A Look Back at the Historic 2020 U.S. Hurricane Season

Home , Hurricane Delta, Hurricane Iota, Hurricane Isaias, Hurricane Paulette, Hurricane Teddy, Hurricane Zeta

Jeffrey Strong, Ph.D. Tim Johnson, Ph.D.

Jeffrey Strong, Ph.D. Tim Johnson, Ph.D. Hurricane Wind Research Scientist Senior Engineer

Season Overview

Notable Storms

Climate Signals and Forecast Validation

Tropical Cyclones & Climate Change

AIR’s Supporting Tools

AIR Hurricane Contest

2020 Avg.

Named 30 14 Storms

Hurricanes 13 7

Major 6 3 Hurricanes

U.S. Hurricane 6 1-2 Landfalls

U.S. Major Hurricane 1 < 1 Landfalls

August September Isaias Josephine Kyle Laura Marco Omar Nana Paulette

October Rene Sally Teddy Vicky Wilfred Alpha Beta Gamma

November Delta Epsilon Zeta Eta Theta Iota

August September Isaias Josephine Kyle Laura Marco Omar Nana Paulette

October Rene Sally Teddy Vicky Wilfred Alpha Beta Gamma

November Delta Epsilon Zeta Eta Theta Iota U.S. Landfalling Tropical Storms

U.S. Landfalling Hurricanes

Most active season

Most landfalling tropical storms Fifth consecutive above average season Most storms formed in July

Highest number of Category 4 hurricanes 27 earliest named storms Most concurrently active storms

Most storms formed in September Fifth consecutive season with at least one Category 5 hurricane

First landfalling storm for Portugal Most storms a single storm outlasted Most storms formed before September

Most storms formed before August Strongest landfalling storm in Louisiana Most storms formed in May

Largest spread in names for currently active storms Most storms formed before October Easternmost forming storm

First time 3 storms named within 24 hours Most active September First Greek alphabet storm to make landfall in USA

Farthest north reverse extratropical transition Sixth consecutive year with pre-season storms

©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 8 “Quantity over Quality” 2005Most activevs. season2020 Most landfallingEstimated tropical storms IndustryFifth consecutive Insured above average Lossesseason Most for storms USA formed in July

Highest$140 number of Category 4* U.S.hurricanes only loss estimates from27 sources earliest* named storms Most concurrently active storms including PCS, Swiss Re, & Munich Re $120 trended to the end of the year 2019 Most storms formed in September Fifth consecutive season with at least one Category 5 hurricane $100

USD, Billions USD, Most storms formed before September First landfalling$80 storm for Portugal Most storms a single storm outlasted Most$60 storms formed before August28 Storms Strongest landfalling storm in Louisiana Most storms formed in May Largest spread$40 in names for currently active storms Most storms formed before October Easternmost forming storm * Range reflects AIR’s loss estimates * based on our ALERT offerings First time$20 3 storms named within 24 hours Most active September First Greek alphabet storm to make landfall in USA $0 30 Storms Farthest north reverse extratropical transition Sixth consecutive year with pre-season storms 2005 2020

푇 2 퐴퐶퐸 = ෍ 푉푚푎푥 200 1 Storm’s 6Intensity-hr max wind speed SumStorm’s over Duration a storm’s lifetime Iota 150

Epsilon Eta ACE ACE Delta 100

Paulette & Teddy 50 Laura

0 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct 1-Nov 1-Dec 1981-20101981-2010 Average Average 2020 2020 2005

Nov 13 18Z

Nov 15 06Z

Nov 16 12Z

Nov 17 00Z

Nov 18 12Z

• First time there were two major hurricanes in November

• First Category 5 hurricane to strike Colombia – Providencia Island

• Strongest recorded landfall in Nicaragua within November

Sep 16 06Z

Sep 17 18Z

Sep 21 12Z

Sep 23 12Z

• 4th largest Atlantic hurricane

• Diameter of gale force winds: 1,370 km • High waves from Lesser Antilles to Atlantic Canada

• One of 5 active storms at once

Sep 08 12Z

Sep 12 18Z

Sep 14 06Z

Sep 16 12Z

Sep 22 06Z

Sep 23 00Z

©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 28 ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 29 Source: AP Hurricane Laura • Heavy rainfall in Guadeloupe, Martinique, and Dominica • Minor flooding in the Netherlands Antilles (Saba, St. Eustatius) and St. Maarten • Heavy precipitation and tropical storm–force winds in the Dominican Republic and Haiti • Flash flooding in the Cayman Islands and Jamaica • Damaging winds and heavy rainfall in southwestern Cuba • Rapidly strengthened to a Category 4 hurricane to make landfall in Cameron, Louisiana

Landfall near Cameron, Louisiana

Vmax: 150 mph Cp: 938 mb

Tied for strongest hurricane to make landfall in Louisiana

Primarily wind-driven event with storm surge impact

Hurricane Laura

Hurricane Delta

Hurricane Zeta

Development and adoption of Louisiana State Prior to 2007, building codes Uniform Construction Code were adopted at the local (LSUCC) in the aftermath of or parish level Building Code Enforcement – Katrina and Rita in 2005; IBHS Rating the States effective as of January 2007 State 2012 2015 2018 Louisiana 73 82 83 Texas 18 36 34 Current version of LSUCC Original LSUCC incorporates 2015 IBC/IRC Mississippi 4 28 28 incorporated 2006 IBC/IRC and was adopted in Florida 95 94 95 February 2018

Damage due to a combination of wind and storm surge effects

1 2 3

(1) Lake Charles, LA (2) Lake Arthur, LA

(3) Abbeville, LA (3) Abbeville, LA (2) Lake Arthur, LA

• Before making landfall in Louisiana, Zeta made landfall north of Tulum, Quintana Roo, Mexico, as a Category 1 hurricane

• Zeta strengthened to a high-end Category 2 hurricane and made landfall in Cocodrie, LA, with 110 mph sustained winds

C B D

A B C E F

D E F

Pensacola, FL Gulf Shores, AL Gulf Shores, AL

Mobile, AL Pensacola, FL

• Isaias moved through the southern Bahamas and hugged Florida's East Coast

• Made landfall in SC as a Cat 1 storm but remained at tropical storm strength as it headed northeast

• Power outages were widespread • Wind damage to trees and power lines • Flooding impacts to DC, MD , PA, NJ, NY, DE, VA

Philadelphia, PA Courtesy: thestreet.com

35 140 * U.S. Insured only loss estimates from sources * including PCS, Swiss Re, & Munich Re trended to the end of the 30 120 year 2019

25 100

20 80

15 60

10 40

Losses Losses (USD,Billions) * Range reflects AIR’s Insured loss

Number Number Events of estimates * based on our ALERT offerings 5 20

0 0 2005 Hurricane 2020 Hurricane 2005 Hurricane 2020 Hurricane Season Season Season Season Events Major Hurricanes (Cat 3+) U.S. Landfalls

Midwest Derecho Courtesy: NOAA George Walker IV/ The Tennessean

Updated through Sept 2020 – NOAA

-1 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

1 NINO 3.4 0

-1

-2 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV 1 NINO 3 0 Cooler than normal across -1 the Tropical Pacific DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

1 NINO 1+2 0 Worsening La Niña -1 conditions all season -2 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

-1 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

1 NINO 3.4 0

-1

-2 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV 1 NINO 3 0

-1

DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV In line with pre-season 1 NINO 1+2 forecast for ENSO Neutral / 0

-1 weak La Niña

-2 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

-1 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

1 NINO 3.4 0

-1

-2 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV 1 NINO 3 0

-1

DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

1 NINO 1+2

-1

-2 DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

June July August September October

From NOAA GlobalTemp v5 per NOAA NCEI

Much warmer than average sea surface temperatures all season

June July August September October

From NOAA GlobalTemp v5 per NOAA NCEI

July August September October

Pre-Season NMME Forecasts:

°C -3 -2 -1 -0.5 -0.25 0.25 0.5 1 2 3 NMME: North American Multi-Model Ensemble ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 55 North Atlantic Sea Surface Temperatures (SST) Cool Phase AMO Atlantic Multidecadal Oscillation

Warm Phase AMO

• “Godzilla” outbreak of Saharan dust mid- to late-June • Brought severe air quality issues all the way to U.S. Midwestern states • One of the most intense outbreaks in the recent historical record • Cooled sea surface temperatures across the Main Development Region (MDR) of the tropical Atlantic Source: NASA/NOAA, Colin Seftor ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 57 Madden-Julian Oscillation (MJO)

AUG

SEP

OCT

NOV

NAO Negative Phase

Isaias Laura Teddy Delta NAO Positive Phase

NOAA CPC Elsner (2003)

https://seasonalhurricanepredictions.bsc.es/

Average of Pre-Season Forecasts

Forecast Number of Named Storms Forecast Number of Hurricanes Forecast Number of Major Hurricanes

30 30-year Average Year to Date

Named Storms Hurricanes Major Hurricanes

LOW MEAN HIGH LOW MEAN HIGH LOW MEAN HIGH

Year to Date 30 13 6

30-Year Average 7 14 28 2 7 15 0 3 7 MARCH – APRIL 13.9 16.9 20.2 6.6 8.4 10.3 3.0 3.9 5.5 Forecast Average MAY – JUNE 13.9 17.2 19.9 6.5 8.3 10.5 2.9 4.2 5.6 Forecast Average JULY – AUGUST 19.2 22.5 25.0 8.1 9.8 12.0 3.4 4.5 6.0 Forecast Average • All forecasts underestimated season’s activity on average • Early season update maintained status quo • July – August updates showed large increase in predicted activity

Average of Early Season Forecasts

Forecast Amount of Named Storms Accumulated Cyclone Energy LOW MEAN HIGH

Year to Date 179.8

30-Year Average 32 119.6 245.3 MARCH – APRIL 109.9 147.6 191.8 Forecast Average MAY – JUNE 111.3 152.3 193.4 Forecast Average JULY – AUGUST 141.3 181.5 225.6 Forecast Average

30-year Average Year to Date

©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 64 Projected Responses to Anthropogenic Warming Most Confidence: • Sea level rise will lead to higher storm inundation levels Medium-to-High Confidence: • Global increase in TC precipitation rates • Global average TC intensity will increase • Increase in global proportion of TCs that reach very intense levels Lower Confidence: • Decrease of global TC frequency • Increase in global very intense TC frequency • Poleward expansion of the latitude of maximum TC intensity • Slowdown in TC translation speed

Source: Knutson, T., and Coauthors, 2020: Tropical Cyclones and Climate Change Assessment: Part II: Projected Response to Anthropogenic Warming. Bull. Amer. Meteor. Soc., 101, E303–E322, https://doi.org/10.1175/BAMS-D-18-0194.1 ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 65 Frequency vs. Intensity Changes

Majority of studies predict fewer but more intense global tropical cyclones

Even more uncertainty when considering individual basins

Physical controls on frequency changes are still uncertain

Observational trends are hard to see

Despite the record number of storms this year, it is exceedingly difficult to attribute this anomaly to climate change alone

Knutson et al. (2020) ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 66 Rapid Intensity Changes 10 systems rapidly intensified (+35mph in 24h) in 2020, tying record from 1995 1. Hanna 40 mph Jul 24–25 2. Laura 65 mph Aug 25–26 2. Sally 40 mph Sep 14 4. Teddy 40 mph Sep 15–16 5. Gamma 35 mph Oct 2–3 6. Delta 85 mph Oct 5–6 7. Epsilon 50 mph Oct 20–21 8. Zeta 45 mph Oct 27–28 9. Eta 80 mph Nov 1–2 10. Iota 70 mph Nov 15–16

Source: Bhatia et al. (2018) ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 67 Rapid Intensity Changes 10 systems rapidly intensified (+35mph in 24h) in 2020, tying record from 1995 1. Hanna 40 mph Jul 24–25 2. Laura 65 mph Aug 25–26 2. Sally 40 mph Sep 14 4. Teddy 40 mph Sep 15–16 5. Gamma 35 mph Oct 2–3 6. Delta 85 mph Oct 5–6 7. Epsilon 50 mph Oct 20–21 8. Zeta 45 mph Oct 27–28 9. Eta 80 mph Nov 1–2 10. Iota 70 mph Nov 15–16 Bhatia et al. (2018) projected increased incidence of rapidly intensifying (and de-intensifying) storms Source: Bhatia et al. (2018) ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 68 Changes to Precipitation Potential

TC precipitation rates are projected to increase

Coupled with observed slowing of TC translation speeds can lead to locally enhanced precipitation amounts

Sally

TC precipitation rates are projected to increase

Coupled with observed slowing of TC translation speeds can Eta lead to locally enhanced precipitation amounts

Kossin (2018) Source: Kossin 2018, 2019; Moon et al. 2019; Lanzante 2019 ©2020 AIR Worldwide CONFIDENTIAL—For Webinar Attendees Only 70 Consecutive Events Laura & Delta 12 miles apart Consecutive hurricanes can lead to increased damage from sequential storms, even if the second storm is weaker • Louisiana had 5 landfalls this season • Laura’s damage enhanced Delta’s later in the season • While Iota was stronger than Eta, flood Eta & Iota damage was magnified from pre-saturated 15 miles apart ground As storm frequency changes in a warming world, we need to consider the frequency of consecutive events potentially changing

Web-based analytics platform

Complete transparency into AIR’s10,000- year catalog of simulated U.S. hurricanes

Hosted entirely on the cloud

Flexible data queries and data analysis

Easily export event sets to Touchstone® and TouchstoneRe™

Development Pre-Landfall Landfall Post-Landfall Event Lifecycle

25 Contest Entries 20 Expert Forecasts 1851-2019 Climatology 15

0 Named Storms Hurricanes Major Hurricanes U.S. Landfalls

***TO DATE*** 30 13 6 12

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