Tropical Cyclones
aka “Hurricanes”
Art Institute of Seattle, 22 May 2009
Where do tropical cyclones occur?
Sea Surface Temperature
Equator
TC’s form over warm water
Locations of Tropical Cyclone Formation
TC’s form near but not on the equator
Typical Tropical Cyclone Tracks
Note that “hurricane”, “typhoon”, and “cyclone” are local
names for the same thing
Many hurricanes form over eastern Atlantic when “easterly waves” move
off Africa and help convection in the ITCZ turn into hurricanes
Tropical Cyclone Structure
Hurricane Katrina
Nickname for a tropical cyclone, which is
an intense tropical low pressure system with
maximum sustained winds of 74 mph or higher.
Known as typhoon in eastern North Pacific and
cyclone in Indian Ocean and South Pacific.
More Definitions
Flying in Hurricanes
To see what’s going on under the upper-level cloud, need
radar observations
NOAA WP-3D “Hurricane Hunter” Aircraft
Radars
Hurricane aircraft instruments
Preparing a dropsonde for
launch
Ready to launch a
dropsonde
Hurricane Katrina
Where should
the plane go
exactly?
Communications during a hurricane aircraft mission
CONFERENCE
INTERNET CHAT
CALL
Boulder
Tampa
Miami
In Miami
Hurricane Katrina--seen from space
How does
this look
from an
airplane
flying in the
eye of the
storm?
Note the
slope of
the eyewall
Inside the eye of Hurricane Rita (2005)
Inside the eye of Hurricane Katrina (2005)
Note the
slope of
the eyewall
QuickTime™ and a
Motion JPEG OpenDML decompressor
are needed to see this picture.
Hurricane Katrina
What does it
look like under
all those clouds?
To see what’s going on under the upper-level cloud, need
radar observations
NOAA WP-3D “Hurricane Hunter” Aircraft
Radars
Hurricane Andrew approaching and moving
over Miami
--movie loop of Miami radar observations
Idealized radar view of a hurricane
Sketch of Mature Hurricane Structure
Vertical cross section along AB in previous slide
Note that
the storm
is a high
aloft and a
low at low
levels
A
B
Note the
slope of
the eyewall
Top of a Tropical Cyclone
Upper-level cloud, wind, & pressure
eye
Satellite photo of the top of a tropical cyclone
High
clouds
swirling
outward
High level clouds spiral anticyclonically outward;
Low-level clouds spiral cyclonically inward
Tropical Cyclone Damage
Types of Hurricane Damage
Wind
Heavy Rain/Floods
Storm surge
Tornadoes
Category
1
2
3
Max sustained wind speed
mph
74-95
96-110
111-130
knots
damage
64-82
Tree damage, small
boats torn from
moorings, roads
flooded
83-95
Roofing, windows,
doors boats, piers,
mobile homes
96-113
Some structural
damage to buildings,
flooding, wave damage
4
131-155
114-135
Lots of structural
damage, major
flooding, storm surge
5
156+
136+
Catastrophic, building
failures
Category 1+
Miami 2005
The Great Galveston Hurricane
Galveston
New Orleans
Cat 4
1-8 September 1900
Cat 3
Cat 0
Category 4 Damage: Galveston 1900
Note: Category 5 is rare
Storm Surge
Types of Hurricane Damage
Storm surge
Types of Hurricane Damage
Storm surge
QuickTime™ and a
BMP decompressor
are needed to see this picture.
Hurricane Forecasting
Important factors that make a
hurricane develop
Warm ocean--hurricanes get their energy
from the ocean
Humid atmosphere--need high humidity to
get clouds to develop
Weak “wind shear” --if wind is stronger at
upper levels than lower levels, storm top
separates from lower part of storm
Forecasting Hurricane Rita (2005)
Map of ocean heat content
Warm Ocean
Satellite view of humidity
Clouds
Moist air
Dry air
Dry
Map of wind shear
Very low wind shear
Map of steering winds
Model forecasts of Rita’s storm track
Numerical Model Simulation of Rita
QuickTime™ and a
BMP decompressor
are needed to see this picture.
End