scholarly journals The College Park, Maryland Tornado of 24 September 2001

2019 ◽  
Author(s):  
Kenneth Pryor ◽  
Tyler Wawrzyniak ◽  
Da-Lin Zhang
Keyword(s):  
Convective Available Potential Energy ◽  
Vertical Shear ◽  
Washington Dc ◽  
Operational Environment ◽  
South Central ◽  
Bow Echo ◽  
Upper Level ◽  
College Park ◽  
Forcing Mechanisms ◽  
Cloud Tops

The 24 September 2001 College Park, Maryland, tornado was a long-track and strong tornado that passed within a close range of two Doppler radars. It was the third in a series of three tornadoes associated with a supercell storm that developed in Stafford County, Virginia, and initiated 3 - 4 km southwest of College Park and dissipated near Columbia, Howard County. The supercell tracked approximately 120 km and lasted for about 126 minutes. This study presents a synoptic and mesoscale overview of favorable conditions and forcing mechanisms that resulted in the severe convective outbreak associated with the College Park tornado. Results show many critical elements of the tornadic event, including a negative-tilted upper-level trough over the Ohio Valley, a jet stream with moderate vertical shear, a low-level warm, moist tongue of the air associated with strong southerly flow over south-central Maryland and Virginia, and significantly increased convective available potential energy (CAPE) during the late afternoon hours. A possible role of the urban heat island effects from Washington, DC in increasing CAPE for the development of the supercell is discussed. Satellite imagery reveals banded convective morphology with high cloud tops associated with the supercell that produced the College Park tornado. Operational WSR-88D data exhibits a high reflectivity “debris ball” or tornadic debris signature (TDS) within the hook echo, the evolution of the parent storm from a supercell structure to a bow echo, and a tornado cyclone signature (TCS). Many of the mesoscale features could be captured by contemporary numerical model analyses. This study concludes with a discussion of the effectiveness of the coordinated use of satellite and radar observations in the operational environment of nowcasting severe convection.

scholarly journals The College Park, Maryland, Tornado of 24 September 2001

Geosciences ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 452
Author(s):  
Kenneth L. Pryor ◽  
Tyler Wawrzyniak ◽  
Da-Lin Zhang
Keyword(s):  
Convective Available Potential Energy ◽  
Vertical Shear ◽  
Washington Dc ◽  
Operational Environment ◽  
South Central ◽  
Bow Echo ◽  
Upper Level ◽  
College Park ◽  
Forcing Mechanisms ◽  
Cloud Tops

The 24 September 2001 College Park, Maryland, tornado was a long-track and strong tornado that passed within a close range of two Doppler radars. It was the third in a series of three tornadoes associated with a supercell storm that developed in Stafford County, Virginia, and initiated 3–4 km southwest of College Park and dissipated near Columbia, Howard County. The supercell tracked approximately 120 km and lasted for about 126 min. This study presents a synoptic and mesoscale overview of favorable conditions and forcing mechanisms that resulted in the severe convective outbreak associated with the College Park tornado. The results show many critical elements of the tornadic event, including a negative-tilted upper-level trough over the Ohio Valley, a jet stream with moderate vertical shear, a low-level warm, moist tongue of the air associated with strong southerly flow over south-central Maryland and Virginia, and significantly increased convective available potential energy (CAPE) during the late afternoon hours. A possible role of the urban heat island effects from Washington, DC, in increasing CAPE for the development of the supercell is discussed. Satellite imagery reveals the banded convective morphology with high cloud tops associated with the supercell that produced the College Park tornado. Operational WSR-88D data exhibit a high reflectivity “debris ball” or tornadic debris signature (TDS) within the hook echo, the evolution of the parent storm from a supercell structure to a bow echo, and a tornado cyclone signature (TCS). Many of the mesoscale features could be captured by contemporary numerical model analyses. This study concludes with a discussion of the effectiveness of the coordinated use of satellite and radar observations in the operational environment of nowcasting severe convection.

scholarly journals The College Park, Maryland Tornado of 24 September 2001

2019 ◽  
Author(s):  
Kenneth Pryor ◽  
Tyler Wawrzyniak ◽  
Da-Lin Zhang
Keyword(s):  
Convective Available Potential Energy ◽  
Vertical Shear ◽  
Operational Environment ◽  
South Central ◽  
Bow Echo ◽  
Close Range ◽  
Upper Level ◽  
College Park ◽  
Forcing Mechanisms ◽  
Cloud Tops

The 24 September 2001 College Park, Maryland, tornado was a long track and strong tornado that passed within a close range of two Doppler radars. It was the third in a series of three tornadoes associated with a supercell storm that developed in Stafford County, Virginia, and initiated 3 - 4 km southwest of College Park and dissipated near Columbia, Howard County. The supercell tracked approximately 120 km and lasted for about 126 minutes. This study presents a synoptic and mesoscale overview of favorable conditions and forcing mechanisms that resulted in the severe convective outbreak associated with the College Park tornado. Results show many critical elements of the tornadic event, including a negative-tilted upper-level trough over the Ohio Valley, a jet stream with moderate vertical shear, a warm, moist tongue of the air associated with strong southerly flow over south-central Maryland and Virginia, and significantly increased convective available potential energy during the late afternoon hours. Satellite imagery reveals banded convective morphology with high cloud tops associated with the supercell that produced the College Park tornado. Operational WSR-88D data exhibits a high reflectivity “debris ball” or tornadic debris signature (TDS) within the hook echo, the evolution of the parent storm from a supercell structure to a bow echo, and a tornado cyclone signature (TCS). Many of the mesoscale environmental features could be captured by contemporary numerical model analyses. This study concludes with a discussion of the effectiveness of the coordinated use of satellite and radar observations in the operational environment of nowcasting severe convection.

scholarly journals The College Park, Maryland Tornado of 24 September 2001

2019 ◽  
Author(s):  
Kenneth Pryor ◽  
Tyler Wawrzyniak ◽  
Da-Lin Zhang
Keyword(s):  
Convective Available Potential Energy ◽  
Vertical Shear ◽  
Operational Environment ◽  
South Central ◽  
Bow Echo ◽  
Close Range ◽  
Upper Level ◽  
College Park ◽  
Forcing Mechanisms ◽  
Cloud Tops

The 24 September 2001 College Park, Maryland, tornado was a long-tracked and violent tornado that passed within a close range of two Doppler radars. It was the third in a series of three tornadoes associated with a supercell storm that developed in Stafford County, Virginia, and initiated 3 - 4 km southwest of College Park and dissipated near Columbia, Howard County. The supercell tracked approximately 120 km and lasted for about 126 minutes. This study presents a synoptic and mesoscale overview of favorable conditions and forcing mechanisms that resulted in the severe convective outbreak associated with the College Park tornado. Results show many critical elements of the tornadic event, including a negative-tilted upper-level trough over the Ohio Valley, a jet stream with moderate vertical shear, a warm, moist tongue of the air associated with strong southerly flow over south-central Maryland and Virginia, and significantly increased convective available potential energy during the late afternoon hours. Satellite imagery reveals banded convective morphology with high cloud tops associated with the supercell that produced the College Park tornado. Operational WSR-88D data exhibits a high reflectivity “debris ball” or tornadic debris signature (TDS) within the hook echo, the evolution of the parent storm from a supercell structure to a bow echo, and a tornado cyclone signature (TCS). Many of the mesoscale environmental features could be captured by contemporary numerical model analyses. This study concludes with a discussion of the effectiveness of the coordinated use of satellite and radar observations in the operational environment of nowcasting severe convection.

scholarly journals Characteristics of Extratropical Cyclones That Cause Tornadoes in Italy: A Preliminary Study

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 180
Author(s):  
Eigo Tochimoto ◽  
Mario Marcello Miglietta ◽  
Leonardo Bagaglini ◽  
Roberto Ingrosso ◽  
Hiroshi Niino
Keyword(s):  
Environmental Conditions ◽  
Convective Available Potential Energy ◽  
Static Stability ◽  
Extratropical Cyclones ◽  
Cool Season ◽  
Southeastern Us ◽  
Different Seasons ◽  
The Difference ◽  
Upper Level ◽  
Strong Evaporation

Characteristics of extratropical cyclones that cause tornadoes in Italy are investigated. Tornadoes between 2007 and 2016 are analyzed, and statistical analysis of the associated cyclone structures and environments is performed using the JRA-55 reanalysis. Tornadoes are distributed sporadically around the cyclone location within a window of 10° × 10°. The difference in the cyclone tracks partially explains the seasonal variability in the distribution of tornadoes. The highest number of tornadoes occur south of the cyclone centers, mainly in the warm sector, while a few are observed along the cold front. Composite mesoscale parameters are examined to identify the environmental conditions associated with tornadoes in different seasons. Potential instability is favorable to tornado development in autumn. The highest convective available potential energy (CAPE) in this season is associated with relatively high-temperature and humidity at low-levels, mainly due to the strong evaporation over the warm Mediterranean Sea. Upper-level potential vorticity (PV) anomalies and the associated cold air reduce the static stability above the cyclone center, mainly in spring and winter. On average, the values of CAPE are lower than for US tornadoes and comparable with those occurring in Japan, while storm relative helicity (SREH) is comparable with US tornadoes and higher than Japanese tornadoes, indicating that the environmental conditions for Italian tornadoes have peculiar characteristics. Overall, the conditions emerging in this study are close to the high-shear, low-CAPE environments typical of cool-season tornadoes in the Southeastern US.

scholarly journals Recent Advances in Our Understanding of Tropical Cyclone Intensity Change Processes from Airborne Observations

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 650
Author(s):  
Robert F. Rogers
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Vertical Shear ◽  
Intensity Change ◽  
Change Processes ◽  
Cyclone Intensity ◽  
Secondary Eyewall Formation ◽  
Warm Core ◽  
Major Hurricane ◽  
Upper Level

Recent (past ~15 years) advances in our understanding of tropical cyclone (TC) intensity change processes using aircraft data are summarized here. The focus covers a variety of spatiotemporal scales, regions of the TC inner core, and stages of the TC lifecycle, from preformation to major hurricane status. Topics covered include (1) characterizing TC structure and its relationship to intensity change; (2) TC intensification in vertical shear; (3) planetary boundary layer (PBL) processes and air–sea interaction; (4) upper-level warm core structure and evolution; (5) genesis and development of weak TCs; and (6) secondary eyewall formation/eyewall replacement cycles (SEF/ERC). Gaps in our airborne observational capabilities are discussed, as are new observing technologies to address these gaps and future directions for airborne TC intensity change research.

Practical and Intrinsic Predictability of Severe and Convective Weather at the Mesoscales

2012 ◽  
Vol 69 (11) ◽  
pp. 3350-3371 ◽  
Author(s):  
Christopher Melhauser ◽  
Fuqing Zhang
Keyword(s):  
Weather Prediction ◽  
Squall Line ◽  
Cold Pool ◽  
Initial Condition ◽  
Large Variability ◽  
Forecast Performance ◽  
Sensitivity Experiments ◽  
Bow Echo ◽  
Upper Level ◽  
Convective Weather

Abstract This study explores both the practical and intrinsic predictability of severe convective weather at the mesoscales using convection-permitting ensemble simulations of a squall line and bow echo event during the Bow Echo and Mesoscale Convective Vortex (MCV) Experiment (BAMEX) on 9–10 June 2003. Although most ensemble members—initialized with realistic initial condition uncertainties smaller than the NCEP Global Forecast System Final Analysis (GFS FNL) using an ensemble Kalman filter—forecast broad areas of severe convection, there is a large variability of forecast performance among different members, highlighting the limit of practical predictability. In general, the best-performing members tend to have a stronger upper-level trough and associated surface low, producing a more conducive environment for strong long-lived squall lines and bow echoes, once triggered. The divergence in development is a combination of a dislocation of the upper-level trough, surface low with corresponding marginal environmental differences between developing and nondeveloping members, and cold pool evolution by deep convection prior to squall line formation. To further explore the intrinsic predictability of the storm, a sequence of sensitivity experiments was performed with the initial condition differences decreased to nearly an order of magnitude smaller than typical analysis and observation errors. The ensemble forecast and additional sensitivity experiments demonstrate that this storm has a limited practical predictability, which may be further improved with more accurate initial conditions. However, it is possible that the true storm could be near the point of bifurcation, where predictability is intrinsically limited. The limits of both practical and intrinsic predictability highlight the need for probabilistic and ensemble forecasts for severe weather prediction.

scholarly journals An Initiation Process of Tropical Depression-type Disturbances under the Influence of Upper-level Troughs

2021 ◽  
Author(s):  
Yuya Hamaguchi ◽  
Yukari N. Takayabu
Keyword(s):  
Large Scale ◽  
Convective Available Potential Energy ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
Dimensional Structure ◽  
Convective Heating ◽  
Upper Troposphere ◽  
Tropical Depression ◽  
Upper Level ◽  
Extratropical Forcing

AbstractIn this study, the statistical relationship between tropical upper-tropospheric troughs (TUTTs) and the initiation of summertime tropical-depression type disturbances (TDDs) over the western and central North Pacific is investigated. By applying a spatiotemporal filter to the 34-year record of brightness temperature and using JRA-55 reanalysis products, TDD-event initiations are detected and classified as trough-related (TR) or non-trough-related (non-TR). The conventional understanding is that TDDs originate primarily in the lower-troposphere; our results refine this view by revealing that approximately 30% of TDDs in the 10°N-20°N latitude ranges are generated under the influence of TUTTs. Lead-lag composite analysis of both TR- and non-TR-TDDs clarifies that TR-TDDs occur under relatively dry and less convergent large-scale conditions in the lower-troposphere. This result suggests that TR-TDDs can form in a relatively unfavorable low-level environment. The three-dimensional structure of the wave activity flux reveals southward and downward propagation of wave energy in the upper troposphere that converges at the mid-troposphere around the region where TR-TDDs occur, suggesting the existence of extratropical forcing. Further, the role of dynamic forcing associated with the TUTT on the TR-TDD-initiation is analyzed using the quasi-geostrophic omega equation. The result reveals that moistening in the mid-to-upper troposphere takes place in association with the sustained dynamical ascent at the southeast side of the TUTT, which precedes the occurrence of deep convective heating. Along with a higher convective available potential energy due to the destabilizing effect of TUTTs, the moistening in the mid-to-upper troposphere also helps to prepare the environment favorable to TDDs initiation.

Multiscale aspects of the 26–27 April 2011 tornado outbreak. Part I: Outbreak chronology and environmental evolution

2021 ◽  
Author(s):  
Manda B. Chasteen ◽  
Steven E. Koch
Keyword(s):  
Mississippi Valley ◽  
Environmental Evolution ◽  
Rossby Wave Breaking ◽  
Convective Systems ◽  
South Central ◽  
Rapid Flow ◽  
Low Level Jet ◽  
Upper Level ◽  
Tornado Outbreaks ◽  
Jet Streak

AbstractOne of the most prolific tornado outbreaks ever documented occurred on 26–27 April 2011 and comprised three successive episodes of tornadic convection that primarily impacted the southeastern U.S., including two quasi-linear convective systems (hereafter QLCS1 and QLCS2) that preceded the notorious outbreak of long-track, violent tornadoes spawned by numerous supercells on the afternoon of 27 April. The ~36-h period encompassing these three episodes was part of a longer multiday outbreak that occurred ahead of a slowly moving upper-level trough over the Rocky Mountains. In this Part I, we detail how the environment evolved to support this extended outbreak, with particular attention given to the three successive systems that each exhibited a different morphology and severity.The amplifying upper-level trough and attendant jet streak resulted from a Rossby wave breaking event that yielded a complex tropopause structure and supported three prominent shortwave troughs that sequentially moved into the south-central U.S. QLCS1 formed ahead of the second shortwave and was accompanied by rapid flow modifications, including considerable low-level jet (LLJ) intensification. The third shortwave moved into the lee of the Rockies early on 27 April to yield destabilization behind QLCS1 and support the formation of QLCS2, which was followed by further LLJ intensification and helped to establish favorable deep-layer shear profiles over the warm sector. The afternoon supercell outbreak commenced following the movement of this shortwave into the Mississippi Valley, which was attended by a deep tropopause fold, cold front aloft, and dryline that promoted two prominent bands of tornadic supercells over the Southeast.

scholarly journals Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1146-1150 ◽  
Author(s):  
Neil Patrick Griffis ◽  
Isabel Patricia Montañez ◽  
Roland Mundil ◽  
Jon Richey ◽  
John Isbell ◽  
...  
Keyword(s):  
Ice Age ◽  
Late Paleozoic ◽  
Karoo Basin ◽  
Base Level ◽  
South Central ◽  
Paraná Basin ◽  
Forcing Mechanisms ◽  
Sequence Boundaries ◽  
Parana Basin ◽  
Order Sequence

Abstract The demise of the Late Paleozoic Ice Age has been hypothesized as diachronous, occurring first in western South America and progressing eastward across Africa and culminating in Australia over an ∼60 m.y. period, suggesting tectonic forcing mechanisms that operate on time scales of 106 yr or longer. We test this diachronous deglaciation hypothesis for southwestern and south-central Gondwana with new single crystal U-Pb zircon chemical abrasion thermal ionizing mass spectrometry (CA-TIMS) ages from volcaniclastic deposits in the Paraná (Brazil) and Karoo (South Africa) Basins that span the terminal deglaciation through the early postglacial period. Intrabasinal stratigraphic correlations permitted by the new high-resolution radioisotope ages indicate that deglaciation across the S to SE Paraná Basin was synchronous, with glaciation constrained to the Carboniferous. Cross-basin correlation reveals two additional glacial-deglacial cycles in the Karoo Basin after the terminal deglaciation in the Paraná Basin. South African glaciations were penecontemporaneous (within U-Pb age uncertainties) with third-order sequence boundaries (i.e., inferred base-level falls) in the Paraná Basin. Synchroneity between early Permian glacial-deglacial events in southwestern to south-central Gondwana and pCO2 fluctuations suggest a primary CO2 control on ice thresholds. The occurrence of renewed glaciation in the Karoo Basin, after terminal deglaciation in the Paraná Basin, reflects the secondary influences of regional paleogeography, topography, and moisture sources.

Bow Echo Sensitivity to Ambient Moisture and Cold Pool Strength

2006 ◽  
Vol 134 (3) ◽  
pp. 950-964 ◽  
Author(s):  
Richard P. James ◽  
Paul M. Markowski ◽  
J. Michael Fritsch
Keyword(s):  
Convective Available Potential Energy ◽  
Three Dimensional ◽  
Cold Pool ◽  
Convective System ◽  
Cold Air ◽  
Convective Systems ◽  
Cold Pools ◽  
Bow Echo ◽  
Dry Conditions ◽  
Water Vapor Mixing Ratio

Abstract Bow echo development within quasi-linear convective systems is investigated using a storm-scale numerical model. A strong sensitivity to the ambient water vapor mixing ratio is demonstrated. Relatively dry conditions at low and midlevels favor intense cold-air production and strong cold pool development, leading to upshear-tilted, “slab-like” convection for various magnitudes of convective available potential energy (CAPE) and low-level shear. High relative humidity in the environment tends to reduce the rate of production of cold air, leading to weak cold pools and downshear-tilted convective systems, with primarily cell-scale three-dimensionality in the convective region. At intermediate moisture contents, long-lived, coherent bowing segments are generated within the convective line. In general, the scale of the coherent three-dimensional structures increases with increasing cold pool strength. The bowing lines are characterized in their developing and mature stages by segments of the convective line measuring 15–40 km in length over which the cold pool is much stronger than at other locations along the line. The growth of bow echo structures within a linear convective system appears to depend critically on the local strengthening of the cold pool to the extent that the convection becomes locally upshear tilted. A positive feedback process is thereby initiated, allowing the intensification of the bow echo. If the environment favors an excessively strong cold pool, however, the entire line becomes uniformly upshear tilted relatively quickly, and the along-line heterogeneity of the bowing line is lost.

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