Why The Hurricane Season Starts TodayAdded : Saturday at 14:30 June 1st is an important date for meteorologists. First of all it's the start of meteorological Summer in the Northern Hemisphere, but it's also the date at which the Atlantic Hurricane Season starts. Of course, hurricanes and tropical storms can develop much earlier and also later than this (the season ends on November 30).
The reason why this period is crucial though is down to the movement of the ITCZ or Inter Tropical Convergence Zone.
If you take a look at the rainfall forecasts for the mid Atlantic, you can see the storms off the East coast of Africa and stretching West towards the Northeast tip of South America :-
You can see the band of storms around the world where the sun is directly overhead up well on the satellite image :-
By the time we get to the end of June, the ITCZ is as its most Northern limit across Africa :-
This is important in terms of hurricane development. It's these storms which are the nucleus of most developing tropical storms and hurricanes. A tropical wave develops which then moves offshore into the Atlantic and with sea temperatures above 27c you have the fuel for development.
The other crucial factor is that the storms must be North of 9 degrees latitude in order for rotation to take place. This force, the Coriolis force increases from the equator to the poles and it's why hurricanes don't form near the equator. When the ITCZ moves between the sweet line of 9-19 degrees North then we have the ingredients of thunderstorms, rotation, warm sea surfaces and low upper level wind shear which aids the development of tropical storms.
So, there you have it, why the Atlantic Hurricane Season runs from June to November and it's all down to the position of the ITCZ.
METEOROLOGIST : MARSH |