" C l o u d c i g a r " o v e r S a i n t - P r o u a n t , F r a n c e
3.1. Horizontal motion of the object
One implication of the reports is that the witnesses, seeing the object appear initially in the direction "where the storm was coming up", were looking into the wind. Given that the synoptic pressure situation indicates a weather development dominated by the influence of Atlantic winds, this would suggest they were looking generally west towards an approaching storm front. (Weather on the Atlantic coast at Bordeaux that day was rain or drizzle, with average relative humidity 89%) .
Another implication of the reports is that the funnel passed, if not quite overhead, then at least not far away from the area where the witnesses were scattered. There is some variation in the orientations of the cigar as reported from different places. MICHEL reports  that some witnesses described the object as leaning towards them, whilst others in nearby villages described it tilting either to the left or to the right, depending on where they were standing, tending to indicate a phenomenon close enough to show some visual parallax which was therefore in the local sky of the observers, not far off on the horizon, whilst being at the same time large enough and high enough to be seen by observers separated typically by distances of 1 or 2 km (see Fig. 2). The detailed description by M. FORTIN at La Gabelière, says that when it became motionless it was at an apparent ground distance of only about 4-500 m and at about 4-500 m apparent altitude (implying an elevation of 45° which is a large enough angle for most people to describe it as "above us", as does FORTIN).
A secondary implication, therefore, is that when the object approached it was probably moving with some component of W-E motion (from the direction of the brewing storm to a position "above us"), which would not be inconsistent with the likely wind direction. One would expect any sort of natural cloud phenomenon to drift generally (but not necessarily exactly) parallel with the wind at the cloud level. Later it "accelerated (...) into the clouds in the distance", said M. FORTIN, in the same direction in which it had approached, still "point forward", i.e. without any rotation about a vertical axis. Similarly Mme PIZOU:
The "carrot" then took an horizontal position, point ahead, and resumed its course
at an accelerated speed before disappearing from our sight [emphasis added] 
This implies a continued generally W-E motion in accordance with the likely winds aloft .
But the witness statements also agree that the object appeared to remain stationary for tens of minutes as though decoupled from the "rapid" motion of the clouds above it. Is this compatible with a weather phenomenon? Apparent decoupling from winds does occur, for example with "mountain wave" clouds. Well-defined altocumulus lenticularis forming in the peaks of standing waves in the lee of topographic barriers may seem to hang motionless although the airstream containing them is moving at many tens of knots. The Saint-Prouant object does not resemble a lenticular cloud, of course, but a similar sort of effect might perhaps result from a vortex forming in a dynamically unstable equilibrium-point at the meeting of differently-moving airstreams, which could fit the sort of funnel-triggering conditions - such as frontal wind-shear - most likely in this case.
On the other hand the arrival of the object in horizontal linear motion, and its final "rapid" or "accelerated" departure towards the horizon in the same fashion whilst (presumably) retaining its form, are features that do seem to sit uncomfortably with such an intervening long static episode of dynamically unstable equilibrium.
3.2. Rotations of the object in the vertical plane
One possible problem with the funnel cloud theory is that, as MICHEL wrote, "it would be a singular tornado, indeed, in which the funnel pointed upward!" This remark indicates that in his understanding the "carrot" rotated in the vertical plane from an initial position with the pointed end tilted towards the ground to a position with the point uppermost, and that the "disc" then came out of the blunt end. This does appear to be consistent with the description given by the primary witness Georges FORTIN of what was seen by himself and a number of his farm employees at La Gabelière, here in the statement quoted by MICHEL:
The object came out of the clouds in an almost horizontal position, slightly tilted towards the ground and pointing forward (like a submerging submarine) (...) Then it stopped and the point rose quickly until the object was in a vertical position, where it became motionless [emphasis added].
and here as quoted in La Résistance De l'Ouest, September 20 1954 :
[it] had the shape of a carrot, coming towards us the point slightly ahead . . . suddenly, similar to the traces which a jet leaves, a white smoke was detached from the "tail" of the apparatus . . . The "carrot" then took an horizontal position, point ahead, and took again its course at an accelerated speed before disappearing from our sight.
i.e., the object moved with the pointed end "ahead" and the small disc with contrail came from "the tail", which was also the bottom of the vertical object, meaning that in its vertical phase the "carrot" was pointed-end-up, blunt-end down (contradicting the drawing produced by the weekly newspaper France-Dimanche and shown in Fig. 1).
The only other description we can find is in an account by Mme PIZOU who was about 1.8 km away, which is less than perfectly explicit:
It came near us, point downward, then straightened up [i.e., became vertical] (...) Finally, when I had been watching for about half an hour, it moved down into a horizontal position again, and went away rapidly in the direction toward which it was slanted [emphasis added].
This could mean either that the point moved down into a horizontal position from a raised position, or that the blunt end did so.
Interpreted literally, rotations of this type would appear to rule out a pendant funnel cloud. On the other hand the descriptions are arguably not clear enough, and their provenance not reliable enough, to guarantee that this behaviour was really observed .
A series of contemporary drawings in the Paris newspaper France-Dimanche (see Fig. 1) shows the pointed end of the carrot rotating only 50° or so from about the 4 or 5 o'clock position to a 6 o'clock point-down position, the blunt end remaining always uppermost. This contradicts the descriptions and would be more consistent with a funnel cloud, although it is only a stylised artist's impression and may be unreliable. (The same paper, October 24, 1954, offers another drawing in which the pointed end is upward at about the 2:30 o'clock position with the blunt end being lower, but a caption suggests that this may be just a generic illustration.)
One other drawing is known which, on the face of it, seems likely to be more reliable because it is associated with a report of an interview of M. FORTIN by investigators for the French Groupement d'Étude de Phénomènes Aériens (GEPA) published in Phénomènes Spatiaux . It also shows the carrot point-down (Fig. 10). But this re-interview was apparently done at least 10 and possibly as much as 13-14 years after event, and was reported with unsatisfactory brevity in an article which notably gets the date wrong and raises as many questions as it answers. Judging from the authors' account of their brief, the drawing appears to have been done by themselves or by the editor of Phénomènes Spatiaux, not by M. FORTIN, whose new account was in various respects inconsistent with the accounts attributed to himself and others in 1954. As argued in more detail later, we should perhaps be cautious in giving this source too much weight.
3.3. The "vapour trail"
The thread of "white smoke" which spiralled "exactly like a vapour trail" around the main cloud perhaps puts one in mind of rope-like cloudlets of water vapour that are sometimes seen swirling around the main condensation funnel of a tornado (see Fig. 11). Condensation funnels vary in density and opacity (some tornado vortices do not show condensation funnels at all). A downward and then upward motion of the vapour could perhaps be explained by a spiralling downdraft inside a semi-transparent funnel wall and a spiralling updraft outside.
It is true, however, that this type of effect is usually much more chaotic and turbulent, with scraps and shreds of cloud condensing and dissolving around the funnel. We have not been able to find a clear example of a "trail" of cloud extruded in the fashion described, nor one which "went on up, turning around, up to the very top of the vertical object, and then started to come down again, turning in the other direction", neither are we aware of any case where such cloud exhibited a distinctly brighter albedo ("white smoke") compared with the "blue-violet" cloud of the parent funnel .
Another possibility to consider is the "satellite tornadoes" which have been filmed and photographed on numerous occasions in the vicinity of large funnels But once again we have seen no film or photo of "satellites" which could be said to resemble the tight spiralling display described here. Satellites may form nearby but tend to move around the parent funnel at some distance . These would not be well described as "vapour trails" or "threads of white smoke", terms which along with the whiteness suggest something very different. We should also remember that this was not a mesocyclonic tornado spawned by a major storm supercell but (hypothetically) only a weak cold-air funnel cloud that did not develop. We have found no reference to satellite funnels associated with such events.
3.4. The "little metallic disc"
A further problematical factor is the separating and flying off of the object apparently seeding the "trail". This was described by one quoted witness whose description was reportedly confirmed by named others, but it was not described by the second directly-quoted witness, who remarked that nearby trees obscured her view below the object. The little reflective disc was seen "darting here and there" over a large area "in every direction over the region between St-Prouant and Sigournais, villages about 4 miles apart" then travelling straight in a 1-mile bee-line back into the base of the cloud, all this lasting "quite a few minutes".
There are many examples on video of debris lofted in the spiralling updrafts around a tornado funnel, sometimes catching sunlight and showing as white specks. But the reported extent and duration of motion would not be easy to explain in this way even in the case of a violent tornado, and as already pointed out there is no catalogue record of a tornado in France on this date. A weaker funnel cloud which did not develop to a touch-down would not be recorded as a true tornado, and might well not be recorded at all given evidence of significant under-reporting - plus the self-evident fact in this case that no-one observing it recognised it as a natural funnel cloud. But a weak funnel that stayed far above ground as described could not have lofted significant debris.
Another possibility is that this bright "flashing" object was ball lightning. Short-lived lightning balls have occasionally been reported inside, and emerging from, tornado funnels. But this example, as described, would be very unusual for ball lightning in any circumstances in terms of motion, appearance and duration, and even in a very violent tornado spawned by a supercell mesocyclone such a phenomenon would be remarkable. In the case of an immature cold-core funnel cloud of the type implied here it seems very implausible. Also the climbing of the object around the cloud could presumably not be explained by spiralling airflow if it were a lightning ball, as studies have found that observed ball lightning motion is independent of wind currents .
It seems conceivable that an object of small angular size "darting here and there" in the sky with intermittent "flashes" of brightness could be a sunlit bird, perhaps a white seabird driven far inland ahead of the storm. The reflectivity of sunlit white plumage can be surprising, especially contrasted against a backdrop of dark storm clouds. In ordinary circumstances such a mistake would be unlikely, although it's not unusual for UFO groups to receive photos of seagulls appearing as bright white dots against dark rainclouds. Perhaps the witnesses were primed by the mysterious appearance of the "carrot" to misconstrue a coincidental illusion .
Such a bird could have been relatively nearby, so its apparent emergence from the "white smoke" around the carrot would have been illusory, caused by an accidental line-of-sight coincidence peculiar to these witnesses . Evidence for this might be found in the fact that people in other locations did not see the little "disc". They generally offer plausible reasons for this - obscuration by farm buildings in one case, and by trees in another - but this might be thought excessively unlucky.
3.5. The cloud "hat"
According to one witness, Mme PIZOU:
It came near us, point downward, and then straightened up. It looked to me as if another, smaller, cloud then formed above the carrot, making a kind of hat for it.
This is as reported by MICHEL . According to the Nantes newspaper:
It had the shape of a carrot with a kind of hat above 
This "hat" of cloud is somewhat reminiscent of the wall cloud which is a strong feature of tornadogenesis from supercell mesocyclones. The wall cloud is a compact ring or cup of cloud that extrudes from the base of the main storm typically 10 or 20 minutes or more before the funnel forms. The funnel usually descends directly from one edge of the wall cloud, which in certain cases might resemble a "hat" on top.
There are two possible problems with this interpretation: (1) the weather conditions do not suggest this type of tornadogenesis from a storm supercell, and it is not clear to the present authors that a feature analogous to the wall cloud ever precedes the formation of cold-air funnels; (2) according to MICHEL's account the well-defined "carrot" had been observed approaching, then stopping and tilting to the vertical, before the cloud "hat" first developed (the newspaper account is not specific as to the sequence of events), but a wall cloud precedes development of a funnel.
3.6. The blue-violet luminosity
One of us has pointed out elsewhere  that the "luminous blue-violet mist" surrounding the object is reminiscent of several descriptions of nocturnal tornados either having a distinct bluish or blue-white appearance or having a blue aura around them . But we would caution that the accent here should be on the word "nocturnal". These rarely-reported and indeed controversial glow effects are not brilliant and it isn't clear to us that there exist any reports of daylight funnel luminosities in the same class as that reported at Saint-Prouant.
According to ALTSCHULER  "luminous tornado clouds with no funnels to the ground are possible causes of several UFO reports," although he offers no specific example or clear argumentation. He states that estimates from radio sferics and magnetometer measurements have indicated likely current flows of 400 amperes and total electrical power generated in the order of 1010 watts per tornado funnel, equivalent to about 20 lightning flashes per second, which would represent "without question, the most concentrated and powerful manifestations of atmospheric electricity" in nature. ALTSCHULER appears to suggest that glowing funnel clouds could occur due to near-continuous lightning flashes. However, these estimates apparently apply to mature supercell tornados rather than to weaker or immature cold-air funnel clouds of the type relevant at Saint-Prouant, and even so the existence of other than nocturnal cases of glowing tornados is doubtful.
ALTSCHULER quotes ten examples of spectacular tornado lighting reports, commenting that to a novice they would seem "more fantastic and incredible" than UFO reports. Again these are evidently cases of violent mature tornados, associated with many other features such as roaring, shrieking and hissing noise, thunder, lightning strikes, sulphurous smells, perceptible heat, fire and wind destruction, and it is not clear that any of these cases of luminosity occurred during daylight. None of them convincingly resembles the "blue-violet glow" illuminating a cloud deck in broad daylight, as allegedly reported. Whilst it was no doubt a grey and cloudy afternoon at Saint-Prouant under a low cloud deck, the sun was of course well up and sky brightness was still considerable . In the St-Prouant case no lightning-like flashes were reported at all. And no thunder was reported either, despite visual parallax evidence and localised distribution of observers tending to fix the phenomenon in the nearby atmosphere.
One study of lightning effects in a very violent Alabama tornado swarm found "few descriptions of lightning or other activity", the main reason being that most observations were made during daylight hours when even seeing brilliant lightning flashes in tornado funnels was "difficult". Some luminous phenomena were observed after dark .
As for the fainter nocturnal glow luminosities suggesting some type of discharge other than lightning which have sometimes been reported in the past, these are regarded by modern tornado experts with much scepticism. For example a recent study has shown that the signature of electrical phenomena other than that of associated lightning storms is apparently "quite weak" within tornadoes, allowing the possibility of detection by ULF radio but not suggesting significant optical emissions . And the eyewitness evidence is given scant credence.
A spectacular example of nocturnal light effects, including one report of an "electric blue" halo, is the destructive double-tornado that hit Toledo, Ohio, on the night of April 11, 1965 (see Fig. 14). Eleven separate reports of luminosities were collected by VONNEGUT and WEYER , some of them quite striking. It is instructive to look at the salient features side by side:
- a great wall of white (...) I could not see through the white;
- just like daylight;
- a white, blue and yellow light the size of a basketball;
- lights of different kinds of colours mixed up in the clouds;
- it turned white outside;
- streaks or arrows of lightning shooting straight ahead in the same direction the cloud was travelling;
- beautiful electric blue light around the tornado (...) balls of orange and lightning came from the cone;
- a surface glow - a general brightness for a few seconds;
- lights darting around in the clouds (...) round in shape;
- all around me, red flashing lights;
- all I could see was this huge reddish yellow light, making the remark; It looks like someone's house is on fire. That was the last I knew;
- a big hole opened in the sky with a mass of cherry red (...) about 1/4 mile long (...) like hot steel melting in a pot.
Notably, apart from the last two descriptions of a red glow made by separate witnesses near the end of the tornado track, which one witness thought was from a house on fire, almost no two witnesses seemed to describe the same type of lights. One of the 11 reports mentions a blue glow which puts one in mind of the Saint-Prouant object (even if this was at night). But only one. In general one is impressed by a lack of coherence in these various accounts of the same event.
According to a Wikipedia article  the present consensus, in spite of reports such as the above, is that true intrinsic luminosity associated with funnels, even in darkness, has probably never been observed. Convincing photographic evidence is lacking . The reported effects are regarded as being due to "misidentification of external light sources such as lightning, city lights, and power flashes from broken lines". Of course, a corollary is that if witnesses can misperceive various ordinary effects as tornado funnel luminosity, then so could witnesses at Saint-Prouant. However at Saint-Prouant the object was apparently far above the ground in a rural area in daylight with almost no sources of ground light, no lightning storm, fires, or power line damage .
On the other hand tornadoes and funnel clouds might sometimes appear luminous because of peculiar light conditions. The high reflectivity of the water drops in a funnel illuminated by the sun against background storm clouds in deep shadow can appear startlingly bright. Some of the photographs taken by Eric NGUYEN  illustrate this apparent radiance of funnel clouds beautifully. Such lighting conditions would also fit the theory that a sunlit bird explains the shiny disc. In our view this is probably the simplest explanation, and on that account might be thought the most likely. The striking detail of the "blue-violet" glow, also reflecting from the clouds - if accurately observed and reported - would be a problem. But it is not certain that this detail in a 1954 newspaper account of M. FORTIN's description is reliable. Other witness accounts do not mention it, and a later interview of FORTIN by GEPA investigators (whilst not itself without problems; see below) contradicts it.
 MICHEL, A., op. cit. p. 25.
 La Résistance De l'Ouest, September 20, 1954.
 It is worth noting that the contemporary newspaper drawing in France-Dimanche purporting to represent the object as seen by M. FORTIN (see Fig. 1) and another produced some years later following an interview with him (see Fig. 10) both show the point of the carrot facing towards the right. Since this would indicate the direction of reported travel, the drawings (assuming they are representative) offer the prospect of a check on the above inference that the object was moving W-E. They imply that the witness was looking roughly north. This bearing is nowhere specified. But M. FORTIN states that the emitted disc was observed travelling below the carrot "over the region between St-Prouant and Sigournais" (Sigournais is a few miles south of Saint-Prouant). If the range of bearings defined by lines of sight to these two locations from "La Gabeliére" brackets a northerly bearing then it would tend to confirm a west-east direction of travel. Unfortunately the lines of sight towards Sigournais and St-Prouant from the likely true location of La Gadbillère are on approximately opposite compass bearings roughly S and NNE respectively, so this is inconclusive with respect to the bearing of the "carrot" but not necessarily inconsistent with a N bearing from La Gadbillère.
 Amended text based on translation by Patrick GROSS.
 It may also be worth noting that a relatively nearby funnel cloud could appear to have a larger bottom diameter for observers underneath it because of perspective foreshortening, whilst observers further away might see it more nearly in profile with a narrower apparent bottom diameter. Different viewing positions would also affect the degree of apparent inclination of the funnel in the vertical plane. But such differences between locations would still not explain a rotational exchange of the "top" and "bottom" ends reported by observers from a single location.
 JAY, Dominique & METAYER, R.P., "Le 'cigare' de Saint-Prouant n'était-il qu'un nuage? Enquête rétrospective et Observation récente" in Phénomènes Spatiaux (GEPA), # 18 December 1968, pp. 26-29.
 Cloud reflectivity is inversely proportional to droplet size and proportional to droplet density. Usually the cloudlets outside the main funnel appear to be less dense than the funnel proper, so would tend to be less reflective.
 ALTSCHULER, Martin D., "Atmospheric Electricity & Plasma Interpretations of UFOs" in: GILMOR, D. (ed.) and CONDON, E.U., Scientific Study of Unidentified Flying Objects, Vision Press, London, 1970, pp. 723-755
 While contemplating a wonderful rainbow a couple of years ago, one of us (VAN UTRECHT) noticed some very bright spots darting around in the sky. Whilst it was soon clear to him that these were seagulls, a photographer who lived a few blocks away contacted him the next day asking him what the white lights were that he had seen (and photographed) moving close to the rainbow.
 But not necessarily. A sunlit bird against dark clouds can be seen from a considerable distance, and it is possible that a bird close to the funnel could have been especially visible from one direction because of the favourable angle for reflection of sunlight. There is some evidence of birds deliberately exploiting vortex updraughts. A 1992 article "On Galahs and Vortices" by McNAUGHT, Robert & GARRADO, Gordon in the journal of the Royal Australasian Ornithologists' Union discusses galahs flying in and out wind vortices: EMU, Vol. 92, pp. 248 -249; www.publish.csiro.au.
 MICHEL, A., Flying Saucers & The Straight Line Mystery (English edition, translation by Lex MEBANE), Criterion, 1958, pp. 23-6.
 La Résistance De l'Ouest, September 20, 1954.
 VAN UTRECHT's earlier article on the case published on the CAELESTIA site, but now replaced by this paper.
 VONNEGUT, B., and WEYER, J. R., "Luminous Phenomena in Nocturnal Tornadoes", Science, Vol. 153, September 9, 1966, pp. 1213-1220
 ALTSCHULER, Martin D., "Atmospheric Electricity & Plasma Interpretations of UFOs" in: GILMOR, D. (ed.) and CONDON, E.U., Scientific Study of Unidentified Flying Objects, Vision Press, London, 1970, pp. 723-755.
 Sun position for geographical coordinates 46°46'N; 0°58'W according to StarCalc (5.73 version): Sun at 1700 hr: Alt. = 22°33' and Az.= 249°26'. Sunset was still nearly 2½ hours away.
 VAUGHAN, O.H & VONNEGUT, B., "Luminous Electrical Phenomena Associated with Nocturnal Tornadoes in Huntsville, Ala., 3 April 1974", Bulletin of the American Meteorological Society, Vol. 57, No. 10, October 1976; journals.ametsoc.org
 LEEMAN, John R. and SCHMITTER, Ernst D., "Electric Signals Generated by Tornados", Atmospheric Research, Vol. 92, issue 2, April 2009, pp. 277-279.
 VONNEGUT, B., & WEYER, J. R., "Luminous Phenomena in Nocturnal Tornadoes", Science, Vol. 153, September 9, 1966, pp. 1213-1220.
 VONNEGUT & WEYER (1966; note 34) offer evidence in the form of faint streaks discovered on a single photograph obtained accidentally by one of the authors in the vicinity of the Toledo double-tornado described above.
 It is true that one of the witnesses, M. BONIFAIT, was an electrician who at the time was working on a "power line" of unspecified type and for unspecified reasons. But as mentioned no electrical storm activity or wind damage was reported by any witness, and it would be unsafe to conclude that what were evidently pre-existing reasons for M. BONIFAIT being called out could have had anything to do with the appearance of the object while he was engaged in repairs.