O’ER WHICH THEY FLEW* By R. H. DOUGLAS

“0, iiever vales to moi tal vlcw Appeared like those o’er which they flew, That land to human spirits given, The lowrr~no<t valw of the \torled heaven : ”

-from K d k e n y ; Jamer Hogg.

The occasions are all too few, I fear, when the meteorologist is able to view the clouds from the vantage point of an aircraft in flight. The “ land-locked ” forecaster is apt to interpret cloud-forms in terms of what he sees from the ground, of what he remembers of the Cloud Atlas, or even of his impressions of the positive area on a tephigram ! These impressions are duly transferred to the cross-section-of-the-flight forecast, which is a cold scientific document and which allows for no speculation as to the attendant beauties of the cloud-forms.

The airline pilot, of course, has a much more intimate and three-dimensional viewpoint of the clouds, for so much of his time is spent in flying over, through, and around the cloud-masses. Few pilots, however, in reporting a flight, desrribe the clouds in anything but the most dry, laconic, and even profane terms !

How well I remember the one and only occasion when a pilot, newly arrived at Gander from Prestwick, gave a truly inspired report of an occlusion, encount- ered several hundred miles off the Irish coast a t sunset. I was extremely intercbted in this occlusion, and pressed him for a report of its characteristics and activity. The captain had the soul of a poet, and treated me to a detailed and artistic description of the tints and hues of the cloud-layers, glowing ruddily in the retting sun. To me, the purple line on my map became a living thing of beauty, thanks to a pilot who had eyes for more than his instrument panel.

My own experiences in flight have been somewhat barren of artistic delight. A grey undewast of stratus is hardly a thing of beauty, nor is an interminable flight through the drab sheets of cloud and rain of a warm front. So i t was with a great deal of pleasant anticipation that I boarded an aircraft of Trans-Canada Airlines, on the morning of 16 May, 1948, bountl for Hermiitla on a familiar- ization flight.

The synoptic situation that morning promised an interesting flight (see Fig. I ) . In particrilar, I was looking forward to an aerial view of the cold front which lay arros5 the track, and, having a keen interest in photography, I was fally-armed with ramera, film, ant1 a red filter, determined to bring back a coinplete photographic record of the cloud formations encountered in flight.

Off the field a t 1606 GM7’. we c4imbd to twelve thousand feet and headed for Boston. Skies were grey after last night’h storm, now centered over the Nova Scotia coast. Above was a drab veil of cirrostratus, and beneath us the mdercast broke occasionally to reveal fleeting patches of countryside. A t Boston, ascent was made to seventeen thousand feet, and just off the coast the lligh cloud vanished, leaving u s bathed in brilliant noontime sunshine.

+ by pt~rini~~io i i i ) i t l w ( ‘ i i i i t i o l h r 01 i h r . Vetwiologi(<d 8orvlc.e o f (’anadn

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WEATHER To face p . 298

A. Looking south-east from positi n A. Note the densest cloud formation to the riglit of centre I

PLATE I11

WEATHER SEPTEMBER 1949 Tofuce p. 299

-1. In the squall line

I

13. The Equal1 line from the south, position C PLATE I V THE SQUALL LINE

By 1800 GMT the cold front was visible, some 250 miles ahead. From northeast to southwest extended an unbroken band of towering cloud lying along the edge of the advancing cold air. "he grey bases seemed almost to rest upon the sea, while dazzling white tops stood hard and firm against the blue sky.

Ahead, the clouds towered to flight level ; to the south-west, tops appeared to be somewhat lower. The highest and densest part of the front was to the south-east. Plate 111 Ashows the view to the south-east, seen from position A

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Fig. 1. Synoptic situation, May 15 (see Fig. 1). The thickest cloud formation of the entire front is plainly visible. Although over most of the front; there was a thin veil of cirrostratus, over this portion, and conspicuous in the picture, the veil had thickened to a dense sheet of cloud. An hour later our aircraft skimmed over the tops of the frontal cloud- bank, while, to port, a dazzling white column of ournulonimbusloomed far above.

Now we had the most spectacular view of the front, looking south-west from position B and shown in Plate I11 B. Far to the south-west a long unbroken and clearly-marked band of cloud stretched below us. So sharp was the leading

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edge, so perfect the unbroken curve of cloud, that I could almcst see a smoothly- drawn blue line following the arc ! Here, in dramatic three-dimensional relief, stood the evidence of the freely-drawn curve on the weather-map, the cold front itself. The tops rose hard and firm, their near sides shadowed ; the bases were lost in the gloom of haze and shadow that covered the sea. The entire effect wns as majestic as only nature can achieve.

This striking spectacle was barely astern when another view presented itself ahead. A short distance away, another wall of cloud loomed, compared to which the front itself seemed a mere picket-fence ! Here was a treat indeed -not only a fine specimen of a cold front, but a first-class squall line as well. More wondrous sky-scapes awaited the lens.

This was literally a wall-an unbroken mass of heavy cumulus and cumu- lonimbus, of which the cliff-like sides were vertical and the anvil-tops flattened far above. As our aircraft approached, a small gap appeared dead ahead-a narrow canyon-over which the anvils merged to form a roof. Into this gloomy tunnel we flew (Plate IVA) and a moment later emerged into the brilliant sun- shine on the other side.

The view of the squall line from the south side was awe inspiring (Plate IVB, On the north side, the cloud had risen vertically,

The grey sides were streaked In the foreground, slim castellated towers of altocumulus reached A slight haze hung over the sea, for we were now well within the

With regret, we watched this spectacular formation fade into the distance

taken from position C). but on the south side the tops were overhanging. with virga. up below us. warm airmass.

astern, and an hour later we landed at Kindley Field, Bermuda.

During the small hours of the following morning the squall line, its vigour sadly depleted, moved past Bermuda, and a few hours later the cold front brought rain to the island. Sleeping soundly, I missed a golden opportunity to view from the ground those very clouds over which we had flown a few hours earlier.

An examination of the synoptic charts, made upon my return to Montreal, revealed an active wave development on the cold front a t 0030 GMT of the sixteenth, just six hours after the view shown in Plate I11 was photographed. The position was about thirty-seven degrees north, sixty-three degrees west (D in Fig. l), and was confirmed by a surface vessel a t that time. This wave continued to develop, and took its place with others in the central North At-. lantic. - Now I speculate. It appears possible, by ‘‘ backcasting ”, that the solid mass of cloud, so conspicuous in Plate IIIA, was associated with this wave during the hours of its birth. Is Plate IIIA then the photograph of the birth of that s tom, of the first successful counter attack of the warm air against the cold ‘I Perhaps the picture is simply of one or more well-developed cumulon- imbus, concentrated at that particular spot on the front. But I like to think that the most apt title for the plate would be “ Birth of a Storm ”.

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