Why are we having so many cyclones?
Lakshmi Kothaneth –
Nov. 1: Why are we having so many cyclones? El Nino is at play. The Multi Hazard Warning Centre at Public Authority for Civil Aviation is busy with weather forecasters drawing and analysing the path way of Chapala, the tropical cyclone which is losing its category status but is strong enough to ensure a downpour of 500 millimetre. The Socotra Island was bashed with wind and rain. Weather forecasters predict heavy rain for coastal towns of Dhofar today.
While the weather experts forecast Chapala’s movement, they are also monitoring another low pressure that is being developed in the Arabian Sea around south eastern side of India.
“Cyclones have their mind of their own,” said Suleiman al Jahdhami, Senior Weather Forecaster at Oman Meteorology. Explaining the chart he pointed out at another small point that is gathering up energy and has caught the attention of analysts.
These are the effects of El Nino.
“The secret of tropical cyclones is that you have to follow its route. We have to go by the flow. This low pressure area has already started in South Eastern Coast of India. It might develop into a cyclone or it might not. If it does become a cyclone, at the beginning it might give a complete different track but in the next few days the path might change. That is what happened with Chapala. It was initially projected to move toward north western direction and then later on, it went from north westerly to westerly direction. At the moment it is heading westerly direction as we see on the satellite image.”
According to Al Jahdhami the cyclone is the most severe part of the system unlike a low pressure system which one can predict — the direction and time. A cyclone has important features to consider such as the water temperature, air masses flow and the profile effect of the tropical cyclone. It is a combination of all these factors that are used by weather forecasters to predict its movement.
“We have to point the central position every three hours and according to the analysis we get the idea of its movement. Just a few km before it reaches land we can predict when exactly the impact would be,” pointed Al Jahdhami while explaining the complexities of tropical cyclones.
What make cyclones change directions?
The first reason that dictates direction is the temperature of the water, said Al Jahdhami, “The warmer the sea the higher the tropical cyclone is going to be. The logic of hot water and steam is the simple explanation. Arabian Sea is huge. The water temperature varies from place to place. We also have to consider what kind of weather system is dominating in the area at that moment.”
And this explains why Chapala did not come directly to Oman — “It did not come directly to Oman because we are at present being influenced by a huge high pressure area over our region and this high pressure area is dominating the lower to the upper levels. This has blocked the cyclone from coming directly towards us and that is why it is going westerly towards Yemen with indirect impact on coasts of Oman in the Dhofar region.”
The most important factor is that Chapala is a direct example of El Nino effect. “I do not remember in Oman ever having a tropical cyclone during October and November with all my 30 years as a weather forecaster. This is quite abnormal. Yemen has never had tropical cyclones during this period either with heavy rains, wind and waves as high as 7 metres. Total amount of rainfall expected is 500 mm which is quite a lot.”
From category 3 Chapala is expected to come down to category 1 and as the weather forecasters say whenever tropical cyclones hit land they dissipate because they get rid of all the moisture and the system dies down.
Chapala will eventually head to Saudi Arabia, explained weather forecaster Mohammed al Sheidhani, “What happens when it hits land is there will be heavy rains with thunder storms and flash floods but the disadvantage of the system is that when it hits land it weakens. It is the water that had strengthened it.”
On November 3rd, Chapala is predicted to reach Oman and Yemen border and eventually reach border of Saudi Arabia on the 4th of November when it is expected to end.