DOCSLIB.ORG

Rapid Intensification of Hurricane Earl in Advanced Hurricane WRF Model Simulations Diamilet Pérez-Betancourt

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Rapid Intensification of Hurricane Earl in Advanced Hurricane WRF Model Simulations Diamilet Pérez-Betancourt Rapid Intensification of Hurricane Earl in Advanced Hurricane WRF Model Simulations Diamilet Pérez-Betancourt Academic Affiliation, Fall 2011: Senior, University of Puerto Rico at Mayagüez SOARS® Summer 2011 Science Research Mentor: Christopher Davis Writing and Communication Mentor: Kimberly Kosmenko ABSTRACT Rapid intensification (RI) is a form of tropical cyclone (TC) intensification that is particularly challenging to predict. Understanding RI is essential for improving hurricane intensity forecast skill and hurricane preparedness. However, the physical processes that lead to RI are not well understood. Hurricane Earl, the second-strongest TC of the 2010 North Atlantic basin season, underwent RI on August 29, in its first day as a hurricane. The Advanced Hurricane Weather Research and Forecasting (AHW) model produced a simulation of Earl that was unsuccessful in predicting intensification, followed closely by a simulation successfully forecasting RI. The purpose of this study is to investigate the environmental and storm structure characteristics that led to Earl’s simulated RI. The unsuccessful and successful simulations were first compared in terms of the environmental vertical wind shear, because this parameter is often negatively correlated with TC intensification. Area averages of the deep-layer and mid-layer vertical wind shear over the storm suggest that this parameter did not influence the intensification of the successful simulation. Initially, the successful simulation featured greater relative humidity throughout the troposphere within the storm’s circulation. This led to a greater upward mass flux throughout the troposphere and a rapid intensification of circulation in the middle troposphere before any significant change occurred at the surface. After this deep vortex had been established, the mass flux (and lower-tropospheric convergence) continued to increase, leading to RI. These results provide a basis for further research to better understand and predict the development of RI. The Significant Opportunities in Atmospheric Research and Science (SOARS) Program is managed by the University Corporation for Atmospheric Research (UCAR) with support from participating universities. SOARS is funded by the National Science Foundation, the National Oceanic and Atmospheric Administration (NOAA) Climate Program Office, the NOAA Oceans and Human Health Initiative, the Center for Multi-Scale Modeling of Atmospheric Processes at Colorado State University, and the Cooperative Institute for Research in Environmental Sciences. 1. Introduction Tropical cyclones (TCs), named hurricanes in the North Atlantic and Eastern Pacific basins, are among Earth’s most devastating natural phenomena. This threat has motivated the efforts to better predict the TC’s track and intensity changes. Despite these efforts, predictions of TC intensification continue to have limited success (DeMaria et al. 2007). One particularly difficult to predict form of TC intensification is rapid intensification (RI), which the National Hurricane Center (NHC) defines as an increase in the maximum sustained surface wind speed of at least 15.4 ms-1 in a 24-hour period (NHC 2011). The physical mechanisms that lead to RI are still poorly understood. Several studies have assessed the processes that influence TC development and intensification (e. g., Gray 1968, Merrill 1988, Frank and Ritchie 1999). However, only a few studies have explicitly examined RI (Kaplan and DeMaria 2003). We base our study on the factors that have been generally related to TC intensification. These factors, which are briefly reviewed below, may be categorized as: atmosphere-ocean interactions, environmental influences, and inner core dynamics (Bosart et al. 2000). Studies focusing on atmosphere-ocean interactions have recognized sea surface temperature (SST) as an indicator of the maximum potential intensity of hurricanes (e.g., Malkus and Riehl 1960; Emanuel 1986). High SSTs enhance the latent heat flux, or transfer of energy, between the sea surface and the atmosphere. This flux supports convection, a mechanism for cloud formation, as water evaporates from the ocean surface. Therefore, high SSTs are expected to be favorable for RI. Nevertheless, Merrill (1988) argued that most hurricanes never reach the SST-dependent maximum intensity. He suggested that unfavorable atmospheric conditions prevent these TCs from intensifying. Thus, Merrill focused on the TC environment-structure interactions. He compared the atmospheric conditions surrounding intensifying and non-intensifying hurricanes with current intensity far below their maximum potential. Merril’s findings indicate that low environmental vertical wind shear is also favorable for TC intensification. This conclusion has been confirmed by more recent studies (Frank and Ritchie 1999, 2001). Thus, the general influence of large-scale environmental flows over TC intensification has been well established. However, we still have much to learn about the specifics of the complex physical processes involved in this interaction, specifically during RI events. Studies of the inner core dynamics of TCs link intensity changes with eyewall replacement cycles (e. g., Shapiro and Willoughby 1982, Willoughby et al. 1982). Other studies link TC intensification with potential vorticity anomalies (e.g., Montgomery and Kallenbach 1997, Molinari et al. 1998, Möller and Montgomery 2000). Numerical Weather Prediction (NWP) models, such as the Advanced Hurricane Weather Research and Forecasting (AHW) model, are utilized to predict the evolution of the TC inner core and TC intensity changes. These models are limited by initial condition errors related to the representation of the TC inner structure (Torn 2010). Understanding the TC inner core dynamics, as well as their relationship with the environment, is necessary to predict RI occurrence. Davis et al. (2008) evaluated the performance of the AHW in forecasting such rapid intensity changes during the 2005 North Atlantic season. The authors found SOARS® 2011, Diamilet Pérez-Betancourt, 2 that the AHW had difficulty capturing RI, particularly when RI occurred soon after initialization. We perform a case study of Hurricane Earl’s RI using AHW model simulations described by Davis et. al. (2010). According to the NHC TC report (Cangialosi 2011), Earl was one of the five major hurricanes of the 2010 North Atlantic season that experienced RI. Data from reconnaissance flights and satellite imagery indicate that Earl’s maximum sustained surface wind speed went from 38.6 ms-1 (August 29, 18:00 UTC) to 59.2 ms-1 (August 30, 18:00 UTC), increasing 20.6 ms-1 over a day. Interestingly, the AHW produced a simulation of Hurricane Earl with almost no intensification (0.7 ms-1 increase in maximum wind in 24-hours) followed closely by a simulation that captured the RI event more accurately (14.0 ms-1 increase in maximum wind in 24-hours) (Figure 1). Figure 1. Evolution of Hurricane Earl’s maximum wind speed. The black curve shows the official estimate from the NHC. The red curve shows the results of the AHW simulation starting in August 27, which produced almost no intensification. The blue curve shows the results of the AHW simulation starting in August 28, which followed closely the observed RI. The purpose of this study is to assess the environmental and structural characteristics that led to Hurricane Earl’s simulated RI. Our approach is to first compare the aforementioned unsuccessful and successful AHW simulations on a large-scale by examining the environmental vertical wind shear. We chose this parameter because it is often considered an unfavorable factor for TC intensification. Vertical wind shear can advect the heat and moisture away from the inner core of the storm necessary for convection (Gray 1968), or can tilt the vortex, producing an anomaly that inhibits convection (DeMaria 1996). SOARS® 2011, Diamilet Pérez-Betancourt, 3 Subsequently, we compare the simulations in terms of Hurricane Earl’s vortex characteristics. We examine the local rate of change of the relative vorticity (ζ) in isobaric coordinates , which is given by: ! !! ! !! ! ! %!V ( = "V •#(! + f ) "" " (! + f )#•V + k •' $ #"* (1) t p p ! ! & ! ) where p is the pressure, is the horizontal wind velocity vector, is the absolute vorticity or Coriolis parameter, and ω is the vertical wind velocity in pressure coordinates (!p / dt ). The area-average of the relative vorticity is defined as the circulation of the storm. Thus, we examine the vorticity equation (1) to identify the processes by which the successful simulation developed a stronger circulation (Figure 2). Initialized at 2010-08-27_00:00:00 Initialized at 2010-08-28_00:00:00 (a) (b) Figure 2. Horizontal wind field of Hurricane Earl at August 30 00:00 UTC from (a) the unsuccesful simulation, and (b) the successful simulation. The successful simulation developed the typical hurricane structure, including the eye and the highest winds in the eyewall. Our expectation is that the mechanism by which the AHW rapidly intensified Earl in the successful simulation is the mechanism by which the observed Earl rapidly intensified. To verify this, our analysis needs to be validated with observations of the storm’s environmental and structural characteristics. This analysis contributes to the understanding of how rapid intensification occurs, therefore improving the accuracy of intensity forecasting. The rest of the paper is organized as follows. Section 2 provides a synopsis of the history of Hurricane
Load more

Recommended publications
  • Observed Hurricane Wind Speed Asymmetries and Relationships to Motion and Environmental Shear
    1290 MONTHLY WEATHER REVIEW VOLUME 142 Observed Hurricane Wind Speed Asymmetries and Relationships to Motion and Environmental Shear ERIC W. UHLHORN NOAA/AOML/Hurricane Research Division, Miami, Florida BRADLEY W. KLOTZ Cooperative Institute for Marine and Atmospheric Studies, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida TOMISLAVA VUKICEVIC,PAUL D. REASOR, AND ROBERT F. ROGERS NOAA/AOML/Hurricane Research Division, Miami, Florida (Manuscript received 6 June 2013, in final form 19 November 2013) ABSTRACT Wavenumber-1 wind speed asymmetries in 35 hurricanes are quantified in terms of their amplitude and phase, based on aircraft observations from 128 individual flights between 1998 and 2011. The impacts of motion and 850–200-mb environmental vertical shear are examined separately to estimate the resulting asymmetric structures at the sea surface and standard 700-mb reconnaissance flight level. The surface asymmetry amplitude is on average around 50% smaller than found at flight level, and while the asymmetry amplitude grows in proportion to storm translation speed at the flight level, no significant growth at the surface is observed, contrary to conventional assumption. However, a significant upwind storm-motion- relative phase rotation is found at the surface as translation speed increases, while the flight-level phase remains fairly constant. After removing the estimated impact of storm motion on the asymmetry, a significant residual shear direction-relative asymmetry is found, particularly at the surface, and, on average, is located downshear to the left of shear. Furthermore, the shear-relative phase has a significant downwind rotation as shear magnitude increases, such that the maximum rotates from the downshear to left-of-shear azimuthal location.
    [Show full text]
  • Conference Poster Production
    65th Interdepartmental Hurricane Conference Miami, Florida February 28 - March 3, 2011 Hurricane Earl:September 2, 2010 Ocean and Atmospheric Influences on Tropical Cyclone Predictions: Challenges and Recent Progress S E S S Session 2 I The 2010 Tropical Cyclone Season in Review O N 2 The 2010 Atlantic Hurricane Season: Extremely Active but no U.S. Hurricane Landfalls Eric Blake and John L. Beven II ([email protected]) NOAA/NWS/National Hurricane Center The 2010 Atlantic hurricane season was quite active, with 19 named storms, 12 of which became hurricanes and 5 of which reached major hurricane intensity. These totals are well above the long-term normals of about 11 named storms, 6 hurricanes, and 2 major hurricanes. Although the 2010 season was considerably busier than normal, no hurricanes struck the United States. This was the most active season on record in the Atlantic that did not have a U.S. landfalling hurricane, and was also the second year in a row without a hurricane striking the U.S. coastline. A persistent trough along the east coast of the United States steered many of the hurricanes out to sea, while ridging over the central United States kept any hurricanes over the western part of the Caribbean Sea and Gulf of Mexico farther south over Central America and Mexico. The most significant U.S. impacts occurred with Tropical Storm Hermine, which brought hurricane-force wind gusts to south Texas along with extremely heavy rain, six fatalities, and about $240 million dollars of damage. Hurricane Earl was responsible for four deaths along the east coast of the United States due to very large swells, although the center of the hurricane stayed offshore.
    [Show full text]
  • Rapid Intensification of a Sheared Tropical Storm
    OCTOBER 2010 M O L I N A R I A N D V O L L A R O 3869 Rapid Intensification of a Sheared Tropical Storm JOHN MOLINARI AND DAVID VOLLARO Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York, Albany, New York (Manuscript received 10 February 2010, in final form 28 April 2010) ABSTRACT A weak tropical storm (Gabrielle in 2001) experienced a 22-hPa pressure fall in less than 3 h in the presence of 13 m s21 ambient vertical wind shear. A convective cell developed downshear left of the center and moved cyclonically and inward to the 17-km radius during the period of rapid intensification. This cell had one of the most intense 85-GHz scattering signatures ever observed by the Tropical Rainfall Measuring Mission (TRMM). The cell developed at the downwind end of a band in the storm core. Maximum vorticity in the cell exceeded 2.5 3 1022 s21. The cell structure broadly resembled that of a vortical hot tower rather than a supercell. At the time of minimum central pressure, the storm consisted of a strong vortex adjacent to the cell with a radius of maximum winds of about 10 km that exhibited almost no tilt in the vertical. This was surrounded by a broader vortex that tilted approximately left of the ambient shear vector, in a similar direction as the broad precipitation shield. This structure is consistent with the recent results of Riemer et al. The rapid deepening of the storm is attributed to the cell growth within a region of high efficiency of latent heating following the theories of Nolan and Vigh and Schubert.
    [Show full text]
  • Rapid Intensification of DOI:10.1175/BAMS-D-16-0134.1 Hurricanes Is Particularly Problematic
    WILL GLOBAL WARMING MAKE HURRICANE FORECASTING MORE DIFFICULT? KERRY EMANUEL As the climate continues to warm, hurricanes may intensify more rapidly just before striking land, making hurricane forecasting more difficult. ince 1971, tropical cyclones have claimed about cyclone damage, rising on average 6% yr–1 in inflation- 470,000 lives, or roughly 10,000 lives per year, and adjusted U.S. dollars between 1970 and 2015 (CRED S caused 700 billion U.S. dollars in damages globally 2016). Thus, appreciable increases in forecast skill and/ (CRED 2016). Mortality is strongly dominated by a or decreases of vulnerability, for example, through small number of extremely lethal events; for example, better preparedness, building codes, and evacuation just three storms caused more than 56% of the tropical procedures, will be required to avoid increases in cyclone–related deaths in the United States since 1900. cyclone-related casualties. Tropical cyclone mortality and injury have been Unfortunately, there has been little improvement reduced by improved forecasts and preparedness, espe- in tropical cyclone intensity forecasts over the period cially in developed countries (Arguez and Elsner 2001; from 1990 to the present (DeMaria et al. 2014). While Peduzzi et al. 2012), but through much of the world hurricane track forecasts using numerical prediction this has been offset by large changes in coastal popula- models have steadily improved, there has been only tions. For example, Peduzzi et al. (2012) estimate that slow improvement in forecasts of intensity by these the global population exposed to tropical cyclone same models. Reasons for this include stiff resolu- hazards increased by almost threefold between 1970 tion requirements for the numerical simulations of and 2010, and they project this trend to continue for tropical cyclone intensity (Rotunno et al.
    [Show full text]
  • Investigation and Prediction of Hurricane Eyewall
    INVESTIGATION AND PREDICTION OF HURRICANE EYEWALL REPLACEMENT CYCLES By Matthew Sitkowski A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Atmospheric and Oceanic Sciences) at the UNIVERSITY OF WISCONSIN-MADISON 2012 Date of final oral examination: 4/9/12 The dissertation is approved by the following members of the Final Oral Committee: James P. Kossin, Affiliate Professor, Atmospheric and Oceanic Sciences Daniel J. Vimont, Professor, Atmospheric and Oceanic Sciences Steven A. Ackerman, Professor, Atmospheric and Oceanic Sciences Jonathan E. Martin, Professor, Atmospheric and Oceanic Sciences Gregory J. Tripoli, Professor, Atmospheric and Oceanic Sciences i Abstract Flight-level aircraft data and microwave imagery are analyzed to investigate hurricane secondary eyewall formation and eyewall replacement cycles (ERCs). This work is motivated to provide forecasters with new guidance for predicting and better understanding the impacts of ERCs. A Bayesian probabilistic model that determines the likelihood of secondary eyewall formation and a subsequent ERC is developed. The model is based on environmental and geostationary satellite features. A climatology of secondary eyewall formation is developed; a 13% chance of secondary eyewall formation exists when a hurricane is located over water, and is also utilized by the model. The model has been installed at the National Hurricane Center and has skill in forecasting secondary eyewall formation out to 48 h. Aircraft reconnaissance data from 24 ERCs are examined to develop a climatology of flight-level structure and intensity changes associated with ERCs. Three phases are identified based on the behavior of the maximum intensity of the hurricane: intensification, weakening and reintensification.
    [Show full text]
  • And Hurricane Michael (2018)
    This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law. Access to this work was provided by the University of Maryland, Baltimore County (UMBC) ScholarWorks@UMBC digital repository on the Maryland Shared Open Access (MD-SOAR) platform. Please provide feedback Please support the ScholarWorks@UMBC repository by emailing [email protected] and telling us what having access to this work means to you and why it’s important to you. Thank you. atmosphere Article Understanding the Role of Mean and Eddy Momentum Transport in the Rapid Intensification of Hurricane Irma (2017) and Hurricane Michael (2018) Alrick Green 1, Sundararaman G. Gopalakrishnan 2, Ghassan J. Alaka, Jr. 2 and Sen Chiao 3,* 1 Atmospheric Physics, University of Maryland, Baltimore County, Baltimore, MD 21250, USA; [email protected] 2 Hurricane Research Division, NOAA/AOML, Miami, FL 33149, USA; [email protected] (S.G.G.); [email protected] (G.J.A.) 3 Department of Meteorology and Climate Science, San Jose State University, San Jose, CA 95192, USA * Correspondence: [email protected]; Tel.: +1-408-924-5204 Abstract: The prediction of rapid intensification (RI) in tropical cyclones (TCs) is a challenging problem. In this study, the RI process and factors contributing to it are compared for two TCs: an axis-symmetric case (Hurricane Irma, 2017) and an asymmetric case (Hurricane Michael, 2018).
    [Show full text]
  • State of the Climate in 2016
    STATE OF THE CLIMATE IN 2016 Special Supplement to the Bullei of the Aerica Meteorological Society Vol. 98, No. 8, August 2017 STATE OF THE CLIMATE IN 2016 Editors Jessica Blunden Derek S. Arndt Chapter Editors Howard J. Diamond Jeremy T. Mathis Ahira Sánchez-Lugo Robert J. H. Dunn Ademe Mekonnen Ted A. Scambos Nadine Gobron James A. Renwick Carl J. Schreck III Dale F. Hurst Jacqueline A. Richter-Menge Sharon Stammerjohn Gregory C. Johnson Kate M. Willett Technical Editor Mara Sprain AMERICAN METEOROLOGICAL SOCIETY COVER CREDITS: FRONT/BACK: Courtesy of Reuters/Mike Hutchings Malawian subsistence farmer Rozaria Hamiton plants sweet potatoes near the capital Lilongwe, Malawi, 1 February 2016. Late rains in Malawi threaten the staple maize crop and have pushed prices to record highs. About 14 million people face hunger in Southern Africa because of a drought that has been exacerbated by an El Niño weather pattern, according to the United Nations World Food Programme. A supplement to this report is available online (10.1175/2017BAMSStateoftheClimate.2) How to cite this document: Citing the complete report: Blunden, J., and D. S. Arndt, Eds., 2017: State of the Climate in 2016. Bull. Amer. Meteor. Soc., 98 (8), Si–S277, doi:10.1175/2017BAMSStateoftheClimate.1. Citing a chapter (example): Diamond, H. J., and C. J. Schreck III, Eds., 2017: The Tropics [in “State of the Climate in 2016”]. Bull. Amer. Meteor. Soc., 98 (8), S93–S128, doi:10.1175/2017BAMSStateoftheClimate.1. Citing a section (example): Bell, G., M. L’Heureux, and M. S. Halpert, 2017: ENSO and the tropical Paciic [in “State of the Climate in 2016”].
    [Show full text]
  • Hurricane & Tropical Storm
    5.8 HURRICANE & TROPICAL STORM SECTION 5.8 HURRICANE AND TROPICAL STORM 5.8.1 HAZARD DESCRIPTION A tropical cyclone is a rotating, organized system of clouds and thunderstorms that originates over tropical or sub-tropical waters and has a closed low-level circulation. Tropical depressions, tropical storms, and hurricanes are all considered tropical cyclones. These storms rotate counterclockwise in the northern hemisphere around the center and are accompanied by heavy rain and strong winds (NOAA, 2013). Almost all tropical storms and hurricanes in the Atlantic basin (which includes the Gulf of Mexico and Caribbean Sea) form between June 1 and November 30 (hurricane season). August and September are peak months for hurricane development. The average wind speeds for tropical storms and hurricanes are listed below: . A tropical depression has a maximum sustained wind speeds of 38 miles per hour (mph) or less . A tropical storm has maximum sustained wind speeds of 39 to 73 mph . A hurricane has maximum sustained wind speeds of 74 mph or higher. In the western North Pacific, hurricanes are called typhoons; similar storms in the Indian Ocean and South Pacific Ocean are called cyclones. A major hurricane has maximum sustained wind speeds of 111 mph or higher (NOAA, 2013). Over a two-year period, the United States coastline is struck by an average of three hurricanes, one of which is classified as a major hurricane. Hurricanes, tropical storms, and tropical depressions may pose a threat to life and property. These storms bring heavy rain, storm surge and flooding (NOAA, 2013). The cooler waters off the coast of New Jersey can serve to diminish the energy of storms that have traveled up the eastern seaboard.
    [Show full text]
  • CCRIFSPC Journey Through T
    CCRIF receives the ‘Reinsurance Initiative of the Year’ Award for the reinsurance initiative that generated the most promising CARICOM Heads of Government approach change to a signifi cant area of the World Bank for assistance to design business – the award was offered and implement a cost-effective risk transfer by The Review, the leading programme for member governments magazine of the international reinsurance industry Hurricane Ivan causes CCRIF makes payout to Turks and billions of dollars of losses Caicos Islands for Hurricane Ike across the Caribbean CCRIF makes the Real-Time Forecasting System (RTFS) available CCRIF is named to members for the fi rst ‘Transaction of time – each year it is the Year’ at the available to members Insurance Day at the beginning of London Market the Atlantic Hurricane Awards Season 2007 2004 2008 The Caribbean Catastrophe Risk Insurance Facility is formed as the fi rst multi-country, multi-peril pooled catastrophe risk insurance facility in the world A Multi-donor Trust Fund (MDTF) is established to support CCRIF’s initial operations CCRIF signs fi rst MOU with the Caribbean Institute CCRIF provides tropical cyclone (hurricane) and earthquake for Meteorology and Hydrology (CIMH) – over the coverage to 16 Caribbean member governments years, CCRIF has signed MOUs with the Caribbean Community Climate Change Centre (CCCCC), United Nations Economic Commission for Latin America and the Caribbean (ECLAC), Caribbean Disaster Emergency Management Agency (CDEMA), Inter- American Development Bank (IDB), University
    [Show full text]
  • Hurricane Eyewall Slope As Determined from Airborne Radar Reflectivity Data: Composites and Case Studies
    368 WEATHER AND FORECASTING VOLUME 28 Hurricane Eyewall Slope as Determined from Airborne Radar Reflectivity Data: Composites and Case Studies ANDREW T. HAZELTON AND ROBERT E. HART Department of Earth, Ocean, and Atmospheric Science, The Florida State University, Tallahassee, Florida (Manuscript received 19 April 2012, in final form 6 December 2012) ABSTRACT Understanding and predicting the evolution of the tropical cyclone (TC) inner core continues to be a major research focus in tropical meteorology. Eyewall slope and its relationship to intensity and intensity change is one example that has been insufficiently studied. Accordingly, in this study, radar reflectivity data are used to quantify and analyze the azimuthal average and variance of eyewall slopes from 124 flight legs among 15 Atlantic TCs from 2004 to 2011. The slopes from each flight leg are averaged into 6-h increments around the best-track times to allow for a comparison of slope and best-track intensity. A statistically significant re- lationship is found between both the azimuthal mean slope and pressure and between slope and wind. In addition, several individual TCs show higher correlation between slope and intensity, and TCs with both relatively high and low correlations are examined in case studies. In addition, a correlation is found between slope and radar-based eye size at 2 km, but size shows little correlation with intensity. There is also a tendency for the eyewall to tilt downshear by an average of approximately 108. In addition, the upper eyewall slopes more sharply than the lower eyewall in about three-quarters of the cases. Analysis of case studies discusses the potential effects on eyewall slope of both inner-core and environmental processes, such as vertical shear, ocean heat content, and eyewall replacement cycles.
    [Show full text]
  • A Preliminary Observational Study of Hurricane Eyewall Mesovortices
    AA PreliminaryPreliminary ObservationalObservational StudyStudy ofof HurricaneHurricane EyewallEyewall MesovorticesMesovortices Brian D. McNoldy and Thomas H. Vonder Haar Department of Atmospheric Science, Colorado State University e-mail: [email protected] ABSTRACT SATELLITE OBSERVATIONS The observational study of fine-scale features in A series of recent case studies will be presented that demonstrate the existence of mesovortices, vortex mergers, polygonal eyewalls, and vortex crystals. All cases were collected from the GOES-8 geosynchronous satellite centered over 0°N 75°W. Some cases were taken from “Normal Operations”, meaning images are taken every 15 or 30 minutes (depending on location). In special cases, the satellite images the storm every seven minutes; this is called “Rapid Scan Operations”. Finally, in high- the eye and eyewall of intense tropical cyclones (TC) priority situations, images can be taken every minute; this is called “Super Rapid Scan Operations”. has been made possible with high temporal and spatial To view loops of all the cases using the highest temporal resolution available, visit http://thor.cira.colostate.edu/tropics/eyewall/. The following four cases are small excerpts from the full loops. resolution imagery from geosynchronous satellites. The current Geosynchronous Operational Environmental BRET, 22Aug99 (1845Z-2010Z) ALBERTO, 12Aug00 (1445Z-1915Z) Satellite (GOES) Series is capable of producing 1-km resolution visible images every minute, resulting in an immense dataset which can be used to study convective cloud tops as well as transient low-level cloud swirls. Computer models have shown that vorticity redistribution in the core of a TC can result in the formation of local vorticity maxima, or mesovortices.
    [Show full text]
  • 1St View 1 January 2011
    1ST VIEW 1 January 2011 Page TABLE OF CONTENTS RENEWALS – 1 January 2011 Introduction 3 Casualty Territory and Comments 4 Rates 6 Specialties Line of Business and Comments 6 Rates 8 Property Territory and Comments 9 Rates Rate Graphs 3 Capital Markets Comments 5 Workers’ Compensation Territory and Comments 5 Rates 5 1st View This thrice yearly publication delivers the very first view on current market conditions to our readers. In addition to real-time Event Reports, our clients receive our daily news brief, Willis Re Rise ’ n shinE, periodic newsletters, white papers and other reports. Willis Re Global resources, local delivery For over 00 years, Willis Re has proudly served its clients, helping them obtain better value solutions and make better reinsurance decisions. As one of the world’s premier global reinsurance brokers, with 40 locations worldwide, Willis Re provides local service with the full backing of an integrated global reinsurance broker. © Copyright 00 Willis Limited / Willis Re Inc. All rights reserved: No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, whether electronic, mechanical, photocopying, recording, or otherwise, without the permission of Willis Limited / Willis Re Inc. Some information contained in this report may be compiled from third party sources we consider to be reliable; however, we do not guarantee and are not responsible for the accuracy of such. This report is for general guidance only, is not intended to be relied upon, and action based on or in connection with anything contained herein should not be taken without first obtaining specific advice.
    [Show full text]