CHIEF OF NAVAL OPERATIONS
The Bombing of Dutch Harbor
June 3-4, 1942
This is one of a series of pamphlets dealing with the weather aspects of Naval and Amphibious Warfare. The data on which these studies are based are taken from official documents and reports submitted to the Navy Department. The material has been collated and presented in a semi-technical form with particular attention given to the operational aspects of weather.
During the preparation of this study, it was found that weather data submitted by the various commands were occasionally at variance. An effort has been made to reconcile these differences in order to provide an accurate account of the sequence of weather conditions as forecast for the Force Commander, to describe the actual weather conditions observed during the operation, and to give a practical explanation of these weather conditions.
It is hoped that these studies will afford a clear view of the use of weather information during the planning, strategical, and tactical phases of the operation, and that they will form a basis for a hotter understanding of the application of weather information in future operations.
The primary objective of these analyses is to assist those officers who are charged with the responsibility for the planning and execution of similar operations.
Vice Admiral, U.S.N.,
Deputy Chief of Naval Operations, (Air).
Throughout the text, an effort has been made to maintain a consistent background of local time. Any departure from this practice has been noted--on the synoptic weather maps, the G.C.T. time of observation of the aircraft weather reports has been entered in parentheses near the report.
The ship's weather report appearing on each synoptic map is an adjusted average taken from the records of the Hornet and the Enterprise.
The Battle of Midway
The Bombing of Dutch Harbor
Following the action in the Coral Sea, May 4-8, 1942, the Japanese were inactive in the Southwest Pacific; the lull apparently being employed to prepare for the launching of a major attack.
The location to be attacked was a matter of surmise though strategists eliminated Australia as the locale by virtue of the almost complete absence of Japanese men-of-war in the Australian area and by the decrease in the intensity of the bombing of Port Moresby and other allied bases.
With Australia eliminated as the probable striking point of the Japanese attack, the defense of other vulnerable bases and of Midway was immediately organized. To protect Midway, two task forces (identified as SUGAR and FOX) were dispatched to the area north of the island, and air and ground forces on the island itself were augmented.
Sequence of weather desirable for an attack on Midway
The weather sequence of greatest strategic and tactical advantage for the attack on Midway followed by a landing operation is given below.
(1) Since low ceilings and visibilities reduced by squalls and showers make adequate scouting difficult by the defending forces, "bad weather" during the approach and rendezvous increase the possibility of a surprise attack.
(2) For the softening up phase, with air and surface bombardment, it is highly desirable to have high ceilings and good visibility over the target area. At the same time, it is advantageous for the carriers to operate in a zone of low ceilings and reduced visibilities with favorable wind direction so that the launching and recovery of aircraft can be accomplished without constant advances and withdrawals.
(3) The actual landing--the final phase--requires clear skies in order to gain the greatest advantage from air superiority established earlier, and light winds to insure a low sea essential to a landing operation.
Weather conditions over the Pacific
The location of Midway and the Aleutian Islands makes it possible to schedule such a combined operation with a good chance of enjoying all the weather conditions favorable to simultaneous attack. The course of storms over the Pacific at this season of the year often results in an active disturbance to the west and northwest of Midway. Subsequently, these storms move northeastward, accompanied by a movement of
related frontal systems toward the east, producing rain, clouds and low visibility ahead of the disturbance. Behind, there is usually rapidly improving weather. Furthermore, during the summer season, frontal systems tend to dissipate in a large percentage of cases in the vicinity of Midway. Thus, it is reasonable to expect favorable landing conditions during this period.
It is not certain at this point whether the Japanese chose the 4th of June as the date of attack for both Midway and Dutch Harbor expecting at that time the simultaneous occurrence in both localities of near-ideal weather conditions suitable to their purposes. There is a strong possibility that the date was selected on the basis of weather conditions known to be approaching Midway; and that the enemy task force commander of the Aleutian Islands operations was probably instructed to attack at a time as near that date as weather considerations permitted.
Due to the movement of storm areas eastward from Japanese controlled territory and waters, it was possible for the enemy aerologist aided by Japanese weather vessels to obtain an accurate "fix" on the orientation, speed, and direction of one such storm under the concealment of which the enemy force could advance to within striking range of Midway.
The enemy chose the time of attack. Our use of the weather was limited to a consideration of the weather situation the enemy might make use of to obtain maximum tactical advantage.
Weather situation prior to the action
During the latter part of May and early June, a large high pressure area centered northeast of Midway dominated the weather around Midway. This system, of moderate intensity (1027 millibars, 30.3 inches), was practically stationary and the circulation around it was sufficient to cause all fronts to the west and northwest to slow down and stagnate. Similarly, to the west and southwest of Midway, the deceleration caused the gradual disappearance of all fronts. Broken clouds, low and intermediate, and reduced visibilities were the only evidence of their former existence.
The Battle of Midway
The weather situation is sown on the 0230 map (Page 3). The was definite evidence that a weak storm center had developed some 650-700 miles to the northwest of Midway. From this center, a weak cold front extended to the south and southwest. The action of this storm as it moved northeastward was complicated by the presence of an old and "masked" warm front which extended in a north-south direction 200 miles west of Midway joining with a major system extending from the Aleutians.
The weather conditions in the Midway area are indicated on the map. In the eastern part of Area A, skies were broken but ceilings were unlimited and visibility good. In a westward direction, the weather became progressively worse: the broken skies developing into an overcast, ceilings lowering from unlimited to 1,000 feet and visibilities decreasing gradually t 6-12 miles and less. In Area B, skies were overcast with rain and showers. Low ceilings
Weather Map for 0230, 3 June, 1942
Weather Map for 1430, 3 June, 1942
Cross Section of the Atmosphere, 1430, June 3,
Showing the Position of the Enemy Task Force to the Southwest Relative to Midway
The enemy task force was discovered in a relatively clear area southwest of Midway. At the time contact was made, and during subsequent high level bombing attacks, the enemy was in the "warm sector" behind a dying warm front.
During the night of 3 June, PBY's from Midway attempted a night torpedo attack. Two planes were lost from the formation while passing through the war front cloud system.
Weather Map for 0230, 4 June, 1942
Cross Section of the Atmosphere, 0230, June 4,
Showing Relative Position of Enemy Carrier Force and U.S. Task Force in the Vicinity of Midway
The enemy carrier force approached Midway from the northwest under cover of a moving cold front. Behind this front were lower broken clouds with scattered showers and a variable ceiling between 1000 and 2300 feet. At the front an area of overcast, towering cumulus clouds, heavy showers, and lowered visibility prevented effective scouting by the defending forces. Father to the east, Task Force SUGAR was operating in an area under a dying warm front. The sky was cloudy, with high broken and lower scattered clouds. Ceilings were unlimited over the task force but lowered to 1000 0feet in a westerly direction.
made flying undesirable. Visibilities varied between 2 and 6 miles. To the west and southwest of Midway, Area C, although skies were partly cloudy, visibility was high and flying conditions ranged from average to good.
At Midway itself, skies were clear, ceilings unlimited, and visibilities were over 12 miles. Light easterly winds prevailed.
Japanese forces to the northwest, advancing under cover of the approaching storm area, remained securely hidden throughout the day. The troop and cargo ships to the west-southwest approaching Midway in the area between the warm and cold fronts were not so fortunate. These fronts were sufficiently weak that they offered no obstacle to scouting from Midway.
First contact with the Japanese force to the west-southwest was reported at 0904, bearing 247°, distance 470 miles. Two long range attacks were made on these ships by planes from Midway without diminishing the enemy's strength to any appreciable extent.
The first of these was a daylight attack by nine B-17's. The other was an "historic mission"--the first night torpedo attack by our patrol planes on surface ships. Four PBY's left Midway at 2115, 3 June, under clear weather conditions. Some hours later while flying toward the enemy (see cross section, Page 5) two of the planes became separated in the clouds outlining the intervening front. Although the darkness prevented them from reuniting with the remainder of the flight, one of these succeeded in finding the enemy alone. The other was forced by fuel shortage to return to base without making contact. The remainder of the flight succeeded in scoring several hits on the enemy ships. [Note the date of this report. These statements are apparently based on the claims of the pilots, not verified observations of hits or damage. --HyperWar]
Weather on June 4th
During the evening of June 3rd and the early morning of June 4th, the storm area to the northwest of Midway intensified. As it moved toward the northeast at 30 knots, the increased circulation around the storm center sharpened the old and stagnant warm front. The increased intensity of the center and related frontal systems produced a large area of overcast skies and low visibility north of Midway. This weather situation is brought out by the maps for 1430, 3 June, (Page 4) and 0230, 4 June, (Page 6) as well as by the diagram of the cross section of the atmosphere lying between our forces and the approaching enemy for 0230 on 4 June (Page 7). Ahead of the fronts, in the region to the east where our task forces were cruising, there was an overcast typical of an approaching warm front system. (Area A on both Page 4 and Page 6). Going through the fronts, the weather became increasingly poor with the height of the ceiling and the visibility diminishing and scattered showers becoming more general over the whole area. Immediately behind the cold front, where the Japanese carrier force was concealed, there was a region of broken ceilings varying between 1,500 and 2,500 feet, scattered showers and good visibilities except within the shower areas (Area B, Page 6).
During the night of June 30-4, the cold front overtook the warm front forcing the warm air aloft and leaving an occluded front at the surface. Our naval forces approached this occluded front from the east, moving to a point about 200 miles north of Midway. At 0545 when reports were received of enemy planes approaching the island, task force SUGAR prepared to carry out an attack against
Weather Map for 1430, 4 June, 1942
the Japanese carrier force. Somewhat later, our forces steaming south-southwest passed through the front encountering by 1000, typical post-frontal weather. Broken to overcast skies with 1,000-2,300 foot ceiling, scattered showers, and good visibility insured average flying conditions but the light southeasterly wind forced our carriers to turn away from the enemy while launching and recovering aircraft.
Although the enemy was not handicapped by the wind direction, the concealment provided by the storm no longer operated in his favor. His aircraft carriers were now in the relatively clear area to the rear of the front and thus exposed to observation and attack.
Action on June 4th
The enemy succeeded in launching planes for an assault on Midway before his carriers were discovered, but while Japanese planes fought through the Midway fighters to bomb the island installations, bombers and torpedo planes from Midway, along with our carrier-based aircraft, attacked the enemy carrier force.
The battle continued throughout the day of the 4th--planes against planes, and planes against ships. The enemy used cloud cover and shower areas for tactical concealment to great advantage during the action. The same cloud cover produced navigational errors by our own planes. [??? Because they couldn't see the "landmarks" on the ocean below? Or did the clouds interfere with their compasses? --HyperWar] In several cases these resulted in imperfect rendezvous and uncoordinated attacks.
Analysis of the 1430 map of June 4th, Page 9, showed little change in the weather situation. In most of the area to the northwest of Midway, where the enemy carrier force was deployed, scattered showers and thick cumulus clouds remained as evidence of the frontal passage during the early morning.
This picture applies as well to the evening situation although scattered showers and squalls further reduced the visibility. It was this condition which prevented the detection of the enemy forces by a group of our planes leaving Midway at 1700. PT boats ordered to launch a torpedo attack later that evening were unable to locate the enemy and lost their chance to use what would otherwise have been ideal conditions for delivering an effective attack. Had there been more accurate reporting of earlier contacts, the course of the enemy during the night might have been followed, and a more disastrous defeat at smaller cost to our forces been possible. As it was, no contact was made with the enemy during the night.
Weather on June 5th
The weather on 5 June typifies "air mass weather". A mass of modified polar air covered the whole Midway area. As the air mass was slightly colder than the water surface over which it flowed, local instability showers with small regions of reduced visibility were characteristic of the whole region. By 1000 these showers stopped with consequent improvement in visibility. By early afternoon, flying conditions became good with unlimited ceilings, scattered clouds, and a light southeast wind. At Midway the weather was clear. With scattered clouds at 8,000 feet and a gentle southeast wind, flying conditions remained good during the day.
Weather Map for 0230, 5 June, 1942
Weather Map for 1430, 5 June, 1942
Analysis of the 0230 map of 5 June (Page 11) indicated the probability of another storm development 900 miles to the northwest of Midway. No positive statement could be made of the specific structure of the system due to the complete lack of reports from this area. However, knowledge of the general circulation of air masses over the Pacific during that season indicated that the approaching storm would increase in intensity so that its effect would be felt in the northwest in 12-24 hours.
Action on June 5th
Aided by favorable flying conditions early in the day, planes made contact with several enemy cruisers, scoring a number of hits and near misses in their bombing attacks. In the direction of the storm area to the northwest, visibility deteriorated rapidly and cloudiness increased until at 1600 it was overcast at 12,000 feet in that region. Thus, all attempts to locate the surviving ships ended in failure.
On June 6th, patrol planes placed the approaching storm 540 miles northwest of Midway. South of the disturbance, there were low scattered clouds and a nigh overcast. With unlimited ceilings, good visibility, gentle southeast surface winds and fresh westerly winds aloft, flying conditions were good. Our own task forces, now west of the 180th meridian, were in this region. Several cruisers and destroyers, apparent stragglers from the landing task force, were discovered and attacked.
But to the northwest, in the probable direction of the enemy retirement, weather was increasingly bad. Lowered ceiling and visibility furnished good cover for the fleeing enemy.
The weather conditions can best be described by reference to the weather maps of June 6th and to the cross section on Page 15. On the 1430 map (Page 16) Area A is the region through which the landing force was steaming, while Area B is the region of the carrier task force retreat. The latter is further illustrated by the atmospheric cross section., Except for the position of our forces to the south and the heavy losses of the enemy, the picture of the Japanese advance on June 3rd and that of the retreat of June 6th are sensibly the same. None of our aircraft ventured into the immediate area of probable enemy retreat, but is indicated that flying conditions there were so poor that air search of that region would have been useless as well as ill-advised.
The pursuit ended in the early evening of the 6th when our forces retired to the northeast.
The bombing attacks staged at Dutch Harbor started on June 3rd and continued sporadically throughout that day and the next.
The Bombing of Dutch Harbor
It has been assumed that two Japanese aircraft carriers advanced in a bad weather area behind the frontal system shown on the map for 0230, 3 June (Page 3) just south of the Alaskan Peninsula. Immediately behind this front there was a region of showers and low ceilings. Farther to the west, between
Weather Map for 0230, 6 June, 1942
Cross Section of the Atmosphere, 0230, June 6,
Showing the Weather Conditions in the Area Northwest of Midway
After his carrier force was destroyed, the enemy withdrew the main body of accompanying ships into an area of extremely bad weather. This excellent tactical use of weather helped to save the surviving force from destruction.
Weather Map for 1430, 6 June, 1942
Weather Map for 0230, 7 June, 1942
this frontal system and a similar one located just to the east of Attu, there was relatively clear weather associated with a wedge of high pressure where flying conditions were average except in isolated fog areas.
Apparently, one of the carriers remained in the Bering Sea. The other advanced behind the frontal system to a point southwest of Unalaska Island and remained in this position as the frontal disturbance continued eastward. When the related weather advanced so that the carriers found themselves in the wedge of high pressure, bombers with a fighter escort were dispatched to Dutch Harbor. With the first front lying between the Aleutian Islands and the west coast of North America, our forces could expect that reinforcement by air would be difficult. At 0545, 3 June, the first enemy planes appeared over the naval air station. Throughout the day, enemy bombers attacked Dutch Harbor and surrounding positions. Heavy anti-aircraft fire at all points and the variable condition of the skies interfered with the accuracy of the horizontal bombers and prevented the attackers from damaging installations too severely.
By 0230 on June 4th, the front which the day before was just east of Attu, had advanced almost to Dutch Harbor, followed, at a distance of 360 miles, by a similar front.
During the morning, these fronts with their accompanying low ceilings and reduced visibilities, prevented the enemy from taking to the air. However, by 1700, the first front had passed Dutch Harbor and the bombings were resumed. The weather cleared. The overcast skies gave way to scattered clouds at 3,000 feet, out of which dive bombers attacked the island.
Tactical misuse of weather
The enemy planes last appeared overhead at 1950. The carrier on which they were based had been discovered and tracked by Navy PBY's. To prevent possible retaliation, it retired into a fog bank and retreated to the west. This action prevented the enemy planes from returning to base as much as it prevented our planes from attacking. Had the Japanese remained at a point just off the fog bank awaiting the return of their air force they would have been able to escape when our forces attacked, and they would not have lost all the planes in the air at the time of the "strategic" withdrawal.
In reviewing accounts of the Battle of Midway and the bombing of Dutch Harbor, it is immediately apparent that various aspects of the weather played a significant role in each phase of the operation.
Defensive use of weather
Consideration of the strategic and tactical use of weather is usually limited to offensive actions. Certainly the attacking force, having the decision concerning the best time for initiating action, possesses a great advantage. However, the strategy of the defenders of Midway emphasizes the extent to which this advantage can be materially neutralized by an intelligent study of weather conditions.
Thus, the time of the first attack could be predicted. Discovery of enemy forces to the southwest by our planes on June 3rd together with a study if the weather conditions led to the assumption that other forces could be hiding behind the weather front known to be approaching Midway from the northwest. This placed the most probable time of attack at dawn June 4th. [Again, note that at the date of this publication, knowledge of the highly successful communications intelligence operation that had pinpointed the Japanese attack was confined to an extremely small group. Weather prediction was no doubt quite useful, but we already knew they were coming, and were waiting in ambush. --HyperWar]
Further, the considerations given above permitted more effective scouting by our planes. Our pilots could be ordered to make an extensive search over a rather limited sector. By directing special attention to the necessity for attempting flight through any intervening front in order to determine what forces might be in or beyond the region of bad weather, the possibility of early discovery of the enemy to the northwest was greatly enhanced. Although his force was not discovered before the planes made the initial attack on Midway, the discovery was made early enough to permit our aircraft to damage and sink the enemy carriers while the enemy planes were refueling for a second attack.
Tactically, our force made good use of weather conditions. During the operations on the 4th and 5th, our bomber and torpedo pilots used cloud cover to make their approaches and to escape pursuit.
Experience in the Battle of Midway emphasizes the importance of a prompt broadcast of selected weather information obtained from a concise description of the weather in the area in which contact is made. Information of this nature furnishes valuable clues as to the future course of the enemy, enabling the command afloat to make the best possible tactical deployment.
The advantage possessed by the enemy in observing the weather as it moves from west to east can be offset to some extent by accurate and complete weather reports from every aircraft breaking radio silence or returning to base.
Perhaps the most important result of a consideration of the relationship between weather and strategy as exemplified in this action is an increasing respect for the high degree of skill possessed by the Japanese aerologists.
Offensive us of weather
The Japanese suffered a severe defeat at Midway. Had they made less skillful use of the weather, defeat might have turned into annihilation. In the initial stages of the attack, their use of the weather furnished concealment for their approaching carrier force behind a moving front. During the battle, their tactical employment of cloud cover and local shower areas decreased their losses by hampering the activities of our scouting planes and the efficiency of our bombing and torpedo squadrons. Later, when their air power was eliminated and retreat was essential, accurate evaluation of the current
weather situation made it possible for the surviving ships of the enemy to retire into an area of bad weather. This maneuver effectively prevented further engagement by our forces, thus enabling a valuable unit of the enemy fleet to escape further attrition.