any explanation on what he was to do. Initially full staffing hours were 0700 to 1600, but changed to 0400 to 0700 then training to 1100 after the 27 November war warning was received, but no training on a Sunday. Opana radar station could normally expect around 40 plots on its 0400 to 0700 shift, the 6 personnel lived about 9 miles away, doing 3 man shifts, but decided to do a 2 man on 7 December.
HQ, 14th Naval District, watch consisting of 1 officer plus 1 Hawaiian enlisted man who spoke little English.
3.42 Minesweeper Condor spots a submarine at 100 yards range closing, around 1,000 yards from the harbour entrance
3.58 Condor blinkers a message to Ward, the duty destroyer, which sounds General Quarters and starts to search
4.43 Ward reverts to normal watch, no submarine found
4.58 anti torpedo net at harbour entrance completes opening, it will be left open
5.30 or so, in response to a radio query Condor tells Ward the submarine course when first spotted, not last seen, Ward moves to an area the submarine could not be.
5.34 Ward send thanks to Condor, Bishop's point radio station follows the exchange, does not make a report.
6.27 about, sunrise
6.30 Antares (towing a barge) passes a mile from Ward which notices something hanging off the tow wire, above a PBY starts circling
6.40 Ward identifies submarine, sounds General Quarters, shortly after the PBY releases smoke markers
6.45 Ward opens fire, then the PBY makes a run dropping depth bombs
6.45 Opana reports to Air Plotting centre a couple of aircraft plots 130 miles North
6.48 Ward intercepts a sampan which tries to escape, starts escorting it to the Coast Guard
6.51 Ward reports "depth bombed sub operating in defensive sea area" in code but lots of debris and whales had been depth bombed over the previous months.
6.53 Ward reports "Attacked, fired on, depth bombed and sunk submarine operating in defensive sea area", in code as per usual orders.
6.54 Opana told it can begin shutting down for the day, the 2 staff decide to stay on air until breakfast truck arrives so they can do more practice.
7.00 Air Plotting centre, time for breakfast for all people except the phone switchboard operator and Lt Tyler
7.00 about, PBY sends combat report, coded.
7.02 Opana picks up a big return, 137 miles north 3 degrees east
7.03 Ward gains a sound contact, deploys depth charges, gets a large black oil bubble as a result, alerts HQ to stand by for more messages, resumes sampan escort
7.06 Opana calls air plotting centre, gets the private on switchboard duty, who talks to Lt Tyler, no need for action
7.12 Ward 6.53 message decoded and in hands of 14th Naval District, phone call to Admiral Bloch's chief of staff, who orders to verify, contact CINCPAC duty officer and 14th Naval District operations officer.
7.15 radar plot a distance 62 miles, then or slightly later Opana operators talk to Lt Tyler direct, who thinks navy planes (carriers out) or the B-17 coming in from the US, hence why the commercial radio had stayed on air all night
7.15 Admiral Bloch on phone to operations centre, a 5 to 10 minute debate, by the end of which no one was sure Ward had seen anything, decision taken current response satisfactory, await further developments.
7.20 (about) CINCPAC HQ gets the Ward message, attempts to call back are blocked by a continual busy signal
7.25 orders for duty destroyer Monaghan to join Ward, then also call the Coast Guard about the sampan and then orders to close the harbour gate, all with separate phone calls, each taking time
7.30 Air plotting centre switchboard operator shift change, one private for another.
7.30 PBY ordered to verify message, air search plan being drawn up, CINCPAC HQ notified
7.30 CINCPAC HQ gets phone call with the PBY report, sunk a submarine, time to compare notes with what Ward reports
7.39 Opana loses the radar plot in its "dead zone", breakfast truck arrives about then
7.40 Fuchida signals for surprise attack plan.
7.40 Admiral Kimmel is informed about Ward's submarine activities, by now the sampan incident is taken by some as an indication nothing important happened.
7.45 Opana staff on way to breakfast
7.50 second call to Admiral Kimmel attempted, this time to report the sampan
7.51 duty destroyer Monaghan gets signal to join Ward.
7.53 Tora Tora Tora success signal sent
7.55 Preparation flag for morning colours hoisted, people begin to notice lots of aircraft. The destroyer Helm is the only ship in harbour under way, receives a wave from planes passing 100 yards away.
7.55 "All ships in harbour sortie"
7.57 Helena torpedoed, Utah, Raleigh already torpedoed.
8.00 around, off course B-17 arrive from the north.
For some in 1940/41 part of the explanation for the sudden collapse of the Netherlands, Belgium and France (and to an extent Norway) was a 5th Column doing sabotage, Hawaii had around 158,000 people of "Japanese blood", nearly half the population, when General Short decided they were the biggest threat and told his superiors he was acting accordingly no one objected. An effective 5th column, as envisaged pre war, would be relatively simple to set up, since the majority of the population was not American. It would also be highly effective. Were the Hawaiians 100% happy with US rule? Did the US have enough Japanese speakers to track the population? There was plenty of opportunity to stockpile enough weapons to make a start, then for example raiding army stores to equip the rest of the saboteurs as part of an attempt to capture the island. Pre war no US person knew how much effort was needed to make a 5th column work, nor how detectable it would be. There were enough Japanese in Hawaii expressing admiration for Japan to make the US assume this meant there were enough volunteers, the idea that people who leave a country often do so because they find a better life was discounted. The US built a picture based on, in one sense, that old colonial revolt fear, the majority of the island's population was not of American origin, a Japanese revolt might have help from the Hawaiians, or at least neutrality. Governing when a large minority hate you and a large majority are not sympathetic to you is very hard to do. Once the picture was formed the inevitable steady stream of ambiguous information was interpreted accordingly.
In November/December 1941 the USN assumed the IJN carriers were either headed south like much of the fleet, or were being held in reserve to counter any setbacks or USN moves, in accordance with the long held and well known IJN strategic defensive war plan against the USA.
1) the IJN could not put a large carrier fleet into Hawaiian waters except from the mandated islands, according to intelligence.
2) Pearl had enough search aircraft to guard this approach.
3) Pearl Harbor had 161 out of the USAAF total of 1,618 fighters at the end of November 1941 (the Philippines had 228, Latin America 231 according to the USAAF Statistical digest). Oahu had several radar sets available, plus the radars on USN ships.
4) Until Shokaku and Zuikaku could be considered operational the carrier raid from the north was 1 IJN carrier.
5) Until at sea refuelling was possible any carriers coming from the north would have minimal escorts.
6) The possibility of an airstrike was always on the table, the point was how probable, how much to tie Pearl Harbor up on that possibility, cutting into the time and material needed for other things like training.
7) The "best" use for the IJN carriers was covering the landings in South East Asia (like the IJN Naval General Staff wanted).
8) The known IJN war plan was to attrition the USN as it advanced, the carriers and most battleships in home waters waiting to engage the advancing USN fitted into this.
In order to actually do the strike commercial tankers had to be used, which caused station keeping problems.
"After a lengthy maritime strike in the winter of 1936-37 General Drum resubmitted his recommendations with the argument that the Army must extend its protection to the outer islands if it wished to assure an adequate supply of food for Oahu in time of war. Oahu produced only 15 percent of its own requirements in food, but the other islands could readily make up the deficiency in an emergency if communication was maintained with them. Again the War Department objected. In both 1935 and 1937, its basic argument against broadening the Army mission in Hawaii was the following: "If the Fleet is in the Pacific and free to act, Oahu will be, with the completion of the existing defense project, secure against any attacks that may be launched against it. It is only in the case that the Fleet is not present or free to act that the security of the Hawaiian Islands can be seriously threatened." (10) That the presence of the fleet in or near Hawaiian waters provided a more or less automatic guarantee against any serious attack on Oahu continued to be a widely held conviction both in Washington and Hawaii until the Japanese demonstration to the contrary in December 1941." (10) Memo, ACofS WPD for Col Miles, WPD, 29 Jul 37, and other papers in WPD 3878-3.
So Hawaii did not need external food supplies provided you could do inter island shipment and the presence of the fleet lessened the threat to Hawaii, which was actually correct, the other side was it raised the threat to the fleet.
The US radar stations on Hawaii tracked the Japanese aircraft as they flew back north. The information was lost in the system, probably fortunately given Enterprise then searched south west, rather then heading north.