Tropical cyclones and Weather extremes Today and in the Future c3we.ucar.edu Greg Holland (gholland@ucar.edu) Supported by NSF, Willis Re, IAG, and Zurich Insurance 1
Topics State of the Climate and its Impact on Weather Extremes Weather Extremes Heatwaves, Droughts, Flood Rains, Hail, Wildfires Changing El Nino Impacts Tropical Cyclones Recent Activity Highlights Increasing Losses Clustering Extreme Rainfall The NCAR Risk Ecosystem Holland Willis 2018 2
State of the Climate 1.0 Global warming Now ~1 o C and higher over land 1.5 o C will almost certainly be passed Planning should be on the basis of 2 o C 1880 1960 2020 Comprehensive information for the globe and subregions: https://www.ametsoc.net/sotc2017/stateoftheclimate2017_lowres.pdf Attribution of Weather Extremes Rapidly increasing frequency of studies on attribution Improving understanding and capacity to define current and future changes Holland Willis 2018 3
Land Anomalies Already Exceed 2 o C July 2018 A recent study has shown that the probability that the globe will exceed 1.5 o C over the next five years is: 10% for a full year 38% or one month. (Smith et al 2018) https://data.giss.nasa.gov/gistemp/maps/ Holland Willis 2018 4
Probability Climate Impact on Extremes Extremes react strongly to relatively small changes in the mean state. 50 % 33 % 0 1 2 3 Northern Hemisphere Temperature Anomaly ( o C) Holland Willis 2018 5
Decadal Land Temperature Trends 0 1 2 o C (Hansen et al 2012) Holland Willis 2018 6
Some 1 o C Global Change Impacts Increasing Trend in: Severe Droughts Extreme Rainfall (examples later) Heat Waves: 10-20% of land mass exceeds previous record Polar Lows: Small decreasing trend in number, possible shift towards Scandinavia Medicanes: Possible increase in west, decrease in east Extratropical Cyclones: Increasing rainfall Little change in intensity Small potential increase in windstorm damage Possible shift southward from Scandinavia to UK and Central Europe Possible increased clustering of extreme storms. Holland Willis 2018 7
Derived Large Hail Climatology Derived climatology of hail >2.5 cm diameter using an algorithm applied to ERA Reanalysis. Period 1979-2011 (Prein and Holland 2018) Data Available at https://doi.pangaea.de/10.1594/pangaea.893160 Large Hail Days per Year Holland Willis 2018 8
Large Hail Trends 1980-2016 Increasing: Central US, Central Canada, Central Europe (significant) Steady: China, Eastern Australia Decreasing: South America, US Eastern Rockies Holland Willis 2018 9
El Nino and La Nina Climate Response an El Niño of a given magnitude that forms in the future is likely to have more influence over our weather than if the same El Niño formed 50 years ago. Fusillo et al (2018) (http://www.greenreport.it/news/agricoltura/onu-60-milioni-persone-colpite-el-ninoora-misure-preventive-la-nina/ Holland Willis 2018 10
ENSO Impacts on Temp. and Fire Temperature ( o C/ o C) Wildfire %/ o C Anthropogenic Climate Change produces systematic increases in the strength of ENSO teleconnections. +30-50% +100% Stronger teleconnection (higher interannual variability) in red, weaker in blue/green % indicates increases in interannual variability Californian precipitation also has a strong relationship with climate change (not shown). (Fasullo et al 2018 https://www.dropbox.com/sh/z48vgivmngb31ko/aad8onoxygcgz dwwapii-mw-a?dl=0 ) Holland Willis 2018 11
Tropical Cyclones Typhoon Jebi, Japan Jebi: Was the most intense to hit Japan since 1993 Preconditioned the soil with moisture for the subsequent quake-initiated mudslides. Holland Willis 2018 12
2017-18 Season Summary 2018 2018 2017-18 (Reynoso 2018) Holland Willis 2018 13
The Global Record Breakers: 2018 Gita: Most intense to hit Tonga Lane: Wettest in Hawaii, 2 nd wettest in US after Harvey Walaka: 2 nd most intense in Central Pacific Michael: Strongest to hit the Florida Panhandle, loss of life and damage well over land Jebi: Strongest to hit Japan since 1993. Marcus: Strongest to hit Darwin since 1974 Yutu: 10 th Cat 5 cyclone for 2018 and 5 th most intense landfalling cyclone on record. Five Cat 4+ hurricanes have hit US and its territories since August 2017. Previous record - two cat 4 s in two years. Holland Willis 2018 14
Global Tropical Cyclone Trends/ o C Frequency: Nil or slight decrease, poleward expansion is occurring Maximum possible intensity: Increasing 5-10% Intensity Distribution: Substantial increase in proportion of Cat 4 and 5, total climate impact may have already occurred Landfall Intensity: Seven of the 10 most intense landfalls on record have occurred since 2006 Storm Surge: Doubling in probability, especially for extreme surges Rainfall: 5-10% increase overall, possible substantial increase in extremes. Holland Willis 2018 15
Changes in Hurricane Losses %/ o C (Ranson et al 2014) Holland Willis 2018 16
Extreme Cyclone Rainfall: Debbie Category 4 US$2.7B Damage 14 deaths Almost all from severe and record flooding (up to 1300 mm) south of the landfall location. Local ocean temperatures ~2 o C above preindustrial levels. Holland Willis 2018 17
Hybrid WRF Cyclone Model Pre-Industrial Current (+1 o C) Future (+2 o C) Pre-Industrial Climate Change Intensity -13% +12% Cyclone Damage Potential -25% +12% Total Precipitation -32% +100% Rain rate / intensity -12% +150% Debbie closely followed the 2 o C simulation in both track and rainfall. Holland Willis 2018 18
Extreme Cyclone Rainfall: Harvey Category 4 US$125B Damage 107 deaths Almost all from severe and record flooding (up to 1000mm) around and east of the landfall location. Moisture came from local evaporation of anomalously-warm Gulf waters (Trenberth et al 2018) Holland Willis 2018 19
Real Time Hurricane Attribution Current Climate Climate Change Removed Real-time attribution of climate change impacts on rainfall for Hurricane Florence. (https://cpb-use1.wpmucdn.com/you.stonybrook.edu/dist/4/945/files/2018/09/09102018 00_Florence-one-pager-2lsrl7n.pdf ) Holland Willis 2018 20
Clustering of Weather Extremes Note that clustering impacts may arise from: Two or more extremes in spatial or temporal proximity Several relatively minor events that provide conditions for a latter system to become disastrous. Holland Willis 2018 21
Why do Storms Cluster? Stochastic Unpredictable? Environmental Predictable? Combining the Two may Provide Predictable Elements Holland Willis 2018 22
A Thought Experiment Chance of rolling two sixes, P=1/36 Weight the dice, P>1/36 Roll 10 times, P~0.5 Turn the 1 s into 6 s, P=1/9 Combine two or more of above More favourable intensification environment More intense hurricanes in a season Increased proportion of Cat4/5 hurricanes Impact of climate change. Add in the increases in exposed populations and infrastructure! Holland Willis 2018 23
e.g. Multiple US Cat 3+ Landfalls 2MH >1/200 (>1/200) 3MH >1/200 2MH 1/25 (1/25) 3MH >1/200 (>1/200) (>1/200) Past 30 y (Future) 2MH 1/40 (1/20) 3MH >1/200 (1/180) 2MH 1/15 (1/7) 3MH >1/60 (>1/30) Current risk lies between these. (Kossin et al 2010; Papachristou and Duan 2018) Holland Willis 2018 24
SST Anomaly by Group (Kossin et al 2010) Holland Willis 2018 25
September 2017 SST Anomaly Favours Clusters 3 and 4 2 MH P~10% 3 MH P=2-3% First recorded Landfall of two Cat 4 Hurricanes - Harvey (Aug) and Irma (Sep, both from Cluster 3) Four Cat 4 hurricane landfalls in 14 months! Holland Willis 2018 26
But For 2017 Let Us Add Low vertical windshear Environmental flow that holds TCs on long E-W trajectory Very high SST in western Caribbean Irma: 2 nd most intense Atlantic Hurricane; longest time >=160 kt; most intense ever in Leeward Islands Climate increases in proportion of Cat 4/5 hurricanes. Perhaps we are able to provide useful information on the likelihood and character of clustering from both stochastic and predictable elements. The question remains on how much weather-extreme clustering cascades down to clustered losses. Holland Willis 2018 27
Likelihood 0.00 0.10 0.20 0.30 NCAR Risk Ecosystem Stochastic Modules Adaptation of Geoscience Australia TCRM Rain, Hail, etc Based on Climate Model Ensembles TC Wind and Rain Footprint Modules Hybrid WRF Boundary-layer Model Rain Surface Wind 50 m/s 10-y Wind Return Period Impact Modules April 1 Forecast July 1 Forecast Historical flag 0 2 4 6 8 10 12 CDP Cyclone Damage Potential Holland Willis 2018 28
Willis Global Wind Footprint Next Presentation Holland Willis 2018 29
Probability Repechage Extremes react strongly to relatively small changes in the mean state. 33 % 0 1 2 3 Northern Hemisphere Temperature Anomaly ( o C) The climate has warmed by 1 o C We already are experiencing associated increases in extremes - for weather systems, clustering, and related damages. Holland Willis 2018 30