Before Hugo

1
Before Hugo
Folly Beach, SC -- 22 September 1989
2
After Hugo
Folly Beach, SC -- 22 September 1989
3
Death of a Hurricane

• Moves out of the warm, moist tropical air.
• Moves over land.
• Loss of moisture source
• Increased surface friction
• Temperature of the land is cooler than the warm
  ocean
• Moved under unfavorable large scale flow.
• High shear can rip a storm apart
• Large scale subsidence can inhibit convection

4
Hurricane Warnings

• Hurricane warnings are designed to protect human
  life and their property.
• Possible Evacuations
• Detection techniques
• Satellites
• Radar
• Aircraft Reconnaissance
• Data Buoys
• Weather Channel Reporters!

5
Satellite Detection of Camille
NIMBUS III Satellite -- 21 August 1969
6
Satellite Tracking of Allen
Hurricane Allen -- August 1980
7
Satellite Tracking of Allen
Hurricane Allen -- August 1980
8
Satellite Tracking of Allen
Hurricane Allen -- August 1980
9
Radar Detection of Hurricanes
Hurricane Andrew -- August 24, 1992
10
Aircraft Detection of Hurricanes
WP-3 Aircraft
Dropsondes
11
Tropical Storm Warnings

• Tropical Storm Watch
• Possible tropical storm conditions expected in
  the next 36 hours.
• Prepare to take appropriate action.
• Tropical Storm Warning
• Tropical storm conditions are expected in the
  next 24 hours.
• Take action!

12
Hurricane Warnings

• Hurricane Watch
• Possible hurricane conditions expected in the
  next 36 hours.
• Prepare to take appropriate action.
• Hurricane Warning
• Hurricane conditions are expected in the next 24
  hours.
• Get out of Dodge!

13
Hurricane Warning!
14
Building for Disaster?

• 45 million people now live along hurricane-prone
  regions in the U.S.
• Gulf Coast population
• 1960 -- 5.2 Million
• 1990 -- 10.1 Million
• Doubled in only 30 years.
• Florida to Virginia
• 1960 -- 4.4 Million
• 1990 -- 9.2 Million

15
Can We Evacuate?

• Hurricane evacuation times currently range from
  15 - 30 hours depending on the locale.
• Current warnings are only valid for 24 hours.
• Can the transportation infrastructure handle such
  a mass exodus quickly enough?

16
Building for Disaster?

• We are constructing more and larger dwellings
  along our hurricane-prone coastlines.

17
Building for Disaster?
Miami, FL
18
Better Construction

• Improved construction techniques may help
  alleviate some storm damage.
• Reinforcing seawalls
• Creating larger sand dunes and beaches
• Building housing on stilts
• Better tie-downs between the foundation and the
  walls and between the walls and the roof.
• Not much will stop a 7 m storm surge.

19
Is This Better?
20
Prediction Difficulty

• We still have difficulty predicting the precise
  landfall of most hurricanes.
• Some hurricanes can loop.
• What if we evacuate and the hurricane goes
  elsewhere -- the Cry Wolf problem.
• False alarms are still high and many people
  become apathetic.
• We see that here with tornado watches and
  warnings!

21
Prediction Difficulty
Hurricane Elena -- 28 August - 4 September 1985
22
Possible Solutions

• Increased Research on Hurricane Prediction
• Evacuation Studies
• Emergency procedures in the event evacuation is
  not feasible
• Population growth management
• Hurricane education
• Improved construction building codes
• Wetland management
• Hurricane Modification ????

23
Saffir-Simpson Intensity Scale
24
Conservation of Angular Momentum

• Quantification of the ice skater analogy
• This is the primary source of high wind speeds
• The quantity VR, known as angular momentum, is
  constant for any given air parcel (can differ
  from parcel to parcel)
• V is the tangential wind
• R is the radial distance of the air parcel from
  the hurricane eye

25
Conservation of Angular Momentum
Eye
V x R Constant
V
V is the tangential wind R is the
radialdistance of the air parcel from the
hurricane eye
Eye
R
Hurricane
26
Conservation of Angular Momentum
Eye
V x R Constant
V
What happens asan air parcelspirals
inwardtoward the centerof the hurricane?
Eye
R
27
Conservation of Angular Momentum
Eye
V1
V x R Constant
What happens asan air parcelspirals
inwardtoward the centerof the hurricane?
Eye
R1
28
Conservation of Angular Momentum
Eye
V1
V x R Constant
What happens asan air parcelspirals
inwardtoward the centerof the hurricane?
Eye
R1
V2
29
Conservation of Angular Momentum
Eye
V1
V x R Constant
What happens asan air parcelspirals
inwardtoward the centerof the hurricane?
Eye
R1
R2
V2
30
Conservation of Angular Momentum
V x R Constantsimply means that
Eye
V1
V1 x R1 V2 x R2
Eye
R1
R2
V2
31
Conservation of Angular Momentum
Eye
V1
Let V1 10 ktsR1 500 km If R2 30 km,
thenusing the equation V1 x R1 V2 x R2 we find
that V2 (V1xR1)/R2 V2 167 kts!!!
Eye
R1
R2
V2
32
Conservation of Angular Momentum
Note spiral bands converging towardthe center
33
Conservation of Angular Momentum

• The same mechanism is at work in tornadoes
• The flow is in the tangential direction, or in
  the direction of spin, but there also exists a
  radial inflow toward the center of the vortex, or
  a spiraling-inward flow

34
Hurricanes Often ProduceTornadoes Distribution
Hurricane Motion
Location of allhurricane-spawnedtornadoes
relativeto hurricane centerand motion
(McCaul, 1991)
35
Hurricanes Often ProduceTornadoes Hodographs
Composite hodographsby hurricane
quadrant (McCaul, 1991)
36
Tornadoes as a functionof range from the
centerof a hurricane. (McCaul, 1991)
37
Tropical Weather Climatology
Tropical Storms
Hurricanes
38
New Technology Dropsondes
39
New Technology Dropsondes
40
New Technology Dropsondes
Slides Showing the Improvement in Hurricane
Track Forecasts with Dropsondes