Weekly Cat Reportcatastropheinsight.aon.com/reports/20200522-1-cat-alert.pdf · 2020-05-22 ·...

Weekly Cat Report May 22, 2020

Weekly Cat Report 2

This Week’s Natural Disaster Events

Event Impacted Areas Fatalities Damaged Structures and/or Filed Claims

PreliminaryEconomic Loss (USD)*

Page

Cyclone Amphan India, Bangladesh 103+ 100,000+ 2+ billion 3

Tropical Storm Arthur United States 0 Hundreds Negligible 7

Typhoon Vongfong Philippines 0 20,000+ 100+ Million 9

Severe Weather United States 0 Thousands 100+ million 11

Flooding United States 1+ Thousands 100+ million 13

Earthquake United States 0 Unknown Negligible 17

Severe Weather Vietnam 3 2,000+ Unknown 17

Severe Weather United States 0 Hundreds Millions 17

*Please note that these estimates are preliminary and subject to change. In some instances, initial estimates may be significantly adjusted as losses develop over time. This data is provided as an initial view of the potential financial impact from a recently completed or ongoing event based on early available assessments.

Along with this report, we continue to welcome users to access current and historical natural catastrophe data and event analysis on Impact Forecasting’s Catastrophe Insight website: http://catastropheinsight.aon.com

Weekly Cat Report 3

Powerful Cyclone Amphan makes India landfall Amphan originated in southern Bay of Bengal and the Joint Typhoon Warning Center began watching it on May 15 when it achieved an intensity equivalent to a tropical storm. Later, Amphan had undergone explosive rapid intensification and became the strongest Super Cyclone recorded in the Bay of Bengal on May 18. At its peak, the JTWC highlighted that the storm had 260 kph (160 mph) winds (1-minute sustained average) – equal to a Category 5 storm on the Saffir-Simpson Scale – before eventually making landfall as a Category 2-equivalent storm with 160 kph (100 mph) winds. Amphan came ashore innortheastern India and adjoining parts of Bangladesh, leaving at least 103 people dead and causing widespread damage in its wake. Total economic losses were expected to exceed USD2 billion; likely higher. Given low insurance penetration, most damage was expected to be uninsured.

Meteorological Recap

A low-pressure system formed over the southeastern Bay of Bengal around 1020 kilometers (635 miles) toward the southeast of Visakhapatnam, India on May 13. The atmospheric and oceanic environmental conditions were favorable for the continued strengthening of the low-pressure system. The Joint Typhoon Warning Center (JTWC) began watching an organized convection in the southern Bay of Bengal on May 15. The system continued to track north through a highly favorable atmospheric and oceanic environment and turned into a severe cyclonic storm on May 16 at 06:00 UTC. The system first attained hurricane-equivalent intensity on May 17 at 06:00 UTC – 120 kph (75 mph); Category 1 on the Saffir-Simpson Hurricane Wind Scale – and became better organized as deemed Tropical Cyclone Amphan. At this point in time, Amphan was still an expansive system with a mean diameter of around 1,111 kilometers (690 miles) and with super-dense, deep, and symmetrically aligned central convection while maintaining a sharply-outlined 19 kilometers (12 miles) diameter eye.

The system continued to strengthen and during one 24-hour stretch ending on May 18 06:00 UTC, the system further intensified by 140 kph (85 mph) to an initial peak intensity of 260 kph (160 mph). Microwave imagery depicted that the system fluctuated in intensity with the eye feature contracting and undergoing eyewall-replacement cycles with presence of twin distinct concentric eyewalls on May 18, according to the JTWC. Later, the cyclonic storm showed weakening due to prevailing moderate wind shear and dry air intrusion conditions on May 18.

Weekly Cat Report 4

This weakening persisted as it continued to travel north in moderate wind shear conditions as the JTWC noted it to have declined to a Category 3 cyclone on May 19 at 06:00 UTC. Later, the system interacted with increasing wind shear due to pre-monsoonal movements in the Bay of Bengal and continued to degrade. Amphan officially made landfall at approximately 2:30 PM local time (09:00 UTC) with estimated 1-minute average sustained winds of 155 kph (100 mph) near Bakkhali, in West Bengal (between Digha (west Bengal, India) and Hatiya Islands (Bangladesh)) close to Sunderbans. This was an equivalent to a Category 2 hurricane.

After coming ashore, the storm quickly lost its tropical characteristics while encountering elevated wind shear and the frictional effects of land before dissipating. However, remnant precipitation and gusty winds led to persistent impacts for another 24 hours.

Event Details

India

Amphan had a devastating impact on eastern states of India. As of this writing, according to the latest media and disaster management agency reports, there were at least 79 fatalities (including 72 from West Bengal and 3 from Odisha) and no fewer than 1,000 injured. Widespread damage occurred in the coastal districts of Odisha and southern West Bengal (North 24 Parganas, Purba Medinipur, Howrah, Kolkata and South 24 Parganas districts) in India, however, minor damage was reported from the various other regions located in the northern and northeastern parts of India. A total of 658,000 people from the states of Odisha and West Bengal were pre-emptively evacuated owing to preparedness measures related to Amphan. Amphan affected coastal districts of the state of Odisha with wind gusts reaching to 106 kph (66 mph) and heavy rainfall (>200 millimeters), affecting nearly 4.5 million people mostly in Jagatsinghpur, Kendrapara, Bhadrak, Balasore, Jajpur and Mayurbhanj districts of Odisha.

Multiple initial reports of damage came from several parts of the state with significant damage reported to the power infrastructure and the farm sector mainly due to strong winds and floods. More than 65 power substations were affected during the event, causing power outages that affected around 2 million people. More than 100,000 hectares of standing crops were damaged in Odisha, according to the local media reports.

The storm wreaked havoc in West Bengal by bringing heavy rain and winds with speeds of up to 190 kph (120 mph); ripped apart polythene and tin roofs, swept away corrugated shades, and broke down portions of temporary homes, flattened old houses, uprooted trees, and caused damage to many electricity poles.

Amphan at landfall on visible satellite & on radar image. Source: NASA

Weekly Cat Report 5

South and North 24 Parganas and East Midnapore districts in West Bengal were noted to be worst-hit by the storm. Communication in large areas was knocked out after the storm’s impact, as electricity poles and electrical infrastructure were severely damaged or destroyed in the wake of the event.

As of this writing, no fewer than 5,500 homes were reported to have sustained severe damage, and severe coastal inundations were reported. This number was expected to substantially increase as broad damage assessments begin. National Disaster Relief Force (NDRF) has already started the restoration work, though the rescue efforts were severely hampered by the prevailing emergency due to COVID-19.

Bangladesh

Severe damage was noted even before the Amphan reached in the territory of Bangladesh, as coastal water levels rose. Damage to embarkments at various places in coastal Bangladesh led to inundation of 17 villages across the Galachipa, Kalapara, and Rangabali. Reported damages were primarily caused due to strong winds, heavy rainfall, and storm surge. Storm surge was particularly impactful in the Noakhali District as predicted water heights rose to 3 to 5 meters (10 to 16 feet).

According to the local media reports, severe initial damage was reported to the power infrastructure, resulting in power outages that left more than 10 million out of 28.5 million customers without electricity. As of this writing, local news agencies reported at least 20 deaths. Flash floods damaged or destroyed around 3,000 shrimp and crab farms. Mango farmers reportedly lost 12 to 15 percent of its crop due to fallen trees. According to the local media reports, more than 83,500 homes sustained partial or total damage, after storm surge damaged several embankments in the low lying coastal areas in Khulna. Total financial losses from Bangladesh were expected to reach USD1.5 billion.

Sri Lanka

Amphan caused flooding, lightning, and wind-related damage to homes and businesses in parts of Sri Lanka. Damage was initially reported from Sabaragamuwa, Central, Uva and Southern Provinces. According to the national Disaster Management Center (DMC), four people were killed. Anomalous flooding rains were recorded in Kegalle and Galle districts (>150 millimeters) on May 16, according to the Department of Meteorology, Sri Lanka. Details on damage on provincial level, as provided by the DMC, are in the table below.

Province Population Affected Fatalities Homes Destroyed Homes Damaged Homes total

Sabaragamuwa 15,269 3 9 533 542

Central 1,602 - - 290 290

Southern 1,416 - 1 283 284

North Central 540 1 0 192 192

Eastern 685 0 0 178 178

Northern 140 0 3 29 32

Uva N/A - 1 22 23

TOTAL 19,652 4 14 1,527 1,541

Weekly Cat Report 6

Thailand

Tropical Cyclone Amphan brought high waves, flash floods, flooding rains, and landslides in the 11 northern and northeastern provinces of Thailand on May 17. The event has damaged at least 1,305 homes in severely affected regions across the country.

Financial Loss Amphan became the strongest cyclone on record to occur in the Bay of Bengal during the month of May. Earlier, in the year 1999, a Super Cyclone with estimated sustained winds of 260 kph (160 mph) struck the Indian state of Odisha, that officially resulted in approximately 10,000 fatalities. The aggregate economic loss was USD4.5 billion in nominal dollars.

Total economic losses attributed to Cyclone Amphan were likely to cross the multi-billion-dollar (USD) threshold. A preliminary report from the Bangladesh government cited that total damage in the country was to approach USD1.5 billion. Given the damage footprint in India – especially in the Kolkata metro region – the economic cost was likely to be substantial. However, economic losses were projected to be minimal in Sri Lanka and Thailand.

Weekly Cat Report 7

Tropical Storm Arthur brings rain, surf to U.S. East Coast On May 16, Tropical Storm Arthur became the first named storm of the 2020 Atlantic Hurricane Season, over two weeks prior to the official start of the season on June 1, marking the 6th consecutive May with a named storm. Tropical Storm Arthur brought locally heavy rainfall and gusty winds to coastal North Carolina. Dangerous surf, rip currents, and tidal flooding were experienced along the Southeast and Mid-Atlantic coasts. At its peak, Arthur produced maximum sustained winds of 60 mph (95 kph) with an estimated minimum central pressure of 991 millibars. Financial losses were likely to be negligible.

Meteorological Recap On May 13, the National Hurricane Center (NHC) began monitoring for the development of an area of low pressure in the Atlantic which would eventually become Tropical Storm Arthur, east of the southern Florida coast and northeast of the Bahamas. Advisories for Tropical Depression One were first issued at 5:00 PM EDT (21:00 UTC) on May 16. By 11:00 PM EDT (03:00 UTC May 17) Air Force reconnaissance aircraft confirmed winds of tropical storm strength, allowing Tropical Storm Arthur to become the first named storm of the 2020 Atlantic Hurricane Season with sustained winds of 40 mph (65 kph). Arthur continued to progress steadily north-northeastward toward the North Carolina Outer Banks. During the next 24-hours, despite entrainment of dry mid-level air, Arthur encoutered marginally favorable conditions for strengthening with low wind shear, and occasion passes over the warmer waters of the Gulf Stream.

On the morning of May 18, with modestly better organization, Arthur remained a Tropical Storm with maximum sustained winds of 50 mph (80 kph) as it neared the North Carolina Outer Banks, traveling north-northeast at 16 mph (26 kph). The center of Arthur did not officially make landfall, however, on May 18 it passed about 20 miles (32 km) southeast of Cape Hatteras, North Carolina. After its closest approach with the U.S., Arthur exhibited slight strengthening, with maximum sustained winds increasing to 60 mph (96 kph) as its track began to shift easterly in association with the mid-latitude westerlies. On May 19, following interaction with a frontal system, Arthur became post-tropical and began to gradually dissipate as it continued east-southeast in the Atlantic.

Event Details In North Carolina, Tropical Storm warnings were posted for a large portion of the coast and barrier islands spanning from Surf City to Duck, including the Pamlico and Albemarle Sounds. The highest wind gusts occurred along coastal regions of North Carolina, especially the Outer Banks, and were generally 35 to 45 mph (56 to 72 kph). The highest measured gust of 49 mph (79 kph) occurred offshore at the Diamond Shoals buoy. Rainfall ranged from 3 to 5 inches (76 to 127 millimeters) in the southern portions of the warned region, decreasing to 1 to 3 inches (25 to 76 millimeters) further north. An automated weather station near Newport (Carteret County) recorded a 36-hour storm total rainfall of 5.01 inches (127 millimeters). Dangerous rip currents, along with high surf were reported along the coast, accompanied by minor inundations with storm surge up to 2 feet (0.6 meters). Economic costs were largely negligible.

In the Mid-Atlantic, in the wake of Tropical Storm Arthur, moderate to major tidal flooding occurred from May 19-20 along vulnerable areas adjacent to the Chesapeake Bay and tidal rives, including the James River. Inundation of 2 to 3 feet (0.6 to 0.9 meters) were measured across multiple high tides cycles.

May 18: Arthur nearing the North Carolina Coast on visible satellite. (Source: NOAA)

Weekly Cat Report 8

Miscellaneous

It is worth noting that 2020 became the sixth consecutive year in which the first named storm developed in the Atlantic Ocean prior to the “official” start of hurricane season on June 1. During the Satellite Era (1965-Present), there has been a notable shift to the first name storms of the season developing earlier in the calendar year (see graphic below). However, when comparing the first development date with overall seasonal Accumulated Cyclone Energy (ACE) – which measures how active a season can be in terms of storm intensity/energy – there is no strong correlation/relationship. For the insurance industry, the most meaningful seasonal statistic is the frequency of landfall.

Weekly Cat Report 9

Update: Typhoon Vongfong impacts in the Philippines Typhoon Vongfong impacted the Philippines on May 14-15, causing notable effects in Eastern Visayas. Local officials cited widespread wind, flood and coastal inundation damage. There were 114 injuries, but no fatalities were reported. Total economic losses to infrastructure and agriculture alone were tentatively estimated at PHP2.18 billion (USD43 million), and likely to rise.


Typhoon Vongfong (known as Ambo in Philippines) became the first named storm of the 2020 Northwest Pacific Typhoon Season. The storm crossed Visayas and Luzon islands of the Philippines archipelago, and made seven separate landfalls on May 14-15. The agency first noted that the system had become better organized and was deemed Typhoon Vongfong as it slowly meandered towards the west on May 13 at 00:00 UTC. The system first attained hurricane-equivalent intensity on May 13 at 12:00 UTC – 150 kph (90 mph); Category 1 on the Saffir-Simpson Hurricane Wind Scale – as it began to steadily strengthen while tracking over the warm waters of the Northwest Pacific. The JTWC began highlighting the possibility of further intensification prior to making landfall on province of Northern Samar in the eastern Philippines.

On May 13, rapid intensification occurred as Typhoon Vongfong neared the eastern Philippines. During a 24-hour stretch ending on May 13 18:00 UTC, the system strengthened by 95 kph (60 mph) alone to an initial peak intensity of 185 kph (115 mph). The system fluctuated in intensity as it neared the Philippines archipelago with the eye feature contracting and undergoing replacement cycles. It officially made landfall on May 14 at San Policarpo, Eastern Samar, Philippines at 04:15 UTC (12:15 PM local time). The JTWC noted that the system was either near or at its peak of 185 kph (115 mph) – Category 2 – at approximately 06:00 UTC on May 14. After coming ashore, the system continued to significantly weaken due to land interaction while crossing the Samar, causing its eye to disappear. Later, the storm started tracking towards Luzon and made a landfall on May 15. Vongfong nearing landfall (Source: NASA)

Weekly Cat Report 10

Vongfong made six additional landfalls on small islands (Dalupiri Island; Capul Island; Ticao Island; Burias Island; San Andres, Quezon and Real Quezon) while tracking between Visayas and Luzon.

Event Details Impact from the storm were largely limited to Eastern and Northern Samar Provinces in the administrative Region VIII (Eastern Visayas), where its first landfall occurred. Additional notable effects were felt in Aurora and Bulacan in Region III (Central Luzon) and Isabela in Region II (Cagayan Valley). The Philippines’ National Disaster Risk Reduction and Management Council (NDRRMC) noted a total of 407,500 people across nine provinces affected by the storm to some extent; there were 114 injuries, but no fatalities were reported as of May 21.

Nearly 20,000 homes were damaged or destroyed, most of which were located in Eastern and Northern Samar. In addition, at least 289 schools and 23 healthcare facilities sustained damage. Approximately 47,000 families (or 183,000 people) were pre-emptively evacuated. Notable economic losses were in agriculture and on infrastructure. Residential damage in Eastern and Northern Visayas, as reported by the NDRRMC on May 21, is provided in the table below:

Province / Municipality Population Affected Destroyed Damaged TOTAL

Northern Samar 240,487 3,076 6,233 9,309

- Lapinig 13,421 1,832 964 2,796

- Rosario 170 114 1,377 1,491

- Victoria 4,881 16 1,277 1,293

- Other 222,015 1,114 2,615 3,729

Eastern Samar 162,845 1,828 8,522 10,350

- San Policarpo 18,103 750 2,650 3,400

- Arteche 18,512 674 1,972 2,646

- Can-Avid 22,929 51 2,264 2,315

- Other 103,301 353 1,636 2,169

TOTAL (Philippines) 407,584 4,911 14,878 19,789

Financial Loss Losses in the agricultural sector were estimated at PHP1.5 billion (USD31 million) while infrastructural losses were noted at around PHP614 million (USD12 million), resulting in aggregate economic loss of PHP2.2 billion (USD43 million). Damage to property is not included in this figure.

Region Infrastructure (PHP million)

Agriculture (PHP million)

TOTAL (PHP million)

TOTAL (USD million)

Calabarzon 35 1,080 1,115 22.0

Region II (Cagayan Valley) 554 N/A 554 10.9

Region V (Bicol) 6.7 242 249 4.9

CAR (Cordillera) 7.5 224 231 4.6 Region VIII (Eastern Visayas)

11 142 153 3.0

Region III (Central Luzon) N/A 78 78 1.5

Mimaropa N/A 20 20 0.4

TOTAL (Philippines) 614 1,562 2,176 43.0


Pattern shift brings severe weather, flash flooding to U.S. An evident pattern shift across the continental United States brought a highly amplified upper level flow resulting in an unsettled and active week across the eastern half of the country. On May 14-15, a severe weather outbreak brought high winds, large hail, and locally heavy rainfall to the Midwest, Northeast, and Southern Plains. During a multi-day period between May 17-21, a vertically stacked upper-level low pressure system gradually meandered from the Midwest southeastward toward the southern Appalachians, before slowly weakening, producing cooler weather, gusty conditions, and prolonged periods of heavy rain and thunderstorms. This event caused many occurrences of extensive riverine and flash flooding across the Midwest, Ohio Valley, Tennessee Valley, and the Carolinas. This low contributed to a major flash flood event in northeastern Illinois and the City of Chicago on May 17, as well as a historic flooding event near Midland, Michigan where two dam failures occurred.

May 14-15


A noticeable pattern shift and amplifying jet stream led to a period of active weather for several regions across the country on May 14-15. The greatest impacts occurred on May 15, when flow around a high-pressure system located off the east coast allowed a plume of moist and humid air to surge northward ahead of a series of complex eastward advancing frontal boundaries expanding from the Southern Plains through the Ohio Valley (see the surface map on the left). This set-up allowed for probabilities of severe weather from southwestern Texas spanning northeastward into New England.

On May 15, the Storm Prediction Center (SPC) highlighted three main regions of concern. An Enhanced Risk for severe weather (level 3 out of 5) encompassed a large portion of central and eastern New York and western New England, with a Slight Risk (level 2 out 5) extending from central Ohio northeastward toward the southern New England coast. Further south, a second region of Enhanced Risk was identified in central Texas northward into southern Oklahoma. To the west, in the Central High Plains, a smaller region of Slight Risk was centered over northeastern Colorado and western Nebraska.

In the Northeast, a frontal system and deepening shortwave trough, which was responsible for localized flooding and severe storms in portions of the Midwest and Great Lakes on May 14, progressed eastward throughout the day toward the New England states. Increasing surface heating and moisture advection in the wake of a northward advancing warm frontal boundary provided increasing atmospheric instability. By the late afternoon, several discrete cells and severe linear storm clusters intensified ahead of the approaching cold front, with the greatest impacts occurring in New York, Vermont, Massachusetts, and New Hampshire. Widespread reports of straight-line winds topping 60 mph (95 kph) were recorded.


In the Southern Plains an intense mesoscale convective system (MCS) persisted behind a south-southwestward progressing convective outflow boundary in eastern and southcentral Oklahoma in the late afternoon and early evening. This MCS was responsible for multiple reports of severe weather and localized flash flooding. Meanwhile, a surface low pressure system and southward extending dryline (boundary that separates a moist air mass from a dry air mass) centered over the southern Texas panhandle, provided a boundary for additional development of severe storm clusters.

The environment to the east of these storms was characterized by very high Convective Available Potential Energy or CAPE (which is directly related to updraft strength in thunderstorms), as well as steep lapse rates (changes in temperature with height), creating an environment conducive for high winds and large hail. The storms rapidly developed into an extensive MCS in the late evening. A nearly continuous line of storms with embedded bowing segments extended from the Red River Valley across central Texas toward the Rio Grande. The main perils associated with these storms were locally heavy rainfall, large hail, and severe straight-line winds. In the wake of the MCS, a closed-low pressure system continued to produce locally heavy rains and severe weather over the ArkLaTex region on May 16.

In the Central High Plains, an approaching mid-level shortwave trough, along with sufficient surface heating and moisture allowed scattered and severe storms to initially develop across central Colorado in the afternoon. These storms led to several reports of marginally severe hail in northcentral Colorado on May 15.

Event Details On May 14, there were 84 reports of severe weather, of which 47 were for wind, 35 for hail, and 2 for tornadoes. The greatest impacts were felt across southeastern Iowa, northern Illinois, and northern Ohio. Training/repeating rounds of heavy rain and thunderstorms over portions of northern Missouri, southern Iowa, and northern Illinois led to localized flash flooding.

May 15 brought 228 reports of severe weather, of which 182 were for wind, 42 for hail, and 4 for tornadoes. The greatest impacts occurred in New York and Southern New England, as well as southern Oklahoma and central Texas. In New York, an EF1 tornado resulted in snapped trees and minor structural damage in Saratoga County. In Herkimer County, a confirmed macroburst with maximum wind gusts between 80 to 100 mph (130 to 160 kph) and a width of approximately 10 miles (16 km), caused significant power outages, and impacted several structures and outbuildings. In Ulster County, a microburst produced maximum wind gusts up to 85 mph (137 kph). In Oklahoma, an EF1 tornado in Muskogee County damaged and destroyed multiple outbuildings and power poles. In Grady and Jackson Counties severe and significant hail, approaching 2.00 inches (5.1 centimeters) were reported. In Haskell County, flash flooding led to the closure of several roadways. In Texas, an EF1 tornado was reported in Orange County. In Childress County, large hailstones approaching 2.00 inches (5.1 centimeters) were reported.

Doppler Radar, May 15 at 21:08 UTC. Outflow boundary ahead of an MCS in southern Oklahoma, while storms in western Texas are intensifying near the dryline.


May 17-21


On May 17, an anomalous cut-off low pressure system, resulting from a highly amplified jet stream, located over eastern Iowa in the morning hours, proceeded to slowly advance eastward throughout the day. Strong southerly low-level winds provided ample moisture advection ahead of the low, aided by the secondary weather disturbance still spinning near the ArkLaTex region. This set-up produced storms and showers spanning from the Gulf Coast northward into Illinois.

By the late afternoon and evening hours, a major flash flooding event was ongoing for large portion of east-central and northeastern Illinois, and northwestern Indiana, this included the Chicagoland area. Heavy rainfall in this region was enhanced from the presence of a warm frontal boundary to the east of the low, extending across central Illinois into Indiana and lifting northward, along with the approaching cold front extending south of the low. This resulted in multiple rounds of heavy rain and thunderstorms, episodes of flash flooding, and reports of two brief tornadoes. Already saturated soils and high stream flows from the previous weeks heavy rainfall compounded the impacts from this event.

Flash flooding on major roadways was reported, as well as numerous impacted structures, especially those adjacent to the Chicago River. Widespread 48-hour rainfall totals of 3 to 5 inches (76 to 127 millimeters) or greater were common across the region.

Between May 18-21, the cut-off low continued to slowly meander east-southeast toward the Ohio River Valley and eventually the central/southern Appalachians where it decelerated in speed while continuing to allow a plume of moist tropical air to produce regions of enhanced rainfall and additional flooding/flash flooding, with the greatest impact occurring in Illinois, Indiana, Michigan, Ohio, Kentucky, West Virginia, Virginia and the Carolinas. The heavy rain aided in the failure of two dams near Midland, Michigan, resulting in a historic flooding event. Flash flooding was common in the central/southern Appalachians where several localities received at least 9 inches (230 millimeters) of precipitation from this event.

7-Day Precipitation Ending May 20 (inches)


Event Details

Illinois/Indiana

As of May 18, the major flash flooding event in northeastern Illinois and Chicago resulted in widespread reports of 48-hour rainfall totals approaching 3 to 5 inches (76 to 127 millimeters), with locally higher amounts. A weather station near Oak Lawn, Illinois reported a 48-hour rainfall total of 5.36 inches (136 millimeters). This continued a stretch of significantly wet and active weather which began on May 14th. According to the National Weather Service (NWS), Chicago recorded 3.53 inches (89.7 millimeters) of rainfall on May 14, breaking the record for the all-time wettest May calendar day. Three days later, an additional 3.11 inches (79 millimeters) fell on May 17, the 5th wettest calendar day on record for the month of May. During the entire four-day period (May 14-17) Chicago received 7.88 inches (200 millimeters) of rain. As of May 19, May 2020 ranks as the wettest May in city history.

During the May 17 event, significant flooding occurred throughout northeastern Illinois and northwest Indiana. This resulted in frequent closed and impassable roadways, including Lower Wacker Drive in Chicago, and major flooding on portions of I-80. The Chicago Transit Authority (CTA) reported service disruptions to local commuter trains resulting from the flash flood. Multiple river gauges along the Des Plaines and Illinois River in northern and central Illinois rose to Major Flooding stages, while the Chicago River in downtown Chicago (Grand Ave) crested near 5.3 feet (1.62 meters), approaching the record high level of 5.7 feet (1.74 meters). The Metropolitan Water Reclamation District (MWRD) was prompted to temporarily reverse the flow of the Chicago River to discharge into Lake Michigan. Numerous reports of water rescues in addition to flooded homes and parking garages occurred throughout the region. The iconic Willis Tower in downtown Chicago remained without power as of May 20, Additionally, two tornadoes were confirmed in LaSalle County and Will/Grundy Counties (Illinois).

Flooding at Lower Wacker Drive in Chicago on May 17. (Source: Chicago Fire Department)


Michigan

On May 19, the failure of two dams upstream from the town of Midland, Michigan (Midland County) generated an extremely dangerous flooding emergency following a prolonged period of heavy rain and storms across the Michigan peninsula, in association with a slow-moving low-pressure system. Breaches at both the Edenville and Sanford dams, combined with the previous days of heavy rainfall, led to record flooding along the Tittabawassee River.

By late afternoon May 20, the river gage at Midland crested at 35.05 feet (10.68 meters). The flooding stage for this portion of the river is 24 feet (7.3 meters), with the previous record height of 33.9 feet (10.3 meters) set in September 1986; records for this station date back to 1867. The Michigan governor declared a state of emergency, as the flooding forced the evacuation of at least 10,000 residents and had the potential to affect up to 3,500 homes. On May 20, Dow Chemical, operating a large facility in Midland, announced a shut down all non-essential operating units. A weather station in Midland recorded a three-day precipitation total of 4.87 inches (124 millimeters) ending the morning of May 20.

Tittabawassee River on May 20, 2020 (right), compared to June 3, 2019 (left) from Landsat 8. (Source: NASA)


Central and Southern Appalachians

On May 20 and 21, as the upper level low remained almost stationary over the eastern Tennessee Valley and central/southern Appalachians, flood warnings and flash flood warnings were posted for numerous regions in southern Virginia and the western Carolinas. By May 21 widespread 4-day precipitation totals of 3 to 6 inches (76 to 152 millimeters) were measured across these regions, with locally higher amounts exceeding 9 inches (230 millimeters). In Yancey County (North Carolina) a weather station recorded a 3-day total precipitation of 9.44 inches (240 millimeters) ending the morning of May 21.

Oversaturated soils in combination with the extended period of heavy rain led to numerous reports of downed trees and power outages, as well as landslides in regions with steeper terrain. Multiple river gages rose to Moderate Flooding stages. In Virginia, Roanoke County Emergency Management officials were forced to evacuate 13 homes downstream of the Spring Valley Dam, due to concerns of a failure. In Salem (Virginia) a landslide washed debris onto a roadway. At least one death occurred in North Carolina, resulting from a tree which fell on a mobile home.

Financial Loss Total aggregate economic and insured losses during the full period from May 14 to 21 were likely to each individually reach into the hundreds of millions (USD). Most of the wind and hail-related damage will be covered by insurance, though a large portion of damage from riverine and flash flooding in the Midwest will be uninsured. The graphic below highlights National Flood Insurance Program (NFIP) take-up by county as of June 2019. Most of the affected counties in the hardest-hit areas of Michigan and Illinois have NFIP take-up rates of less than 5 percent.


Natural Catastrophes: In Brief Earthquake (United States) According to the United States Geological Survey (USGS), a preliminary magnitude 6.5 (M6.5) earthquake struck Nevada on May 15 at 4:03 AM local time (11:03 UTC). The tremor struck near the California border, approximately 35 miles (56 km) west of Tonopah, Nevada, and 120 miles southeast of Carson City, Nevada. The event was felt throughout central California and as far away as Utah. The USGS cited that more than 5.4 million people felt Weak (MMI II-III), and more than 349,000 felt Light (MMI IV) shaking. The earthquake was the result of strike slip faulting in the shallow crust of the North America plate at a depth of 1.7 miles (2.8 km). The Nevada Highway Patrol Northern Command reported road closures and damage to US-95 in Esmeralda County (Nevada). Multiple aftershocks succeeded the event. During the past century, two M6.0+ earthquakes were recorded in this region, the most recent of which was an M6.5 earthquake that occurred 25 miles (40 km) to the northwest in January 1934. Given the sparsely populated regions surrounding the earthquakes epicenter, economic losses are expected to be minimal.

Severe Weather (Vietnam) A period of severe weather with a combination of heavy rain, strong winds and lightning affected parts of Vietnam on May 15-19; claiming at least three lives and causing seven injuries. According to the data form Vietnam Disaster Management Authority, at least 14 structures collapsed, and 1,752 homes were damaged on May 15-18, of which 703 were in Ha Giang, 354 in Thanh Hoa and 254 in Bac Kan. Notable effects occurred to local agriculture.

Severe Weather (United States) On May 20, severe storms developed in a narrow corridor stretching north to south from eastern Montana to northeastern Colorado and tracked east-northeast in association with a surface trough and a low-pressure system centered over southern Montana. The main hazards associated with these storms were strong winds and large hail, with the greatest impact in Montana, Wyoming, and Colorado. Hailstones approaching 2.50 inches (6.40 centimeters) occurred in Custer County (Montana), maximum wind gusts of 80 mph (130 kph) were reported in McCone County (Montana). A tornado was reported in Weld County (Colorado). Further south, severe storms swept across a region in western and central Texas, ahead of an approaching dryline. Large hail was the dominant hazard associated with this event. Hail measuring 2.00 inches (5.08 centimeters) and larger were reported in Lubbock County (Texas).


Global Temperature Anomaly Forecast

Source: Climate Reanalyzer, Climate Change Institute, University of Maine, USA


Global Precipitation Forecast

Source: Climate Reanalyzer, Climate Change Institute, University of Maine, USA


Weekly Sea Surface Temperature (SST) Anomalies (°C)

The SST anomalies are produced by subtracting the long-term mean SST (for that location in that time of year) from the current value. This product with a spatial resolution of 0.5 degree (50 kilometers) is based on NOAA/NESDIS operational daily global 5 kilometer Geo-polar Blended Night-only SST Analysis. The analysis uses satellite data produced by AVHRR radiometer.

Select Current Global SSTs and Anomalies Location of Buoy Temp (°C) Departure from Last Year (°C)

Eastern Pacific Ocean (1,020 miles SW of San Salvador, El Salvador) 23.78 -2.09

Niño3.4 region (2°N latitude, 155°W longitude) 25.26 -1.02

Western Pacific Ocean (700 miles NNW of Honiara, Solomon Islands) 30.33 +0.29

Sources: ESRL, NOAA, NEIS, National Data Buoy Center


El Niño-Southern Oscillation (ENSO) ENSO-neutral conditions are currently present. NOAA notes that there is a roughly 65 percent chance of neutral conditions lingering through the Northern Hemisphere (boreal) summer months. The agency further states that a decreasing chance (lowering to 45 to 50 percent) into the boreal autumn.

El Niño refers to the above-average sea-surface temperatures (+0.5°C) that periodically develop across the east-central equatorial Pacific. It represents the warm phase of the ENSO cycle. La Niña refers to the periodic cooling of sea-surface temperatures (-0.5°C) across the east-central equatorial Pacific. It represents the cold phase of the ENSO cycle. El Niño and La Niña episodes typically last nine to 12 months, but some prolonged events may last for years. While their frequency can be quite irregular, El Niño and La Niña events occur on average every two to seven years. Typically, El Niño occurs more frequently than La Niña. ENSO-neutral refers to those periods when neither El Niño nor La Niña conditions are present. These periods often coincide with the transition between El Niño and La Niña events. During ENSO-neutral periods the ocean temperatures, tropical rainfall patterns, and atmospheric winds over the equatorial Pacific Ocean are near the long-term average. El Niño (La Niña) is a phenomenon in the equatorial Pacific Ocean characterized by a five consecutive 3-month running mean of sea surface temperature (SST) anomalies in the Niño 3.4 region that is above the threshold of +0.5°C (-0.5°C). This standard of measure is known as the Oceanic Niño Index (ONI).


Global Tropics Outlook

Source: Climate Prediction Center


Current Tropical Systems

Location and Intensity Information Name* Location Winds Storm Reference from Land Motion**

CY Mangga 10.3°S, 93.4°E 40 mph 1,635 miles (2,630 kilometers) WNW of Learmonth, AUS SE at 8 mph

* TD = Tropical Depression, TS = Tropical Storm, HU = Hurricane, TY = Typhoon, STY = Super Typhoon, CY = Cyclone ** N = North, S = South, E = East, W = West, NW = Northwest, NE = Northeast, SE = Southeast, SW = Southwest Sources: National Hurricane Center, Joint Typhoon Warning Center, Central Pacific Hurricane Center


Global Earthquake Activity (≥M4.0): May 15-21

Significant EQ Location and Magnitude (≥M6.0) Information Date (UTC) Location Magnitude Depth Epicenter

05/15/2020 38.16°N, 117.87°W 6.5 3 km Monte Cristo Range Earthquake (Nevada, USA)

Source: United States Geological Survey


U.S. Weather Threat Outlook

Potential Threats Flooding concerns will continue throughout the Great Lakes, Ohio Valley, and central/southern

Appalachians as recent prolonged episodes of heavy rainfall resulted in oversaturated soils and elevated stream flows.

Regions of severe drought continue to expand across the Plains and central/southern Rockies, as well as portions of the Pacific Northwest.

Heavy rain is forecasted for a large portion of the central and southern Plains on May 24-25, continuing through May 27 for southern Texas, as a slow-moving trough and southerly flow allow for multiple days of showers and storms.

A building ridge of high pressure is anticipated to bring much above normal temperatures to California and the central Great Basin May 27-28.


U.S. Wildfire: Significant Fire Risk Outlook & Activity The National Interagency Fire Center has highlighted an extended risk of elevated wildfire conditions across parts of the Desert Southwest, Plains, Southeast, Midwest, and the Northeast into the last week of May.

Annual YTD Wildfire Comparison: May 21* Year Number of Fires Acres Burned Acres Burned Per Fire

2016 18,692 1,555,535 83.22

2017 23,192 2,132,937 91.97

2018 22,478 1,625,864 72.33

2019 13,174 236,887 17.98

2020 16,682 349,344 20.94

10-Year Average (2010-2019) 20,792 1,025,949 49.34

*Last available update from NIFC Source: National Interagency Fire Center

Top 5 Most Acres Burned by State: May 21 State Number of Fires Acres Burned Acres Burned Per Fire

Oklahoma 526 74,815 142.23

Texas 1,193 51,957 43.55

Florida 1,459 50,276 34.46

Arizona 481 45,059 93.68

Kansas 34 21,796 641.06

Source: National Interagency Fire Center


Current U.S. Streamflow Status

A ≥99th percentile indicates that estimated streamflow is greater than the 99th percentile for all days of the year. This methodology also applies for the other two categories. A steam in a state of severe drought has 7-day average streamflow of less than or equal to the 5th percentile for this day of the year. Moderate drought indicates that estimated 7-day streamflow is between the 6th and 9th percentile for this day of the year and ‘below normal’ state is between 10th and 24th percentile.

Top 5 Rivers Currently Nearing or Exceeding Flood Stage Location Current Stage (ft) Flood Percentile

Minnesota River at Mankato, Minnesota 15.83 99.13

Milwaukee River at Milwaukee, Wisconsin 5.43 99.06

Fox River at Dayton, Illinois 11.83 99.05

Holston River near Saltville, Virginia 4.60 99.00

Manistee River near Sherman, Michigan 14.81 99.00

Source: United States Geological Survey


Source Information Powerful Cyclone Amphan makes India landfall National Disaster Relief Force India Disaster Management Center, Sri Lanka Department of Disaster Prevention and Mitigation, Thailand India Meteorological Department, India Dhaka Tribune, Cyclone Amphan: 83,000 homes destroyed in Khulna The Hindu, Cyclone Amphan kills 72 in West Bengal, brings life to a halt Hindustan Times, 3 dead as Cyclone Amphan crosses Odisha before making landfall in Bengal

Tropical Storm Arthur brings rain, surf to U.S. East Coast U.S National Weather Service National Hurricane Center

Update: Typhoon Vongfong impact in the Philippines National Disaster Risk Reduction and Management Council, Philippines Joint Typhoon Warning Center

Pattern shift brings severe weather, flash flooding to U.S. U.S. National Weather Service U.S. Storm Prediction Center Chicago Fire Department Chicago Tribune, ‘Unreal’ rains flood homes, knock out power and put Chicago on the cusp of wettest May ever CNN, Catastrophic flooding in Michigan as dams fail The Associated Press, Thousands evacuated as river dams break in central Michigan Roanoke County Emergency Management WSET 13 News, Rain creates hazardous conditions in the Roanoke Valley

Natural Catastrophes: In Brief Nevada Highway Patrol Northern Command, United States United States Geological Survey, United States U.S. National Weather Service, United States U.S. Storm Prediction Center, United States


Contact Information Steve Bowen Director & Meteorologist Head of Catastrophe Insight Impact Forecasting Aon [email protected] Michal Lörinc Senior Catastrophe Analyst Impact Forecasting Aon [email protected]


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© Aon plc 2019. All rights reserved. The information contained herein and the statements expressed are of a general nature and are not intended to address the circumstances of any particular individual or entity. Although we endeavor to provide accurate and timely information and use sources we consider reliable, there can be no guarantee that such information is accurate as of the date it is received or that it will continue to be accurate in the future. No one should act on such information without appropriate professional advice after a thorough examination of the particular situation.

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Cat Alerts use publicly available data from the internet and other sources. Impact Forecasting® summarizes this publicly available information for the convenience of those individuals who have contacted Impact Forecasting® and expressed an interest in natural catastrophes of various types. To find out more about Impact Forecasting or to sign up for the Cat Reports, visit Impact Forecasting’s webpage at impactforecasting.com.

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