SWIFT Team Reports on Cyclone Idai

Report prepared by:

From the University of Leeds: Beth Woodhams, Hellen Msemo, Declan Finney, Sam Hardy, Emmanuel Likoya

From the Kenya Meteorological Department: David Koros

Described by the World Meteorological Organization (WMO) as one of the ‘worst weather-related disasters to ever hit the southern hemisphere’, Cyclone Idai caused devastation over south eastern Africa during the first two weeks of March 2019. Mozambique, Malawi and Zimbabwe were the worst-hit countries, with almost 3 million people estimated to have been affected.

Figure: 500 mb geopotential height anomaly during Cyclone Idai, made using images from http://www.atmos.albany.edu/student/abentley/realtime/anom.php

Idai began as a cluster of thunderstorms just off the Mozambique coast. This cluster, with associated wind speeds of ~35 mph, was designated as a ‘tropical depression’ on 4 March. Initially, the system moved northward, weakening to a ‘low pressure system’ as it moved over Mozambique and into southern Malawi. Between 7 and 8 March, the track of the low pressure system looped and curved back toward the east, guided by the steering flow around a near-equatorial ridge to the north. During this time, southern Malawi was particularly affected by heavy rains. The associated flooding caused the President of Malawi to declare a state of disaster.

As the system moved back into the Mozambique channel, low vertical wind shear and high sea surface temperatures (exceeding 30°C) caused it to re-intensify. The system was designated as a cyclone and named Idai at 23Z on 9 March, with wind speeds of ~75mph (equivalent to category 1 on Saffir-Simpson scale).

By 11 March, the near-equatorial ridge to the north had weakened and a subtropical ridge was strengthening to the south-west, causing the cyclone to change direction toward the south west. During this time, Idai strengthened to an equivalent category 2 cyclone. On 12 March, the cyclone underwent an eyewall replacement cycle which temporarily weakened it back to a category 1 storm. Still under the influence of the subtropical ridge, Idai’s track became more westward during 13-14 March and the system strengthened to an equivalent category 3 cyclone, with wind speeds around 125 mph.

Idai made landfall in Beira, Mozambique late on 14 March. Although wind speeds weakened during 15 March as the cyclone moved inland, the remains of the circulation persisted, causing heavy rains in Mozambique, Zimbabwe and Malawi (which was still recovering from the previous flooding).

Cyclone Idai was forecast well in advance, with prediction by the Météo-France La Réunion office that a ‘mature, high-intensity, system’ would make landfall over Mozambique during 14-15 March at least 4 days in advance. During the formation and lifetime of the system, the MJO was in phases 3-4, initially with relatively high amplitude. Klotzbach (2014) have showed that these phases are associated with increased cyclone activity close to eastern Africa in the Indian Ocean.

In addition to heavy rain and flooding in the south, Idai affected countries further north by delaying the onset of the long rains. In Kenya and Tanzania, dry conditions prevailed as moisture influx into the countries was reduced. This delay was not anticipated in the initial seasonal forecast, which predicted a timely onset of the rains. However, both Kenya Meteorological Department and Tanzania Meteorological Agency issued updates to their seasonal outlook to reflect the effect of Idai.

The impact of Idai has been wide-ranging and long-lasting. Whilst it was well-forecast by models and information and warnings generally appear to have been issued, it is unclear whether appropriate actions were taken by organizations working on the disaster risk reduction and the general public.

The GCRF African-SWIFT project aims to increase public trust of weather forecasts by working with meteorologists and decision-makers in the region to improve the communication of severe weather events. The project will also improve methods for forecasting a range of other weather systems in Africa, including storms, squalls and droughts and which are often predicted very badly, in comparison to the relatively good forecasts of Idai.

References

SWIFT Stakeholder Workshop on Climate and Weather Information Services takes place in Nigeria

This week African SWIFT holds its Stakeholder Workshop in Abuja, Nigeria. The central theme of the workshop is, “how to support users’ understanding of weather forecast and services in Nigeria”. The 2-day workshop (26-27 March) is hosted by SWIFT partners, the Nigerian Meteorological Agency, National Weather and Climate Research Centre (NiMet), and organised in collaboration with the Federal University of Technology, Akure (FUTA). The workshop provides an excellent opportunity for both forecast users from numerous economic sectors across Nigeria, and SWIFT operational forecasters and researchers to meet and discuss weather information services and to strengthen partnerships.

The workshop will identify which weather events have the greatest impact on decision-making within each sector; assess how forecast information and its delivery might be improved; and identify communication pathways and early warning systems currently in operation between users and forecasters, and agree how best practice can be identified and shared. Stakeholders from key sectors including Disaster Risk Reduction, Agriculture, Fisheries, Water, Construction and Health are taking part in the discussions. Important questions being addressed by stakeholders include, how well is current forecasting information understood and trusted within their sector; is the level of forecast uncertainty associated with a particular forecasting tool clear to users; and where and how improvements can be made. The workshop is paying particular attention to impact-based weather forecasting and warnings, with the aim to identify areas where an increased forecasting capacity, and the availability of additional/better forecasting tools could assist decision-making processes within the different sectors. The workshop will also identify which methodologies and tools are proving effective in integrating climate information services across time scales and sectors, to ensure the most timely, accurate and comprehensive forecasting information is made available to all.

Links to further news:

SWIFT Stakeholder Workshop in Dakar, Senegal

Dakar Stakeholders (Photo Elias Nkiaka)

Following the Ghana workshop in November 2018, this week sees the second African SWIFT Stakeholder Workshop taking place in Dakar, Senegal. The two-day workshop is hosted by SWIFT partners, Agence Nationale de l’Aviation Civile et de la Météorologie (ANACIM) and is organised by ANACIM and the Centre for Ecology & Hydrology (CEH). As part of African SWIFT Work Package 1, ‘User engagement’, these two SWIFT partners are currently working to improve weather forecasting and warning systems, to help meet the needs of emergency responders and important sectors in Senegal such as agriculture and fisheries. The SWIFT project is keen to engage key stakeholders early in the programme to ensure that stakeholder experience and needs can be used to inform the design of new forecasting techniques, products and services.

Senegal Floods (Photo ANACIM)

Severe weather in the Sahel, such as the 2009 and 2012 floods in Dakar, is often due to intense rain from convective storms, and the recent increase in the number of severe weather events appears to be linked to global warming. This climate change signal indicates that the socio-economic impacts on sectors like agriculture and fisheries are likely to become even more devastating in the coming years. The central aim of the Dakar workshop is to ensure that such weather forecast users can take appropriate action in response to weather warnings issued by national meteorological services. The SWIFT workshop is attended by the Director and forecasters from national meteorological services, high level and technical representatives from key sectors within Senegal, including disaster management, agriculture and fisheries, as well as stakeholders from other climate services initiatives in Senegal including WMO Global Framework for Climate Services (GFCS), and Global Facility for Disaster Reduction and Recovery Senegal (GFDRR).
(GFDRR).

Anticipated outcomes from the workshop include:

  • A better understanding of the impacts of weather by forecasters in national meteorological services, leading to refinement of weather warnings and services.
  • An improved understanding of the uncertainties and issues involved in issuing weather services (i.e. warnings) by users of the forecasts.
  • Enhanced engagement (during the forecasting of an event) between the users and producers of weather services.

Link to further coverage on the ANACIM website

The Dakar workshop is second in a series of four SWIFT Stakeholder Workshops taking place across tropical Africa. In the coming weeks we will report on further events due to take place in Nigeria and Kenya.

Organisations involved in the African SWIFT Stakeholder Workshop in Dakar, Senegal include:

  • ADM Agence de Développement Municipale
  • ANACIM Agence Nationale de l’Aviation Civile et de la Météorologie
  • ARD Agence Régionale de Développement
  • CEH Centre for Ecology and Hydrology
  • CSE Centre de Suivie Ecologique
  • DEEC Direction de l’Environnement  et des Etablissements classes
  • DGPI Direction de la Prévention et de la Gestion des Inondations
  • DGPRE Direction Générale de la Planification et des Ressources en Eau
  • MRUHCV Ministère du Renouveau Urbain, de l’Habitat et du Cadre de Vie
  • MWG Multi-disciplinary Working Group
  • CLPA leaders of the local artisanal fishers’ council

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