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Storms

Matthew: A storm of three tales

Hurricane Matthew was the first Atlantic hurricane for almost ten years to reach the highest category 5 status. It caused enormous damage during its passage through the Caribbean and onwards to the United States.

27.03.2017
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After developing from a tropical wave off the west coast of Africa and moving westwards across the Atlantic ocean, Matthew became a tropical storm off the coast of Barbados on 28 September. Despite developing in a region with high vertical wind shear, which ordinarily acts to suppress hurricane intensification, Matthew rapidly intensified over a 36-hour period on 29 and 30 September, ultimately reaching category 5 strength. This rapid intensification can, in part, be explained by high ocean heat content values in the Caribbean during its development, which acted to limit the hurricane’s self-induced negative feedback from ocean cooling to favour intensification. Matthew thus became the most southerly (13.3°N) hurricane to reach category 5 strength in the Atlantic.

Losses

After reaching its peak intensity, Matthew deflected to the northwest and reduced in intensity to a category 4 storm. It then tracked northwards close to Jamaica before making landfall over Haiti’s southern Tiburon Peninsula and over Cuba’s eastern Guantanamo province as a category 4 storm on 4 October. With wind gusts exceeding 250 km/h, prolific rainfall and surge heights exceeding 3 metres, Matthew was the strongest storm to hit Haiti since Hurricane Cleo in 1964. The consequences for Haiti were devastating, especially as the country was still struggling with the effects of the 2010 earthquake.

Matthew weakened to a category 3 storm after passing over Haiti and Cuba. However, on 5 and 6 October, while approaching the Bahamas, Matthew underwent a reintensification process as it once again encountered areas of high ocean heat content, resuming category 4 strength. The sea surface temperatures and ocean heat content in this section of the Caribbean were close to record highs for this time of the year.

Hurricane Matthew was the first Atlantic hurricane for almost ten years to reach the highest category 5 status. It caused enormous damage during its passage through the Caribbean and onwards to the United States. © Munich Re
America
Hurricane Matthew 2016

USA spared the worst

The next landfall was on 6 October, when Matthew made landfall on the most populated islands of the Bahamas, becoming the most damaging hurricane to hit the country since Hurricane Frances in 2004. After passing Grand Bahama, Matthew then took a northwesterly path towards the United States. A small deviation westwards would have brought Matthew ashore in Florida and exposed the landfall region to its worst winds, while a more northerly motion would have resulted in Matthew brushing or travelling parallel to the coast for hundreds of miles, potentially damaging a much larger section of US coastline. 

Ultimately, Matthew stayed just offshore of the states of Florida and Georgia as it moved around the western periphery of an area of high pressure. This resulted in Matthew’s strongest winds remaining offshore, limiting the severity of wind damage. However, the near-parallel motion along the coast aggravated surge flooding to the north of the storm, where easterly winds and storm motion combined to enhance surge heights and destructive wave action along the coast.

During this period, Matthew continued to slowly weaken in intensity as it started to turn northwards, then northeastwards, off the coast of Georgia, ultimately making its final landfall as a minimal category 1 storm near Charleston, South Carolina. Although the winds had decreased significantly, the rainfall associated with Matthew had not. Heavy precipitation, with totals of 300 mm across a large section of North and South Carolina, triggered the worst flooding in the region since Hurricane Floyd in 1999. Once ashore, Matthew started moving faster to the northeast, exited the United States over Cape Hatteras and sped out to sea as an extratropical storm.

Haiti: Humanitarian crisis

Haiti is one of the poorest countries in the world, with 59% of the population living on less than US$ 2 a day. Weak infrastructure, poor building quality and a lack of strong state institutions, coupled with devastation of the local ecosystem through practices such as large-scale deforestation, leave the population particularly vulnerable to any type of natural disaster.

Destruction by wind and rain

The areas of Haiti that were hit by hurricane Matthew constitute some of its poorest regions. Three departments in the southwest of the country were badly affected by damaging winds gusting up to 250 km/h, with many settlements in these departments experiencing near total destruction of all non-concrete buildings. Other departments were more affected by torrential rainfall, with three-day totals reaching up to 700 mm in places. This torrential rainfall not only caused widespread flooding in these departments, but also triggered deadly landslides which Haiti is particularly vulnerable to as a result of widespread deforestation in recent decades.

Official statistics from the Haitian government list 546 deaths, although the true figure is likely to be considerably higher. Figures from the UN estimate that over 2.1 million people (approximately 20% of Haiti’s total population) were directly affected by the storm, two thirds of whom were in need of immediate assistance in the aftermath of the event. An estimated 175,000 people were displaced as a result of the storm and were in need of emergency shelter, while over 800,000 people were identified as suffering extreme food insecurity. Crops in the worst-affected areas were more or less completely destroyed. Hurricane Matthew accelerated an existing cholera epidemic in Haiti as drinking water was contaminated as a result of flooding.

Low insurance penetration

Overall losses on the island came to approximately US$ 1.4bn. Only an extremely small portion of this was insured. Haiti is a participant in the Caribbean Catastrophe Risk Insurance Facility (CCRIF) with the Caribbean Development Bank (CDB) paying Haiti’s insurance premiums over the past few years in support of Haiti’s overall disaster risk management strategy. Haiti will receive US$ 23m as a result of Matthew. This represents the largest payment ever made by the CCRIF. The UN’s Office for the Coordination of Humanitarian Affairs (OCHA) set a target of raising US$ 139m in aid for Haiti.

Bahamas: A close shave

Hurricane Matthew was the first Atlantic hurricane for almost ten years to reach the highest category 5 status. It caused enormous damage during its passage through the Caribbean and onwards to the United States. © THONY BELIZAIRE / AFP/Getty Images
A direct hit by a hurricane on the two main islands of New Providence and Grand Bahama is rare. Forecasts in the days leading up to landfall in the Bahamas were predicting a worst-case scenario: a likely direct hit by Matthew as a category 4–5 hurricane on the capital Nassau in New Providence, followed by a subsequent direct hit on the largest settlement in Grand Bahama, Freeport. These two cities combined account for over 75% of the Bahamas‘ total population of 400,000. Luckily, Nassau was spared such a scenario as the storm track deflected 25 km to the west compared with the original forecast.

Fortunate track deviation from forecast

Hurricane Matthew was the first Atlantic hurricane for almost ten years to reach the highest category 5 status. It caused enormous damage during its passage through the Caribbean and onwards to the United States. © Pacific Disaster Center
Forecast and reality
The path and storm surge levels that the NOAA predicted 48 hours before landfall in the Bahamas would have indeed caused enormous losses.

The images on page 41 show a comparison of Matthew’s observed track and modelled wind field with the track and storm surge forecast by the NOAA two days prior to landfall. They illustrate just how lucky Nassau was, as it is situated in the northeast of the island New Providence. Without the observed 25 km deviation in Matthew’s path, gusts of up to 230 km/h could have been experienced in Nassau, resulting in much greater storm damage. Nassau actually experienced peak wind speeds of 150 km/h, which is in line with the modelled wind gusts. 

The residents of New Providence and Grand Bahama were fortunate in two other crucial respects. Firstly, instead of the predicted three to four metres, the storm surge was only half a metre to a metre high, penetrating only as far as one kilometre inland. Secondly, unlike in Haiti and Cuba, the Bahamas saw only 100 to 200 mm of rain. There was consequently much less flooding than would have occurred with a category 4 hurricane.

Hurricane Matthew was the first Atlantic hurricane for almost ten years to reach the highest category 5 status. It caused enormous damage during its passage through the Caribbean and onwards to the United States. © Munich Re, based on H-Wind data (RMS)
Reality
After Matthew had passed, Munich Re calculated the peak wind speeds (three-second gusts) on the basis of the observed wind field.

Insured losses overestimated

Initial loss estimates from the risk modelling community two weeks after the event estimated insured losses in the Caribbean in the range of US$ 1–3bn (with the Bahamas accounting for approximately 90% of this figure). Post-event reconnaissance trips by Munich Re to the Bahamas reported insured loss figures of US$ 500–700m for the Caribbean (the Bahamas accounted for US$ 450–600m of this). While such deviations in observed insured losses compared with modelled losses may seem large, they are not surprising when considering that the location of the track and associated wind speeds cannot be precisely known shortly after an event and small deviations in either can lead to highly diverging loss estimates.

USA: Storm surge and rain drive up losses

Hurricane Matthew was the first Atlantic hurricane for almost ten years to reach the highest category 5 status. It caused enormous damage during its passage through the Caribbean and onwards to the United States. © Anadolu Agency / Getty Images
Since the strongest winds associated with a tropical cyclone in the northern hemisphere are on the right-hand side of the eye (with respect to forward motion), Matthew’s track – just offshore and parallel to the Florida coast – kept the storm’s strongest winds out to sea. However, Matthew’s near-miss exposed over 250 miles of Florida’s east coast to damaging winds, with localised gusts exceeding hurricane force.

Protective measures effective

Most of the wind damage was light, consisting of lost shingles and siding. Only older buildings, not subject to Florida’s strict wind codes, occasionally showed signs of more severe wind damage to their roofs. In Georgia and the Carolinas, wind damage was primarily limited to tree-fall damage that was exacerbated by torrential rains loosening root systems. 

Matthew’s strong winds pushed Atlantic waters ashore ahead of its path, generating surge flooding, damaging waves, and coastal erosion in Florida from Cape Canaveral northwards. The worst surge damage was centralised around the barrier islands near St. Augustine, Florida, some lowlying back bay communities on these barrier islands received upwards of one metre of surge flooding in their homes. Some houses collapsed and others had to be condemned due to the safety risk. However, the extent and severity of Matthew’s surge was less than that experienced along the Florida east coast in Hurricanes Frances and Jeanne in 2004.

Coastal and inland flooding

More damaging were the torrential amounts of rain that Matthew dropped across the southeastern United States, which triggered widespread flooding in both North and South Carolina. Ample tropical moisture from a record-warm western Atlantic, combined with a slow rate of storm motion and the development of a frontal boundary along the Carolina coast, generated rainfall totals in excess of 150 mm over the eastern half of the Carolinas, with rainfall totals in excess of 250 mm common in a swathe from Myrtle Beach, South Carolina, northeastwards to Norfolk, Virginia. The rapid rise of local rivers devastated local communities, and it would take weeks for water levels in this lowlying region to return to normal.

Hurricane damage less than expected

For the USA, initial loss estimates from the risk modelling community were in the range of US$ 1–4bn. Post-event reconnaissance trips by Munich Re to Florida and the Carolinas indicated that insured losses (excluding those covered by the National Flood Insurance Program, NFIP) would be well below the US$ 4.5bn insured loss (original dollars) from 2004’s Hurricane Frances. Reports by Property Claims Services in early 2017 of a US$ 2.8bn insured loss from Matthew further validated this viewpoint. Claims to the NFIP are likely to add an additional several hundred million to this total. However, compared with the storms of 2004 and 2005, Matthew was a minor event for the United States, and was easily handled by the US insurance market.

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