(Karen Braun is a Reuters market analyst. Views expressed are
her own.)
By Karen Braun
May 24 (Reuters) - The Atlantic Ocean could be gearing up
for an active hurricane season, meaning North American residents
may want to pay attention.
In recent years, single hurricanes have led to thousands of
deaths across the Caribbean, North and Central America, and have
caused several billion dollars in damage.
When a hurricane bears down on a region, it not only puts
people in peril, but it affects just about every major industry
in the area, adding extra importance to the annual hurricane
forecast.
On average, the Atlantic Basin observes around 11 named
tropical storms, six hurricanes, and two major hurricanes during
any given season, which runs from June through November. But
those numbers could be a bit higher this year thanks to the
atmospheric set-up that is currently brewing.
The expected introduction of a cool-water La Niña pattern in
the Pacific over the next couple of months is generally
favorable for tropical development. This, together with a few
other dominant variables, will provide Mother Nature with all
the ingredients to wreak havoc on the Atlantic Basin if she so
wishes.
HURRICANE CRASH COURSE
Hurricanes need three main ingredients to form: warm sea
surface temperatures, minimal to no wind shear, and an area of
organized, long-lasting thunderstorms. These storms tend to
originate off the western coast of Africa.
Wind shear simply characterizes how wind speed and direction
change with height. Strong thunderstorms, and thus hurricanes,
rely on strong vertical motion in the atmosphere. Too much wind
shear prevents the vertical development of the storms, reducing
their intensity.
Once formed, hurricanes must be fed by constant moisture to
stay in business. When dry Saharan Desert air is transported
into the tropics en masse, it disrupts tropical systems and
essentially "starves" the storm to death.
The Atlantic hurricane season officially begins on June 1
and runs through Nov. 30. The peak occurs when the Northern
Atlantic is at its warmest - around the second week of September
- and this is statistically the most common time for a hurricane
to occur.
However, hurricanes and tropical storms can form outside of
this six-month window if the conditions are just right. In fact,
the 2016 hurricane season already has one storm under its belt
with Hurricane Alex, which formed under extremely rare
circumstances this January.
Once a cluster of thunderstorms starts to display organized
rotation with sustained wind speeds of 39 to 73 miles per hour,
it is classified as a "tropical storm" and is assigned a human
name by the U.S. National Hurricane Center. The name will stick
with the storm through its life as a hurricane, if it becomes
one.
Since 1953, the NHC has used an alphabetical fixed list of
names that alternate male and female. Each list is cycled every
six years, and storm names can be "retired" in any given year
given the sensitive nature of particularly devastating storms.
Recent retirees include Sandy, Katrina and Ike.
If sustained winds reach 74 mph, the tropical storm becomes
a category 1 hurricane on the Saffir-Simpson scale, which rates
hurricanes by intensity on a scale of 1 through 5, with 5 being
the most extreme (http://reut.rs/25iK0NP).
If the winds increase to 111 mph, the hurricane is upgraded
to a category 3. Hurricanes of categories 3 and above are
considered "major" hurricanes.
Hurricanes are only labeled as such in the Atlantic Ocean
and northeastern Pacific. A "hurricane" that occurs in the
northwestern Pacific is called a typhoon and one that occurs in
the Indian Ocean or Southern Pacific is known as a cyclone.
2016: PERFECT STORM?
One of the most important factors playing into this season
is the imminent presence of La Niña, the cold phase of the
eastern equatorial Pacific Ocean. La Niña tends to decrease the
wind shear over the tropical Atlantic Ocean, which is one
enabling ingredient in hurricane formation.
Therefore, it is not surprising that some of the more active
hurricane seasons over the past several decades were often
associated with La Niña. Seasons with below-normal hurricane
activity have coincided with La Niña in the past, but this has
not occurred since 1978 (http://reut.rs/1OJQKak).
Since 1950, the only above-average hurricane season to occur
during El Niño was 2004, right in the middle of a four-year
stretch of anomalously warm global oceans. The following year,
2005, remains the most active Atlantic hurricane season in
recorded history.
But this year, both La Niña and warm oceans side with the
hurricanes. Global ocean temperatures have been breaking new
record highs over the past several months, meaning that together
with reduced wind shear via La Niña, the atmosphere is
practically rolling out the red carpet for the procession to
begin.
And the favorability does not end there, as there should be
plenty of fuel available for tropical development. Year-to-date
precipitation over the African Sahel has been above average,
which will reduce both the availability and distribution of dry,
hurricane-disruptive air into the tropics during the season.
WHAT WE NEED TO KNOW
First and foremost, in no way should this forecast incite
fear. An expected above-average forecast for the hurricane
season does not specify whether these storms will make landfall.
But either way, there are some important implications of these
storms that should be considered.
The impact on commodity markets can be significant. Oil
production in the Gulf of Mexico can grind to a halt if a
hurricane is expected to approach. The Energy Information
Administration projected that the Gulf produced 17 percent of
U.S. crude oil in 2015. This is down from 27 percent in 2003,
but any tropical disturbance in the Gulf could certainly give an
upward jolt to generally suppressed oil prices.
Major agricultural commodities are generally less affected
by hurricanes, although there are several instances where
hurricanes made a difference. One occurred during the active
hurricane season of 2012 when remnants of Hurricane Isaac
traveled onshore to the U.S. interior in late August and gave
parched soybeans a much-needed drink amid the historic drought.
Finally, there are things that we as humans need to
remember. Hurricane advisories are generally issued several days
in advance of the storm, and sometimes up to a week or more, so
there is almost always enough time to prepare and evacuate if
necessary.
If a hurricane watch is issued, then hurricane conditions
are possible within the next 48 hours. A hurricane warning
denotes that hurricane conditions are expected within 36 hours.
But keeping a close eye on the news and the weather will
help to anticipate these watches and warnings several days in
advance. Above all, anyone living along coastal areas of the
western Atlantic Basin needs to keep alert for any such
hazardous conditions and should follow all recommended measures,
including evacuation, in order to ensure maximum safety.
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Graphic- Saffir-Simpson Hurricane Wind Scale http://reut.rs/25iK0NP
Graphic- Tropical Storm Frequency in the Atlantic vs. ENSO,
1950-2015 http://reut.rs/1OJQKak
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