1. It all starts with the Monsoon
In the Maldives there are two seasons (monsoons). The first one is the Halhangu from May until the end of October and the second monsoon is the Iruvai from November to the end of April. In the Halhangu the wind blows from the south-west and the wind driven current comes from the west. As the wind arrives over the Indian ocean it is relative moist , which means more chance of rain. In the other season, the Iruvai the wind blows from the North-East, and the current comes from the east. Coming from India it brings relative dry wind which means mostly dry and more stable weather.
During the monsoon change in May, weather can be unpredictable and very rough, more about that in one of my other blogs coming up.
The monsoon driven current is the main current influencing the current in the Maldives.
2. Add some Tidal current
Now imagine a tsunami approaching a coastal line. You probably have seen disaster movies where something like this happens. The water is retracting towards the wave and the beach falls dry. In other words: if the wave (high tide) is approaching the water moves towards the wave and if the wave passes and it becomes low tide again we see the opposite effect and the water follows the direction of the wave.
If we translate this to our situation: the tidal wave comes in from the east so when the tide rises the tide induced current moves towards the wave so is running from the west and when the tide lowers, the tide induced current is running from the east.
Divers who have been diving in Europe know something about tides and know the tide heights change during the month depending with the moon phase. Two times a month it is spring tide, when the tide difference between high and low tide is very high. This is 2 days after new moon and 2 days after full moon when gravitational pull from sun and moon align.
In the Maldives the difference around spring tide (full & new moon) is about 90cm, around first or last quarter it is about 30cm. Current is corresponding. Tidal induced current is very strong around spring tide and very weak around first and last quarter.
3. Put the two current systems together: superposition !
Superposition is nothing more than addition of the two current systems.
Above: current when monsoon and tidal current line up. 4 knots, a great experience!
Lets start with the assumption we are in the Iruvai, the East monsoon with the current coming from the East. Upon that we can add the tide induced current. West-current when the tide comes up and East-current when the tide goes down.
From this we can deduct that in the East monsoon we have very strong current from the East when the tide goes down and little East (or maybe even West current) when the tide goes up.
From experience we know that around spring tide the current from the tide going up is strong enough to overcome the East current from the monsoon.
So we have East current all month long except the 3 or 4 days around full and new moon, when the current runs from the West 2 times a couple of hours a day when the tide comes up and the rest of the day we have East current and very strong East current when the tide goes down and monsoon and tide induced current allign.
This is something most guides in the Maldives do not understand. They expect the current to run from the East in the East monsoon and are surprised when sometimes the current runs from the West. They just go to the dive site and, when you’re lucky, they’ll check the current, but they cannot anticipate on what will happen the next days.
With the ability to predict what the current will be on a certain moment A knowledgeable guide can squeeze better dives out of the Maldives than others. This knowledge can make the difference between a great dive on a place that is not dived by others at that time or a crappy dive at a great dive site because of the wrong circumstances.
The above is all an approximation but gives you more foundation than most. When we have strong winds or storm (even when the storm is 500km away) or if the monsoon changes (in May & November) the tide tables can be totally inaccurate and predictions about current are very difficult.
We use our understanding of current and the way (big) fish behave to make sure our guests experience unforgettable dives. How? Read about it in my next blog!