As can be calculated by counting up the alphabet to M, Michelle is the 13th Atlantic hurricane this year. Coincidentally, the storm of this kind most vividly remembered from the recent past was also the 13th of its season, and was at the peak of its destructive powers very near to this date three years ago.
Hurricane Mitch caused havoc in Honduras and its associated floods and mudslides were responsible for at least 10,000 deaths as October-November 1998.
Loss of life from hurricanes on such a scale is nowadays unusual. Better tracking and forecasting techniques normally allow vulnerable areas to be evacuated in good time, as has been the case in recent days with Hurricane Michelle in Cuba. Damage to property, however, is often catastrophic.
Hurricanes form in the humid low latitudes of the Atlantic, between 5 and 15 degrees north, and typically move westwards for a time towards the Caribbean or the southern United States before turning north-eastwards.
As it moves farther north into a cooler environment or over land where its plentiful supply of moisture is cut off, a hurricane gradually loses energy and dissipates.
Apart from the obvious effects of very strong winds, the worst consequences of a hurricane are the result of what is often called a "tidal wave", but which is more properly referred to as a storm surge. Hurricane-force winds over the open ocean bring wind-generated waves of quite spectacular heights.
The swell produced in this way propagates tangentially outwards from the storm in all directions; but whereas a hurricane typically advances 500 miles in 24 hours, these storm-generated waves propagate much faster and may cover 800 miles in a single day.
Before satellites and aircraft, the arrival of this massive swell was often the only warning for coastal dwellers of a hurricane.
The surge, a large and sudden rise in sea level, occurs as the "eye" of the storm approaches land. It is produced by a combination of the very low atmospheric pressure near the centre of the hurricane and the very strong winds which tend to "pile up " sea water against a coastline.
The height of the surge depends on tides, the shape of the coastline and sea bed and several other factors, but typically a raised "dome" of water 10 to 15 feet above the normal tide level, and 40 to 50 miles across, might be expected, with the potential to cause flooding and loss of life on a massive scale.