1. By:Caroline McCormack Laura Mals Nick Chignoli Erin Rembold
Hurricanes
By:Caroline McCormack
Laura Mals
Nick Chignoli
Erin Rembold

2. The Birth of a Tropical Cyclone
A Tropical Cyclone forms and strengthens when these three conditions occur:
A Pre-existing disturbance with thunderstorms
Warm (at least 80 degrees Fahrenheit) ocean temperatures to a depth of about 150 feet
Light upper level winds that do not change much in direction and speed throughout the depth of the atmosphere (low wind shear)
Heat and energy are gathered by the disturbance through contact with the warm ocean waters.
The winds near the ocean surface spiral into a low pressure area.
Warm ocean waters add moisture and heat to the rising air, which adds energy to power the storm. ER

3. Growth and Maturity There are three stages of a Hurricane Development:
Tropical Depression-(winds less than 38mph) when storms begin to take on the spiral appearance due to the flow of the winds and the rotation of the earth.
Tropical Storm-(winds 39-73mph) when the storm strengthens and the thunderstorms contribute additional heat and moisture to the storm.
Hurricane-(winds at least 74mph) this is when the cloud-free hurricane eye typically forms because rapidly sinking air at the center dries and warms the area.
Hurricanes can last for more than two weeks and travel up the entire Atlantic Coast. ER

4. Hurricane’s End
There are many factors that can attribute to a Hurricane’s decay. Some factors are:
Wind shear (when air currents rise and fall within the same cloud) can tear a hurricane apart.
Moving over cooler water or drier areas can lead to weakening as well.
Landfall typically shuts off the hurricane’s main moisture source, and surface circulation can be reduced.
However, a weakening hurricane or tropical cyclone can intensify once again if it moves into a more favorable region. ER

5. Structure
There are three parts of a hurricane, which are rainbands, the eye, and the eyewall.
Air spirals in toward the center in a counter-clockwise pattern, and out the top in the opposite direction. In the very center of the storm, air sinks, forming the cloud-free eye. ER

6. Structure Continued The Eye: The Eyewall: Rainbands:
The hurricane’s center is a relatively calm, clear area usually miles across.
The Eyewall:
The dense wall of thunderstorms surrounding the eye has the strongest winds within the storm.
Rainbands:
The storm’s outer rainbands can extend a few hundred miles from the center. They range from a few miles to 300miles long and spiral clockwise.
Below: The eyewall, or clouds surrounding the clear eye. ER

7. Where Hurricanes Form
The map to the right shows places throughout the world where tropical cyclones originate.
At the equator, ocean surface temperatures are warm enough to produce hurricanes, but none form. This is because there is not enough coriolis force (air or water currents caused by the rotation of the Earth) to create spin and induce a potential hurricane.
They are most commonly found in the northern hemisphere, but can also be produced in the Pacific and Indian Oceans in the southern hemisphere. Note: In other parts of the world a Hurricane is also known as a typhoon, tempest, or a monsoon. ER

8. Who Tracks Hurricanes? The National Hurricane Center (NHC)
Located in Miami, Florida
Tracks Tropical cyclones from the tropical depression stage through the hurricane stage over the following areas:
North Atlantic Ocean
Caribbean Sea
Gulf of Mexico
Eastern Pacific Ocean LM

9. How Does NHC Track Hurricanes?
To forecast the track and intensity of tropical cyclones, NHC uses mathematical computer models.
Models – represent tropical cyclone and its environment.
Computers – forecast the future motion and intensity of a cyclone
Hurricane Forecasters – interpret model results to arrive at a final track and intensity forecast LM

10. What Models are Used to Forecast Hurricanes?
The mathematical models used at NHC are of three basic types:
Statistical – Uses current information about hurricanes and comparing it to historical knowledge.
Dynamical – Uses results of global atmospheric model forecasts; Takes current wind, temperature, pressure and humidity observations and make forecasts on the atmosphere.
Combination (Statistical and Dynamical together) – Dynamical models ignore the behavior or historical storms, thus combination models were constructed to capitalize on the strength of both the statistical and dynamical models. LM

11. When & How Do They Warn People at Risk?
A hurricane watch is issued when there is a threat of hurricane conditions within hours.
A hurricane warning is issued when hurricane conditions (winds of 74 miles per hour or greater, or dangerously high water and rough seas) are expected in 24 hours or less.
They make announcements and provide official instructions through radio broadcasts and television reports. LM

12. Emergency Officials
Emergency Officials LM

13. What is a Typical Evacuation Procedure?
If officials indicate evacuation is necessary:
They should determine an appropriate shelter with the National Emergency Organization.
People must leave as soon as possible. They should avoid flooded roads and watch for washed-out bridges.
People should not leave unless it is under the direction of emergency officials. LM

14. 2004 Hurricane Season
Extremely disastrous summer due to the powerful hurricanes.
Hurricanes this year were longer lasting, and had an abnormal number of spin- off tornadoes. NC

15. Totals
By the end of September, nearly 2000 have died from the 2004 Hurricane season.
It is impossible to know the raw totals of damage. It is, however, said to range from several hundred million dollars, all the way into the billions.
Many people have been left homeless and powerless. NC

16. 2004 Hurricane Season Very unusual storm patterns this year.
Storm season starts in June, however this a tropical cyclones formed as early as March 25th.
First named storm August 1st, much later than usual.
Storms rapidly formed. Eight named storms in August alone, and into September. NC

17. Pre-Season Outlook
On May 17, prior to the start of the season, NOAA forecasters predicted a 50% probability of activity above the normal range.
NOAA predicted tropical storms, 6-8 of those becoming hurricanes, and 2-4 of those hurricanes reaching at least Category 3 strength
William Gray, noted forecaster, predicted 14 named storms, 8 reaching hurricane strength, and 3 reaching Category 3 strength.
has 6 to 14 tropical storms, 4 to 8 of which reach hurricane strength, and 1 to 3 of those reaching Category 3 strength. NC

18. Powerful 2004 Hurricanes
Hurricane Frances: Hit Florida September 5th. Brought Florida to state of Emergency.
Hurricane Ivan: 70 dead in Carribean, and 52 in the United States. (sixth most intense storm on record.) It held winds of up to 165 MPH
Hurricane Jeanne: killed 1600 people in Haiti before ever hitting Florida. The people of Florida were unprepared for this storm, as they were still recovering from Ivan NC

19. "Overall, this has been a very destructive and costly hurricane season
"Overall, this has been a very destructive and costly hurricane season. The official totals are not in yet, but this will likely go down as the costliest hurricane season on record in the U.S." Stu Ostro of the Weather Channel. NC

20. Ways to determine most destructive hurricanes…
Category if falls in.
Number of people hurt or killed.
Total area destroyed.
How long the hurricane lasted.
How fast the hurricane moved compared to damage done.
Storm intensity.
Total cost of damage done. CM

21. Deadliest Hurricane
Between 1900 and 2000, the Hurricane that caused the most damage in the US was in Galveston Texas. It occurred in 1900 and was considered a category 4 Hurricane deaths were recorded as a result of this hurricane, but records show that it could have caused anywhere from 10,000 to 12,000 deaths CM

22. Most Costly Hurricane
Rank
Hurricane
Year
Category
Damage $$$ 1
Andrew SE FL, SE LA
1992 5
26,500,000,000 2
Hugo SC
1989 4
7,000,000,000 3
loyd Mid Atlantic
1999
4,500,000,000
Fran NC
1996
3,200,000,000
Opal NW FL, AL
1995
F3,000,000,000 6
Georges FA Keys. MS, AL
1998
2,310,000,000 7
Frederic AL MS
1979
2,300,000,000 8
Agnes FA NE U.S
1972
2,100,000,000 9
Alicia N TX
1983
2,000,000,000 10
Bob NC NE U.S
1991
1,500,000,000
The Hurricane that caused the most damage economically occurred in 1992 in South Eastern Florida and South Eastern Louisiana. It was considered a category 5 hurricane and it had a total cost of $26,500,000,000. CM

23. Most Intense…
Hurricanes are ranked by estimated central pressure at time of landfall.
The most intense Hurricane that hit the mainland of the U.S. occurred in It was unnamed and was considered a category 5 Hurricane. It struck the Florida Keys.
The minimum pressure was 892 (mb)
The maximum pressure was (in) CM

24. Striking Facts…
Ten of the twelve deadliest hurricanes were equivalent of a category 4 or higher.
However, only one-sixth of the costliest hurricanes were of category 4 or higher.
Large death totals were primarily a result of the 15 to 20 feet or greater rise of the ocean (storm surge) associated with many of these major hurricanes.
All but six of the thirty deadliest hurricanes were major hurricanes.
Only one of the deadliest hurricanes occurred during the past twenty five years in contrast to two-thirds of the costliest hurricanes. This may be a result of inflation and better protection and tracking of these hurricanes.
On the average, a category 4 or stronger hurricane strikes the United States once every 6 years. CM

25. What makes Hurricanes so destructive?
Storm surges: Huge waves caused by intense winds generated by the powerful tropical storm or hurricane. The waves can reach over 20 feet in height.
Winds: They can reach up to 74 miles per hour. However, winds over 110 miles per hour are not uncommon. This can cause flying debris which can be very destructive.
Flooding: Storm surges and heavy rain have a direct effect on the death rate and total amount of destruction that occurs. CM

26. Resources http://hurricanes.noaa.gov/prepare/origin.htm