Joanne Kennell, Meteorologist, CatIQ
The destruction ensued by Hurricane Matthew and its remnants, not only in Canada, but in Haiti, Cuba, the Bahamas, the Dominican Republic, and the United States, is heartbreaking. Lives were lost and people’s homes and possessions have been damaged or are in complete ruins. Our thoughts and prayers go out to everyone who is suffering because of this record-breaking storm.
Hurricane Matthew (2016-10-Cat-0081) began as a tropical
wave the originated off the west coast of Africa and passed south of Cape Verde
– a section of islands located 570 kilometers off the coast of Africa and is a
region known for spawning long-lived tropical cyclones. What made Matthew such
a record breaker was its intensity and endurance (Erdman, 2016). Not only was
Matthew the longest lived Category 4-5 Hurricane on the Saffir-Simpson Hurricane Wind Scale in
October in the Atlantic Basin, it was also the southernmost Category 5
Hurricane in the Atlantic Basin.
Tropical cyclones and hurricanes require a set of
specific ingredients to form, but generally they need:
1)
A pre-existing disturbance such as a tropical wave
2)
Warm sea-surface temperatures of at least 26oC
3)
At least 5 degrees south or 5 degrees south of
the equator for the Coriolis Force to take effect
4)
Lots of moisture in the lower and mid-levels of
the atmosphere
5)
Weak vertical wind shear – a change in wind speed
and/or direction with height
6)
Atmospheric instability
According to Dr. Philip Klotzbach, a meteorologist at CSU
who specializes in Atlantic Basin seasonal hurricane forecasts, Matthew’s perseverance
in the Atlantic Basin was due to a relative lack of wind shear and minimal dry
air – exactly two of the key ingredients needed for tropical storm formation. But
Matthew did not only break a nine-year streak without an Atlantic Basin
Category 5 hurricane, it was also categorized as a Category 5 very far south
and close to the equator. On September 30th, just before midnight
EDT, Matthew transitioned into a Category 5 hurricane with its centre at 13.3
degrees north.
However, what made Matthew such a record breaker, also
made it extremely destructive and devastating. Although Matthew was no longer a
hurricane as it impacted Canada’s Maritime Provinces, its leftover moisture,
which was absorbed into a frontal zone, intensified a low-pressure system that
inundated Nova Scotia and Newfoundland with heavy rains and gusty winds.
According to Environment Canada, the town of Sydney, Nova Scotia, received
224.8 mm of rainfall and Gander, NL, received up to 124 mm of rain – both of
which were one day record-breaking rainfall totals in each city.
Washed out Road in Buchans, Newfoundland
Photo credit: Tammy @tammyharris96/Twitter
Unfortunately, all of this rain led to significant
flooding in Sydney, including flooded homes and businesses, and many roads and
bridges were washed out in Newfoundland. States of emergencies were declared in
some Nova Scotia and Newfoundland communities, including Sydney, as well as
Lewisporte, Little Burnt Bay, and St. Alban, Newfoundland.
Although the cost of this catastrophic event is unknown,
it is expected to exceed CatIQ’s Catastrophe (CAT) threshold of $25M (insured
industry loss). But how does this event compare to previous, similar
incidents in the past?
Looking back to Hurricane Earl (2010), which did not meet
the $25M threshold, but rather industry losses were estimated between $10M and
$25M, it also originated from the Cape Verde region. In fact, Earl
(2010-09-NE-0090) reached a peak intensity of a Category 4 hurricane and even
made landfall near Liverpool, Nova Scotia as a Category 1 hurricane
(Cangiolosi, 2011). So why was Earl’s
damage not as extensive like with Hurricane Matthew? Earl was a weakening
hurricane at the time, and it was relatively fast moving, so there was not
enough time to severely flood cities with massive amounts of rain. However,
Matthew’s moisture acted as fuel to intensify a very slow-moving often stalled,
low-pressure system. This resulted in unprecedented amounts of rain to fall in
both Nova Scotia and Newfoundland.
Track of Hurricane Earl (2010)
Photo credit: Anhamirak and Cyclonebiskit/Wikipedia
Finally, let’s take a look at Hurricane Arthur (2014).
Arthur (2014-07-Cat-0058) became an extratropical cyclone on July 5th while
over the Bay of Fundy (Berg, 2015), which is located just west of Nova Scotia.
Arthur continued to travel northeast toward the Gulf of St. Lawrence while
producing strong winds and intense rains over Nova Scotia, Prince Edward
Island, and New Brunswick. The system then reached eastern Labrador and Newfoundland.
Arthur did in fact reach CatIQ’s Catastrophe (CAT) threshold of $25M by causing
localized flooding, damaging properties and structures, downing trees, and
causing massive power outages. What Arthur and Matthew had in common is the
fact that their remnants of moisture were enhanced along a frontal boundary,
which allowed for prolonged periods of rain and strong winds.
Downed Tree of Power Lines in Nova Scotia
Photo credit: Ken Stronach @kstronach24/Twitter
Although every catastrophic and notable event is unique,
we can sometimes look for patterns in past events to try to determine potential
damages of future, similar systems. Will Hurricane Nicole - who is now the longest-lived Atlantic named storm forming this late in the year - impact Canada as
intensely as Matthew? No, it won’t. Parts of Atlantic Canada, predominately
eastern Newfoundland including the southern Grand Banks, will only see some
ocean swells and gale force winds this weekend. Thank goodness.
References:
Berg, Robbie. 2015. Tropical Cyclone Report: Hurricane
Arthur. National Hurricane Center. URL: http://www.nhc.noaa.gov/data/tcr/AL012014_Arthur.pdf
Cangialosi, John P. 2011. Tropical Cyclone Report:
Hurricane Earl. National Hurricane Center. URL: http://www.nhc.noaa.gov/data/tcr/AL072010_Earl.pdf
Erdman, Jon. 2016. Hurricane Matthew Shatters Record.
Weather.com. URL: https://weather.com/storms/hurricane/news/hurricane-matthew-records-notables-2016
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