Transcript El Niño, Trop Cyclones

El Niño is characterized by
unusually warm temperatures that move eastward
toward Peru’s coast
La Niña is characterized by
unusually cool temperatures in that same area of the
Pacific.
The term “El Niño” is so commonly known that it was
combined with the scientific term “Southern Oscillation”
to form the acronym, ENSO, “El Niño-Southern Oscillation”
Why is it called “El Niño”?
Oscillation is the action of something that
shifts back-and-forth
An oscillating fan cooled the room as it moved to
the right and then to the left.
The Southern Oscillation is an alternating
pattern of warmer- or cooler-than-normal
ocean surface temperatures. Each cycle
of the pattern can take years.
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 Anomalies
are deviations from normal, or
“nominal”, temperatures
Unusually warm temperatures are shown in
red, unusually cold anomalies in blue. Here
are the actual temperatures in the top slide,
then the anomalous temperatures in the
bottom slide.
 http://www.cpc.ncep.noaa.gov/products/an
alysis_monitoring/enso_update/sstanim.sht
ml

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 Each cycle can be strong or weak.
• The unusually warmer or cooler temperatures
can be a few degrees or several degrees away
from what has historically been recorded.
 Strong
ENSO seasons can result in severe
weather disruptions in many areas far
from the equatorial (tropical) Pacific
• On the next slide, record 3 events caused by an
El Niño event.
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 ENSO
is not the normal situation.
 ENSO cycles are deviations from data
recorded over many years
 ENSO seems to follow a pattern of every
2-7 years…but lately has been 3-4 years.
 ENSO can last 12-18 months, or LONGER!
 Unpredictability is a hallmark of this
phenomenon
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 Carla-1961
 Ike-
2008
 Katrina-2005
 Rita- 2005
 Tropical Storm Allison-2001
 Alicia-1983
 And …the Great Storm of 1900!
 All
are tropical cyclones that have
affected our region.
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 It
is an area of disturbed weather
(storms) that has a closed circulation in
tropical regions and it is not connected to
a low pressure frontal boundary.
• Closed Circulation means the winds blow
around it in a circular pattern
• It has its origins in the tropics
• It has low pressure in its center, meaning air is
rising
• It is isolated, i.e., not part of a cold front
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 Warms
the air in the
tropics
 This warm, humid air
rises
 Convergence of wind
currents in the ITCZ are
believed to start the
rising air to spin,
causing a cyclonic
action

(See where the winds converge,
then diverge…this starts the rising
air to spin.)
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 Is
carried “aloft”, meaning high into the
atmosphere
 The core of a tropical cyclone is warmer
than the air surrounding it- that is what
makes it “tropical”
 It is one method for excess heat to be
spread to higher latitudes from the tropics
• The enormous amount of water in a tropical cyclone
carries heat with it as the storm moves away from the
Inter Tropical Convergence Zone (ITCZ)
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…are used to detect tropical
cyclones far out at sea
They also track developments
as the storms move
o Such devices as
o
o
o Buoys,
o Ships,
o Weather Balloons,
o Satellites,
o and Aircraft
o all play an important role in
measuring the intensities of
storms.
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Total estimated property damage, 2005 USD
 1 MIAMI 1926 $157 billion
 2 GALVESTON 1900 $99.4 billion
 3 KATRINA 2005 $81.0 billion
 4 GALVESTON 1915 $68.0 billion
 5 ANDREW 1992 $55.8 billion
 6 NEW ENGLAND1938 $39.2 billion
 7 CUBA-FLORIDA 1944 $38.7 billion
 8 OKEECHOBEE 1928 $33.6 billion
 9 DONNA 1960 $26.8 billion
 10 CAMILLE 1969 $21.2 billion
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