Typhoon

• A Typhoon, also known as a Tropical Cyclone or Hurricane, is a low pressure rotating storm system.
• They occur mainly in the Indian Ocean and the South China Sea.

Description

• They develop over warm water, can have a diameter of between 60-1,240 miles (100-1100km) and are characterised by heavy rain and squalls with wind speeds between 64 – to over 140 knots.
• There are almost no Cyclones south of Latitude 5° North, and they usually lose strength when they pass over land.

Northern Indian Ocean

• Cyclones occur in the Northern Indian Ocean, east of the Horn of Africa and west of the Malay Peninsula.
• This area divides into two main Seas, the Arabian Sea up to Sri Lanka, and the Bay of Bengal from Sri Lanka to the Malay Peninsular.

Cyclone Season

• The Season varies, but usually operates between May to December, with the worst month for cyclones being November.
• The direction of a cyclone varies, but tends to develop in the Bay of Bengal, and then track North, Northwest or West, occasionally turning unexpectedly. The cyclone usually makes landfall in Eastern India and Bangladesh, but they occasionally track across the Arabian Sea to Somalia and Socotra.

During the Age of Sail

Going East

• Sailing ships used the South West Monsoon (May to September).
  • Aden to Sri Lanka, the Arabian Sea.
    • Sailing ships departed in July as there are no cyclones in the Arabian Sea during August.
    • They returned with the Northwest Monsoon in starting in October.
  • Sri Lanka to Singapore, the Bay of Bengal.
    • Sailing vessels had to leave Sri Lanka no later than early October to avoid the worst cyclone month of November. May or June being the best months to cross as cyclones are rare.
    • Calms can be encountered at any time of year.
    • In the event of encountering a cyclone, the vessel turned due south, as below Five Degrees Latitude North, there are no cyclones.
  • Singapore to Hong Kong, the South China Sea.
    • There is no safe month during the cyclone season of May to December. However, below the Five Degree Latitude North there are no cyclones. The best months to sail are May and June as destructive cyclones are rare. Sailing during January, February and March wa safe, but the vessel had to tack against the North Westerly Monsoon.

Going West

• In the reverse direction, going West, sailing vessels used the Northeast Monsoon (October to March).

The Indian Ocean and the South China Sea