Tropical cyclone risk combines the destructive force of tropical cyclones with growing concentration of population and assets in coastal zones. Additional concern is the potential impact of climate change on distribution, frequency and intensity of tropical storms on exposed regions across the world. Developing greater confidence and control over tropical cyclone risk is a major focus for the Willis Research Network involving many of the world's leading experts and research infrastructures.
Economic losses are driven by the risk of tropical cyclones making landfall. A major priority of the WRN is a continued analysis of the historical storms with the benefit of new records, improved statistical techniques for evaluating extreme distributions and a greater understanding of the global processes that influence tropical cyclone variability.
Global Climate Models.
We are reaching the limits of what historical records alone can tell us about tropical cyclone risk. Detailed historic records are only available for the last 30 to 40 years and therefore not sufficient to estimate low-probability events, tail risks and extremes. The WRN is at the centre of employing the outputs of a new generation of high resolution climate models which have the power to model realistically the distribution and intensities of current climate tropical cyclones on a regional and global scale. New opportunities arise from the convergence of low-resolution global climate models and dynamic high-resolution weather models, as well as global-scale variable grid climate models. With these resources we are at the beginning of a new era in our assessment of global and local patterns of tropical cyclone activity opening major possibilities for catastrophe risk protection and management.
Seasonal and Multi-Year Forecasting.
The improvements of global climate and numerical weather modelling systems as well as advances in quality-controlled historic ‘Best Track’ data sets enables meteorological and research agencies to develop hybrid forecast systems. These forecast models build on regional high-resolution climate models and statistical relationships with climate variables. The lead-times of operational weather forecasting extends from of around fourteen days to long-term forecasting with a scope of months or even several seasons ahead. The potential of developing a statistically robust forecast of annual tropical cyclone risk relative to reference-level regional norms offers an important improvement in our ability to manage risk and allocate capital to regions with greatest need.
Potential tropical cyclone damage is triggered by wind, storm surge and/or extreme precipitation. The effect of wind is described by a footprint of cumulated maximum windspeeds observed during the storm. The footprint depends on the strength and extend of the rotational windfield as well as on the track and forward speed of the storm. Regional damages from flood and/or storm surge can differ from regions affected by wind and are usually modelled independently from the wind hazard. The treatment of these components within tropical cyclone models has a significant influence on expected losses. Within the WRN resources are combined to fully understand the complete damageability of tropical cyclones using new methods and indices to translate cyclone characteristics into effective estimates of destructive potential.
Understanding Exposure and Vulnerability.
The impact of tropical cyclones is driven by their interactions with the built environment, systems, networks and populations. Our understanding of exposure and vulnerability is insufficient in most developed and developing regions so that enhancing the quality of exposure data is a major priority for disaster risk reduction in communities at local and global scales. Facilities within the WRN also test buildings against cyclone wind and flood forces.
Economics, Insurance, Finance & Public Policy.
Developing sustainable solutions for tropical cyclone risk presents major challenges for administrations and insurance systems throughout the world. The research network combines the strength of its physical modelling with an extensive understanding of WRN's members institutions at the forefront of the economics, financing and public policy around tropical cyclone risk. This coupled with Willis role as a global insurance and reinsurance broker provides a comprehensive range of knowledge required to confront these challenges.
Date: Oct 25, 2013 | Type: Paper |
Journal: American Meteorological Society | Ext. Link: Click Here ›
Summary: An understanding of the potential drivers of local scale hurricane losses is developed through a case study analysis. Two recent Category Three US landfalling hurricanes (Ivan in 2004 and Dennis in 2005) are analyzed that, although similar in terms of maximum wind speed at their proximate coastal landfall locations, caused vastly different loss amounts.
Date: May 17, 2013 | Type: Paper |
Journal: Journal of Climate, 26 (1). pp. 133-152 | Ext. Link: Click Here ›
Authors: Strachan, J., Vidale, P. L., Hodges, K., Roberts, M. and Demory, M.-E
Summary: The ability to run General Circulation Models (GCMs) at ever-higher horizontal resolutions has meant that tropical cyclone simulations are increasingly credible. A hierarchy of atmosphere-only GCMs, based on the Hadley Centre Global Environmental Model (HadGEM1), with horizontal resolution increasing from approximately 270km to 60km (at 50N), is used to systematically investigate the impact of spatial resolution on the simulation of global tropical cyclone activity, independent of model formulation.
Date: Apr 04, 2013 | Type: Paper | Attachment: Download File ›
Authors: Dr. James Done and Dr. Greg Holland
Summary: Global Climate Model (GCM)-based Tropical Cyclone (TC) data hold considerable promise as an adjunct to the historical TC record. Multiple GCM simulations commonly extend for over one hundred years thereby substantially complementing the shorter observational record
Date: Mar 19, 2013 | Type: Paper |
Journal: Climate Dynamics | Ext. Link: Click Here ›
Authors: Greg Holland, Cindy L. Bruyère
Summary: Recent community consensus has concluded that it is likely that the frequency of intense hurricanes will increase with future anthropogenic climate change. IPCC (2007) also concluded that the current ‘warming of the climate system is unequivocal’. Yet IPCC (2012) concluded that ‘There is low confidence in any observed long-term increases in tropical cyclone activity’, based largely on potential errors in the observed data. Here we investigate this apparent anomaly and find that there has been an increase in the proportion of intense hurricanes relative to all hurricanes, and that is strongly related to an Anthropogenic Climate Change Index (ACCI).
Date: Jan 29, 2013 | Type: Paper |
Ext. Link: Click Here ›
Summary: Insurance Institute for Business and Home Safety (IBHS), a WRN partner released three new papers focusing on building codes in New York and New Jersey; guidance for repairing and rebuilding residential and commercial structures post-Sandy; and business protection lessons learned from Sandy. These papers contain valuable information related to building codes in New York and New Jersey and highlights the importance of building mitigation measures to wind and flood.
Date: Dec 10, 2012 | Type: Paper | Attachment: Download File ›
Authors: Dr. Habil. Michael Kunz & Prasad Gunturi
Summary: Sandy was a storm system with special meteorological characteristics causing widespread damage from the Caribbean to the U.S. East Coast. At the U.S. coast, especially in New York, New Jersey and Pennsylvania, Sandy resulted in a relatively high death toll compared to historic events. Critical infrastructure failures (electricity, transportation) are expected to lead to a high amount of indirect damages.
Date: Nov 08, 2012 | Type: Paper | Attachment: Download File ›
Authors: Chris Kilsby
and Jim Hall. Bernhard Mühr. Michael Kunz, Tina Kunz -Plapp, James Daniell, Bijan Khazai, Marjorie Vannieuwenhuyse, Tina Comes, Florian Elmer, Kai Schröter, Adrian Leyser, Christian Lucas, Joachim Fohringer, Thomas Münzberg, Werner Trieselmann, Jochen Zschau
Summary: Hurricane Sandy was a storm system with special meteorlogical characteristics. It caused widespread damage from the Caribbean to the U.S. East Coast.
Date: Nov 01, 2012 | Type: Article | Attachment: Download File ›
Authors: James Done, Jeffrey Czajkowski
Summary: This study provides new insights into the drivers of hurricane losses that have implications for existing approaches to hurricane loss modeling.
Date: Oct 31, 2012 | Type: Paper | Attachment: Download File ›
Authors: Prof David B. Stephenson; Dr. Leon Hermanson; Dr Angelika Werner
Summary: A two page paper looking at the impact of North Atlantic Oscillation on European Windstorms
Date: Aug 30, 2012 | Type: Paper | Attachment: Download File ›
Authors: Ed Hawkins and Pier Luigi Vidale
Summary: Tropical Atlantic storms impact the lives of many thousands of people each year. A study describes how different future anthropogenic emission pathways may change the frequency of these storms.
Date: Aug 01, 2012 | Type: Paper |
Journal: Journal of Climate | Ext. Link: Click Here ›
Authors: J. Strachan, P.L. Vidale, K.I. Hodges, MJ Roberts, and M.E. Demory,
Summary: Tropical cyclones are among the most destructive environmental hazards, with intense, landfalling storms leading to significant socioeconomic impacts. Tropical cyclones account for four of the five most costly insurance losses from natural disasters over the period 1950 to 2009 (Munich Re, 2010), with U S. hurricanes responsible for the highest natural catastrophe insurance losses. It is therefore essential that risk assessment takes into account our best understanding of how the naturally and anthropogenically varying climate system modulates storm behaviour
Date: May 15, 2012 | Type: Article | Attachment: Download File ›
Authors: David Brayshaw, Angelika Werner
Summary: A 2-page summary on the current state of Tropical Cyclone Seasonal Forecasting: methods and sources...
Date: May 01, 2012 | Type: Presentation | Attachment: Download File ›
Authors: Angelika Werner, Brigitte Balthasar
Summary: 2011 hat RMS ein neues europäisches Windsturmmodell veröffentlicht. Die Willis-interne Einschätzung des Sturm-risikos in Europa hat sich durch die Modelländerung zwar nicht signifikant verändert, allerdings haben die regional sehr groβen Unterschiede zum Vorgängermodell eine Dis-kussion zu Modellunsicherheiten und Modelladjustierungen angestoβen. Im Naturgefahrenbereich sind die Modellunsicherheiten sehr vielfältig, ferner kann die regionale Einschätzung des Risikos zwischen zwei verschiedenen Modellen sehr divergieren: - Teilweise müssen kundenspezifische Adjustie-rungen vorgenommen werden - Own View Of Risk notwendig für das interne Risikomanagement (u.a. auch für Solvency II) und Rückversicherungseinkauf
Date: May 01, 2012 | Type: Article | Attachment: Download File ›
Authors: Jane Strachan, Angelika Werner
Summary: A 2-page summary of El Niño and La Niña (ENSO) and its relevance to the insurance industry
Date: Feb 29, 2012 | Type: Paper | Attachment: Download File ›
Authors: Dr. James Done, Dr. Greg Holland and Dr. Angelika Werner
Fields: Statistics & Modelling
Summary: This study was triggered by recent papers from Daily et al. (2009) and Wang et al. (2011) on hurricane activity and U.S. landfall potential in the North Atlantic basin as a consequence of the extent of the ‘Atlantic Warm Pool (AWP)’, an area of warm water in the tropical and subtropical Atlantic. Warmer sea surface temperatures (SSTs) in that area lead to a well-established increase of North Atlantic tropical cyclone (TC) activity.
Date: Jan 25, 2012 | Type: Paper |
Journal: Weather | Ext. Link: Click Here ›
Authors: Jane Strachan
Summary: This article, based on a presentation to the RMetS's National Meeting on ‘Understanding the weather of 2011’ on 4 February 2012, reviews the predictions for the northern hemispheres tropical cyclone basins and looks at if the seasons turned out as expected.
Date: Sep 04, 2011 | Type: Paper | Attachment: Download File ›
Authors: Anil Kumar • James Done • Jimy Dudhia • Dev Niyogi
Summary: In this paper the predictability of Cyclone Sidr in the Bay of Bengal is explored in terms of track and intensity using the Advanced Research Hurricane Weather Research Forecast (AHW) model
Date: Jul 11, 2011 | Type: Presentation |
Ext. Link: Click Here ›
Authors: Gabriele Villarini, Gabriel A. Vecchi, James A. Smith
Fields: Atlantic Ocean, North America, Hurricanes, Extreme events, Hurricanes, North Atlantic Oscillation, Sea surface temperature, Tropical cyclones, Hurricanes, Statistical techniques, Statistics, Interannual variability, Interdecadal variability, Trends
Summary: Time series of U.S. landfalling and North Atlantic hurricane counts and their ratios over the period 1878–2008 are modeled using tropical Atlantic sea surface temperature (SST), tropical mean SST, the North Atlantic Oscillation (NAO), and the Southern Oscillation index (SOI). Two SST input datasets are employed to examine the uncertainties in the reconstructed SST data on the modeling results. Because of the likely undercount of recorded hurricanes in the earliest part of the record, both the uncorrected hurricane dataset (HURDAT) and a time series with a recently proposed undercount correction are considered.
Date: Jun 30, 2011 | Type: Article | Attachment: Download File ›
Authors: Angelika Werner, Angela M. Maharaj, Neil J. Holbrook
Summary: In this paper, the authors introduce a simple but effective means of removing ENSO-related variations from the Indian Ocean Dipole (IOD) in order to better evaluate the ENSO-independent IOD contribution to Australian climate—specifically here interannual variations in Australian region tropical cyclogensis (TCG) counts
Date: May 06, 2011 | Type: Paper | Attachment: Download File ›
Authors: Angelika Werner, Neil J. Holbrook
Summary: A new and potentially skillful seasonal forecast model of tropical cyclone formation [tropical cyclogenesis (TCG)] is developed for the Australian region.