Suresh Boodhoo, former Director of the Meteorological Services
“It was extremely difficult to predict the heavy downpours we had on Saturday, because of the rapidity with which they occurred and their being confined to some areas”
“We cannot stop development but a careful revisiting of our existing activities and the impact of extreme weather events on them has to be undertaken”
In light of the flash floods of last Saturday, we have sought some clarifications from Mr Suresh Boodhoo, former Director of the Meteorological Services, especially in view of some criticisms levelled about these services. Mr Boodhoo explains various aspects of the science of weather forecasting, throwing much-needed light on the complexities of the science, as well as on the climatic phenomena which are involved in the genesis of the quasi-unpredictable phenomena that they are associated with. He gives illustrations in support of what he advances, and also advises caution in the interpretation and acceptance of inputs received from elsewhere. He gives an overview of the situation regarding equipment and pleads for optimising available local expertise and potential in the further development of the Met Services.
Mauritius Times: There is a perception, rightly or wrongly, that our Meteorological Services has not been to the mark during the last months in its meteorological readings? It would indeed appear that the Met Services would have been overtaken or at times caught unawares by local climatic conditions. What would you attribute that to? Human failure? Lack of support – both internally (due to inadequate equipment or breakdowns) and externally (from data provided by foreign met agencies)? Or is it all due to climate change?
Suresh Boodhoo: It is a fact that in any field of activity, you may be right a thousand times, but if you go wrong even once you are judged by this single error. Has there really been any error on the part of the Met Services (Mets)? I don’t think so. The atmosphere, where our weather system evolves, is very complex one. From the meteorological point of view, it extends from ground level to 40-50000 feet. Furthermore, Mauritius is located in an area where up to a height of 15-20000 feet weather systems from the east predominate whereas higher up it is systems from the west that predominate. The systems from the east, due to their shallow extent, give only slight rain and prevail in winter. On the other hand, those from the west are potentially more dangerous as regards rainfall. But the most dangerous situation arises when both systems coincide and become what is known technically as being ‘in phase’, which leads to a sort of funnel-like situation. This results in the worst of imaginable weather situations: from heavy downpours to water spots (at sea) or even tornadoes. However, and fortunately for us in Mauritius, tornadoes are extremely rare.
I must here strongly underline that forecasting of weather may be very difficult on small islands. Just think: a pen-dot on the forecaster’s chart represents 10 km! So it is very easy to find rain pouring at Réduit whereas in fact it should be lower down at Mount Ory! Moreover, in a situation where two systems are likely to get in phase, it is practically impossible to state the time, place and extent of that phasing in. This was the reality of the situation on Saturday last. Over continents such movements of systems and their occurrences can be followed with a greater degree of accuracy as there is much more information from land stations and observations made either by humans or automatic stations.
Under such circumstances one cannot rely on conclusions coming from elsewhere unless one is convinced of their unfailing reliability. Having worked for several decades, and being in constant touch with these services, at the Mets we are in a position to judge who is capable of what.
* What’s your reading of the climatic conditions which prevailed here since the morning of Thursday 28 March 2013 to Saturday 30 March 13?
From the weather bulletins of the previous Thursday, it is seen that the Mets alluded to unstable atmospheric conditions and to a wet Easter weekend. However, as the system took time to show up, the language was toned down on the next day. But on Saturday morning we again heard about rainy conditions, mostly on the high grounds than elsewhere.
But it was extremely difficult to predict the heavy downpours we had on Saturday, because of the rapidity with which they occurred and their being confined to some areas; in a way one can say fortunately for the island – otherwise one cannot imagine the extent of the havoc that might have resulted. But mind you such an occurrence is not a first timer. Unfortunately this time round, the physical features of the land where the rain fell magnified the effect and increased several-fold the severity of its impact.
* In his reply to last Tuesday’s PNQ, the Prime Minister stated that the “Meteorological Services detected a zone of instability since Thursday 28 March 2013 in the morning (…) This situation, the Met Services predicted, would coincide with a jet stream, thus intensifying the instability. But, it was difficult according to them, to predict the timing and the precise location of the incident. On Saturday 30 March 2013, at 04.30 hours the Met Services predicted the persistence of unstable atmospheric conditions with heavy showers on the Central Plateau, in the East and South. However, in the early afternoon, a sudden outbreak of heavy showers caused massive local flooding in a limited area. (…) Meteo Reunion went on vigilance in its bulletin of Saturday 30 March 2013 at 06.56 hours when the island was already under the influence of the heavy rains.” Does this mean that Meteo Reunion had been smarter than ours by going on ‘vigilance’ when we had nothing of the sort over here?
The analysis of the cause of the downpour is correct. I must also add that a jet stream is an area where the wind may be blowing at a speed of over 100km/hr and up to 500+km/hr. It is an area where air is forced to rise, which is the key ingredient allowing atmospheric instability to form at the surface. In its wake it sucks air from all sides. It is just like the draught created on pavements by a fast moving car. The jet stream while sucking air from below enhances cloud formation. The whole process is exacerbated if there is already instability at low level. The time and point of the phasing in of all the parameters is very difficult to predict. Which explains why the phenomenon lasts for a little while only.
As for the forecast of our Meteo Reunion, it went correct this time. I stress on “this time” for during the past few weeks I noted at least two other advisories of “vigilance”, one in respect of heavy rains and the other in respect of thunderstorms. None of these materialised. This illustrates the complexity of weather forecasting and the danger for us to take advice from outside at their face value.
Besides, and as far as I can recollect, only one station up in the mountains of the SE of La Reunion received 400mm of rain. There was much less elsewhere in the island, which explains the limited damage there.
* The PM also stated that “the facts and figures concerning the quantity, intensity and suddenness of the Saturday last heavy rains no doubt testify to the fact that we are indeed the victim of flash floods on that day.” Is this a correct and comprehensive assessment of what actually happened?
Yes, it was a flash flood that we had. This is a phenomenon which is very difficult to predict. This is why the word ‘flash’ has been utilised. During all the years that I was involved with WMO, there has been much debate about devising the proper system for forecasting flash floods especially in small islands. Let me here digress a bit by stating that this difficulty should not be a stumbling block for us and for our technicians to work on some mechanism that may sometime in the future help us avoid calamities. Why cannot Mauritius devise its own system of defence? Do we need foreign consultants to do this for us?
* What do past data regarding rainfall and flash floods in Mauritius tell you with respect to what we experienced on Saturday last?
There have been several events of heavy downpours of similar intensity. During most of the cyclones we have experienced larger volumes of water all around us flooding houses and fields and industries. Gervaise in 1975 poured more that 400mm in a single day. More recently, cyclone Dina in Jan 2002 gave us more that 300mm in a day. And most of us should remember cyclone Gamede in Feb 2007, which although it had stayed in the vicinity of St Brandon, kept us drenched for more than two days with more that 500mm of rain. But let us look down memory lane to recall Hyacinthe and Jacinthe in January and February 1980 respectively when for two weeks Mauritius was under water! But in spite of that we did not and fortunately so, have the consequences we have just experienced. What we saw last Saturday may reflect some dark sides of our development and point to some areas which may require particular consideration, for example the capacity of our drains and their adequacy among other things.
* Does the topography of certain regions of Mauritius, like Port Louis, Flacq, the northern region, etc., imply that they are more prone to the occurrence of flash floods?
The topography definitely exacerbates the impact that a torrent can cause. Water, or any moving body, will gain momentum while on a downhill track. When rocks and mud join in, the result is even more disastrous. On Saturday the flash flood that occurred is a clear demonstration of this phenomenon.
But it’s not only the sloping part of the island that is at stake during such events. We remember March 2008 in Mon Gout. We have had other instances and locations of flooding: Flacq, the south and the centre. I would say the whole of Mauritius is flood prone although some places may be more at risk than others. We certainly need to take a fresh look at our infrastructure. We cannot stop development but a careful revisiting of our existing activities and the impact of extreme weather events on them has to be undertaken.
* There seems to be some confusion regarding the warning protocol adopted by our Met Services. There have been instances when warnings had been issued and communicated to the public after school children and private/public sector employees had already left home for school or for the workplace. One Met Officer even stated after the tragedy of Saturday last that there was no requirement to issue a Notice of Torrential Rain on that day as it was not a weekday working day. Doesn’t all this call for a review of the warning system in place at our Met Office?
Unfortunately, this is the perception. Torrential rain warning was in fact designed specifically for schools. Allow me to quote from the scheme: ‘As soon as climatic conditions prevailing over Mauritius or Rodrigues produced 100 mm of widespread rains in less than 12 hours and that this heavy rain is likely to continue for several hours, the Meteorological Services will advise the Ministry of Education, Culture and Human Resources and issue warnings at regular intervals through the MBC, private radio stations and the Police to keep the public informed of the situation.’
The protocol so far is clear. Schools are closed or will not convene if the warning is issued before school starts. There is no provision intended for the other sectors. For example, what will happen to the public and private sectors, to enterprises? Will they shut down too? Probably a new protocol will need to be devised. But one has to be very careful while doing so. Torrential rain may be localised and may occur several times a year. But given the mobility of Mauritians, one has to tread carefully while devising such a new warning system which may be badly needed. As an example, let’s take a scenario whereby the centre of the island is to go under a torrential rain warning on a particular working or school day. What will a person from the south of the island do if he/she has to go to work in Port Louis?
* The question of climate change is now very much on the agenda. But the extent of climatic changes, which would have occurred and is still on, is subject to debate in the scientific world. There is no doubt that Mauritius has not been spared by climate change, but can we measure the extent to which our climate in Mauritius has indeed been affected?
The question of whether we have climate change or not is no longer debated. It is a fact that climate has been changing, with nefarious consequences to the planet and its inhabitants. There are only a few sceptics worldwide who, for personal or corporate reasons, want us to believe otherwise. If we recall the inaugural speech of President Obama at the beginning of this year, we will see his intention of addressing climate change. So let there be no doubt that the climate has been changing. In a report published in 2008 by the Mets, it was clearly pointed out that during the past 50 years, the average temperature in the island has increased by about one degree and that during the same period the amount of rainfall has decreased by between 8 to 10 per cent. The report further went on to stress on the increasing duration of the dry intermediate period from winter to summer. This period used to last through September and October. At present it extends to mid-December. The report also highlighted the phenomenon of more intense rain. I remember that Hon Lomesh Bundhoo, who was Minister of Environment and NDU at that time, rang me to request for more detailed information, following which he requested for funds to launch his project of improvement in the storm-water drainage system.
Even if the one-degree increase of temperature may sound little, we must understand that during summer this increase may manifest itself more harshly that during the cooler months. One may recall that during this summer it was not unusual to hear about maximum temperatures reaching 34 degrees in Port Louis, whereas 10-15 years ago maximum temperatures used to be around 31 degrees!
Furthermore, the Inter-Governmental Panel on Climate Change (IPCC), which is the world authority in matters of Climate Change (CC), indicated years back that climate change is likely to manifest itself, inter-alia, through weather events, i.e. either dry place turning drier, wet places turning wetter and hot become hotter and so on. This is what we have been experiencing over the years. Only some ten years ago we had to rely on cyclones to replenish our reservoirs. Since 2002 and except for a couple of years since we did not have the direct effect of cyclones. Yet we managed with the water supply. Furthermore, the same IPCC indicated that it is likely that some regions (including ours) will experience patterns of rainfall of higher intensities although the global amount is likely to be less than decades earlier.
In 2009, if my memory serves me right, four episodes of heavy rain other than cyclones helped our reservoirs to fill up. The temperature rise, reduction in rainfall amount and changes in rainfall patterns are clear signs of climate change.
* If Mauritius will also not be spared by climate change — whatever its extent – does this fact of climate change in itself call for a review of the protocols put in place and the methodology used in relation to weather forecasting and public warning systems?
Yes definitely, these practices will have to change. But there is much more. We will have to change many of the norms and habits: engineers and architects will need to consider new thresholds for designs of buildings (higher winds, more intense rainfall episodes), farmers will need to adapt their crop varieties towards those that are resistant to higher temperature, drier climates and new pests which may proliferate in warmer temperatures.
Our houses will need to be more climate friendly, our environment will require more meticulous safeguarding if we are to stay healthy. The health authorities will need to be more vigilant as more pests and diseases are expected to take advantage of ideal, for them, conditions. The water sector must be ready to cater for more frequent and longer dry spells. Every single sector will be impacted upon and in most cases, negatively rather than positively.
* Would you be in a position to affirm that our Mets are appropriately equipped in terms of equipment availability and know-how and that we can rely on inputs provided by better equipped Met Services of other countries for local weather forecasting purposes, especially in view of the new climatic environment unfolding before us? In other words, has the service been improving in terms of precise weather forecasting in keeping with demands of new weather patterns?
The Mets has the basic equipment for monitoring of weather elements and producing forecasts. It can access the satellites of the latest generation, has good connectivity with world centres such as Washington, UK, Toulouse and the others. It should be able to produce a route forecast from Mauritius to any airport in Europe for planes flying these routes. And up to now there have been no complaints from airlines which access the services of the Mets. Probably Met services the world over have a privileged connectivity with each other since the setting up of the World Meteorological Organisation in 1949, antedating by far the advent of the electronic and internet era. This grid of connection has dedicated routes via satellites (presently); earlier there used to be other means (Morse, radio, telegraph).
There has been much improvement in practices at the Mets. However as said earlier there are so many changes as a result of climate change, for example the forecaster of the day needs to be more vigilant and alert and to constantly keep abreast of new findings.
Moreover, I strongly feel that there is urgency for the Mets to be equipped with a modern weather radar. This is an important tool though not an end in itself. Doppler radars (all jetliners, ships must imperatively be equipped with such a radar) allow the detection of not only cloud formation visible to the eye, but can also detect the rising or subsiding motion of the air. These motions respectively indicate cloud formation or their decay. Cloud formations, if they are significant, indicate likelihood of rainfall. If these formations are on site we may have 3 hours or so to predict the resulting event. If these formations are kms away (the radar can see within a radius of 400km) we have many more hours to monitor the movement and provide adequate advisories.
This reminds me of 23rd December 1979 when we forecasters had just been trained to use our brand new weather radar at Trou-aux-Cerfs, and we utilised our newly acquired skill to exactly predict the path and time of landfall of cyclone Claudette. It had, as predicted, touched land at Cap Malheureux at midnight and left Souillac at six the next morning. Warnings, from all aspects, were accurate and timely. As it was my first experience with a radar I took much pleasure in carefully analysing the structure of the inside of the cyclone; such equipment allows us to see weather systems in 3-D.There have been several other success stories thanks to that dear old radar. Modern radars offer more sophisticated possibilities.
* If we ascribe everything to uncontrollable factors such as ‘climate change’, would that not abstract from the necessary extra efforts one needs to make to ward off loss of lives as occurred during the last weekend? Does one have to give those incidents a broader reading, including the avoidance of contributory negligence by way of having inefficient water evacuation systems?
Climate change is here to, like it or not, render our lives more miserable. We have become more vulnerable as a result. But we should not throw all the blame on CC and adopt a complacent attitude. We have to learn from our mistakes and fast track our responses to meet future challenges, and avoid loss of human lives. I believe that decisions should be taken with a cool mind, without trying to find culprits when these do not exist.
We need to take a fresh look at all our bridges and waterways, keep the river reserves free of obstacles and illegal constructions (for these get washed away during floods), redesign our drainage systems to adapt them to higher intensities of rain and peak flows. But in order to do all these and more, government should assemble all the brains of the country and start work immediately.
* Published in print edition on 5 April 2013