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Who’s shocked July weather is cold?

The diagram shows types of interactions considered in a weather forecast model. Most weather forecasts today are based on the output of complex computer programs, known as forecast models. The forecast models run on supercomputers and provide predictions on many atmospheric variables such as temperature, pressure, wind and rainfall. The diagram and text by The University of Arizona, Department of Hydrology and Atmospheric Science.
The diagram shows types of interactions considered in a weather forecast model. Most weather forecasts today are based on the output of complex computer programs, known as forecast models. The forecast models run on supercomputers and provide predictions on many atmospheric variables such as temperature, pressure, wind and rainfall. The diagram and text by The University of Arizona, Department of Hydrology and Atmospheric Science.

Kenya Meteorology Department gives weather advices whose aim is to save life, protect property and conserve environment. Few people follow the reports and many people are surprised when the weather changes. Some of the ignored early warnings range from the current cold season to the devastating famine in 2011.

On 31 May 2021 Kenya Meteorological Department said 14 counties would experience cool and cloudy conditions during June-July-August season. The counties are Nairobi, Nyandarua, Nyeri, Kirinyaga, Murang’a, Kiambu, Meru, Embu, Marsabit, parts of Isiolo, Kajiado, Machakos, Kitui and Makueni.

It said the counties will occasionally experience prolonged hours of overcast skies (cloudy conditions) resulting in cold and chilly conditions.

“A few days may turn out to be extremely cold with daytime temperatures falling below 18C,” the department said.

While the department had advised people the cold season was coming, some people were shocked when cold season finally arrived.

June-July-August season is predominantly cold for central highlands (including Nairobi), south eastern bordering Nairobi and some highlands west of Rift Valley (including Kericho).

The department’s Ms Mary Kilavi, assistant director for public weather service, said although it’s known June-July-August is cold some people might not have prepared adequately.

“We had forecasted [weather would be cold] but people seem surprised it’s cold,” Ms Kilavi told Water Tower.

In addition, she said the forecast wasn’t given much attention by the media until when the cold weather set in.  “The department has had to issue statements to reiterate the forecast.”

Ms Kilavi said that there could be serious consequences when forecast reports are not used for planning. She gave an example of the Greater horn of Africa drought and famine event of 2010-11

Drought and famine in 2010-2011

Kenya Meteorological Department had warned in August 2010 that large parts of the country would experience depressed rainfall during October-November-December season.

In addition, the following long rains season (March-April-May) in 2011 was poor in southeastern and coastal lowlands. This was the second failed season in northern, north eastern and eastern.

On 31 May 2011 the government declared the drought a national disaster. The government pledged to expedite supply of food and other supplies to affected Kenyans.

The 2010-2011 drought affected a total of 3.7 million people, almost 8% of the population.

Pastures were depleted and livestock water was scarce leading to poor livestock body condition and rising death. An exceptionally poor July crop harvest led to reduced food availability.

Ms Kilavi said the department’s forecasts in 2010 and 2011 clearly indicated that there would be below normal rainfall.

“The reasons for inaction despite the clear early warning could have been either due to scepticism or lack of a financial mechanism to act on forecast information.  she said. “As a result, the country experienced an unprecedented drought that slowly deteriorated to a famine.”

Kenya rainfall pattern

Most parts of Kenya receive rainfall twice in a year. The first season’s rainfall starts in March, peaks in April and ends in May. This rainfall is also known as long rains.

The second rain season begins in October, peaks in November and ends in December. This season is also known as short rains.

The Western and coastal regions experience a third rain season which begins from June and ends in August.

Kenya Meteorological Department operates 42 manual stations, 142 automatic stations and makes use of observations taken by weather instruments in aircrafts (Kenya Airways) and some ships as well as remote sensed data for weather forecasting.

Observations of atmospheric and earth’s surface conditions that give rise to the weather are taken multiple of times in a day. The observed data is assimilated into weather forecast computer models to generate the forecasts.

Ms Kilavi said the processes governing weather and climate are complex.

“It’s a whole complex system involving interactions between atmosphere, the oceans and various other systems on the earth surface.”

She said that some of these processes haven’t been fully understood.

“That’s is why meteorology is still under study,” Ms Kilavi said. “Even the processes that have already been understood are very complex and have to be simplified in order to represent them in computer models.”

How do computer forecasting models work?

“The observations are assimilated into mathematical models that simulate the already understood processes and powerful computers are used to compute the forecasts by integrating the models forward in time.

Why is Indian Ocean important to Kenya?

Rainfall in East Africa depends a lot on what happens in Indian Ocean.

Higher than average rainfall usually occurs over East Africa if the Indian Ocean warms near the East African coastline and cools on its eastern boundary with Indonesia. This is because of increased evaporation over the warmer waters coupled with enhanced easterly wind flow from the cooler to the warmer region which transfers the moist air inland.

On the other hand, East Africa normally experiences drier than usual conditions if the western Indian Ocean adjacent to East African coastline cools and it warms further to the east near Indonesia.

“This is known as Indian Ocean Dipole,” Ms Kilavi said. “It’s positive when Indian Ocean warms closer to our region and cools farther away.”

There is a similar effect on Pacific Ocean.

Kenya generally receives enhanced rainfall during the short rains season when there’s warming on eastern equatorial Pacific Ocean and cooling of western Equatorial Pacific Ocean (El-Nino). This however only occurs when the Indian Ocean responds to the warming signal.  When the signal is reversed and cooling occurs over eastern Equatorial Pacific Ocean (La Nina), the country experiences poor rainfall.

Why are weather forecasts sometimes inaccurate?

Air pressure, temperature, mountain ranges, ocean currents and many other factors combine to produce an enormous quantity of interacting variables.

These variables can alter the weather to a greater or lesser extent, according to World Meteorological Organisation.

The intergovernmental organisation says greater understanding of the science, plus the use of powerful computer models, continue to improve our ability to make more accurate predictions.

Ms Kilavi said that technological advancement has helped Kenya Meteorological Department to improve weather forecasts.

She said that the department’s forecasts even though are not 100% accurate, they are reliable.

What causes inaccuracies in forecasting?

  • Processes not fully understood. Air pressure, temperature, mountain ranges, ocean currents and many other factors combine to produce an enormous quantity of interacting variables. Theses interactions aren’t fully understood.
  • Limited observation points. Even if all the processes and interactions were fully understood, perfect forecasts would only be achieved if we had observations taken at every point on the Earth but this isn’t possible. Kenya Meteorological Department has 42 manual stations and 142 automatic stations. It’s in the processes of installing more automatic stations. This is expected to improve the reliability of the forecasts over time. Weather observation equipment are expensive. There are therefore huge observation gaps over much of Africa but developed countries have more observation points.
  • Strong solar insolation. Being at the tropics, means Kenya receives strong heat from the sun.  The sun shines more directly on the tropics than on higher latitudes (at least in the average over a year), which makes the tropics warm. Therefore, clouds and rain storms in the tropics can occur more spontaneously compared to those at higher latitudes.  This makes our systems more chaotic and harder to predict.

Ms Kilavi said that the accuracy of the seasonal forecasts depends on the knowledge of the drivers for different seasons.

The drivers of October-November-December rainfall are better understood than those of the March-April-May season.  Continuous research is gradually contributing towards improvement in the forecasts. Those who have taken note of the improvements in our forecasts are taking them seriously but there are some people who still dwell on the past when the department’s forecasts were not as reliable.

How can we improve weather and climate forecasts?

Observations from various instruments are crucial to understand how the atmosphere, oceans, rivers and lakes, land surface as well as plants influence our weather.

Powerful computers in global centres process these data from instruments and Earth-observing satellites to produce weather forecasts.

In Kenya and over much of Africa, little attention is given to the daily weather reports especially during seasons with minimum variation.

Kenya is a member of Global Data-Processing and Forecasting System (GDPFS). This is an international mechanism to prepare and make meteorological analyses and forecasts available to all members.

Ms Kilavi said that the department uses outputs of various models from several global weather and climate prediction centres to quantify uncertainties in the forecasts.

She said that while in the tropics weather reports are often ignored, the reports are taken very seriously in countries over the high latitude regions that experience extreme weather. In these countries people are very keen on the day to day changes due to their serious implications. Their day-to-day survival depends on weather.

“In Kenya and over much of Africa, little attention is given to the daily weather reports especially during seasons with minimum variation,” Ms Kilavi said. “In Africa, unless we’ve extreme weather situation, the media doesn’t give weather reports much prominence.

She said that everyday people should be reminded of how the weather will look like. And when extreme weather is expected, the message should be sounded out loud and clear.

Benefits of weather forecasts

Meteorological services involve the provision of information on the state of the atmosphere, ocean, land surface and inland surface water.

People could use Kenya Meteorological Department’s data and reports. The department’s data when studied historically it shows how a region has behaved over the years.

  1. Crop farming. Ms Kilavi said that information on the average rainfall and temperature over a location derived from historical observations can help farmers determine which crops are suitable in the area.
  2. Expected rainfall. When forecast reports are released, the historical information can be used to translate the probabilistic forecast into the amount of rainfall is expected. For example, if the forecast says an area is likely to receive ‘above normal rainfall,’ one knows the rainfall is likely to be more than 125% of the average for the area. It is therefore important to know the normal rainfall for any given area.

In addition to national weather forecasts, Kenya Meteorological Department issues county weather reports. Ms Kilavi said these are detailed meteorological reports to help communities with local advice. They are issued by the County Directors of Meteorology who represent the department at the county level and they give detailed information up to sub-county level.

The county directors of meteorology do further analysis on the forecasts and interpret it better for the people at the grassroots. The county directors also collect more information, for example, the indigenous people’s knowledge about the area.

In addition to the forecast information, Kenya Meteorology Department indicates the expected impacts on various sectors.  This is mainly intended for various government agencies.

“We expect the various government institutions to give detailed guidance to sectors of the economy,” Ms Kilavi said. “For example, ministry of Agriculture can give better advice to farmers on what cultivars to plant given certain level of rainfall.”

Misconception about weather forecasting

In some communities, people think weather forecasting is a presumptuous attempt to do what only God is capable of doing and therefore shun the whole idea of using the forecasts, said Ms Kilavi.

“It’s true that it is only God who can accurately foretell the future,” she said. “We’re only trying to understand the physical laws that He has put in place to govern the climate system much the same way that a doctor tries to understand the human body.”

Ms Kilavi said that sometimes people fail to pay attention to some of the information within the forecasts. She emphasised the need for people to read the forecasts together with definition of terms used in the reports.

“For example, when we say it will rain over ‘few places’ in Nairobi, people take it to mean it will rain all over Nairobi,” she said. “What we mean by rain in ‘few places’ in Nairobi is that the rainfall will cover less than 33% of Nairobi.”

There are two other rainfall coverage categories.

Rainfall in ‘most places’ mean between 66% and 100% of the mentioned place while rainfall in ‘several places’ mean the place referred to will receive rainfall covering between 33% and 66% of its area.

About Kaburu Mugambi

Kaburu Mugambi is a veteran of business reporting having worked with two national newspapers in Kenya. He is a graduate of economics from Kenyatta University. He started his journalism career in 2000 with The People Daily as a business reporter before becoming a business sub-editor. He joined Daily Nation in 2004 as a business writer. He holds a post-graduate diploma in mass communication from University of Nairobi's School of Journalism and an MBA in marketing from the same university. In 2016, he founded Water Tower, a media firm focused on water, energy and climate. Its content cuts across water, energy and climate with emphasis on adaptation and sustainability.

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