The Channel storm

On 19 June 1944, thirteen days after the Normandy landings, a powerful storm swept over the English Channel from the north-east. It blew for four days, until 22 June, straight onto the invasion beaches. It destroyed the American Mulberry A artificial harbour off Omaha Beach, damaged the British Mulberry B off Arromanches, threw hundreds of landing craft and other vessels ashore and for several days almost completely halted the unloading of supplies for the armies fighting inland.

It is often stressed that the storm destroyed one of the Allied Mulberry harbours in Normandy. That is true – the American harbour off Omaha was never rebuilt. The British harbour at Arromanches also suffered, but it could be repaired, and largely with components salvaged from the wreck of the American one.

Harbours of concrete and steel

From the start of invasion planning the Allies knew they would not capture a large French port straight away. Big supply ships needed deep water and quays with cranes, and the Germans defended the ports most strongly and were ready to destroy them. The preparations for the invasion therefore included building two artificial harbours, codenamed Mulberry, which were towed across the Channel in sections and assembled off the Normandy coast.

Each harbour consisted of several layers of protection. Furthest from the shore were moored the Bombardons – floating cruciform steel breakwaters meant to break the waves before they reached the harbour. Closer in, old ships (“corncobs”) were scuttled to form sheltered anchorages called “gooseberries”, together with huge reinforced-concrete Phoenix caissons displacing from about two to six thousand tons. Inside this shelter stood the Lobnitz (“Spud”) pierheads – floating unloading platforms that rose and fell with the tide on steel legs resting on the seabed. They were linked to the shore by floating Whale roadways on Beetle pontoons. Along these roadways lorries could drive straight from the ships to the beach, whatever the state of the tide.

The harbour components set out from England on the afternoon of 6 June. The first blockships were sunk as a breakwater on 7 June, the first Phoenix caisson off Omaha was placed on 9 June, and the shelter of sunken ships was complete on 11 June. On 16 June, according to the American official history (Roland G. Ruppenthal, Logistical Support of the Armies), the first vehicles and troops came ashore over the piers of the Omaha harbour. By 18 June two piers and four pierheads were working there. Mulberry A off Saint-Laurent-sur-Mer, commanded by Captain Augustus Dayton Clark, was almost finished, as was the British Mulberry B off Arromanches, which served Gold Beach.

Four days of storm

Early on the morning of 19 June the north-easterly wind strengthened. The rising sea soon stopped the DUKW amphibious trucks and the ferries working off both Omaha and Utah. Within a few hours the crews of the anti-aircraft guns had to abandon their positions on the Phoenix caissons of the outer breakwater off Omaha, because the waves were sweeping away the railings and shields. Spans of the piers began to break away from their mooring cables. Normal work in the harbour stopped, and nearly everyone turned to saving equipment and craft.

Towards evening the wind grew stronger still and began throwing dozens of landing craft onto the beach. Some ended up intact above the high-water mark and could not be refloated for many days; others were smashed against the sea wall at Utah or the shingle bank at Omaha. The harbour was battered not only by the sea but by helplessly tossing vessels crashing into the piers. On 20 June the eastern mooring cables parted and one of the piers began drifting west. All 24 Bombardons broke from their moorings – some struck the piers, some ended up on the beach, others threatened ships in the anchorage. On the morning of 21 June, according to Ruppenthal, of the 32 Phoenix caissons placed off Omaha only eight were still doing their job, and during the night the waves tore loose both pierheads and threw them onto the shallows.

The storm eased on 22 June, and on 23 June the amphibious trucks could work again. Omaha Beach then looked like a graveyard of equipment. Ruppenthal calculates that nearly a hundred LCVPs and LCMs and many larger craft were lost there, and of twenty Rhino ferries only one remained serviceable. Opposite a single beach exit alone lay eighty craft, including landing craft piled one on top of another. Mulberry A was lost – except for the sunken blockships, and even half of those had broken in two. The figure of about 800 craft stranded or damaged on all the beaches, often cited in the literature, is an estimate and covers mainly small landing craft.

It was, as is usually stated, the strongest June storm on that coast in forty years. Ruppenthal points out, however, that by ordinary measures it was not particularly violent: the wind reached 25–32 knots, no more than force 7 on the Beaufort scale. It was destructive because it blew from the north-east, straight onto the exposed beaches, for several days in a row, and the artificial harbours had been designed for summer weather. At the same time it was a warning that the Mulberries could not be relied on in winter.

Arromanches

The British harbour at Arromanches was luckier. As is usually explained, it was partly sheltered by the offshore Calvados rocks, and its caissons had been placed and anchored more carefully. The harbour was damaged – the waves damaged the breakwaters, piers and floating roadways, and some of the Bombardons also broke loose – but it remained usable. After the storm it was repaired and strengthened, largely with components salvaged from the ruins of the Omaha harbour. Known as Port Winston, it served the Allies much longer than intended: designed to last about three months, it operated for ten, and millions of tons of supplies, hundreds of thousands of vehicles and more than two million troops passed over its quays.

A supply crisis

The most dangerous effect was the near-total halt to unloading. On 19 June, when the storm was only beginning, the American engineer special brigades on the beaches still unloaded more than 8,300 tons of supplies and 3,000 vehicles, and about 17,750 men came ashore. On 20 June only 1,000 tons, 738 vehicles and 3,300 men were landed, on 21 June 1,000 tons, and on 22 June a mere 500. According to Ruppenthal’s figures, during the four days of the storm 12,253 tons of supplies were unloaded instead of the planned 64,100, 4,205 vehicles instead of 13,337 and 23,460 men instead of 77,081. The proportion of planned deliveries achieved fell from 72.8 per cent on 18 June to 57.4 per cent on 22 June.

Above all there was a shortage of ammunition. The American VII Corps had just cut across the Cotentin peninsula and was setting off north towards Cherbourg. The First Army restricted ammunition expenditure to a third of the daily allowance; for three days 500 tons a day of the most needed calibres were flown in, and several small ammunition ships were deliberately beached so that they could be unloaded at low tide – sometimes by cutting holes in their sides to get at the cargo. Ships in British ports were held back, because there was no way of unloading them on the other side of the Channel.

The storm also delayed the British offensive at Caen. General Bernard Law Montgomery intended to strike west of the city with the fresh VIII Corps, but the storm held back some of its units and ammunition in England. The attack, codenamed Operation Epsom, originally planned for 22 June, began only on 26 June. In the meantime the Germans were bringing more panzer divisions up to Caen, including II SS Panzer Corps, which was being transferred from the east.

Beaches instead of a harbour

The storm also taught an unexpected lesson. The brigades on the beaches had worked throughout: salvaging equipment, clearing lanes, building new transfer points and improving roads. When the wind dropped, unloading resumed faster than ever before. On 23 June Omaha Beach received 10,000 tons and Utah 6,400 tons – more than on any day before the storm. In the last week of June Omaha handled an average of 13,500 tons a day, 115 per cent of the plan, and Utah 7,000 tons, 124 per cent – without an artificial harbour, straight over the open beaches, onto which landing craft and LSTs were deliberately grounded so that at low tide they could be unloaded directly into lorries.

The commander of the Western Naval Task Force, Admiral Alan Kirk, who inspected the damage, judged that rebuilding Mulberry A would be pointless. On 24 June the naval commanders accepted his recommendation, and on 26 June General Dwight Eisenhower approved it. It was decided to reinforce the blockship shelter off Omaha with twelve additional hulks and to hand the surviving pier spans over to the British harbour. According to Ruppenthal, Eisenhower considered it fortunate that the storm had come early enough to serve as a warning, and counted on the swift capture of Cherbourg. The storm also showed how narrowly disaster had been avoided. Had Eisenhower in early June postponed the landing not by a day but until the next window of suitable tides, which fell on 18–20 June, the invasion fleet would have been off the French coast precisely during the storm.

Place in the war

The storm did not stop the invasion, but for several days it cut the armies ashore off from their base at a time when the Germans were bringing reinforcements into Normandy. The beachhead, which had been expanding inland since the liberation of Bayeux on 7 June, came through this period without significant loss of ground, and the shortfall in supplies was made up within a week. The price was delayed attacks and depleted ammunition stocks just before the assault on Cherbourg.

The most important lesson concerned ports. The storm proved that artificial harbours could not be relied on after the summer, and that far more could be moved over open beaches than the planners had thought. That made the capture of a real port all the more urgent. Cherbourg fell on 26 June, but German engineers had wrecked its quays so thoroughly that it began receiving its first ships only in mid-July and reached full capacity much later. The Americans therefore went on supplying themselves over Omaha and Utah beaches until the autumn, and the problem of ports – Cherbourg, the Breton ports and finally Antwerp – became one of the main constraints on the Allied offensive in the West until the winter of 1944.

Port Winston at Arromanches operated until 1945. Its remains – the Phoenix caissons visible in the sea off the town – are still there today and are among the most recognisable relics of the invasion. Off Omaha, little more remains of Mulberry A than memories and photographs of twisted piers from June 1944.