scholarly journals A snow forecasting decision tree for significant snowfall over the interior of South Africa

2016 ◽  
Vol Volume 112 (Number 9/10) ◽  
Author(s):  
Jan Hendrik Stander ◽  
Liesl Dyson ◽  
Christien J. Engelbrecht ◽  
◽  
◽  
...  
Keyword(s):  
South Africa ◽  
Decision Tree ◽  
Weather Forecasting ◽  
Second Step ◽  
Loss Of Life ◽  
Surface Conditions ◽  
Circulation Patterns ◽  
Weather Forecasters ◽  
Physical Attributes ◽  
Synoptic Circulation

Abstract Snowfall occurs every winter over the mountains of South Africa but is rare over the highly populated metropolises over the interior of South Africa. When snowfall does occur over highly populated areas, it causes widespread disruption to infrastructure and even loss of life. Because of the rarity of snow over the interior of South Africa, inexperienced weather forecasters often miss these events. We propose a five-step snow forecasting decision tree in which all five criteria must be met to forecast snowfall. The decision tree comprises physical attributes that are necessary for snowfall to occur. The first step recognises the synoptic circulation patterns associated with snow and the second step detects whether precipitation is likely in an area. The remaining steps all deal with identifying the presence of a snowflake in a cloud and determining that the snowflake will not melt on the way to the ground. The decision tree is especially useful to forecast the very rare snow events that develop from relatively dry and warmer surface conditions. We propose operational implementation of the decision tree in the weather forecasting offices of South Africa, as it is foreseen that this approach could significantly contribute to accurately forecasting snow over the interior of South Africa.

scholarly journals Forecasting Intense Cut-Off Lows in South Africa Using the 4.4 km Unified Model

Climate ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 129
Author(s):  
Tshimbiluni Percy Muofhe ◽  
Hector Chikoore ◽  
Mary-Jane Morongwa Bopape ◽  
Nthaduleni Samuel Nethengwe ◽  
Thando Ndarana ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
Weather Forecasting ◽  
Daily Rainfall ◽  
Heavy Precipitation ◽  
Unified Model ◽  
Severe Weather ◽  
Economic Activities ◽  
Circulation Patterns ◽  
Extreme Cold

Mid-tropospheric cut-off low (COL) pressure systems are linked to severe weather, heavy rainfall and extreme cold conditions over South Africa. They occur during all the above and often result in floods and snowfalls during the winter months, disrupting economic activities and causing extensive damage to infrastructure. This paper examines the evolution and circulation patterns associated with cases of severe COLs over South Africa. We evaluate the performance of the 4.4 km Unified Model (UM) which is currently used operationally by the South African Weather Service (SAWS) to simulate daily rainfall. Circulation variables and precipitation simulated by the UM were compared against European Centre for Medium-Range Weather Forecast’s (ECMWF’s) ERA Interim re-analyses and GPM precipitation at 24-hour timesteps. We present five recent severe COLs, which occurred between 2016 and 2019, that had high impact and found a higher model skill when simulating heavy precipitation during the initial stages than the dissipating stages of the systems. A key finding was that the UM simulated the precipitation differently during the different stages of development and location of the systems. This is mainly due to inaccurate placing of COL centers. Understanding the performance and limitations of the UM model in simulating COL characteristics can benefit severe weather forecasting and contribute to disaster risk reduction in South Africa.

scholarly journals Severe weather over the Highveld of South Africa during November 2016

Water SA ◽  
2018 ◽  
Vol 44 (1 January) ◽  
Author(s):  
Lee-ann Simpson ◽  
Liesl L Dyson
Keyword(s):  
South Africa ◽  
Prediction Models ◽  
Weather Forecast ◽  
Severe Weather ◽  
Severe Thunderstorm ◽  
Weather Events ◽  
Circulation Patterns ◽  
Conditional Instability ◽  
Synoptic Circulation

November months are notorious for severe weather over the Highveld of South Africa. November 2016 was no exception and a large number of severe events occurred. Very heavy rainfall, large hail and tornadoes were reported. The aim of this paper is to compare the synoptic circulation of November 2016 with the long-term mean November circulation and to investigate some sounding derived parameters. Furthermore, a few of the severe weather events are described in detail. The surface temperatures and dewpoint temperatures were found to be higher than normal resulting in increased conditional instability over the Highveld. Low-level moisture originated over the warm Mozambique Channel and the 500 hPa temperature trough was located favourably over the Highveld; further east than normal. The combination of these factors and weak steering winds resulted in flash flooding on the 9th while favourable wind shear conditions caused the development of a tornado on 15 November. The favourable circulation patterns and moisture gave rise to an atmosphere in which severe weather was a possibility, and the awareness of such factors is used as one of many tools when considering the severe weather forecast. The consideration of the daily variables derived from sounding data were good precursors for the prediction of severe thunderstorm development over the Highveld during November 2016. It is recommended that an operational meteorologist incorporates upper air sounding data into the forecasting process and not to rely on numerical prediction models exclusively.

scholarly journals Forecasting Intense Cut-Off Lows in South Africa Using the 4.4 Km Unified Model

2020 ◽  
Author(s):  
Tshimbiluni Percy Muofhe ◽  
Hector Chikoore ◽  
Mary-Jane Bopape ◽  
Nthaduleni S Nethengwe ◽  
Thando Ndarana ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
Heavy Rainfall ◽  
Weather Forecasting ◽  
Daily Rainfall ◽  
Heavy Precipitation ◽  
Unified Model ◽  
Severe Weather ◽  
Economic Activities ◽  
Circulation Patterns

Mid-tropospheric cut-off low (COL) pressure systems are linked to severe weather, heavy rainfall and extreme cold conditions over South Africa. They often result in floods and snowfalls in winter disrupting economic activities. This paper examines the evolution and circulation patterns associated with severe COLs over South Africa. We evaluate the performance of the 4.4 km Unified Model (UM) which is currently used operationally by the South African Weather Service to simulate daily rainfall. Circulation variables and precipitation simulated by the UM were compared against ECMWF’s ERA Interim reanalyses and GPM precipitation at 24-hour timesteps. We present five recent (2016-2019) severe COLs that had high impact and found higher model skill when simulating heavy precipitation during the initial stages than the dissipating stages of the systems. A key finding was that the UM underestimated precipitation mainly due to inaccurate placing of COL centers and areas of heavy rainfall by up to 5° of latitude away from the actual location, due to the poor formulating of cumulus and microphysics schemes in the model. Understanding the performance and limitations of the UM model in simulating COL characteristics can benefit severe weather forecasting and contribute to disaster risk reduction in South Africa.

A stochastic approach for assessing the effect of changes in synoptic circulation patterns on gauge precipitation

1993 ◽  
Vol 29 (10) ◽  
pp. 3303-3315 ◽  
Author(s):  
James P. Hughes ◽  
Dennis P. Lettenmaier ◽  
Peter Guttorp
Keyword(s):  
Stochastic Approach ◽  
Circulation Patterns ◽  
Synoptic Circulation

scholarly journals Visitation patterns of principal species of the insect-complex at carcasses in the Kruger National Park

Koedoe ◽  
1981 ◽  
Vol 24 (1) ◽  
Author(s):  
L.E.O Braack
Keyword(s):  
South Africa ◽  
National Park ◽  
Kruger National Park ◽  
Physical Attributes ◽  
Principal Species ◽  
Aepyceros Melampus

Two full-grown impala rams Aepyceros melampus were shot on 1978.01.07 in the Pafuri area of the Kruger National Park, Republic of South Africa. The carcasses were placed in enclosures 2,7 km apart and used to monitor the visitation patterns of insects. Collections of insects were made at four-hourly intervals for the first six days after placement of the carcasses, and thereafter every six hours up to the eleventh and final day. A figure is given to describe changes in the physical attributes of the carcasses through time. Twelve figures depict the patterns of arrival of insects at the carrion habitat. Species from the following families are represented: Cleridae, Dermestidae, Histeridae, Scarabaeidae, Silphidae, Staphylinidae, Trogidae (Coleoptera); Calliphoridae, Muscidae, Piophilidae, Sepsidae (Diptera); Diapriidae and Formicidae (Hymenoptera). The results indicate that species have distinctive periods of abundance and presents an overall picture of insect succession at carrion.

scholarly journals Contamination of the Bushveld Complex (South Africa) magmas by basinal brines: Stable isotopes in phlogopite from the UG2 chromitite

Geology ◽  
2021 ◽  
Author(s):  
Haoyang Zhou ◽  
Robert B. Trumbull ◽  
Ilya V. Veksler ◽  
Ilya N. Bindeman ◽  
Johannes Glodny ◽  
...  
Keyword(s):  
South Africa ◽  
Stable Isotopes ◽  
Hydrogen Isotope ◽  
Bushveld Complex ◽  
Isotope Ratios ◽  
Second Step ◽  
Merensky Reef ◽  
Oxygen Isotope Ratios ◽  
Abundant Evidence ◽  
Hydrogen Isotope Ratios

There is abundant evidence for significant H2O in evolved melts from the platinum-rich UG2 chromitite and the Merensky Reef of the Bushveld Complex (South Africa), but there is no consensus about the source of H2O. We report triple-oxygen and hydrogen isotope ratios of interstitial, late-magmatic phlogopite from three localities of the UG2 layer. The phlogopite yielded δD values of –43‰ to –23‰, which is >30‰ higher than previously known from Bushveld rocks and far above the mantle values of ~–75‰. The phlogopite triple-oxygen isotope ratios are the first to be reported for Bushveld rocks, with values of Δ′17O0.5305 (17O excess relative to the reference line 0.5305) from –0.069‰ to –0.044‰ (δ18O 5.2‰–6.2‰). The oxygen data support existing models of as much as 30%–40% contamination of mantlederived magmas in the lower to middle crust. However, the high δ values require a second step of contamination, which we attribute to brines from the marine sediments in the Transvaal Basin at the emplacement level.

scholarly journals Saharan Dust Events over the Valencian Community (Eastern Iberian Peninsula): Synoptic Circulation Patterns and Contribution to PM10 Levels

2020 ◽  
Vol 20 (11) ◽  
pp. 2519-2528
Author(s):  
Ariadna Huerta-Viso ◽  
Javier Crespo ◽  
Nuria Galindo ◽  
Eduardo Yubero ◽  
Jose Francisco Nicolás
Keyword(s):  
Iberian Peninsula ◽  
Saharan Dust ◽  
Circulation Patterns ◽  
Dust Events ◽  
Synoptic Circulation

scholarly journals Maintaining the Role of Humans in the Forecast Process: Analyzing the Psyche of Expert Forecasters

2007 ◽  
Vol 88 (12) ◽  
pp. 1893-1898 ◽  
Author(s):  
Neil A. Stuart ◽  
David M. Schultz ◽  
Gary Klein
Keyword(s):  
Decision Making ◽  
Information Technology ◽  
Weather Forecasting ◽  
Time Constraints ◽  
Learning Gap ◽  
Weather Forecasters ◽  
The Future ◽  
Mental Modeling ◽  
And Training

The Second Forum on the Future Role of the Human in the Forecast Process occurred on 2–3 August 2005 at the American Meteorological Society's Weather Analysis and Forecasting Conference in Washington, D.C. The forum consisted of three sessions. This paper discusses the second session, featuring three presentations on the cognitive and psychological aspects of expert weather forecasters. The first presentation discussed the learning gap between students (goal seekers) and teachers (knowledge seekers)—a similar gap exists between forecasters and researchers. In order to most effectively train students or forecasters, teachers must be able to teach across this gap using some methods described within. The second presentation discussed the heuristics involved in weather forecasting and decision making under time constraints and uncertainty. The final presentation classified the spectrum of forecasters from intuitive scientists to the disengaged. How information technology can best be adapted so as not to inhibit intuitive scientists from their mental modeling of weather scenarios is described. Forecasters must continuously refine their skills through education and training, and be aware of the heuristic contributions to the forecast process, to maintain expertise and have the best chance of ensuring a dynamic role in the future forecast process.

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