Zimbabwe Weather Forecasting Critical in Fight Against Climate Change

30 MARCH 2022

The Herald (Harare)

By Elita Chikwati Senior Agriculture

Recently, Zimbabwe joined the rest of the world in marking the World Meteorological Day on March 23 at a time when extreme-weather events have increased dramatically and now dominate the disaster landscape in the 21st Century. In this interview, Senior Agriculture Reporter Elita Chikwati (EC) speaks to Meteorological Services Department (MSD) director Mrs Rebecca Manzou (RM) on the importance of climate information in disaster risk reduction.

EC: The MSD forecast normal to above normal rains for the 2021/22 cropping season, raising prospects of another bumper harvest. However, the season was characterised by late on-set rains and longer dry spells leading to wilting of crops. Was the forecast a miss or a hit? What is happening now since the rains are gone?

RM: This question can be answered fully at the end of the season. The forecasts are monthly accumulations and while the distribution could have been bad, maybe the three-month totals will still be in the normal to above normal range. So, this is best answered at the end of the rainfall season. Southern areas have less rain, other areas are currently experiencing substantial rainfalls.

EC: What systems are there to bring rains to Zimbabwe and are we still going to receive rains or the rainfall season is almost coming to an end?

RM: The systems that bring rainfall over Zimbabwe include the Inter-Tropical Convergence Zone (ITCZ), westerly cloud bands and high pressure systems off the south-east coast of Southern Africa. Depending on the prevailing winds over the northern half of the country and availability of moisture, this can lead to a process called convergence - resulting in thunderstorms and localised heavy rainfall in places where convergence would have occurred. Frontal systems from the Atlantic Ocean towards the Indian Ocean usually south of the sub-region contribute towards pulling down the ITCZ and activating it. In addition, tropical cyclones, depressions, storms that form in the south west Indian Ocean (SWIO) may result in significant rainfall over Zimbabwe depending on their trajectory. Not all tropical cyclones that form in the SWIO reach Zimbabwe and not all of them bring rainfall. In fact, sometimes the tropical cyclones bring dry conditions over Zimbabwe depending on their trajectory and location.

EC: When can we expect the rainfall season to end?

RM: The summer rainfall season usually ends on March 31 of each year. One of the main rain-bearing systems (ITCZ)'s southern limit will be retreating northwards and hence not much rainfall is expected unless a tropical cyclone that can bring significant rainfall over us develops.

Westerly cloud bands and high-pressure systems can also form and bring rainfall over Zimbabwe. It is important though to note that the peak rainfall months for Zimbabwe are mostly December, January and February termed (DJF) and hence in March rainfall activity will start to reduce significantly. It does not mean that it will not rain. Mid-March to end of March is the tail end of the rainfall season.

EC: What is pushing the rains away from Zimbabwe?

RM: Tropical cyclones contributed significantly to the dry spells. Due to the positions of the TCs they drew moisture from Zimbabwe resulting in the dry spells. Dry spells in Zimbabwe, especially in the southern part of the country from around January 25 to around the end of February were due to the impact of two tropical cyclones - Batsirai and Emnati.

Due to the trajectories that these cyclones took they ended up drawing a lot of moisture away from Zimbabwe. They contributed much to the prolonged period of dry spell. On the other hand, the southern limit of the ITCZ migrates northwards as is normal during this time of the year (unless there are other systems that may pull it downwards), rainfall will be reduced quite significantly over northern Zimbabwe when the ITCZ migrates further north.

EC: Who names the cyclones? How is the naming done?

RM: Tropical cyclones are named to provide ease of communication among meteorologists and the public and also to reduce confusion of having tropical cyclones appearing with the same names or with no names. The tropical storm that is judged to have a 10-minute sustained wind speed of 64km/hr for at least six hours is assigned a name by the Regional Specialised Meteorological Centre in La Reunion.

The name is chosen following the alphabetic order from a pre-defined list of names starting each season with a name with the initial letter A. Names are proposed by the 15 member states of the South West Indian Ocean (SWIO) Tropical Cyclone Committee meeting held every two years. These are mostly made up of members from the southern Africa region.

EC: What are the advantages and disadvantages brought up by cyclones to Zimbabwe?

RM: Tropical cyclones bring notable rainfall over Zimbabwe which can lead to a bumper harvest, raise dam levels, raise water tables and increase grass and vegetation for animals among other things.

Disadvantages include strong winds and heavy rain that can result in the destruction of infrastructure, property and can also lead to loss of human and animal life.

Flooding can be detrimental to crops while landslides can disturb the natural ecosystem. Cyclone Idai is one example of a cyclone that negatively affected Zimbabwe. In as much as it had positives of having dams filling up it also caused untold hardships and destroyed property, infrastructure and crops in addition to loss of lives.

EC: Any lessons the MSD has learnt from the past tropical cyclones?

RM: Tropical cyclones can lead to disasters and a collective effort from the general public, MSD, other government departments (Department of Civil Protection), development partners who are working with disaster risk reduction (DRR) issues is key. We also learnt that strengthening of all departments who form part of the hydro-met Early Warning System is very critical as it takes teamwork to overcome the challenges that come with tropical cyclones. Most communities are now aware and are alert to the extent of the disasters that can be brought by tropical cyclones.

EC: Do you feel the public believe your forecasts or they rely more on foreign weather updates?

RM: More than 50 percent of the population of Zimbabwe uses the forecasts produced by the MSD. This is evidenced by the increase in the number of people who reach the MSD Public Weather Office requesting weather briefings via the telephone, emails, and WhatsApp platforms.

Feedback from clients on social media also shows that the MSD clientele uses the products and services offered and that they need more, especially area and sector specific products, this shows that the public still has confidence in us.