graduate

Tropical Cyclones

Satellite photograph of tropical cyclone

NOAO

Tropical cyclones, known as typhoons in the Far East and as hurricanes in the Western Hemisphere, are probably the most destructive storms on earth. They begin as disturbances near the Intertropical Convergence that move away from the equator and begin spinning under the influence of the Earth's rotation. If the disturbance is over very warm waters, and if other conditions are just right (and not all the necessary conditions are understood, even today) then the disturbance creates the right conditions for the rapid rising and cooling of the warm air over the ocean, driven by the heat released by the condensation of the ample moisture in the air. More warm, moist air flows into the storm, which becomes a powerful heat engine, up to three hundred miles across, which converts the energy of the warm ocean waters into violent winds and torrential rain. A central eye forms, in which there is no precipitation and only light winds, which is surrounded by a wall cloud in which winds can exceed 160 miles per hour (260 km/h). The force of the winds pulls the ocean surface into the storm, producing a storm surge that combines with the rain and wind to produce flooding.

Map of cyclone tracks showing breeding grounds

Wikipedia

There are six breeding grounds for tropical cyclones around the world. Five are relevant to the Pacific War. The first is the eastern Pacific off the coast of Mexico. The typhoons formed here tend to drift west and die out over open water, but they pose some hazard to shipping coming through the Panama Canal, and occasionally one will drift north and east and threaten Mexico. The second breeding ground is in the waters along northern Australia through the Solomons to Polynesia. The storms formed here drift east and south, sometimes threatening the South Seas islands or the north coast of Australia. The third breeding ground, and the largest in the world, is the west Pacific around the Philippines. Many typhoons are spawned here every year, and they proved to be a great hazard during the Pacific War. The fourth breeding ground is the south Indian Ocean, and the storms that form here tend to drift south and die out over open water far from shipping lanes. The fifth and smallest breeding ground is the Bay of Bengal; though few storms form here, those that do are among the most deadly, because they tend to drift north and bring catastrophic flooding to the shallow delta of the Ganges and Brahmaputra Rivers. The sixth breeding ground is in the Atlantic west of Africa and does not concern us here.

Tropical Storms and War

Because of the great importance of weather to the conduct of the war, both sides took pains to gather as much weather information as possible. It was during the Pacific War that a U.S. Navy Avenger became the first aircraft to deliberately fly into a tropical storm with a meteorologist on board. Submarines regularly reported weather information from ocean areas inaccessible to conventional reconnaissance. But cyclone detection and track prediction remained primitive, and tropical cyclones could spring a most unpleasant surprise on a military commander. 3 Fleet under Halsey twice blundered into the path of typhoons (on 18 December 1944 and 5 June 1945), and Yamamoto's successor, Koga, was lost when his plane went down in a typhoon off the Philippines.

The typhoon of 18 December 1944 illustrates the threat posed by these storms. The typhoon struck as 3 Fleet (seven fleet carriers; six light carriers; eight battleships; 15 cruisers; and 50 destroyers) and its replenishment group (12 fleet oilers, three fleet tugs, five destroyers, ten destroyer escorts, and five escort carriers) rendezvoused for refueling on the morning of 17 December in the eastern Philippine Sea. A 25 knot (45 km/h) trade wind slowed refueling, but there was no particular indication of any oncoming storm. The rapid advance of the Allies meant that the area was not yet well covered by weather stations, and reconnaissance aircraft tended to avoid poor weather and to delay reporting weather conditions until they landed. This left the fleet vulnerableto a small, rapidly intensifying storm, which is exactly what happened.

The 3 Fleet meteorologist estimated on the afternoon of 17 December that there was a weather disturbance 450 miles (720 km) east of the Fleet, too far out to be of immediate concern, and the worsening sea conditions were attributed to the brisk trade wind. Halsey ordered his fleet to steer northwest to an alternate refueling rendezvous that he though would take the fleet away from the disturbance. In fact, the "disturbance" was a small but powerful tropical cyclone that had rapidly intensified and was now just 120 miles (200 km) southeast of 3 Fleet.  As the weather continued to worsen, Halsey changed course two more times, but the final course took part of 3 Fleet directly into the storm's path. By 0400 on 18 December weather conditions were becoming alarming, but the barometer held steady, leading Halsey and his weather officer to believe that conditions were not that bad. At 1000 the barometer began rapidly falling, and the seas had become "mountainous" by 1130. The eye of the storm could now be seen on SG radar. At 1345 Halsey finally issued a typhoon warning.

The battleships and fleet carriers rode the storm out reasonably well, the latter losing no aircraft. The light carriers fared much worse, and many of their aircraft tore loose from their lashings and were washed overboard or crashed into each other and burst into flames. Monterey and Cowpens caught fire from burning aircraft, though the fires were quickly brought under control. A total of 146 aircraft were lost or had to be jettisoned. Light cruiser Miami was also damaged. However, it was the destroyers that suffered worst. A number of destroyer commanders had refrained from ballasting partially empty fuel tanks in anticipation of refueling, which reduced their ships' stability, and when the typhoon hit there was not enough time to ballast. Hull, which was at 70% fuel capacity and had not ballasted, was capsized by a 110 knot (126 mph) gust. Monaghan suffered a similar fate. Both were Farragut-class destroyers whose design was notoriously top heavy, but Fletcher-class destroyer Spence also capsized, in spite of its more stable design. Three other destroyers barely escaped the storm. The destroyer escorts, whose design had been criticized by the British for being too stable, fared better than the fleet destroyers. In addition to the three destroyers and nearly 800 sailors lost, seven other ships were seriously damaged. Nimitz described this as the largest uncompensated loss to the Navy since Savo Island.

As a result of the typhoon, the Americans hastened to establish more weather stations throughout the area, and weather reconnaissance flights became more frequent and regular. Three PCEs were converted to weather ships to operate in the breeding ground of the Philippine Sea.

Halsey was unlucky. During the opening moves of the Okinawa campaign, Turner ordered an LST force to continue on to Okinawa in spite of a typhoon forecast. Unlike Halsey, Turner got away with it: The LSTs encountered no storm core and just managed  to make their operational schedule.


Photograph of Pittsburgh with bow torn away

U.S. Navy. Via Morison (1959).

Photograph of Attu with wrecked aircraft on flight deck

U.S. Navy. Via Wikimedia Commons

Halsey tangled with a second typhoon on 5 June 1945. This storm formed around 1 June north of Palau and was being tracked on 4 June as Halsey refueled. The exact position of the storm remained uncertain until 2200 June 4 when Ancon got a radar bearing on its center. This gave the storm a speed of 26 knots (30 mph or 48 km/h) which Halsey simply refused to believe. As with the earlier storm, Halsey misjudged its course and sailed part of his fleet directly into the path of the storm. Pittsburgh had her bow torn off, but because the crew were at battle stations, there were no men in the forward berths and no loss of life. The bow remained afloat and was eventually towed to Guam. Two other cruisers, a destroyer, and four carriers suffered less serious damage, and six sailors and 76 aircraft were lost,

Halsey's second blunder into the path of a typhoon nearly ended his career. The court of inquiry recommended that "'serious consideration' be given to assigning Admirals Halsey and McCain 'to other duty'" (Morison 1959). Secretary of the Navy Forrestal wanted Halsey retired but relented after being persuaded that this would boost Japanese morale.

References

Morison (1959)

Typhoons and Hurricanes: The Effects of Cyclonic Winds on Naval Operations (accessed 2008-1-11)



Valid HTML 4.01 Transitional
Web Site Counters