 Figure 1 : The anomalous change in zonal winds, sea surface temperature and depth of 20 degC isotherm from September 2017 to September 2018. [Source : https://www.pmel.noaa.gov/elnino/status]
The El Niño/Southern Oscillation (ENSO) is a naturally occurring phenomenon involving fluctuating ocean surface temperatures in the equatorial Pacific, coupled with changes in the overlying atmospheric circulation. It has a major influence on weather patterns over many parts of the world. Most of the weather signs highlight a switch from La Nina to the forecast El Nino climate pattern and despite a 70% chance of an El Nino developing by the end of this year, its intensity is currently uncertain, and a strong event appears unlikely according to the latest update from the World Meteorological Organization (WMO). The last El Nino-induced drought from 2014-2016 led to 40 million people requiring food assistance across southern Africa. Madagascar and Zimbabwe were among some of the worst hit countries. WMO also stated that although the anticipated El Nino will not be as powerful as the last one, it will still have considerable impacts. For the first time, the WMO coupled the El Nino update with a global seasonal climate outlook for the September-November period; the forecast predicts the sea surface temperature to be above normal in several areas including Africa. Usually, El Nino events occur every five-seven years but the recurrence of this coming event is so close to the previous one which may suggest the impact of climate change. The La Nina event that started at the beginning of the year was very weak and its cooling effect was not enough to reduce the overall warming trend, which implies that late 2018-mid 2019 would be the warmest on record globally. As the end of the rainy season approaches, so far, the six major dams in Cape Town are now 90% full. If an El Niño event does occur, it will mean that South Africa’s already swelteringly hot summers will become even hotter, which could eventually affect the water resources that have been building up during the winter rainy season. To learn more about other climate-related stories occurring across Africa, be sure to click here! © 2018 Oceanographer Daneeja Mawren”
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 DISCUSSION: As we now approach the heart of the 2018 tropical Atlantic hurricane season, there is little to no debate across the atmospheric science community that the tropical Atlantic Ocean basin has indeed finally fired up. As a result of this recent spike in tropical development across a good portion of the tropical Atlantic, there has continued to be substantial conversation regarding how long this increased activity may persist for an how much of an influence Africa may continue to have during the course of this more active period. The reason for why Africa is being so closely watched during this active period is due to the fact that on a seasonal basis there are often dozens and dozens of tropical waves which emerge off the west coast of Africa. These tropical waves are the "seed" which helps to "plant the foundation" for further potential tropical cyclone development once these tropical waves begin to interact with the warmer waters of the tropical Atlantic Ocean.
Hence, the reason for why many meteorologists are becoming increasingly concerned about Africa and the eastern tropical Atlantic Ocean is a result of the persistent progression of convectively invigorated tropical waves which are emerging one after another at the present time. Thus, the predominant thought process had by many right now is that since the earlier onslaught of Saharan Dust has finally begun to slightly abate and the corresponding average decrease in vertical wind shear associated with the African Easterly Jet (AEJ) for the time being (i.e., a factor which has been found historically unfavorable for tropical cyclone development), there is a concern for a semi-lengthy active period for basin-wide tropical activity. Even despite the fact that sea-surface temperatures across key tropical development zones have been slightly below-normal, many areas have still continued to remain sufficiently warm to support tropical cyclone development. Thus, as shown in the graphic above (courtesy of NBC 6 Miami's Chief Meteorologist John Morales), there are a pair of waves emerging off of Africa right now with even more on the way soon. Therefore, as we continue to go through the remainder of September, and then October as well as November, be sure to stay tuned and keep the future role of Africa in mind in future website articles as well as Twitter and/or Facebook posts in the coming days and weeks ahead. To learn more about other high-impact weather events and topics occurring across Africa, be sure to click here! © 2018 Meteorologist Jordan Rabinowitz |
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