scholarly journals Mesoscale Convective Systems: A Case Scenario of the ‘Heavy Rainfall’ Event of 15–20 January 2013 over Southern Africa

Climate ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 73
Author(s):  
Modise Wiston ◽  
Kgakgamatso Marvel Mphale
Keyword(s):  
Atlantic Ocean ◽  
Southern Africa ◽  
Heavy Rainfall ◽  
Rainfall Event ◽  
Mesoscale Convective Systems ◽  
Heavy Rainfall Event ◽  
Convergence Zone ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Upper Level

Southern east Africa is prone to some extreme weather events and interannual variability of the hydrological cycle, including tropical cyclones and heavy rainfall events. Most of these events occur during austral summer and are linked to shifts in the intertropical convergence zone, changes in El Niño Southern Oscillation signatures, sea surface temperature and sea level pressure. A typical example include mesoscale convective systems (MCSs) that occur between October and March along the eastern part, adjacent to the warm waters of Mozambique Channel and Agulhas Current. In this study we discuss a heavy rainfall event over southern Africa, focusing particularly on the period 15–20 January 2013, the period during which MCSs were significant over the subcontinent. This event recorded one of the historic rainfalls due to extreme flooding and overflows, loss of lives and destruction of economic and social infrastructure. An active South Indian Convergence Zone was associated with the rainfall event sustained by a low-level trough linked to a Southern Hemisphere planetary wave pattern and an upper-level ridge over land. In addition, also noteworthy is a seemingly strong connection to the strength of the African Easterly Jet stream. Using rainfall data, satellite imagery and re-analysis (model processed data combined with observations) data, our analysis indicates that there was a substantial relation between rainfall totals recorded/observed and the presence of MCSs. The low-level trough and upper-level ridge contributed to moisture convergence, particularly from tropical South East Atlantic Ocean, which in turn contributed to the prolonged life span of the rainfall event. Positive temperature anomalies favored the substantial contribution of moisture fluxes from the Atlantic Ocean. This study provides a contextual assessment of rainfall processes and insight into the physical control mechanisms and feedback of large-scale convective interactions over tropical southern Africa.

scholarly journals An Observational Study of Mesoscale Convective Systems with Heavy Rainfall over the Korean Peninsula

2006 ◽  
Vol 21 (2) ◽  
pp. 125-148 ◽  
Author(s):  
Hyung Woo Kim ◽  
Dong Kyou Lee
Keyword(s):  
Observational Study ◽  
Korean Peninsula ◽  
Wind Shear ◽  
Heavy Rainfall ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Mesoscale Convective Systems ◽  
Low Level ◽  
Convective Systems ◽  
Mesoscale Convective

Abstract A heavy rainfall event induced by mesoscale convective systems (MCSs) occurred over the middle Korean Peninsula from 25 to 27 July 1996. This heavy rainfall caused a large loss of life and property damage as a result of flash floods and landslides. An observational study was conducted using Weather Surveillance Radar-1988 Doppler (WSR-88D) data from 0930 UTC 26 July to 0303 UTC 27 July 1996. Dominant synoptic features in this case had many similarities to those in previous studies, such as the presence of a quasi-stationary frontal system, a weak upper-level trough, sufficient moisture transportation by a low-level jet from a tropical storm landfall, strong potential and convective instability, and strong vertical wind shear. The thermodynamic characteristics and wind shear presented favorable conditions for a heavy rainfall occurrence. The early convective cells in the MCSs initiated over the coastal area, facilitated by the mesoscale boundaries of the land–sea contrast, rain–no rain regions, saturated–unsaturated soils, and steep horizontal pressure and thermal gradients. Two MCSs passed through the heavy rainfall regions during the investigation period. The first MCS initiated at 1000 UTC 26 July and had the characteristics of a supercell storm with small amounts of precipitation, the appearance of a mesocyclone with tilting storm, a rear-inflow jet at the midlevel of the storm, and fast forward propagation. The second MCS initiated over the upstream area of the first MCS at 1800 UTC 26 July and had the characteristics of a multicell storm, such as a broken areal-type squall line, slow or quasi-stationary backward propagation, heavy rainfall in a concentrated area due to the merging of the convective storms, and a stagnated cluster system. These systems merged and stagnated because their movement was blocked by the Taebaek Mountain Range, and they continued to develop because of the vertical wind shear resulting from a low-level easterly inflow.

Physical Processes Associated with Heavy Flooding Rainfall in Nashville, Tennessee, and Vicinity during 1–2 May 2010: The Role of an Atmospheric River and Mesoscale Convective Systems

2012 ◽  
Vol 140 (2) ◽  
pp. 358-378 ◽  
Author(s):  
Benjamin J. Moore ◽  
Paul J. Neiman ◽  
F. Martin Ralph ◽  
Faye E. Barthold
Keyword(s):  
Water Vapor ◽  
Heavy Rainfall ◽  
Convective Available Potential Energy ◽  
Mesoscale Convective Systems ◽  
Water Vapor Transport ◽  
Mississippi Valley ◽  
Physical Processes ◽  
Convective Systems ◽  
Atmospheric River ◽  
Mesoscale Convective

A multiscale analysis is conducted in order to examine the physical processes that resulted in prolonged heavy rainfall and devastating flash flooding across western and central Tennessee and Kentucky on 1–2 May 2010, during which Nashville, Tennessee, received 344.7 mm of rainfall and incurred 11 flood-related fatalities. On the synoptic scale, heavy rainfall was supported by a persistent corridor of strong water vapor transport rooted in the tropics that was manifested as an atmospheric river (AR). This AR developed as water vapor was extracted from the eastern tropical Pacific and the Caribbean Sea and transported into the central Mississippi Valley by a strong southerly low-level jet (LLJ) positioned between a stationary lee trough along the eastern Mexico coast and a broad, stationary subtropical ridge positioned over the southeastern United States and the subtropical Atlantic. The AR, associated with substantial water vapor content and moderate convective available potential energy, supported the successive development of two quasi-stationary mesoscale convective systems (MCSs) on 1 and 2 May, respectively. These MCSs were both linearly organized and exhibited back-building and echo-training, processes that afforded the repeated movement of convective cells over the same area of western and central Tennessee and Kentucky, resulting in a narrow band of rainfall totals of 200–400 mm. Mesoscale analyses reveal that the MCSs developed on the warm side of a slow-moving cold front and that the interaction between the southerly LLJ and convectively generated outflow boundaries was fundamental for generating convection.

scholarly journals Roles of Land and Topography on Propagating Convective Systems During the Heavy Rainfall Event of the 2002 Jakarta Flood, Indonesia

2021 ◽  
Author(s):  
Erma Yulihastin ◽  
Danang Eko Nuryanto ◽  
Robi Muharsyah
Keyword(s):  
Heavy Rainfall ◽  
Weather Prediction ◽  
Rainfall Event ◽  
Movement Direction ◽  
Heavy Rainfall Event ◽  
Convective System ◽  
Upward Motion ◽  
West Java ◽  
Convective Systems

The movement direction of propagating convective systems originating from both inland and offshore over the north coast of West Java in Indonesia is determined primarily by the prevailing wind. However, the role of a land-sea contrast and a rugged topography over southern West Java is also expected to affect propagating convective systems by increasing land-sea breezes and enhancing upward motion. These hypotheses are tested using a weather prediction model incorporating convection (up to 3 km height) to simulate the heavy rainfall event during 26–29 January associated with the 2002 Jakarta flood. First, we addressed the influence of land-sea contrast and topography on the local circulation, particularly in the area surrounding Jakarta, by replacing the inland topography over western Indonesia (96°–119°E, 17°S–0°) with a water body with an altitude of 0 m. We then compared the results of model simulations with and without topography. The results show that the main role of the topography here is enhancing the upward motion and generating a deep convective cloud in response to the land-based convective system during 26–27 January 2002, which then continuously and rapidly propagates offshore due to the cold pool mechanism. Furthermore, the land-sea contrast has a significant role in increasing sea breeze under the rapidness of the landward propagation system during 28–29 January 2002, which was strengthened by the gravity waves and resulted in early morning convection over coastal regions.

scholarly journals Study of three days duration coupling between jets in South América

2021 ◽  
Vol 12 (2) ◽  
pp. 240-248
Author(s):  
Emily Claudia Pereira Ramos ◽  
Luiz Gabriel Cassol Machado ◽  
André Becker Nunes
Keyword(s):  
South America ◽  
Reanalysis Data ◽  
Mesoscale Convective Systems ◽  
Southern Brazil ◽  
Vertical Movements ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Low Level Jet ◽  
Upper Level ◽  
Upper Level Jet

It can be understood by coupling between jets when Upper-Level Jet (ULJ) superimposes the Low-Level Jet (L LJ). The literature shows that such couplings tend to generate or intensify surface instabilities. Thus, the objective of this study was to analyze the synoptic configuration and the coupling between the jets associated with storms during the period of October 28-30, 2019, when instabilities hit southern Brazil causing intense precipitation and several damages. This work was carried out through the analysis of meteorological fields employing ERA5 reanalysis data and GOES-16 satellite imagery. The coupling between jets was verified in the three days of study. Upward vertical movements at 500 hPa was observed in the same area of occurrence of the upper level difluent flow, as well as an intense 850 hPa northerly flow, a large amount of moisture due to the action of the Northwestern Argentinean Low, and the presence of a frontal system between Uruguay and RS, except on the first day.  Storms developed east (downstream) of the area where the coupling took place. The coupling was observed before and during the development of the mesoscale convective systems, and its dissipation occurred simultaneously with the storm. However, on the 30th, the peak of coupling did not occur together with the most intense phase of the system, it occurred before.

Effects of Upper-Level Shear on the Structure and Maintenance of Strong Quasi-Linear Mesoscale Convective Systems

2006 ◽  
Vol 63 (4) ◽  
pp. 1231-1252 ◽  
Author(s):  
Michael C. Coniglio ◽  
David J. Stensrud ◽  
Louis J. Wicker
Keyword(s):  
Three Dimensional ◽  
Vertical Wind Shear ◽  
Vertical Displacement ◽  
Mesoscale Convective Systems ◽  
Cold Pool ◽  
Density Currents ◽  
3D Simulations ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Upper Level

Abstract Recent observational studies have shown that strong midlatitude mesoscale convective systems (MCSs) tend to decay as they move into environments with less instability and smaller deep-layer vertical wind shear. These observed shear profiles that contain significant upper-level shear are often different from the shear profiles considered to be the most favorable for the maintenance of strong, long-lived convective systems in some past idealized simulations. Thus, to explore the role of upper-level shear in strong MCS environments, a set of two-dimensional (2D) simulations of density currents within a dry, statically neutral environment is used to quantify the dependence of lifting along an idealized cold pool on the upper-level shear. A set of three-dimensional (3D) simulations of MCSs is produced to gauge the effects of the upper-level shear in a more realistic framework. Results from the 2D experiments show that the addition of upper-level shear to a wind profile with weak to moderate low-level shear increases the vertical displacement of parcels despite a decrease in the vertical velocity along the cold pool interface. Parcels that are elevated above the surface (1–2 km) overturn and are responsible for the deep lifting in the deep-shear environments, while the surface-based parcels typically are lifted through the cold pool region in a rearward-sloping path. This deep overturning helps to maintain the leading convection and greatly increases the size and total precipitation output of the convective systems in more complex 3D simulations, even in the presence of 3D structures. These results show that the shear profile throughout the entire troposphere must be considered to gain a more complete understanding of the structure and maintenance of strong midlatitude MCSs.

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