ATSC 5160 Synoptic Meteorology Spring 2003
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Predictability of Explosive Cyclogenesis Over the Northwestern Pacific Region Using Ensemble Reanalysis
NOVEMBER 2013 K U W A N O - Y O S H I D A A N D E N O M O T O 3769 Predictability of Explosive Cyclogenesis over the Northwestern Pacific Region Using Ensemble Reanalysis AKIRA KUWANO-YOSHIDA Earth Simulator Center, Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa, Japan TAKESHI ENOMOTO Disaster Prevention Research Institute, Kyoto University, Uji, Kyoto, Japan (Manuscript received 1 June 2012, in final form 24 May 2013) ABSTRACT The predictability of explosive cyclones over the northwestern Pacific region is investigated using an en- semble reanalysis dataset. Explosive cyclones are categorized into two types according to whether the region of the most rapid development is in the Sea of Okhotsk or Sea of Japan (OJ) or in the northwestern Pacific Ocean (PO). Cyclone-relative composite analyses are performed for analysis increments (the differences between the analysis and the 6-h forecast) and ensemble spreads (the standard deviations of ensemble members of the analysis or first guess) at the time of the maximum deepening rate. The increment composite shows that the OJ explosive cyclone center is forecast too far north compared to the analyzed center, whereas the PO explosive cyclone is forecast shallower than the analyzed center. To understand the cause of these biases, a diagnosis of the increment using the Zwack–Okossi (Z-O) development equation is conducted. The results suggest that the increment characteristics of both the OJ and PO explosive cyclones are associated with the most important cyclone development mechanisms. The OJ explosive cyclone forecast error is related to a deeper upper trough, whereas the PO explosive cyclone error is related to weaker latent heat release in the model. -
An Examination of the Mesoscale Environment of the James Island Memorial Day Tornado
19.6 AN EXAMINATION OF THE MESOSCALE ENVIRONMENT OF THE JAMES ISLAND MEMORIAL DAY TORNADO STEVEN B. TAYLOR NOAA/NATIONAL WEATHER SERVICE FORECAST OFFICE CHARLESTON, SC 1. INTRODUCTION conditions also induced weak cyclogenesis along the front near the vicinity of KVDI. By 1200 UTC A cluster of severe thunderstorms the surface low was located between KNBC and moved across portions of south coastal South KCHS. This low and its influences on the Carolina during the early morning hours of 30 kinematic environment as well as the eventual May 2006. Around 1135 UTC, a severe position of the surface frontal boundary will prove thunderstorm spawned an F-1 tornado in the to be the main contributing factors leading to the James Island community of Charleston, SC. The development of the James Island tornado. tornado produced wind and structural damage as it moved rapidly NE through several residential neighborhoods. The tornado was on the ground for approximately 0.1 mi before it emerged into the Atlantic Ocean as a large waterspout near the entrance to the Charleston Harbor. Timely tornado warnings were issued by the NOAA/National Weather Service Forecast Office (WFO) in Charleston, SC (CHS), despite the event occurring during a climatologically rare time of day. This study will concentrate on the mesoscale factors that supported the genesis of the tornado and its parent severe thunderstorm. Radar data generated by the KCLX WSR-88D will also be presented. 2. SYNOPTIC ENVIRONMENT The synoptic environment supported the development of scattered convective precipitation Fig 1. Map of eastern SC/GA across much of the coastal areas of the Carolinas and Georgia. -
Explosive Cyclogenesis: a Global Climatology Comparing Multiple Reanalyses
6468 JOURNAL OF CLIMATE VOLUME 23 Explosive Cyclogenesis: A Global Climatology Comparing Multiple Reanalyses JOHN T. ALLEN,ALEXANDRE B. PEZZA, AND MITCHELL T. BLACK The University of Melbourne, Melbourne, Victoria, Australia (Manuscript received 17 September 2009, in final form 23 August 2010) ABSTRACT A global climatology for rapid cyclone intensification has been produced from the second NCEP reanalysis (NCEP2), the 25-yr Japanese Reanalysis (JRA-25), and the ECMWF reanalyses over the period 1979–2008. An improved (combined) criterion for identifying explosive cyclones has been developed based on preexisting definitions, offering a more balanced, normalized climatological distribution. The combined definition was found to significantly alter the population of explosive cyclones, with a reduction in ‘‘artificial’’ systems, which are found to compose 20% of the population determined by earlier definitions. Seasonally, winter was found to be the dominant formative period in both hemispheres, with a lower degree of interseasonal variability in the Southern Hemisphere (SH). Considered over the period 1979–2008, little change is observed in the frequency of systems outside of natural interannual variability in either hemisphere. Significant statistical differences have been found between reanalyses in the SH, while in contrast the Northern Hemisphere (NH) was characterized by strong positive correlations between reanalyses in almost all examined cases. Spatially, explosive cyclones are distributed into several distinct regions, with two regions in the northwest Pacific and the North Atlantic in the NH and three main regions in the SH. High-resolution and modern reanalysis data were also found to increase the climatology population of rapidly intensifying systems. This indicates that the reanalyses have apparently undergone increasing improvements in consistency over time, particularly in the SH. -
The Effects of Diabatic Heating on Upper
THE EFFECTS OF DIABATIC HEATING ON UPPER- TROPOSPHERIC ANTICYCLOGENESIS by Ross A. Lazear A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science (Atmospheric and Oceanic Sciences) at the UNIVERSITY OF WISCONSIN - MADISON 2007 i Abstract The role of diabatic heating in the development and maintenance of persistent, upper- tropospheric, large-scale anticyclonic anomalies in the subtropics (subtropical gyres) and middle latitudes (blocking highs) is investigated from the perspective of potential vorticity (PV) non-conservation. The low PV within blocking anticyclones is related to condensational heating within strengthening upstream synoptic-scale systems. Additionally, the associated convective outflow from tropical cyclones (TCs) is shown to build upper- tropospheric, subtropical anticyclones. Not only do both of these large-scale flow phenomena have an impact on the structure and dynamics of neighboring weather systems, and consequently the day-to-day weather, the very persistence of these anticyclones means that they have a profound influence on the seasonal climate of the regions in which they exist. A blocking index based on the meridional reversal of potential temperature on the dynamic tropopause is used to identify cases of wintertime blocking in the North Atlantic from 2000-2007. Two specific cases of blocking are analyzed, one event from February 1983, and another identified using the index, from January 2007. Parallel numerical simulations of these blocking events, differing only in one simulation’s neglect of the effects of latent heating of condensation (a “fake dry” run), illustrate the importance of latent heating in the amplification and wave-breaking of both blocking events. -
Chapter 10: Cyclones: East of the Rocky Mountain
Chapter 10: Cyclones: East of the Rocky Mountain • Environment prior to the development of the Cyclone • Initial Development of the Extratropical Cyclone • Early Weather Along the Fronts • Storm Intensification • Mature Cyclone • Dissipating Cyclone ESS124 1 Prof. Jin-Yi Yu Extratropical Cyclones in North America Cyclones preferentially form in five locations in North America: (1) East of the Rocky Mountains (2) East of Canadian Rockies (3) Gulf Coast of the US (4) East Coast of the US (5) Bering Sea & Gulf of Alaska ESS124 2 Prof. Jin-Yi Yu Extratropical Cyclones • Extratropical cyclones are large swirling storm systems that form along the jetstream between 30 and 70 latitude. • The entire life cycle of an extratropical cyclone can span several days to well over a week. • The storm covers areas ranging from several Visible satellite image of an extratropical cyclone hundred to thousand miles covering the central United States across. ESS124 3 Prof. Jin-Yi Yu Mid-Latitude Cyclones • Mid-latitude cyclones form along a boundary separating polar air from warmer air to the south. • These cyclones are large-scale systems that typically travels eastward over great distance and bring precipitations over wide areas. • Lasting a week or more. ESS124 4 Prof. Jin-Yi Yu Polar Front Theory • Bjerknes, the founder of the Bergen school of meteorology, developed a polar front theory during WWI to describe the formation, growth, and dissipation of mid-latitude cyclones. Vilhelm Bjerknes (1862-1951) ESS124 5 Prof. Jin-Yi Yu Life Cycle of Mid-Latitude Cyclone • Cyclogenesis • Mature Cyclone • Occlusion ESS124 6 (from Weather & Climate) Prof. Jin-Yi Yu Life Cycle of Extratropical Cyclone • Extratropical cyclones form and intensify quickly, typically reaching maximum intensity (lowest central pressure) within 36 to 48 hours of formation. -
Chapter 16 Extratropical Cyclones
CHAPTER 16 SCHULTZ ET AL. 16.1 Chapter 16 Extratropical Cyclones: A Century of Research on Meteorology’s Centerpiece a b c d DAVID M. SCHULTZ, LANCE F. BOSART, BRIAN A. COLLE, HUW C. DAVIES, e b f g CHRISTOPHER DEARDEN, DANIEL KEYSER, OLIVIA MARTIUS, PAUL J. ROEBBER, h i b W. JAMES STEENBURGH, HANS VOLKERT, AND ANDREW C. WINTERS a Centre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom b Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York, Albany, New York c School of Marine and Atmospheric Sciences, Stony Brook University, State University of New York, Stony Brook, New York d Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland e Centre of Excellence for Modelling the Atmosphere and Climate, School of Earth and Environment, University of Leeds, Leeds, United Kingdom f Oeschger Centre for Climate Change Research, Institute of Geography, University of Bern, Bern, Switzerland g Atmospheric Science Group, Department of Mathematical Sciences, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin h Department of Atmospheric Sciences, University of Utah, Salt Lake City, Utah i Deutsches Zentrum fur€ Luft- und Raumfahrt, Institut fur€ Physik der Atmosphare,€ Oberpfaffenhofen, Germany ABSTRACT The year 1919 was important in meteorology, not only because it was the year that the American Meteorological Society was founded, but also for two other reasons. One of the foundational papers in extratropical cyclone structure by Jakob Bjerknes was published in 1919, leading to what is now known as the Norwegian cyclone model. Also that year, a series of meetings was held that led to the formation of organizations that promoted the in- ternational collaboration and scientific exchange required for extratropical cyclone research, which by necessity involves spatial scales spanning national borders. -
Track Analysis of Cyclones Related to Tornadoes Over Western Greece
Proceedings of the 14th International Conference on Environmental Science and Technology Rhodes, Greece, 3-5 September 2015 TRACK ANALYSIS OF CYCLONES RELATED TO TORNADOES OVER WESTERN GREECE MATSANGOURAS I.T.1,2, NASTOS P.T.1, KOUROUTZOGLOU J.2,3, FLOCAS H.A.3 and HATZAKI M.1 1 Laboratory of Climatology and Atmospheric Environment, Faculty of Geology and Geoenvironment, University of Athens, University Campus GR-15784, Athens, Greece, 2 Hellenic National Meteorological Service, Hellinikon GR-16777, Athens, Greece, 3 Department of Environmental Physics-Meteorology, Faculty of Physics, University of Athens, University Campus GR-15784, Athens, Greece E-mail: [email protected] ABSTRACT Extreme weather phenomena, posing a significant threat to public health, causing injuries and even more fatalities, have been considered of high concern by the scientific community so that to mitigate the impacts and contribute to the adaptation and resilience of the society. Tornadoes and waterspouts have been characterized as the most violent of all small-scale natural phenomena. They are associated with extremely high winds, inside and around the tornado’s funnel, causing extended damage and in many cases loss of life. The goal of this study is to examine the cyclonic tracks associated to the incidence of tornadoes over western Greece, within the cold period of the year, from 2000 to 2012. The Laboratory of Climatology and Atmospheric Environment (LACAE, http://lacae.geol.uoa.gr) of the University of Athens has undertaken a systematic effort in recording tornadoes, waterspouts, and funnel clouds in Greece since 2007. LACAE developed in 2009 an open-ended online tornado report database web system (http://tornado.geol.uoa.gr), contributing to the compilation of a climatology of these extreme weather events. -
The Rapid Growth and Decay of an Extratropical Cyclone Over the Central Paci®C Ocean
358 WEATHER AND FORECASTING VOLUME 19 The Rapid Growth and Decay of an Extratropical Cyclone over the Central Paci®c Ocean JONATHAN E. MARTIN Department of Atmospheric and Oceanic Sciences, University of WisconsinÐMadison, Madison, Wisconsin JASON A. OTKIN Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of WisconsinÐMadison, Madison, Wisconsin (Manuscript received 22 April 2003, in ®nal form 6 November 2003) ABSTRACT The life cycle of a central Paci®c cyclone, characterized by a 48-h interval of rapid ¯uctuation in its intensity, is examined. The cyclone of interest underwent a period of explosive cyclogenesis from 1200 UTC 4 November to 1200 UTC 5 November 1986, followed 12 h later by a period of unusually rapid decay. Output from a numerical simulation of this event, run using the ®fth-generation Pennsylvania State University±National Center for Atmospheric Research (PSU±NCAR) Mesoscale Model (MM5), is used to perform a piecewise potential vorticity (PV) inversion in order to diagnose the life cycle of this unusual cyclone. The analysis reveals that the presence of lower-tropospheric frontogenetic forcing in an environment char- acterized by reduced static stability (as measured by high values of the K index) produced a burst of heavy precipitation during the development stage of the cyclone's life cycle. The associated latent heat release produced a substantial diabatic PV anomaly in the middle troposphere that was, in turn, responsible for the majority of the lower-tropospheric height falls associated with the explosive cyclogenesis. Subsequent height rises during the rapid cyclolysis stage resulted from the northward migration of the surface cyclone into a perturbation geopotential ridge associated with a negative tropopause-level PV anomaly. -
Tropical Cyclones: Formation, Maintenance, and Intensification
ESCI 344 – Tropical Meteorology Lesson 11 – Tropical Cyclones: Formation, Maintenance, and Intensification References: A Global View of Tropical Cyclones, Elsberry (ed.) Global Perspectives on Tropical Cylones: From Science to Mitigation, Chan and Kepert (ed.) The Hurricane, Pielke Tropical Cyclones: Their evolution, structure, and effects, Anthes Forecasters’ Guide to Tropical Meteorology, Atkinsson Forecasters Guide to Tropical Meteorology (updated), Ramage ‘Tropical cyclogenesis in a tropical wave critical layer: easterly waves’, Dunkerton, Montgomery, and Wang Atmos. Chem. and Phys. 2009. Global Guide to Tropical Cyclone Forecasting, Holland (ed.), online at http://www.bom.gov.au/bmrc/pubs/tcguide/globa_guide_intro.htm Reading: An Introduction to the Meteorology and Climate of the Tropics, Chapter 9 A Global View of Tropical Cyclones, Chapter 3, Frank Hurricane, Chapter 2, Pielke GENERAL CONSIDERATIONS Tropical convection acts as a heat engine, taking warm moist air from the surface and converting the latent heat into kinetic energy in the updraft, which is then exhausted into the upper troposphere. If the circulation can overcome the dissipating effects of friction it can become self-sustaining. In order for a convective cloud cluster to result in pressure falls at the surface, there must be a net removal of mass from the air column (net vertically integrated divergence). Since there is compensating subsidence nearby, outside of a typical convective cloud, there really isn’t much integrated mass divergence. Pressure really won’t fall unless there is a mechanism to remove the mass that is exhausted well away from the convection. Compensating subsidence near the convection also serves to decrease the buoyancy within the clouds, because the subsiding air will also warm. -
Low-Level Mesovortices Within Squall Lines and Bow Echoes. Part I: Overview and Dependence on Environmental Shear
NOVEMBER 2003 WEISMAN AND TRAPP 2779 Low-Level Mesovortices within Squall Lines and Bow Echoes. Part I: Overview and Dependence on Environmental Shear MORRIS L. WEISMAN National Center for Atmospheric Research,* Boulder, Colorado ROBERT J. TRAPP1 Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma (Manuscript received 12 November 2002, in ®nal form 3 June 2003) ABSTRACT This two-part study proposes fundamental explanations of the genesis, structure, and implications of low- level meso-g-scale vortices within quasi-linear convective systems (QLCSs) such as squall lines and bow echoes. Such ``mesovortices'' are observed frequently, at times in association with tornadoes. Idealized simulations are used herein to study the structure and evolution of meso-g-scale surface vortices within QLCSs and their dependence on the environmental vertical wind shear. Within such simulations, signi®cant cyclonic surface vortices are readily produced when the unidirectional shear magnitude is 20 m s 21 or greater over a 0±2.5- or 0±5-km-AGL layer. As similarly found in observations of QLCSs, these surface vortices form primarily north of the apex of the individual embedded bowing segments as well as north of the apex of the larger-scale bow-shaped system. They generally develop ®rst near the surface but can build upward to 6±8 km AGL. Vortex longevity can be several hours, far longer than individual convective cells within the QLCS; during this time, vortex merger and upscale growth is common. It is also noted that such mesoscale vortices may be responsible for the production of extensive areas of extreme ``straight line'' wind damage, as has also been observed with some QLCSs. -
Tracking Mesoscale Convective Systems That Are Potential Candidates for Tropical Cyclogenesis
FEBRUARY 2020 N ÚÑEZ OCASIO ET AL. 655 Tracking Mesoscale Convective Systems that are Potential Candidates for Tropical Cyclogenesis KELLY M. NÚÑEZ OCASIO,JENNI L. EVANS, AND GEORGE S. YOUNG Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, Pennsylvania (Manuscript received 15 March 2019, in final form 15 November 2019) ABSTRACT This study introduces the development of the Tracking Algorithm for Mesoscale Convective Systems (TAMS), an algorithm that allows for the identifying, tracking, classifying, and assigning of rainfall to me- soscale convective systems (MCSs). TAMS combines area-overlapping and projected-cloud-edge tracking techniques to maximize the probability of detecting the progression of a convective system through time, accounting for splits and mergers. The combination of projection on area overlapping is equivalent to setting the background flow in which MCSs are moving on. Sensitivity tests show that area-overlapping technique with no projection (thus, no background flow) underestimates the real propagation speed of MCSs over Africa. The MCS life cycles and propagation derived using TAMS are consistent with climatology. The rainfall assignment is also more reliable than with previous methods as it utilizes a combination of regridding through linear interpolation with high temporal and spatial resolution data. This makes possible the identi- fication of extreme rainfall events associated with intense MCSs more effectively. TAMS will be utilized in future work to build an AEW–MCS dataset to study tropical cyclogenesis. 1. Introduction that 60% of total cloud cover is due to such long-lived convective systems, which play an essential role in a. Mesoscale convective systems current the hydrological cycle. -
Subtropical Cyclogenesis Over the Central North Pacific*
APRIL 2006 CARUSO AND BUSINGER 193 Subtropical Cyclogenesis over the Central North Pacific* STEVEN J. CARUSO AND STEVEN BUSINGER Department of Meteorology, University of Hawaii at Manoa, Honolulu, Hawaii (Manuscript received 15 November 2004, in final form 20 October 2005) ABSTRACT The occurrence of subtropical cyclones over the central North Pacific Ocean has a significant impact on Hawaii’s weather and climate. In this study, 70 upper-level lows that formed during the period 1980–2002 are documented. In each case the low became cut off from the polar westerlies south of 30°N over the central Pacific, during the Hawaiian cool season (October–April). The objectives of this research are to document the interannual variability in the occurrence of upper-level lows, to chart the locations of their genesis and their tracks, and to investigate the physical mechanisms important in associated surface devel- opment. Significant interannual variability in the occurrence of upper-level lows was found, with evidence suggesting the influence of strong El Niño–Southern Oscillation events on the frequency of subtropical cyclogenesis in this region. Of the 70 upper-level lows, 43 were accompanied by surface cyclogenesis and classified as kona lows. Kona low formation is concentrated to the west-northwest of Hawaii, especially during October and November, whereas lows without surface development are concentrated in the area to the east-northeast of Hawaii. Kona low genesis shifts eastward through the cool season, favoring the area to the east-northeast of Hawaii during February and March, consistent with a shift in the climatological position of the trough aloft during the cool season.