Aerology and the Hawaiian Flight

The unknown quantity of the longest mass flight ever attempted by any nation was our old friend, the “weather.” Many thought it unwise to attempt such a hazardous flight during the month of January, as the storms are more frequent and intense during this period. Even in the summer months of fair weather, when all previous flights to the islands were attempted, only 50 per cent had been successful. During the record-breaking flight of Ernie Smith and Emery Bronte in July, 1925, the conditions over the same route were exceptionally bad. In this particular flight the fog extended from the surface up to 9,000 feet practically all the way from San Francisco to Honolulu thus forcing them to fly above 9,000 feet, and thereby losing advantage of the strong tail winds which are usually associated with the north Pacific high-pressure areas. The majority of the adverse weather critics failed to realize that there are generally several days of exceptionally good weather following the passage of the January storms inland from the northern eastern Pacific Ocean. These periods of good weather are more favorable for the ocean flight than the “fair weather” of the summer months. In contrast to the fog, mist, and low visibility of the summer “fair weather” the probability of encountering fog and mist is much less and the visibility much higher. The improved conditions are undoubtedly due to the lack of the subsidence inversions caused by stagnation of the summer “highs.”

A meteorological plan was decided upon to insure proper reception and dissemina­tion of weather information prior to and during the flight. Much had to be done in the way of gathering information, some of which was sadly lacking. For instance, there was no data on the upper air be­tween the mainland and Hawaii and the first problem was to work out a plan for obtaining this information. A fairly ac­curate network of upper air soundings would give an excellent indication of the expected direction and force of the winds at the proposed flying altitude (1,500 feet) and, in addition, would greatly aid the forecaster in determining the position and movement of the low-pressure centers. It was finally decided to form a network of upper-air observing stations consisting of San Diego, Sunnyvale, Seattle, Dutch Harbor, Honolulu, and a few station ships. By correlating the data from these sta­tions a fairly accurate picture could be formed of the upper air over the proposed route. The plan provided for the base force aerological officer to work in the Weather Bureau at San Francisco. This was un­doubtedly the logical place for the one who was to furnish all concerned with the weather information pertinent to the flight. The Weather Bureau, San Fran­cisco, is the center of all necessary infor­mation required, such as weather reports from ships, land stations, and airway ob­servation stations. In addition to having access to these reports, he is in immediate communication with all outlying naval weather observing stations and the flight commander through the naval radio, San Francisco.

Due to the limited number of qualified aerographers in the fleet, it was not prac­ticable to assign trained personnel to the station ships for the purpose of taking weather observations. The task of training the regularly assigned personnel on these ships was undertaken by the aerological officer, Fleet Air Base, Pearl Harbor, for the vessels detailed from Honolulu and by the flight aerological officer for the vessels detailed from San Diego. The result was that all station ships, prior to their de­parture, had on board personnel who had been thoroughly trained in the standard methods of observing and coding weather. After a careful study of the areas trans­versed by the January Pacific storms, it was decided to station a weather observing ship about 900 miles north northeast of Honolulu to act as a “watch dog.” She was to take the much-needed upper-air soundings and also send advance information of approaching storms which so fre­quently transverse this area on their way to the Pacific coast. This ship, together with the six station ships, Pearl Harbor, Dutch Harbor, and our naval coastal sta­tions, completed the network for special weather observations. The station ships were assigned positions at 300-mile in­tervals along the line of flight. All weather observations were taken at times cor­responding to 120th meridian time. The daily weather reports from merchant ves­sels were used to great advantage.

Summaries of the existing weather con­ditions in the vicinity of Honolulu and Dutch Harbor were obtained twice daily. This information proved invaluable and greatly aided the preparation of the weather forecasts prior to the departure of the squadron for Honolulu.

The preliminary study of weather con­ditions began on January 3 at San Fran­cisco. A series of weather maps were drawn using the theory of frontal analysis. The positions of the warm, cold, and occluded fronts of the various lows were verified on each preceding weather map. Upper air observations, from the various stations; were analyzed and “practice anticipated forecasts” were made.

It was very desirable to get the squad­ron off as near to the schedule date, Jan­uary 12, as possible. Any delay on account of bad weather conditions would certainly tend to lower the morale considerably. The difficult problem confronting the flight aerological officer was to be able to inform the squadron, in advance, of the day on which the weather conditions over the entire route would be “ideal” or at least favorable for more than 24 hours. Ideal conditions constituted clear or partially clear skies, favorable winds from an east­erly direction, good visibility, good con­ditions for a take-off and landing, a fairly smooth sea, and an extensive high pressure area which would deviate the storms approaching the route from the northwest. Conditions were considered favorable if the visibility was fairly good; the sea reasonably smooth, a ceiling of at least 1,000 feet especially during the night, good conditions for a take-off and landing no strong head winds, and no approaching storms. It was fully realized that all the elements constituting “ideal weather” could not be obtained at the same time. The lengthy time required for the desired high pressure to form over the entire route would also be favorable for the formation of a subsidence inversion and result in scattered fog along the central portion. A compromise was made and favorable landing, a fair visibility and a high pressure area over the entire route were given preference over the other elements.

The distribution of barometric pressure over the Aleutian Islands, Gulf of Alaska northwestern Canada, and the plateau states, on the day preceding and during the flight, was to be the controlling factor in our weather. A high-pressure area over the Aleutian Islands and moving southeasterly would tend to force the low immediately preceding it to take a southeasterly course instead of the desired easterly or northeasterly. A low in the Gulf of Alaska and moving east would be ideal on account of its favorable influence on the formation and movement of our 'high" between the mainland and Hawaii. The sudden appearance of a low-pressure area over northwestern Canada and the Plateau states would cause our "high" to diminish in intensity.

The synoptic weather map on the evening of January 7 gave the first indications that the conditions might become favorable within the next three or four days. The distribution of pressure shown on this map would cause the high between San Francisco and Honolulu to gradually form with its center at about the middle and to the northward of the route, thus giving favorable tail winds for practically the entire flight. The first appearance of a gradual building up of high pressure over the Bering Sea and a simultaneous fall of pressure over the plateau states would indicate that our ideal high was soon to be distorted and diminished in intensity. The deep low shown on this map, with its front extending south southwesterly, was predicted to move inland, in the vicinity of Juneau, Alaska, not later than Wednesday, January 10. A movement in this direction would cause the high-pressure area centered between Honolulu and the Midway Islands to move slowly eastward and gradually merge with the high centered southwest of San Francisco. Any further northward movement or a "filling up" of the Alaskan low would cause the center of our ideal high to be displaced to the northward of the proposed route, thus giving us the Conditions we had hoped for. An easterly movement of the Honolulu-Midway Island high would undoubtedly cause instability showers along the front or boundary surface separating the two air masses. However, it was believed that the showers would dissipate prior to noon Thursday, January 11, the probable time of arrival of the squadron in Honolulu. Weather reports in the Bering Sea indicated that a secondary low center was forming in the vicinity of St. Paul Island. This was an excellent indication that the high to the northward would not move down over the Aleutian Islands for at least a few days. Favorable conditions were developing so rapidly that a recommendation was made to have the scheduled flight advanced one day.

The morning weather map for Monday, January 8 indicated that the conditions were rapidly becoming favorable over at least half of the proposed route. Two well-defined low centers now appear over the Alaskan coast, both having a very favorable influence on the formation and movement of our high. After a careful study of this map it was further recommended that the squadron arrive in San Francisco not later than noon the following day and be ready to take off for Honolulu by noon Wednesday, January 10. Weather conditions were not particularly good for a flight northward from San Diego. Strong head winds prevailed north of Santa Barbara but on the other hand foggy weather was beginning to settle in the San Francisco Bay area. Any decrease in the wind velocity would result in the much-feared Tulare fog at San Francisco. The final preparations were completed in San Diego Monday evening, and, after a short delay, the squadron departed 10:00 A.M., Tuesday morning. The flight up the coast was an uneventful one except for fighting strong head winds for the first 200 miles. All six planes landed on the smooth but hazy waters of Paradise Cove about 4:20 P.M.

After a short conference on board the Gannet, it was tentatively decided to start the planes off on the long hazardous flight to Honolulu Wednesday morning. How­ever, the final decision was to be reserved until after completion of the evening weather map. The evening weather map was completed and on board the Gannet by 9:00 p.m. A fairly deep low (29.50 inches) was estimated in latitude 40^o north, longitude 165^o west, but the lack of weather reports caused considerable doubt as to its existence. Its influence upon the high was seriously considered, however, and it was decided that if it did exist it would travel along the cold front of the Alaskan low and pass well to the north­ward. This estimated path of the second­ary low would not greatly influence the formation of our ideal high. The rapid development of our high as shown on this map was most gratifying. Ship reports gave the surface visibility between 10 and 15 miles with partly cloudy to cloudy skies and favorable tail winds. The much- feared, high-pressure area again appeared over the Bering Sea and the desired high- pressure area over the plateau states was beginning to decrease in intensity. After all the factors had been carefully weighed and the prepared forecast thoroughly studied and analyzed, Commander Mc­Ginnis decided to take off with his six planes about 11:00 a.m. the following day. His decision was received most enthusi­astically by all hands. The plane crews worked diligently into the late hours of the night fueling and loading the planes while the pilots were carefully preparing their navigation charts. A light fog settled over San Francisco Bay late Tuesday night and the wind had rapidly decreased to almost a calm. This condition further confirmed the forecast of fog and light winds in San Francisco Bay the next day or two, and it was very important that the flight should start as soon as possible be­fore weather conditions became too bad.

Wednesday morning was ushered in with scattered fog and low-lying clouds over the bay region. The water was fairly smooth and a light north wind was blow­ing off Paradise Cove. The fog which had formed in the valley to the northward, during the night was not exceptionally thick and had been transported to the scene of the take-off by the light northerly winds. It was estimated that the fog would burn off by 10:00 a.m. The Wednes­day morning weather map was rushed aboard the Gannet and it portrayed the most pertinent features of the ideal flying conditions over most of the proposed route. Our high was now centered slightly to the northward and at approximately the mid-point of the route. The surface winds were light to moderate northerly over the first part of the course and moderate to strong southeasterly and north­easterly over the remaining portion. The upper-air chart for this map indicated moderate northwesterly winds at 2,000 feet for the first 400 miles and strong southeast to east winds over the remaining portion, at the same altitude. Visibility was above the average, 7-9 on the Beaufort scale. The moderate northwesterly winds off the California coast together with the 12-hour-pressure tendencies, reported by the land stations over the plateau states, gave an excellent indication that the plateau states high would soon be displayed by a low-pressure area. Practically every station north and east of San Francisco reported a fall in barometric pressure varying from .02 " to .08" during 1 the past 12 hours. This fall was undoubtedly due to the transport of warm moist air aloft and the simultaneous melting and disappearance of the snow which had covered the ground in these states for the week previously. The assumed low, on the weather map of the evening before, was now confirmed by ship reports and its center was estimated in latitude 48^o north and longitude 160^o west. The upper-air report from the Tanager (SE. 22 knots at

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 2,000 feet) indicated that it would pass to the northward of the center of our ideal high. The high-pressure area over the Bering Sea was increasing considerably in intensity and was moving southeasterly. Its movement in this direction would cause the secondary low to distort our ideal high to such an extent that the axis would lie in a line extending northeast- southwest instead of the desired east-west direction. This distortion would cause the winds to back into the northwest over the first portion of the route but not until the squadron had passed through this area. After a careful study of this map, the weather forecast over the San Francisco-Honolulu route for the next twenty-four hours was as follows:

Average to good and at places excellent flying conditions with cloudy skies for the first 500 to 700 miles with possibility of the sky becoming clear between 1,000 and 1,400 miles, partly cloudy to clear between 1,400 and 2,000 miles, partly cloudy with scattered light showers in the vicinity of Honolulu with clear skies and sunshine at intervals. Visibility good to excellent over route with possibility of light scattered fog about 150 to 200 miles off the California coast toward the late afternoon, fog 100 to 300 feet thick. Cloudiness consists mostly of high scattered cirrus with occasional altocumulus which will dissipate in the night. Winds up to 500 feet moderate northerly 12 to 16 knots for the first 200 miles, North 10 knots next 300 miles, northwest 4 to 6 knots next 250 miles, east to southeast 8 to 10 knots next 700 miles, easterly 12 to 16 knots within 300 miles of Honolulu shifting to northeast 20 to 25 knots for the remainder of distance. No storm warnings. May expect light scattered showers from 100 to 200 miles northeast of Honolulu, but the visibility should be good and the showers should not hinder flying. Winds aloft north 12 to 15 knots first 500 miles at 2,500 feet shifting to moderate northwest above 3,000 feet, east-southeast 16 to 18 knots next 500 miles at 2,500 feet with fresh east-southeast above 3,000 feet, east to east-northeast 20 to 25 knots remainder of route at an altitude of 2,500 feet. Average head winds 5 knots for 3 hours, average tall winds 13 knots for 21 hours.

The low clouds over the bay region began to break and clear about 9:30 a.m. The wind had veered into the northeast with a slight increase in velocity. All planes were manned promptly at 10:15 a.m. after the unceremonious but sincere send-off. The engines were warmed up and everything was set for the take-off shortly after 11:00 A.M. The moderate northeast wind was rapidly decreasing and when the squadron leader in 10-P-1 attempted his take-off it was practically a calm. The two section leaders taxied back and forth in an attempt to take the air and finally did at 12:45 p.m. with the aid of the utility planes from VJ-2. The two planes circled over lower San Pablo Bay awaiting the take-off of the remaining four. The tremendous load, about 25,000 pounds, almost pre­vented the start of the squadron on its long journey. The last plane succeeded in taking off at 2:08 p.m. about two hours after the first. The squadron was formed expeditiously and passed through the Golden Gate, in perfect formation, at 2:26 P.M.

The planes reported fog banks about 200 miles off the California coast and a moderate wind from 330^o true. At this time they were flying at an altitude of 1,500 feet, on course 237^o true. The wind was increasing slightly from the northwest (16-19 knots), which necessitated a change of course to 250^o true. At 5:52 p.m. the first station ship (Sandpiper) was sighted and a few minutes later all planes were overhead. The wind was beginning to de­crease in velocity and had veered into a more northerly direction. The course was again set at 237^o true. Shortly after dark­ness, a light fog began to settle over the route and, from the reports received from the squadron, it was apparent that the fliers were beginning to worry about the weather ahead. A message of encourage­ment was drafted and sent to the squad­ron. It read as follows:

Exceptionally good weather ahead, you will be flying in bright sunshine tomorrow morning. The evening weather map indicated mod­erate to strong easterly winds from the posi­tion of the second station ship (Schenck) into Honolulu. The surface visibility had decreased slightly. This was undoubtedly due to light mist over the central portion of the route. At 9:00 p.m. the lights of the Schenck were sighted and the squadron passed over her fifteen minutes later at an altitude of 1,500 feet. Broken clouds pre­vailed and the moon and stars were visible, at intervals, until 11:41 p.m. The wind had veered into the east with a velocity of about 10 knots. The third station ship, the Breese, was sighted at 2:30 a.m. The fact that the first three station ships were sighted without difficulty indicated that the surface visibility was fairly good. At 3:30 a.m. the following weather report was sent to the squadron from the Wright:

Vicinity Wright visibility good with occasional broken clouds. From 1,000 to 2,000 feet wind east 24 knots, 2,000 feet to 3,000 feet wind east 22 knots, above 3,000 feet wind east 15 knots. Pre­dict good weather conditions into Honolulu.

The fourth station ship, Whippoorwill, was sighted and passed over at 4:50 a.m. At daylight on the morning of January 11, the squadron was in the vicinity of the

Wright and less than 700 miles from their goal.

The great throngs which had been gathering in Honolulu since dawn sighted the six planes, about 2:40 p.m. approach­ing Koko Head from the northeast. The weather was almost perfect; a bright sun­shine and a balmy east wind greeted the fliers after showers had fallen during the early morning. At 3:08 p.m. all planes had landed at Pearl Harbor, after success­fully completing the longest mass flight in the history of aviation and breaking the previous speed record between the mainland and the islands by approximately an hour.

The weather maps for Thursday even­ing and Friday morning gave indications that the lowering clouds and sheets of rain formed hazardous obstacles along the great-circle route over which the six sea­planes of Patrol Squadron Ten flew the preceding 24 hours. The visibility was low and conditions much more adverse than those conquered by the naval squadron. “The weather,” which had destroyed great fleets of fighting ships in the past, was forced to concede victory to a well-trained foe.