By Anesu Chakanetsa

LAST year in September, the Southern Regional Climate Outlook Forum (SRCOF) forecasting programme predicted that in the 2016/2017 season, most parts of Southern Africa would experience normal to above normal rainfall driven by a phenomenon called La-Nina.
La-Nina is a climate pattern that describes the cooling of surface ocean waters along the tropical west coast of mainly South America and where variations of sea surface temperatures cause abnormal rainfalls.
La-Nina is considered to be the counterpart to El-Nino, which is characterised by unusually warm ocean temperatures in the equatorial region of the Pacific Ocean.
In 2015, the same forecasting programme also predicted that there would be normal-to-below-normal rainfall during the 2015/16 season precipitated by the El-Nino phenomenon.
The Meteorological Service Department (MSD) also warned the nation of the El-Nino in 2015/16 and of possible floods caused by La-Nina in 2016/17 wet season.
The difference and relationship between the two are distinct.
El-Nino and La-Nina are opposite phases of what is known as the El-Nino Southern Oscillation (ENSO).
The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and the atmosphere in the east-central Equatorial Pacific.
So La-Nina is the cold phase of ENSO and El-Nino is the warm phase.
These deviations from normal surface temperatures can have large scale impacts not only on ocean processes, but also on global weather and climate.
El-Nino and La-Nina episodes typically last between nine to 12 months, but some prolonged events can take to more than a year.
While their frequency can be quite regular, El-Nino and La-Nina events occur on overage every seven to 23 years.
Typically, El-Nino occurs more than La-Nina.
But the 2016/17 wet season is coupled with relentless rains, which at first brought hope to farmers.
These relentless rains experienced from mid-December to January, which could also last until April might also be following the climatic change pattern being experienced globally.
Worldwide, La-Nina is usually known to occur after 23 years, but due to climate change, its frequency might increase.
If an El-Nino occurs, a La-Nina is usually expected to follow the next season.
According to the MSD, the unusual cold spells swept the country during the 2016 winter, with daytime temperatures in Harare dropping to as low as 18 degrees Celsius.
These predictions were premised on past El-Nino years in Zimbabwe.
In 1979, 1982, 1992, 1999, 2006 and 2015, Zimbabwe faced El-Nino-induced drought, but the following seasons’ rain season would usually bring incessant rain.
La-Nina is usually forecast basing on prevalence of cool moist south easterlies (wind type) during the winter season which is usually associated with a good upcoming rain season.
And that is the case with Zimbabwe, because when the cool and moist south-easterlies prevail in winter, good rains follow.
In Zimbabwe, rain does not only define seasons, but 13,1 million people depend on it, according to the national statistics agency, ZIMSTATS.
In good times, precipitation averages between 300mm and 1 000mm, with regions in the south-west receiving the least amount of rain and those in the east along the border with Mozambique, the highest.
However, changes in climate have seen rainfall decline by between five and 15 percent countrywide since the 1960s.
And the El-Nino-induced drought that occurred last season left farmers counting losses and contributed to heat stress on national forests.
Water bodies evaporated leading to water shortage for use in homes, irrigation in farming and for animal and plant life.
El-Nino was also coupled with lots of unusual heatwaves that contributed to the onset of several heat-based diseases like skin cancer, head-aches and dehydration.
It left animals weak and plants wilting.
However, the results of the current La-Nina are not yet clear, but by May, there will be noticeable impacts, according to the MSD.
La-Nina-induced rains are very good for farmers, if they control the plants and get normal forecasting.
These rains are also feeding wetlands that have been losing moisture due to the previous El-Nino-induced drought.
Water bodies and tables have recorded an increase, leaving the nation hopeful of abundant tape and borehole water.
National forest ecosystems are also taking advantage of the moisture.
But immediate environmental negative impacts of relentless rains are manifesting in Zimbabwe, especially in urban areas.
The relentless rain has caused some stress on national roads that have led the Government to declare the situation a state of emergency.
Most roads in Zimbabwe that were already potholed have worsened in the wake of recent rains.
And while there has been a typhoid scare, it must be noted that since 2015, the onset of rains has led to several cases of typhoid and other waterborne diseases around the country, with most of them occurring in Harare.
It must also be noted that several rivers in Zimbabwe have overflowed due to the La-Nina-induced rains.
Several ill-informed people have been captured on camera trying to cross flooded rivers despite warnings from the Civil Protection Unit (CPU).
If the phenomena continues till April, the Government and the CPU in particular will need to ensure measures are put in place to deal with natural disasters because it’s not only people who suffer, but the environment too.