Meteorology and the Pathfinders

Featured photograph: the famous image of 1409 Met Flight Mosquito, ML897, D-Dog, which was one of those carrying out the weather reportage for the D-Day landings. RAF Pathfinders Archive.

In The Right of the Line, the historian John Terraine wrote that Bomber Command’s ‘first and everlasting enemy’ was the weather. Throughout the Second World War, guessing what the weather would do was a central preoccupation of the Command, and considerable effort was devoted to making forecasts as accurate as possible.

The Path Finder Force was a small but vital facet of Bomber Command. Created in August 1942 to improve bombing accuracy, it led the other squadrons of Bomber Command, collectively known as Main Force, by marking the routes and bombing targets. So vital was the Pathfinders’ job that on 1 April 1943, after some months of campaigning by their Air Officer Commanding, Donald Bennett, the PFF acquired its own meteorological flight.

1409 Met Flight was created when eight PAMPA Mosquitos (PAMPA being Photoreconnaissance and Meteorological Photography Aircraft) were withdrawn from Coastal Command’s 521 Squadron at Bircham Newton, Norfolk, to join the Pathfinders at RAF Oakington, Cambridgeshire. Over the next two years, the eight two-man crews and their successors would fly numerous reconnaissance missions over Europe, bringing back the data from which weather forecasts for bombing operations could be made.

The usual procedure was that meteorological flights gathering information over Germany and other Continental targets would land back in England sometime before the bombers were scheduled to take off. However, as the article below makes clear, a coded message from a Met Mosquito in flight could also be sent back to base after the bombers had left their stations; this might warn of such serious bad weather that the bombing force had to be recalled.

Weather forecasting was even more important for the Pathfinders than for Main Force because the weather over the target could dramatically affect the Pathfinders’ target-marking techniques. An entry in the Operations Record Book for 83 Squadron on 7 October 1943 illustrates this perfectly:

  • Unfortunately there was a Met boob and the warriors found ten-tenths cloud [complete cloud cover] over the target and reverted to Wanganui technique with somewhat doubtful success. We now await the PRU [Photographic Reconnaissance Unit] results to see what measure of success attended our efforts.

Weather forecasting for the Pathfinders and the other Groups in Bomber Command had three key elements: the forecast for the weather on the routes and over the targets; the forecast for the British Isles for when aircraft took off and returned; and the localised forecasts for Groups and their squadrons.

There were a number of weather hazards which the forecasters tried to anticipate. Strong head winds could slow the speed of the bombers and use up vital fuel which was tightly calculated for long journeys, such as to Berlin. (A safety margin of around one hour’s extra flying time would have been included in the fuel load.) Alternatively, strong winds behind a bomber could increase its speed, a good thing on the journey home, not so good when the time of arrival at a target had to be split-second accurate.

Icing could pose a considerable threat. On an operation to Duisburg on 18 December 1944, two 405 Squadron Pathfinder crews reported considerable icing difficulties when they returned. The Dailey crew stated:

  • Icing from French coast at 17,000 feet and increased until target. Perspex covered with ice at target.

The Laing crew stated:

  • Grim weather conditions from French coast inwards and chiefly near target, icing severe, air frames and props static electricity.

From their earliest training, aircrew were taught how ice formed and what could be done to combat its negative effects. The above sheet is part of notes issued by the Directorate of Flying Training, the Air Ministry, in September 1942, the month after the Path Finder Force was formed. These were notes for new cadets, not the seasoned crews who were flying on operations. Image courtesy of David Nevans.

Under Air Ministry orders, a crew which encountered ice formation was duty-bound to report it on return to base, hence the very specific descriptions given by the crews of Dailey and Laing. The information about the icing would be passed via station meteorological ground staff to PFF HQ at Huntingdon and thence on to Bomber Command HQ at High Wycombe.

It is impossible to tell how many crews were lost over Europe because of icing, which could cause an aircraft to crash or make it more vulnerable to flak or fighters. But an even more dangerous and seemingly innocuous weather hazard was lack of cloud cover. (As already noted, dense cloud cover was relevant to Pathfinder marking techniques, as well as to the assessment of bombing results by photograph and photoflash.) Lack of cloud cover was particularly hazardous on nights when the moon was bright, leaving bombers dangerously exposed to enemy attack. The immense Bomber Command losses on the Nuremburg raid of 30/31 March 1944, when 545 men died, were due to two main factors: errors in route planning, apparently on the insistence of the Air Officer Commanding of 5 Group, Ralph Cochrane; and the moon’s brightness and lack of cloud cover, which horribly benefitted the German night-fighters. A 97 Squadron pilot, Charles Owen, noted in his Ops Diary:

  • Moon far too bright for comfort, and the sky swarming with fighters. Saw combats all over the sky right from the coast to the target, and a very large number of aircraft shot down. I weaved a lot more than usual, and was not attacked, although we saw fighters attacking other aircraft. Target was partially covered by cloud, and bombing was rather scattered. Ran into heavy cloud soon after leaving target, and stayed in almost to French coast. Not at all a pleasant trip.

Charles Owen, courtesy of Oliver Owen.

For crews on bombing operations who survived both the weather and the enemy, there were also potential weather hazards on return to base. The greatest of these was fog. Fog could obscure the lights of the airfield circuit, which ended in a funnel pinpointing where the landing should be made. It could also blank out the angle of glide indicators which ensured the correct approach to the runway — an amber if too high, a red if too low, a green if on the correct glide path.

In 1943, technical aids for landing in fog were in their infancy. Gee, a radio navigational aid which was very accurate over England, could help the returning aircraft to locate their home airfield, but it was too imprecise to direct them down onto a runway. The only real facilities available to land in low cloud and fog were FIDO (Fog Investigation and Dispersal Operation) and a system known as SBA. For further details see the article below.

FIDO, which was by far the best fog-buster, did not begin to come into operation until towards the end of 1943. The other aid, SBA, had considerable drawbacks. It was for these reasons that, prior to the full development of the FIDO network, local weather forecasting, which ran alongside national forecasting, was the best way of stopping take-off and landing accidents even though it might mean the complete grounding of operational aircraft.

Every Pathfinder station had its own Met Office, which monitored local weather and forwarded the data for collation to Pathfinder and Bomber Command HQs. From these local reports an assessment would be made of what the weather would be like at base, both at take-off and on return. Many bombing operations were cancelled, even when the crews were on the aircraft ready to leave, because the weather was thought to be too threatening. Spells of bad weather could produce multiple cancellations over consecutive days or lead to operations not being planned at all. One such period occurred in December 1943.

The Met Office at RAF Station Bourn was on the ground floor of the Control Tower; met readings were often taken from the roof. Photograph taken 1942, with the Duke of Kent third from left; the Duke was killed in a flying accident in Scotland that August. RAF Pathfinders Archive.

Bomber Command’s Battle of Berlin had commenced the previous month on 17 November. The campaign was deemed critically important: it was an all-out effort to win the war by bombing alone. So when many days were lost to bad weather in early to mid-December, there was great pressure to resume operations as soon as possible. The Berlin operation of 16/17 December 1943 went ahead despite reservations about how the weather would turn out. Unfortunately, the weather became considerably worse than forecast and the result was Bomber Command’s worst night of the war for bad-weather crashes.

The Pathfinder squadrons were badly affected: 97 Squadron lost 28 men, 405 Squadron lost 15, 156 Squadron lost 6, and 83 Squadron lost 1. In total, 50 Pathfinder aircrew were killed. Moreover, survivors of the crashes had often been so seriously injured that they would never fly on operations again. One of these crashes was that of the Thackway crew of 97 Squadron, the reason why the RAF Pathfinders Archive began. See full article below.

Interestingly, 1409 Met Flight had no losses on 16/17 December 1943. Their Mosquitoes were tiny, nimble aircraft which needed far less room to land than a heavy bomber like a Lancaster. The fog is scarcely mentioned in their Operations Record Book. However, 7 Squadron, the heavy bomber squadron at the same base, Oakington, also had no bad weather losses, although it can have been of little consolation as they had lost four crews on the Berlin raid.

The inevitable conclusion is that the Berlin operation should have been cancelled. The Met Officer at RAF Station Bourn, the worst affected station, stated that he thought it would be, but the order to scrub never came through. Sending the force out on such a night was a huge tactical blunder, but no commander whose operations so closely depended on the weather could hope never to make such a mistake. Harris, the AOC-in-C of Bomber Command, would write in his study of the campaign, Bomber Offensive, that amongst the very worst strains of his command had been ‘the continuous and fearful apprehension about what the weather may do’:

  • Meteorology is an inexact science; in fact it is still in the condition of being an art rather than a science. This being so, and our climate being what it is, I should have been able to justify myself completely if I had left the whole force on the ground, if I had done nothing whatever, on nine occasions out of ten.

The thousands of Bomber Command aircrew who died before or after ops in bad weather accidents were casualties of acute wartime pressures. The deaths of these unfortunate crews was recorded as being due to war operations even if the actual cause of death was the British weather.


A slightly different version of this article was published in RAFA’s magazine, AIR MAIL, October to December 2022 issue, under the title of The Night of the Fog.

1409 Met Flight newspaper images are from PFF ARCHIVES ONLINE, Catalogue No: 2023.1.002, originating archive the Pathfinder Collection, RAF Wyton.

See also Archived Articles: The Dangers of the Weather: Icing