"June too soon, July standby, August come it must, September remember, October all over" - or is it?

The old mariner's rhyme must have been based on observation only. Back in those days when schooners and steam ships were state-of-the-art transport, it would have appeared as though October was the end of the Atlantic Hurricane Season - at least for Barbados - but in fact the season continues right through until November 30. So the rhyme should really read:

There are a number of factors ( such as surface pressure, sea surface temperature, wind speed and direction, location etc) which must come together in order for a tropical cyclone to form and strengthen. These would normally be present during the summer months when the Sun makes the atmosphere and ocean temperatures warmer than the rest of the year, creating the conditions for spawning tropical depressions, storms, and hurricanes.

Within that six-month period is a 60-day period (from August 15 to October 15) which is the peak of the season when conditions are ripe for cyclones to form. Cyclones can also form in any month of the year but the likelihood of formation is using between June to November while the extreme likelihood is August 15 to October 15 - under normal conditions. There are times when conditions are not normal such as during El Nino and La Nina.

The combination of all the right elements, together with historical records, is known as climatology. In simpler terms, this is the probability of where cyclones are likely to form and the direction that they are likely to move.

Sources:

• FAQ: Hurricanes, typhoons, and tropical cyclones
• The Weather Channel