An Electrical and Polarimetric Analysis of the Overland Reintensification of Tropical Storm Erin (2007)

2014 ◽  
Vol 142 (6) ◽  
pp. 2321-2344 ◽  
Author(s):  
Erica M. Griffin ◽  
Terry J. Schuur ◽  
Donald R. MacGorman ◽  
Matthew R. Kumjian ◽  
Alexandre O. Fierro
Keyword(s):  
Tropical Cyclones ◽  
Inner Core ◽  
Open Water ◽  
Tropical Storm ◽  
Sea Level Pressure ◽  
Core Convection ◽  
Lightning Detection ◽  
Mapping Array ◽  
Total Lightning ◽  
Abundant Data

Abstract While passing over central Oklahoma on 18–19 August 2007, the remnants of Tropical Storm Erin unexpectedly reintensified and developed an eyelike feature that was clearly discernable in Weather Surveillance Radar-1988 Doppler (WSR-88D) imagery. During this brief reintensification period, Erin traversed a region of dense surface and remote sensing observation networks that provided abundant data of high spatial and temporal resolution. This study analyzes data from the polarimetric KOUN S-band radar, total lightning data from the Oklahoma Lightning Mapping Array, and ground-flash lightning data from the National Lightning Detection Network. Erin’s reintensification was atypical since it occurred well inland and was accompanied by stronger maximum sustained winds and gusts (25 and 37 m s−1, respectively) and lower minimum sea level pressure (1001.3 hPa) than while over water. Radar observations reveal several similarities to those documented in mature tropical cyclones over open water, including outward-sloping eyewall convection, near 0-dBZ reflectivities within the eye, and relatively large updraft velocities in the eyewall as inferred from single-Doppler winds and ZDR columns. Deep, electrified convection near the center of circulation preceded the formation of Erin’s eye, with maximum lightning activity occurring prior to and during reintensification. The results show that inner-core convection may have played a role in the reinvigoration of the storm.

Lagrangian Description of Air Masses Associated with Latent Heat Release in Tropical Storm Karl (2016) during Extratropical Transition

2019 ◽  
Vol 147 (7) ◽  
pp. 2657-2676 ◽  
Author(s):  
Christian Euler ◽  
Michael Riemer ◽  
Tobias Kremer ◽  
Elmar Schömer
Keyword(s):  
Inner Core ◽  
Vertical Wind Shear ◽  
Conveyor Belt ◽  
Tropical Storm ◽  
Vertical Shear ◽  
Lagrangian Description ◽  
Environment Impact ◽  
Extratropical Transition ◽  
Air Masses ◽  
Core Convection

Abstract Extratropical transition (ET) of tropical cyclones involves distinct changes of the cyclone’s structure that are not yet well understood. This study presents for the first time a comprehensive Lagrangian description of structure change near the inner core. A large sample of trajectories is computed from a convection-permitting numerical simulation of the ET of Tropical Storm Karl (2016). Three main airstreams are considered: those associated with the inner-core convection, inner-core descent, and the developing warm conveyor belt. Analysis of these airstreams is performed both in thermodynamic and physical space. Prior to ET, Karl is embedded in weak vertical wind shear and its intensity is impeded by excessive detrainment from the inner-core convection. At the start of ET, vertical shear increases and Karl intensifies, which is attributable to reduced detrainment and thus to the formation of a well-defined outflow layer. During ET, the thermodynamic changes of the environment impact Karl’s inner-core convection predominantly by a decrease of θe values in the inflow layer. Notably, notwithstanding Karl’s weak intensity, its inner core acts as a “containment vessel” that transports high-θe air into the increasingly hostile environment. Inner-core descent has two origins: (i) mostly from upshear-left above 4-km height in the environment and (ii) boundary layer air that ascends in the inner core first and then descends, performing rollercoaster-like trajectories. At the end of the tropical phase of ET, the developing warm conveyor belt comprises air masses from several different source regions, and only partly from the cyclone’s developing warm sector, as expected for extratropical cyclones.

The 29 June 2000 Supercell Observed during STEPS. Part II: Lightning and Charge Structure

2005 ◽  
Vol 62 (12) ◽  
pp. 4151-4177 ◽  
Author(s):  
Kyle C. Wiens ◽  
Steven A. Rutledge ◽  
Sarah A. Tessendorf
Keyword(s):  
Positive Charge ◽  
Lightning Activity ◽  
Structure Evolution ◽  
Severe Thunderstorm ◽  
Charge Structure ◽  
Flash Rate ◽  
Lightning Detection ◽  
Mapping Array ◽  
Total Lightning ◽  
Mexico Tech

Abstract This second part of a two-part study examines the lightning and charge structure evolution of the 29 June 2000 tornadic supercell observed during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). Data from the National Lightning Detection Network and the New Mexico Tech Lightning Mapping Array (LMA) are used to quantify the total and cloud-to-ground (CG) flash rates. Additionally, the LMA data are used to infer gross charge structure and to determine the origin locations and charge regions involved in the CG flashes. The total flash rate reached nearly 300 min−1 and was well correlated with radar-inferred updraft and graupel echo volumes. Intracloud flashes accounted for 95%–100% of the total lightning activity during any given minute. Nearly 90% of the CG flashes delivered a positive charge to ground (+CGs). The charge structure during the first 20 min of this storm consisted of a midlevel negative charge overlying lower positive charge with no evidence of an upper positive charge. The charge structure in the later (severe) phase was more complex but maintained what could be roughly described as an inverted tripole, dominated by a deep midlevel (5–9 km MSL) region of positive charge. The storm produced only two CG flashes (both positive) in the first 2 h of lightning activity, both of which occurred during a brief surge in updraft and hail production. Frequent +CG flashes began nearly coincident with dramatic increases in storm updraft, hail production, total flash rate, and the formation of an F1 tornado. The +CG flashes tended to cluster in or just downwind of the heaviest precipitation, which usually contained hail. The +CG flashes all originated between 5 and 9 km MSL, centered at 6.8 km (−10°C), and tapped LMA-inferred positive charge both in the precipitation core and (more often) in weaker reflectivity extending downwind. All but one of the −CG flashes originated from >9 km MSL and tended to strike near the precipitation core.

scholarly journals Cluster Analysis Tailored to Structure Change of Tropical Cyclones Using a Very Large Number of Trajectories

2020 ◽  
Vol 148 (10) ◽  
pp. 4209-4229
Author(s):  
Tobias Kremer ◽  
Elmar Schömer ◽  
Christian Euler ◽  
Michael Riemer
Keyword(s):  
Tropical Cyclones ◽  
Inner Core ◽  
Temporal Evolution ◽  
Dimensional Space ◽  
Physical Space ◽  
Large Degree ◽  
Temporal Consistency ◽  
Core Convection ◽  
Large Numbers ◽  
Low Dimensional

AbstractMajor airstreams in tropical cyclones (TCs) are rarely described from a Lagrangian perspective. Such a perspective, however, is required to account for asymmetries and time dependence of the TC circulation. We present a procedure that identifies main airstreams in TCs based on trajectory clustering. The procedure takes into account the TC’s large degree of inherent symmetry and is suitable for a very large number of trajectories . A large number of trajectories may be needed to resolve both the TC’s inner-core convection as well as the larger-scale environment. We define similarity of trajectories based on their shape in a storm-relative reference frame, rather than on proximity in physical space, and use Fréchet distance, which emphasizes differences in trajectory shape, as a similarity metric. To make feasible the use of this elaborate metric, data compression is introduced that approximates the shape of trajectories in an optimal sense. To make clustering of large numbers of trajectories computationally feasible, we reduce dimensionality in distance space by so-called landmark multidimensional scaling. Finally, k-means clustering is performed in this low-dimensional space. We investigate the extratropical transition of Tropical Storm Karl (2016) to demonstrate the applicability of our clustering procedure. All identified clusters prove to be physically meaningful and describe distinct flavors of inflow, ascent, outflow, and quasi-horizontal motion in Karl’s vicinity. Importantly, the clusters exhibit gradual temporal evolution, which is most notable because the clustering procedure itself does not impose temporal consistency on the clusters. Finally, TC problems are discussed for which the application of the clustering procedures seems to be most fruitful.

A Lightning Data Assimilation Technique for Mesoscale Forecast Models

2007 ◽  
Vol 135 (5) ◽  
pp. 1732-1748 ◽  
Author(s):  
Edward R. Mansell ◽  
Conrad L. Ziegler ◽  
Donald R. MacGorman
Keyword(s):  
Mesoscale Model ◽  
Initial Conditions ◽  
Deep Convection ◽  
Cold Pool ◽  
Cold Pools ◽  
Heating And Cooling ◽  
Lightning Detection ◽  
Forecast Models ◽  
Mapping Array ◽  
Total Lightning

Abstract Lightning observations have been assimilated into a mesoscale model for improvement of forecast initial conditions. Data are used from the National Lightning Detection Network (cloud-to-ground lightning detection) and a Lightning Mapping Array (total lightning detection) that was installed in western Kansas–eastern Colorado. The assimilation method uses lightning as a proxy for the presence or absence of deep convection. During assimilation, lightning data are used to control the Kain–Fritsch (KF) convection parameterization scheme. The KF scheme can be forced to try to produce convection where lightning indicated storms, and, conversely, can optionally be prevented from producing spurious convection where no lightning was observed. Up to 1 g kg−1 of water vapor may be added to the boundary layer when the KF convection is too weak. The method does not employ any lightning–rainfall relationships, but rather allows the KF scheme to generate heating and cooling rates from its modeled convection. The method could therefore easily be used for real-time assimilation of any source of lightning observations. For the case study, the lightning assimilation was successful in generating cold pools that were present in the surface observations at initialization of the forecast. The resulting forecast showed considerably more skill than the control forecast, especially in the first few hours as convection was triggered by the propagation of the cold pool boundary.

scholarly journals An Objective Climatology of Tropical Cyclone Diurnal Pulses in the Atlantic Basin

2019 ◽  
Vol 147 (2) ◽  
pp. 591-605 ◽  
Author(s):  
Sarah D. Ditchek ◽  
John Molinari ◽  
Kristen L. Corbosiero ◽  
Robert G. Fovell
Keyword(s):  
Brightness Temperature ◽  
Tropical Cyclones ◽  
Inner Core ◽  
Heat Content ◽  
Atlantic Basin ◽  
Core Convection ◽  
Difference Fields ◽  
Upper Level ◽  
Cloud Tops ◽  
Favorable Conditions

Abstract Storm-centered IR brightness temperature imagery was used to create 6-h IR brightness temperature difference fields for all Atlantic basin tropical cyclones from 1982 to 2017. Pulses of colder cloud tops were defined objectively by determining critical thresholds for the magnitude of the IR differences, areal coverage of cold-cloud tops, and longevity. Long-lived cooling pulses (≥9 h) were present on 45% of days overall, occurring on 80% of major hurricane days, 64% of minor hurricane days, 46% of tropical storm days, and 24% of tropical depression days. These cooling pulses propagated outward between 8 and 14 m s−1. Short-lived cooling pulses (3–6 h) were found 26.4% of the time. Some days without cooling pulses had events of the opposite sign, which were labeled warming pulses. Long-lived warming pulses occurred 8.5% of the time and propagated outward at the same speed as their cooling pulse counterparts. Only 12.2% of days had no pulses that met the criteria, indicating that pulsing is nearly ubiquitous in tropical cyclones. The environment prior to outward propagation of cooling pulses differed from warming pulse and no pulse days by having more favorable conditions between 0000 and 0300 LT for enhanced inner-core convection: higher SST and ocean heat content, more moisture throughout the troposphere, and stronger low-level vorticity and upper-level divergence.

scholarly journals Analysis of Thundersnow Storms over Northern Colorado

2015 ◽  
Vol 30 (6) ◽  
pp. 1469-1490 ◽  
Author(s):  
Matthew R. Kumjian ◽  
Wiebke Deierling
Keyword(s):  
Electrical Properties ◽  
Electric Fields ◽  
Warm Season ◽  
Radar Data ◽  
Lightning Detection ◽  
Northern Colorado ◽  
Lightning Discharges ◽  
Mapping Array ◽  
Total Lightning ◽  
Convective Cells

ABSTRACT Lightning flashes during snowstorms occur infrequently compared to warm-season convection. The rarity of such thundersnow events poses an additional hazard because the lightning is unexpected. Because cloud electrification in thundersnow storms leads to relatively few lightning discharges, studying thundersnow events may offer insights into mechanisms for charging and possible thresholds required for lightning discharges. Observations of four northern Colorado thundersnow events that occurred during the 2012/13 winter are presented. Four thundersnow events in one season strongly disagrees with previous climatologies that used surface reports, implying thundersnow may be more common than previously thought. Total lightning information from the Colorado Lightning Mapping Array and data from conterminous United States lightning detection networks are examined to investigate the snowstorms’ electrical properties and to compare them to typical warm-season thunderstorms. Data from polarimetric WSR-88Ds near Denver, Colorado, and Cheyenne, Wyoming, are used to reveal the storms’ microphysical structure and determine operationally relevant signatures related to storm electrification. Most lightning occurred within convective cells containing graupel and pristine ice. However, one flash occurred in a stratiform snowband, apparently triggered by a tower. Depolarization streaks were observed in the radar data prior to the flash, indicating electric fields strong enough to orient pristine ice crystals. Direct comparisons of similar lightning- and nonlightning-producing convective cells reveal that though both cells likely produced graupel, the lightning-producing cell had larger values of specific differential phase and polarimetric radar–derived ice mass. Compared to warm-season thunderstorms, the analyzed thundersnow storms had similar electrical properties but lower flash rates and smaller vertical depths, suggesting they are weaker, ordinary thunderstorms lacking any warm (>0°C) cloud depth.

scholarly journals Necessary Conditions for Tropical Cyclone Rapid Intensification as Derived from 11 Years of TRMM Data

2013 ◽  
Vol 26 (17) ◽  
pp. 6459-6470 ◽  
Author(s):  
Haiyan Jiang ◽  
Ellen M. Ramirez
Keyword(s):  
Brightness Temperature ◽  
Tropical Cyclones ◽  
Inner Core ◽  
Necessary Conditions ◽  
Tropical Rainfall Measuring Mission ◽  
Intensity Change ◽  
Rapid Intensification ◽  
Minimum Threshold ◽  
Near Surface ◽  
Total Lightning

Abstract Rainfall and convective properties of tropical cyclones (TCs) are statistically quantified for different TC intensity change categories by using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2008. Four 24-h future intensity change categories are defined: rapidly intensifying (RI), slowly intensifying, neutral, and weakening. It is found that RI storms always have a larger raining area and total volumetric rain in the inner core. The maximum convective intensity in the inner core is not necessarily more intense prior to undergoing an RI episode than a slowly intensifying, neutral, or weakening episode. Instead, a minimum threshold of raining area, total volumetric rain, and convective intensity in the inner core is determined from the RI cases examined in this study. The following necessary conditions for RI are found in the inner core: total raining area > 3000 km2, total volumetric rain > 5000 mm h−1 km2, maximum near-surface radar reflectivity > 40 dBZ, maximum 20-dBZ (40 dBZ) echo height > 8 (4) km, minimum 85-GHz polarization–corrected brightness temperature (PCT) < 235 K, and minimum 10.8-μm brightness temperature < 220 K. To the extent that these thresholds represent all RI cases, they should be of value to forecasters for ruling out RI. This study finds that total lightning activities in the inner core (outer rainband) have a negative (positive) relationship with storm intensification.

scholarly journals Impact of the Hydrometeor Vertical Advection Method on HWRF’s Simulated Hurricane Structure

2020 ◽  
Vol 35 (2) ◽  
pp. 723-737
Author(s):  
Shaowu Bao ◽  
L. Bernardet ◽  
G. Thompson ◽  
E. Kalina ◽  
K. Newman ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Vertical Profile ◽  
Diabatic Heating ◽  
Inner Core ◽  
Cloud Water ◽  
Sea Level Pressure ◽  
Vertical Advection ◽  
Advection Schemes ◽  
The Difference ◽  
The Impact

Abstract The impact of different hydrometeor advection schemes on TC structure and intensity forecasts is examined through the evaluation of HWRF’s simulation of tropical cyclones using the operational Ferrier–Aligo (FA) microphysics that uses total condensate advection versus the same scheme but with separate hydrometeor advection (FA-adv). Results showed that FA-adv simulated larger storms. Idealized simulations revealed that the cause of the simulation differences is the characteristics of the vertical profile of cloud water (Qc), which has a sharp gradient near 850 hPa, and rainwater (Qr), which is vertically uniform below the melting layer. In FA, the resultant total condensate profile has a gradient near 850 hPa that is smaller than that of Qc but larger than that of Qr. In FA when the total condensate is advected and partitioned back to Qc and Qr, the advection of Qc is underestimated and that of Qr is overestimated than that in FA-adv. The separate advection of hydrometeors in the FA-adv scheme corrected this problem and caused the difference in microphysics and dynamics fields between the two schemes. The greater vertical advection of Qc in FA-adv represents a continual source of extra diabatic heating that leads to a greater integrated kinetic energy (IKE) in the storm simulated by FA-adv than FA. However, the radial distribution of the azimuthally averaged additional diabatic heating in FA-adv caused a sea level pressure adjustment that leads to a weaker maximum wind speed. The warming in the outer rainbands strengthens wind away from the inner core, which causes the simulated storm size to increase.

scholarly journals Why Do Model Tropical Cyclones Grow Progressively in Size and Decay in Intensity after Reaching Maturity?

2016 ◽  
Vol 73 (2) ◽  
pp. 487-503 ◽  
Author(s):  
Gerard Kilroy ◽  
Roger K. Smith ◽  
Michael T. Montgomery
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclones ◽  
Diabatic Heating ◽  
Inner Core ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
Core Convection ◽  
Tangential Wind ◽  
Hurricane Isabel ◽  
Boundary Layer Dynamics

Abstract The long-term behavior of tropical cyclones in the prototype problem for cyclone intensification on an f plane is examined using a nonhydrostatic, three-dimensional numerical model. After reaching a mature intensity, the model storms progressively decay while both the inner-core size, characterized by the radius of the eyewall, and the size of the outer circulation—measured, for example, by the radius of the gale-force winds—progressively increase. This behavior is explained in terms of a boundary layer control mechanism in which the expansion of the swirling wind in the lower troposphere leads through boundary layer dynamics to an increase in the radii of forced eyewall ascent as well as to a reduction in the maximum tangential wind speed in the layer. These changes are accompanied by changes in the radial and vertical distribution of diabatic heating. As long as the aggregate effects of inner-core convection, characterized by the distribution of diabatic heating, are able to draw absolute angular momentum surfaces inward, the outer circulation will continue to expand. The quantitative effects of latitude on the foregoing processes are investigated also. The study provides new insight into the factors controlling the evolution of the size and intensity of a tropical cyclone. It provides also a plausible, and arguably simpler, explanation for the expansion of the inner core of Hurricane Isabel (2003) and Typhoon Megi (2010) than that given previously.

scholarly journals Complex network approach for detecting tropical cyclones

2021 ◽  
Author(s):  
Shraddha Gupta ◽  
Niklas Boers ◽  
Florian Pappenberger ◽  
Jürgen Kurths
Keyword(s):  
Sea Level ◽  
Tropical Cyclones ◽  
Complex Network ◽  
Time Scales ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
Network Approach ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Climate Networks

AbstractTropical cyclones (TCs) are one of the most destructive natural hazards that pose a serious threat to society, particularly to those in the coastal regions. In this work, we study the temporal evolution of the regional weather conditions in relation to the occurrence of TCs using climate networks. Climate networks encode the interactions among climate variables at different locations on the Earth’s surface, and in particular, time-evolving climate networks have been successfully applied to study different climate phenomena at comparably long time scales, such as the El Niño Southern Oscillation, different monsoon systems, or the climatic impacts of volcanic eruptions. Here, we develop and apply a complex network approach suitable for the investigation of the relatively short-lived TCs. We show that our proposed methodology has the potential to identify TCs and their tracks from mean sea level pressure (MSLP) data. We use the ERA5 reanalysis MSLP data to construct successive networks of overlapping, short-length time windows for the regions under consideration, where we focus on the north Indian Ocean and the tropical north Atlantic Ocean. We compare the spatial features of various topological properties of the network, and the spatial scales involved, in the absence and presence of a cyclone. We find that network measures such as degree and clustering exhibit significant signatures of TCs and have striking similarities with their tracks. The study of the network topology over time scales relevant to TCs allows us to obtain crucial insights into the effects of TCs on the spatial connectivity structure of sea-level pressure fields.

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