Case Study on Convection Initiation Associated with an Isolated Convective Storm Developed over Flat Terrain during TOMACS

Abstract A nocturnal maximum in rainfall and thunderstorm activity over the central Great Plains has been widely documented, but the mechanisms for the development of thunderstorms over that region at night are still not well understood. Elevated convection above a surface frontal boundary is one explanation, but this study shows that many thunderstorms form at night without the presence of an elevated frontal inversion or nearby surface boundary. This study documents convection initiation (CI) events at night over the central Great Plains from 1996 to 2015 during the months of April–July. Storm characteristics such as storm type, linear system orientation, initiation time and location, and others were documented. Once all of the cases were documented, surface data were examined to locate any nearby surface boundaries. The event’s initiation location relative to these boundaries (if a boundary existed) was documented. Two main initiation locations relative to a surface boundary were identified: on a surface boundary and on the cold side of a surface boundary; CI events also occur without any nearby surface boundary. There are many differences among the different nocturnal CI modes. For example, there appear to be two main peaks of initiation time at night: one early at night and one later at night. The later peak is likely due to the events that form without a nearby surface boundary. Finally, a case study of three nocturnal CI events that occurred during the Plains Elevated Convection At Night (PECAN) field project when there was no nearby surface boundary is discussed.

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Environmental Analysis of GOES-R Proving Ground Convection-Initiation Forecasting Algorithms

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-14-0190.1 ◽

2015 ◽

Vol 54 (7) ◽

pp. 1637-1662 ◽

Cited By ~ 1

Author(s):

Jason M. Apke ◽

Daniel Nietfeld ◽

Mark R. Anderson

Keyword(s):

Environmental Variables ◽

Environmental Influences ◽

Principal Component ◽

University Of Alabama ◽

Algorithm Performance ◽

University Of Wisconsin ◽

Improve Algorithm ◽

Convection Initiation ◽

The University

AbstractEnhanced temporal and spatial resolution of the Geostationary Operational Environmental Satellite–R Series (GOES-R) will allow for the use of cloud-top-cooling-based convection-initiation (CI) forecasting algorithms. Two such algorithms have been created on the current generation of GOES: the University of Wisconsin cloud-top-cooling algorithm (UWCTC) and the University of Alabama in Huntsville’s satellite convection analysis and tracking algorithm (SATCAST). Preliminary analyses of algorithm products have led to speculation over preconvective environmental influences on algorithm performance. An objective validation approach is developed to separate algorithm products into positive and false indications. Seventeen preconvective environmental variables are examined for the positive and false indications to improve algorithm output. The total dataset consists of two time periods in the late convective season of 2012 and the early convective season of 2013. Data are examined for environmental relationships using principal component analysis (PCA) and quadratic discriminant analysis (QDA). Data fusion by QDA is tested for SATCAST and UWCTC on five separate case-study days to determine whether application of environmental variables improves satellite-based CI forecasting. PCA and significance testing revealed that positive indications favored environments with greater vertically integrated instability (CAPE), less stability (CIN), and more low-level convergence. QDA improved both algorithms on all five case studies using significantly different variables. This study provides an examination of environmental influences on the performance of GOES-R Proving Ground CI forecasting algorithms and shows that integration of QDA in the cloud-top-cooling-based algorithms using environmental variables will ultimately generate a more skillful product.

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A Case Study on the Impact of Moisture Variability on Convection Initiation Using Radar Refractivity Retrievals

Journal of Applied Meteorology and Climatology ◽

10.1175/2010jamc2360.1 ◽

2010 ◽

Vol 49 (8) ◽

pp. 1766-1778 ◽

Cited By ~ 15

Author(s):

D. Bodine ◽

P. L. Heinselman ◽

B. L. Cheong ◽

R. D. Palmer ◽

D. Michaud

Keyword(s):

Inversion Layer ◽

Small Scale ◽

Low Level ◽

Dewpoint Temperature ◽

Observation Network ◽

Convergence Zones ◽

Convection Initiation ◽

The Impact ◽

Moisture Variability

Abstract A case study illustrating the impact of moisture variability on convection initiation in a synoptically active environment without strong moisture gradients is presented. The preconvective environment on 30 April 2007 nearly satisfied the three conditions for convection initiation: moisture, instability, and a low-level lifting mechanism. However, a sounding analysis showed that a low-level inversion layer and high LFC would prevent convection initiation because the convective updraft velocities required to overcome the convective inhibition (CIN) were much higher than updraft velocities typically observed in convergence zones. Radar refractivity retrievals from the Twin Lakes, Oklahoma (KTLX), Weather Surveillance Radar-1988 Doppler (WSR-88D) showed a moisture pool contributing up to a 2°C increase in dewpoint temperature where the initial storm-scale convergence was observed. The analysis of the storm-relative wind field revealed that the developing storm ingested the higher moisture associated with the moisture pool. Sounding analyses showed that the moisture pool reduced or nearly eliminated CIN, lowered the LFC by about 500 m, and increased CAPE by 2.5 times. Thus, these small-scale moisture changes increased the likelihood of convection initiation within the moisture pool by creating a more favorable thermodynamic environment. The results suggest that refractivity data could improve convection initiation forecasts by assessing moisture variability at finer scales than the current observation network.

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Convection Initiation Resulting From the Interaction Between a Quasi‐Stationary Dryline and Intersecting Gust Fronts: A Case Study

Journal of Geophysical Research Atmospheres ◽

10.1029/2018jd029832 ◽

2019 ◽

Vol 124 (5) ◽

pp. 2379-2396 ◽

Cited By ~ 7

Author(s):

Lanqiang Bai ◽

Zhiyong Meng ◽

Yipeng Huang ◽

Yunji Zhang ◽

Shuzhen Niu ◽

...

Keyword(s):

Gust Fronts ◽

Convection Initiation

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A case study of a low level jet during OPALE

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-31091-2014 ◽

2014 ◽

Vol 14 (22) ◽

pp. 31091-31109 ◽

Cited By ~ 1

Author(s):

H. Gallée ◽

H. Barral ◽

E. Vignon ◽

C. Genthon

Keyword(s):

Three Dimensional ◽

East Antarctica ◽

Low Level ◽

Thermal Wind ◽

Flat Terrain ◽

Dimensional Version ◽

Low Level Jet ◽

Oxidant Production

Abstract. A case study of a low level jet during the OPALE (Oxidant Production over Antarctic Land and its Export) summer campaign is presented. It has been observed at Dome C (East Antarctica) and is simulated accurately by the three-dimensional version of the Modèle Atmosphérique Régional (MAR). It is found that this low level jet is not related to an episode of thermal wind, conforting that Dome C may be a~place where turbulence on flat terrain can be studied.

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A numerical case study on short-time strong convection initiation of a southwest vortex

International Conference on Information Science and Technology ◽

10.1109/icist.2011.5765076 ◽

2011 ◽

Author(s):

Qin Du ◽

Hongru Xiao ◽

Zhong Wang

Keyword(s):

Southwest Vortex ◽

Strong Convection ◽

Convection Initiation ◽

Short Time ◽

Numerical Case Study

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Economical Design of Sewer Line in Flat Terrain: A Case Study of Rajapur Sewerage System

SCITECH Nepal ◽

10.3126/scitech.v13i1.23503 ◽

2018 ◽

Vol 13 (1) ◽

pp. 60-63

Author(s):

Bibhuti Ojha

Keyword(s):

Cost Estimation ◽

Ground Surface ◽

Efficient Design ◽

Sewer System ◽

Sewerage System ◽

Flat Terrain ◽

Sewer Network ◽

Economical Design ◽

Minimum Velocity

Design of sewer line in flat terrain is a great challenge due to high excavation depth involved in laying a sewer line required for maintaining minimum velocity, slope and clear cover. Sewer design presented in this paper is result of sewer modelling software Bentley SewerCAD V8i. Estimation and cost analysis of a sewer system shows cost is directly related to the excavation depth. For economically efficient design of sewer line in a flat terrain of Rajapur-Bardia, sewer is designed in the gentle slope and flushing tanks are provided at sections where velocities are less than the minimum value recommended by Codes. Design and cost estimation of sewer network of 4.554 km with and without use of flushing tank are presented in this paper and two major benefits - cost and low invert level of outfall from ground surface elevation are achieved with flushing tank provision.

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