Background on Typhoons in Viet Nam

The World Meteorological Organization (WMO) uses the generic term "tropical cyclone" to cover weather systems in which winds exceed "gale-force" (minimum of 34 knots or 63 kph).  Tropical cyclones are rotating, intense low-pressure systems of tropical oceanic origin.  "Hurricane-force" (63 knots or 117 km/h) winds mark the most severe type of tropical storm.  They are called hurricanes in the Caribbean, the United States, Central American and parts of the Pacific;  typhoons in the Northwest Pacific and East Asia;  severe cyclonic storms in the Bay of Bengal and severe tropical cyclones in the South Indian, South Pacific and Australian waters.  To facilitate identification and tracking, the storms are generally given alternating masculine and feminine names, or numbers which identify the year and annual sequence.
Tropical cyclones are the most destructive of seasonally recurring rapid onset natural hazards.  Between 80 to 100 tropical cyclones occur around the world each year.  Devastation by violent winds, torrential rainfall and accompanying phenomena including storm surges and floods can lead to massive community disruption.

In Vietnam, typhoons start hitting the north coast in May/June in the north, and generally, as the year proceeds, the typhoons move more to south until December when the typhoon season is over.