An Objective Algorithm for Detecting and Tracking Tropical Cloud Clusters: Implications for Tropical Cyclogenesis Prediction

Abstract An algorithm to detect and track global tropical cloud clusters (TCCs) is presented. TCCs are organized large areas of convection that form over warm tropical waters. TCCs are important because they are the “seedlings” that can evolve into tropical cyclones. A TCC satisfies the necessary condition of a “preexisting disturbance,” which provides the required latent heat release to drive the development of tropical cyclone circulations. The operational prediction of tropical cyclogenesis is poor because of weaknesses in the observational network and numerical models; thus, past studies have focused on identifying differences between “developing” (evolving into a tropical cyclone) and “nondeveloping” (failing to do so) TCCs in the global analysis fields to produce statistical forecasts of these events. The algorithm presented here has been used to create a global dataset of all TCCs that formed from 1980 to 2008. Capitalizing on a global, Gridded Satellite (GridSat) infrared (IR) dataset, areas of persistent, intense convection are identified by analyzing characteristics of the IR brightness temperature (Tb) fields. Identified TCCs are tracked as they move around their ocean basin (or cross into others); variables such as TCC size, location, convective intensity, cloud-top height, development status (i.e., developing or nondeveloping), and a movement vector are recorded in Network Common Data Form (NetCDF). The algorithm can be adapted to near-real-time tracking of TCCs, which could be of great benefit to the tropical cyclone forecast community.

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An Intraseasonal Prediction Model of Atlantic and East Pacific Tropical Cyclone Genesis

Monthly Weather Review ◽

10.1175/mwr-d-12-00268.1 ◽

2013 ◽

Vol 141 (6) ◽

pp. 1925-1942 ◽

Cited By ~ 26

Author(s):

Stephanie A. Slade ◽

Eric D. Maloney

Keyword(s):

Logistic Regression ◽

Tropical Cyclone ◽

Southern Oscillation ◽

Selection Procedure ◽

Ocean Basin ◽

Tropical Cyclogenesis ◽

Tropical Cyclone Genesis ◽

East Pacific ◽

Skill Scores ◽

Cyclone Genesis

Abstract A real-time statistical model based on the work of Leroy and Wheeler is developed via multiple logistic regression to predict weekly tropical cyclone activity over the Atlantic and east Pacific basins. The predictors used in the model include a climatology of tropical cyclone genesis for each ocean basin, an El Niño–Southern Oscillation (ENSO) index, and two indices representing the propagating Madden–Julian oscillation (MJO). The Atlantic model also includes a predictor representing the variability of sea surface temperature (SST) in the Main Development Region (MDR). These predictors are suggested as useful for the prediction of tropical cyclogenesis based on previous work in the literature and are further confirmed in this study using basic statistics. Univariate logistic regression models are generated for each predictor in each region to ensure the choice of prediction scheme. Using all predictors, cross-validated hindcasts are developed out to a seven-week forecast lead. A formal stepwise predictor selection procedure is implemented to select the predictors used in each region at each forecast lead. Brier skill scores and reliability diagrams are used to assess the skill and dependability of the models. Results show an increase in model skill over the time-varying climatology at predicting tropical cyclogenesis by the inclusion of the MJO out to a three-week forecast lead for the east Pacific and a two-week forecast lead for the Atlantic. The importance of ENSO and MDR SST for Atlantic genesis prediction is highlighted, and the uncertain effects of ENSO on east Pacific tropical cyclogenesis are revisited.

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A First Look at the Structure of the Wave Pouch during the 2009 PREDICT–GRIP Dry Runs over the Atlantic

Monthly Weather Review ◽

10.1175/mwr-d-10-05063.1 ◽

2012 ◽

Vol 140 (4) ◽

pp. 1144-1163 ◽

Cited By ~ 33

Author(s):

Zhuo Wang ◽

Michael T. Montgomery ◽

Cody Fritz

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Deep Convection ◽

Vertical Shear ◽

Recirculation Region ◽

Necessary Condition ◽

Tropical Cyclogenesis ◽

Sufficient Condition ◽

Easterly Waves ◽

Tropical Cyclone Formation

In support of the National Science Foundation Pre-Depression Investigation of Cloud-systems in the tropics (NSF PREDICT) and National Aeronautics and Space Administration Genesis and Rapid Intensification Processes (NASA GRIP) dry run exercises and National Oceanic and Atmospheric Administration Hurricane Intensity Forecast Experiment (NOAA IFEX) during the 2009 hurricane season, a real-time wave-tracking algorithm and corresponding diagnostic analyses based on a recently proposed tropical cyclogenesis model were applied to tropical easterly waves over the Atlantic. The model emphasizes the importance of a Lagrangian recirculation region within a tropical-wave critical layer (the so-called pouch), where persistent deep convection and vorticity aggregation as well as column moistening are favored for tropical cyclogenesis. Distinct scenarios of hybrid wave–vortex evolution are highlighted. It was found that easterly waves without a pouch or with a shallow pouch did not develop. Although not all waves with a deep pouch developed into a tropical storm, a deep wave pouch had formed prior to genesis for all 16 named storms originating from monochromatic easterly waves during the 2008 and 2009 seasons. On the other hand, the diagnosis of two nondeveloping waves with a deep pouch suggests that strong vertical shear or dry air intrusion at the middle–upper levels (where a wave pouch was absent) can disrupt deep convection and suppress storm development. To sum up, this study suggests that a deep wave pouch extending from the midtroposphere (~600–700 hPa) down to the boundary layer is a necessary condition for tropical cyclone formation within an easterly wave. It is hypothesized also that a deep wave pouch together with other large-scale favorable conditions provides a sufficient condition for sustained convection and tropical cyclone formation. This hypothesized sufficient condition requires further testing and will be pursued in future work.

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A product form for the general stochastic matching model

Journal of Applied Probability ◽

10.1017/jpr.2020.100 ◽

2021 ◽

Vol 58 (2) ◽

pp. 449-468

Author(s):

Pascal Moyal ◽

Ana Bušić ◽

Jean Mairesse

Keyword(s):

Stationary Distribution ◽

Product Form ◽

Necessary Condition ◽

Matching Model ◽

Bipartite Matching ◽

Compatibility Graph ◽

Stochastic Matching ◽

Dynamic Reversibility ◽

Original Dynamic ◽

Do So

AbstractWe consider a stochastic matching model with a general compatibility graph, as introduced by Mairesse and Moyal (2016). We show that the natural necessary condition of stability of the system is also sufficient for the natural ‘first-come, first-matched’ matching policy. To do so, we derive the stationary distribution under a remarkable product form, by using an original dynamic reversibility property related to that of Adan, Bušić, Mairesse, and Weiss (2018) for the bipartite matching model.

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The Role of Equatorial Rossby Waves in Tropical Cyclogenesis. Part I: Idealized Numerical Simulations in an Initially Quiescent Background Environment

Monthly Weather Review ◽

10.1175/2009mwr3114.1 ◽

2010 ◽

Vol 138 (4) ◽

pp. 1368-1382 ◽

Cited By ~ 15

Author(s):

Jeffrey S. Gall ◽

William M. Frank ◽

Matthew C. Wheeler

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Phase Speed ◽

Tropical Cyclogenesis ◽

Initial Amplitude ◽

Low Level ◽

Wave Simulation ◽

Horizontal Momentum ◽

Good Agreement

Abstract This two-part series of papers examines the role of equatorial Rossby (ER) waves in tropical cyclone (TC) genesis. To do this, a unique initialization procedure is utilized to insert n = 1 ER waves into a numerical model that is able to faithfully produce TCs. In this first paper, experiments are carried out under the idealized condition of an initially quiescent background environment. Experiments are performed with varying initial wave amplitudes and with and without diabatic effects. This is done to both investigate how the properties of the simulated ER waves compare to the properties of observed ER waves and explore the role of the initial perturbation strength of the ER wave on genesis. In the dry, frictionless ER wave simulation the phase speed is slightly slower than the phase speed predicted from linear theory. Large-scale ascent develops in the region of low-level poleward flow, which is in good agreement with the theoretical structure of an n = 1 ER wave. The structures and phase speeds of the simulated full-physics ER waves are in good agreement with recent observational studies of ER waves that utilize wavenumber–frequency filtering techniques. Convection occurs primarily in the eastern half of the cyclonic gyre, as do the most favorable conditions for TC genesis. This region features sufficient midlevel moisture, anomalously strong low-level cyclonic vorticity, enhanced convection, and minimal vertical shear. Tropical cyclogenesis occurs only in the largest initial-amplitude ER wave simulation. The formation of the initial tropical disturbance that ultimately develops into a tropical cyclone is shown to be sensitive to the nonlinear horizontal momentum advection terms. When the largest initial-amplitude simulation is rerun with the nonlinear horizontal momentum advection terms turned off, tropical cyclogenesis does not occur, but the convectively coupled ER wave retains the properties of the ER wave observed in the smaller initial-amplitude simulations. It is shown that this isolated wave-only genesis process only occurs for strong ER waves in which the nonlinear advection is large. Part II will look at the more realistic case of ER wave–related genesis in which a sufficiently intense ER wave interacts with favorable large-scale flow features.

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A Simple Trajectory Model for Climatological Study of Tropical Cyclones

Journal of Climate ◽

10.1175/jcli-d-20-0285.1 ◽

2020 ◽

Vol 33 (18) ◽

pp. 7777-7786

Author(s):

Kaiyue Shan ◽

Xiping Yu

Keyword(s):

Tropical Cyclone ◽

North Pacific ◽

Western North Pacific ◽

Deterministic Model ◽

North Atlantic Ocean ◽

North Pacific Ocean ◽

Computational Cost ◽

Ocean Basin ◽

Trajectory Model ◽

Proposed Model

AbstractThe establishment of a tropical cyclone (TC) trajectory model that can represent the basic physics and is practically advantageous considering both accuracy and computational cost is essential to the climatological studies of various global TC activities. In this study, a simple deterministic model is proposed based on a newly developed semiempirical formula for the beta drift under known conditions of the environmental steering flow. To verify the proposed model, all historical TC tracks in the western North Pacific and the North Atlantic Ocean basins during the period 1979–2018 are simulated and statistically compared with the relevant results derived from observed data. The proposed model is shown to well capture the spatial distribution patterns of the TC occurrence frequency in the two ocean basins. Prevailing TC tracks as well as the latitudinal distribution of the landfall TC number in the western North Pacific Ocean basin are also shown to agree better with the results derived from observed data, as compared to the existing models that took different strategies to include the effect of the beta drift. It is then concluded that the present model is advantageous in terms of not only the accuracy but also the capacity to accommodate the varying climate. It is thus believed that the proposed TC trajectory model has the potential to be used for assessing possible impacts of climate change on tropical cyclone activities.

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An Efficient GPU Implementation of a Coupled Overland-Sewer Hydraulic Model with Pollutant Transport

Hydrology ◽

10.3390/hydrology8040146 ◽

2021 ◽

Vol 8 (4) ◽

pp. 146

Author(s):

Javier Fernández-Pato ◽

Pilar García-Navarro

Keyword(s):

Water Flow ◽

Numerical Models ◽

Global Analysis ◽

Coupled Model ◽

Pollutant Transport ◽

Pollutant Dispersion ◽

Quality Analysis ◽

Storm Events ◽

Graphic Processing Units ◽

Intense Storm

Numerical simulation of flows that consider interaction between overland and drainage networks has become a practical tool to prevent and mitigate flood situations in urban environments, especially when dealing with intense storm events, where the limited capacity of the sewer systems can be a trigger for flooding. Additionally, in order to prevent any kind of pollutant dispersion through the drainage network, it is very interesting to have a certain monitorization or control over the quality of the water that flows in both domains. In this sense, the addition of a pollutant transport component to both surface and sewer hydraulic models would benefit the global analysis of the combined water flow. On the other hand, when considering a realistic large domain with complex topography or streets structure, a fine spatial discretization is mandatory. Hence the number of grid cells is usually very large and, therefore, it is necessary to use parallelization techniques for the calculation, the use of Graphic Processing Units (GPU) being one of the most efficient due to the leveraging of thousands of processors within a single device. In this work, an efficient GPU-based 2D shallow water flow solver (RiverFlow2D-GPU) is fully coupled with EPA’s Storm Water Management Model (SWMM). Both models are able to develop a transient water quality analysis taking into account several pollutants. The coupled model, referred to as RiverFlow2D-GPU UD (Urban Drainge) is applied to three real-world cases, covering the most common hydraulic situations in urban hydrology/hydraulics. A UK Environmental Agency test case is used as model validation, showing a good agreement between RiverFlow2D-GPU UD and the rest of the numerical models considered. The efficiency of the model is proven in two more complex domains, leading to a >100x faster simulations compared with the traditional CPU computation.

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An intercomparison of tropical cyclone best-track products for the southwest Pacific

Natural Hazards and Earth System Science ◽

10.5194/nhess-16-1431-2016 ◽

2016 ◽

Vol 16 (6) ◽

pp. 1431-1447 ◽

Cited By ~ 11

Author(s):

Andrew D. Magee ◽

Danielle C. Verdon-Kidd ◽

Anthony S. Kiem

Keyword(s):

Tropical Cyclone ◽

Vertical Wind Shear ◽

Geostationary Satellite ◽

Vertical Shear ◽

Tropical Cyclogenesis ◽

Southwest Pacific ◽

Zonal Winds ◽

Spatio Temporal ◽

Joint Typhoon Warning Center

Abstract. Recent efforts to understand tropical cyclone (TC) activity in the southwest Pacific (SWP) have led to the development of numerous TC databases. The methods used to compile each database vary and are based on data from different meteorological centres, standalone TC databases and archived synoptic charts. Therefore the aims of this study are to (i) provide a spatio-temporal comparison of three TC best-track (BT) databases and explore any differences between them (and any associated implications) and (ii) investigate whether there are any spatial, temporal or statistical differences between pre-satellite (1945–1969), post-satellite (1970–2011) and post-geostationary satellite (1982–2011) era TC data given the changing observational technologies with time. To achieve this, we compare three best-track TC databases for the SWP region (0–35° S, 135° E–120° W) from 1945 to 2011: the Joint Typhoon Warning Center (JTWC), the International Best Track Archive for Climate Stewardship (IBTrACS) and the Southwest Pacific Enhanced Archive of Tropical Cyclones (SPEArTC). The results of this study suggest that SPEArTC is the most complete repository of TCs for the SWP region. In particular, we show that the SPEArTC database includes a number of additional TCs, not included in either the JTWC or IBTrACS database. These SPEArTC events do occur under environmental conditions conducive to tropical cyclogenesis (TC genesis), including anomalously negative 700 hPa vorticity (VORT), anomalously negative vertical shear of zonal winds (VSZW), anomalously negative 700 hPa geopotential height (GPH), cyclonic (absolute) 700 hPa winds and low values of absolute vertical wind shear (EVWS). Further, while changes in observational technologies from 1945 have undoubtedly improved our ability to detect and monitor TCs, we show that the number of TCs detected prior to the satellite era (1945–1969) are not statistically different to those in the post-satellite era (post-1970). Although data from pre-satellite and pre-geostationary satellite periods are currently inadequate for investigating TC intensity, this study suggests that SPEArTC data (from 1945) may be used to investigate long-term variability of TC counts and TC genesis locations.

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Measuring Environmental Favorability for Tropical Cyclogenesis by Statistical Analysis of Threshold Parameters

Journal of Climate ◽

10.1175/2011jcli4176.1 ◽

2011 ◽

Vol 24 (23) ◽

pp. 5968-5997 ◽

Cited By ~ 31

Author(s):

Michael G. McGauley ◽

David S. Nolan

Keyword(s):

Tropical Cyclone ◽

Threshold Value ◽

New Method ◽

Tropical Cyclogenesis ◽

Tropical Cyclone Genesis ◽

Threshold Values ◽

Reanalysis Dataset ◽

Statistical Probability ◽

Saturation Deficit ◽

Meteorological Features

Abstract As the climate changes, the ability to predict changes in the frequency of tropical cyclogenesis is becoming of increasing interest. A unique approach is proposed that utilizes threshold values in potential intensity, wind shear, vorticity, and normalized saturation deficit. Prior statistical methods generally involve creating an index or equation based on averages of important meteorological parameters for a given region. The new method assumes that threshold values exist for each important parameter for which cyclogenesis is unlikely to develop. This technique is distinct from previous approaches that seek to determine how each of these parameters interdependently favors cyclogenesis. To determine three of the individual threshold values (shear, potential intensity, and vorticity), an idealized climate is first established that represents the most advantageous but realistic (MABR) environment. An initial numerical simulation of tropical cyclone genesis in the MABR environment confirms that it is highly favorable for cyclogenesis. Subsequent numerical simulations vary each parameter individually until no tropical cyclone develops, thereby determining the three threshold values. The new method of point downscaling, whereby background meteorological features are represented by a single vertical profile, is used in the simulations to greatly simplify the approach. The remaining threshold parameter (normalized saturation deficit) is determined by analyzing the climatological record and choosing a value that is statistically observed to prevent cyclogenesis. Once each threshold value is determined, the fraction of time each is exceeded in the location of interest is computed from the reanalysis dataset. The product of each fraction for each of the relevant parameters then gives a statistical probability as to the likelihood of cyclogenesis. For predicting regional and monthly variations in frequency of genesis, this approach is shown to generally meet or exceed the predictive skills of earlier statistical attempts with some failure only during several off-season months. This method also provides a more intuitive rationale of the results.

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