Hurricane Earl, September 1, 2010/NOAA

Tropical Cyclones 

A PREPAREDNESS GUIDE

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Weather Service

Revised March 2011
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Tropical cyclones are among nature’s most powerful 

and destructive phenomena. If you live in an area prone 

to tropical cyclones, you need to be prepared. Even 

areas well away from the coastline can be threatened 

by destructive winds, tornadoes and flooding from these 

storms. How great is the danger? For 1970-2010, the 

average numbers per year were as follows:

 Atlantic Ocean, Caribbean or Gulf of Mexico:

11 tropical storms, 6 of which became hurricanes 

 East Pacific Ocean: 15 tropical storms, 8 of which 

became hurricanes

 Central Pacific Ocean: 4 tropical storms, 2 of 

which became hurricanes

Over a typical 2-year period, the U.S. coastline is struck 

by an average of 3 hurricanes, 1 of which is classified as 

a major hurricane.

While hurricanes pose the greatest threat to life and 

property, tropical storms and depressions also can 

be devastating. Floods from heavy rains and severe 

weather, such as tornadoes, can cause extensive 

damage and loss of life. For example, Tropical Storm 

Allison produced over 40 inches of rain in the Houston 

area in 2001, causing about $5 billion in damage and 

taking the lives of 41 people.

Tropical cyclones forming between 5 and 30 degrees 

North latitude typically move toward the west. 

Sometimes the winds in the middle and upper levels 

of the atmosphere change and steer the cyclone 

toward the north and northwest. When tropical 

What is a Tropical Cyclone?

cyclones reach latitudes near 30 degrees North, they 

often move northeast. 

Hurricane seasons and their peaks are as follows:

 Atlantic and Caribbean: 

June 1 to November 30 

with peak season midAugust to late October. 

 Central Pacific (Hawaii): 

June 1 to November 30 

with peak season from 

July to September. 

 East Pacific: May 15 to 

November 30 

 Western North Pacific: 

Tropical cyclones can 

strike year round 

Understanding the Terminology

A tropical cyclone is a rotating, organized system 

of clouds and thunderstorms that originates over 

tropical or subtropical waters and has a closed 

low-level circulation. Tropical cyclones rotate 

counterclockwise in the Northern Hemisphere. 

They are classified as follows:

 Tropical Depression—A tropical cyclone with 

maximum sustained winds of 38 mph (33 knots) 

or less.

 Tropical Storm— A tropical cyclone with 

maximum sustained winds of 39 to 73 mph 

(34 to 63 knots).

 Hurricane—A tropical cyclone with maximum 

sustained winds of 74 mph (64 knots) or higher. 

In the western North Pacific, hurricanes are 

called typhoons; similar storms in the Indian 

Ocean and South Pacific Ocean are 

called cyclones.

 Major Hurricane—A tropical cyclone with 

maximum sustained winds of 111 mph (96 knots) 

or higher, corresponding to a Category 3, 4 or 5 

on the Saffir-Simpson Hurricane Wind Scale.

Tropical cyclone formation regions with mean tracks/NWS JetStream Online School
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Saffir-Simpson Hurricane Wind Scale

The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating based on a hurricane’s sustained wind speed. 

This scale estimates potential property damage. Hurricanes reaching Category 3 and higher are considered 

major hurricanes because of their potential for significant loss of life and damage. Category 1 and 2 storms 

are still dangerous, however, and require preventative measures. In the western North Pacific, the term “super 

typhoon” is used for tropical cyclones with sustained winds exceeding 150 mph. 

Saffir-Simpson Hurricane Wind Scale for the Continental United States

Scale 

Number 

(Category) 

Sustained 

Winds 

(MPH)

Types of

Damage Due to

Hurricane Winds

Hurricanes

1 74-95 Very dangerous winds will produce some damage: Well-constructed 

frame homes could have damage to roof, shingles, vinyl siding and 

gutters. Large branches of trees will snap and shallowly rooted trees may 

be toppled. Extensive damage to power lines and poles likely will result in 

power outages that could last a few to several days.

Dolly (2008)

on South Padre 

Island, Texas

2 96-110 Extremely dangerous winds will cause extensive damage: 

Well-constructed frame homes could sustain major roof and siding 

damage. Many shallowly rooted trees will be snapped or uprooted and 

block numerous roads. Near-total power loss is expected with outages 

that could last from several days to weeks. 

Frances (2004) 

in coastal Port 

St. Lucie, Florida

3 111-130 Devastating damage will occur: Well-built framed homes may incur 

major damage or removal of roof decking and gable ends. Many trees will 

be snapped or uprooted, blocking numerous roads. Electricity and water 

will be unavailable for several days to weeks after the storm passes.

Ivan (2004) 

in coastal Gulf 

Shores, Alabama

4 131-155 Catastrophic damage will occur: Well-built framed homes can sustain 

severe damage with loss of most of the roof structure and/or some 

exterior walls. Most trees will be snapped or uprooted and power poles 

downed. Fallen trees and power poles will isolate residential areas. 

Power outages will last weeks to possibly months. Most of the area will be 

uninhabitable for weeks or months.

Charley (2004) 

in coastal Punta 

Gorda, Florida

5 >155 Catastrophic damage will occur: A high percentage of framed homes 

will be destroyed, with total roof failure and wall collapse. Fallen trees 

and power poles will isolate residential areas. Power outages will last 

for weeks to possibly months. Most of the area will be uninhabitable for 

weeks or months.

Andrew (1992) 

in coastal parts 

of Cutler Ridge, 

Florida

For more information on the Saffir-Simpson 

Hurricane Wind Scale, go to: 

www.nhc.noaa.gov/aboutsshs.shtml

For more information on the Saffir-Simpson 

Hurricane Wind Scale as it affects Hawaii, go to:

www.prh.noaa.gov/cphc/pages/aboutsshs.php

Wind damage from Hurricane Charley, August 2004, 

Orlando, FL/Orlando Sentinel, copyright 2004
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Historical Storm Tide Events

 1900: Galveston, TX, hurricane, resulted in more than 8,000 deaths, most by storm tide.

 1969: Hurricane Camille produced a 24-foot storm tide in Mississippi.

 1989: Hurricane Hugo generated a 20-foot storm tide in South Carolina.

 1992: Hurricane Iniki produced a 6-foot storm tide on the island of Kauai in Hawaii.

 2005: Hurricane Katrina generated a 27-foot storm tide in Mississippi.

 2008: Hurricane Ike produced a 20-foot storm tide in Texas.

Hurricane Hazards

Storm Surge/Tide

Storm surge and large waves produced by hurricanes pose 

the greatest threat to life and property along the coast.

STORM SURGE is an abnormal rise of water generated by 

a storm’s winds. Storm surge can reach heights well over 

20 feet and can span hundreds of miles of coastline. In the 

northern hemisphere, the highest surge values typically 

occur in the right front quadrant of a hurricane coincident 

with onshore flow; in the southern hemisphere, the left front 

quadrant. More intense and larger hurricanes produce higher 

surge. In addition, shallower offshore waters contribute to 

higher storm surge inundation. Storm surge is by far the 

greatest threat to life and property along the immediate coast. 

STORM TIDE is the water level rise during a storm due to 

the combination of storm surge and the astronomical tide. 

For example, if a hurricane moves ashore at a high tide of 2 

feet, a 15 foot surge would be added to the high tide, creating 

a storm tide of 17 feet. The combination of high winds 

and storm tide topped with battering waves can be deadly 

and cause tremendous property damage along an area of 

coastline hundreds of miles wide.

The destructive power of storm 

surge and large battering waves 

can result in loss of life, buildings 

destroyed, beach and dune erosion 

and road and bridge damage along 

the coast. Storm surge can travel 

several miles inland. In estuaries 

and bayous, salt water intrusion 

endangers public health and the 

environment.

Before and after Hurricane Ike on the Bolivar 

Peninsula, TX, September 2008/USGS
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Rip Currents

The strong winds of a tropical cyclone can cause 

dangerous waves that pose a significant hazard to 

mariners and coastal residents and visitors. When the 

waves break along the coast, they can produce deadly 

rip currents—even at large distances from the storm. 

Rip currents are channeled currents of water flowing 

away from shore, usually extending past the line of 

breaking waves, that can pull even the strongest 

swimmers away from shore. 

In 2008, despite the fact that Hurricane Bertha was 

more than a 1,000 miles offshore, the storm resulted 

in rip currents that killed three people along the New 

Jersey coast and required 1,500 lifeguard rescues in 

Ocean City, Maryland, over a 1 week period. 

In 2009, all six deaths in the United States directly 

attributable to tropical cyclones occurred as the result 

of drowning from large waves or strong rip currents.

Tornadoes

Hurricanes and tropical storms can also produce 

tornadoes. These tornadoes most often occur in 

thunderstorms embedded in rain bands well away 

from the center of the hurricane; however, they can 

also occur near the eyewall. Usually, tornadoes 

produced by tropical cyclones are relatively weak and 

short-lived, but they still pose a significant threat.

Winds

Hurricane-force winds, 74 mph or more, can destroy 

buildings and mobile homes. Debris, such as signs, 

roofing material, siding and small items left outside 

become flying missiles during hurricanes. Winds can 

stay above hurricane strength well inland. In 2004, 

Hurricane Charley made landfall at Punta Gorda on 

the southwest Florida coast and produced major 

damage well inland across central Florida with gusts 

of more than 100 mph.

Rainfall 

Tropical cyclones often produce widespread, torrential 

rains in excess of 6 inches, which may result in deadly 

and destructive floods. In fact, flooding is the major 

threat from tropical cyclones for people living inland. 

Flash flooding, defined as a rapid rise in water levels, 

can occur quickly due to intense rainfall. Longer term 

flooding on rivers and streams can persist for several 

days after the storm. 

Hurricane Ivan flooding, Asheville, NC, September 2004

/Leif Skoogfors, FEMA

Rainfall amounts are not directly related to the 

strength of tropical cyclones but rather to the speed 

and size of the storm, as well as the geography of the 

area. Slower moving and larger storms produce more 

rainfall. In addition, mountainous terrain enhances 

rainfall from a tropical cyclone.

Hurricane Frances tornado damage, Sumter County, SC, 

September 2004/Marvin Mauman, FEMA
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Tropical Cyclone Graphical Products

To convey analysis and forecast information on tropical cyclones, the National Hurricane Center (NHC) and the 

Central Pacific Hurricane Center (CPHC) produce graphics that provide important information for those who 

rely on tropical cyclone forecasts. Weather forecasting isn’t an exact science. Many of these graphics have 

been designed to address the inherent uncertainties in tropical cyclone forecasts.

Track Forecast Cone 

and Watches/Warning

This graphic shows coastal areas under a 

hurricane warning (red), hurricane watch 

(pink), tropical storm warning (blue), and a 

tropical storm watch (yellow). The orange 

circle denotes the current position of the 

tropical cyclone. The black dots indicate the 

forecast positions and cyclone classification 

over the next 5 days. 

Forecast errors and uncertainty of the future 

tropical cyclone center location are accounted 

for by the track forecast cone. The solid white 

area denotes the uncertainty for days 1-3. 

The white stippled area shows the uncertainty 

for days 4 and 5. On average, the center of 

the tropical cyclone will remain inside the 

cone 60%–70% of the time. It is important to 

remember that a tropical cyclone is not a point 

and that the associated hazards can extend 

well outside of the track forecast cone.

Graphical Tropical Weather Outlook

Track Forecast Cone and Watches/Warnings

Graphical Tropical Weather Outlook

This graphic highlights areas of disturbed 

weather in the tropics and subtropics and 

assesses the potential for these systems 

to become tropical cyclones over the next 

48 hours. Each disturbance is circled and 

numbered with an accompanying text 

description. You also can view the text 

description by moving your mouse over the 

circled area. The color of the circles reflect 

the probability that the system will become a 

tropical cyclone over the next 48 hours:

 Yellow: low chance, <30%

 Orange: medium chance, 30%–50%

 Red: high chance, >50%

Active tropical cyclones are depicted on the 

graphic as an “L” for tropical depressions, a 

tropical storm symbol, or a hurricane symbol.
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Tropical Cyclone Storm Surge Probabilities

Tropical Cyclone Surface Wind Speed Probabilities

Tropical Cyclone Surface 

Wind Speed Probabilities

This graphic indicates the chance 

of locations experiencing at least 

tropical storm (39 mph or greater) 

sustained winds over the following 

5 days. The graphic is also 

available at thresholds of 58 mph 

and 74 mph (hurricane force) 

sustained winds. The product is 

unique in that it takes into account 

uncertainty in the track, peak winds 

and size of the storm. 

This graphic also highlights the 

fact that tropical cyclone winds can 

extend well away from the storm’s 

center. It is important to realize that 

probabilities that seem relatively 

low may still be quite significant. 

For example, if a location has 

a 10% chance of experiencing 

hurricane force sustained winds, 

you should prepare for an extreme 

event. A 1 in 10 chance is too high 

to ignore.

Tropical Cyclone Storm 

Surge Probabilities

Like surface wind speed probability 

products, storm surge probability 

products show the percentage 

chance of storm surge exceeding 

various thresholds. The thresholds 

are available at 1-foot intervals from 

a minimum of 2 feet to a maximum 

of 25 feet.

The graphic shows the chance 

that locations along the Texas and 

Louisiana coasts would experience 

a storm surge of at least 8 feet from 

Hurricane Ike based on the forecast 

issued at 11 AM EDT on September 

12, 2008. The graphic is created 

from many simulations of the NWS 

storm surge computer model, and 

accounts for uncertainty in track, 

intensity and size.
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Ways to Stay Informed

NOAA Weather Radio All Hazards

The National Weather Service (NWS) continuously broadcasts warning, 

watches, forecasts and non-weather related hazard information on 

NOAA Weather Radio All Hazards (NWR). The average range of the 

1000+ NWR transmitters is 40 miles, depending on topography. For the best 

performing NWR receivers, NWS suggests you look at devices certified to 

Public AlertTM standards. 

These radios meet specific technical standards and come with many features 

such as Specific Area Message Encoding (SAME), a battery backup, both 

audio and visual alarms, selective programming for the types of hazards you 

want to be warned for, and the ability to activate external alarm devices for 

people with disabilities. Similar to a smoke detector, an NWR can wake you up 

in the middle of the night to alert you of a dangerous situation.

Current Storm Information

 National Weather Service: 

www.weather.gov 

 National Hurricane Center: 

www.nhc.noaa.gov

 Central Pacific Hurricane Center: 

www.prh.noaa.gov/cphc

Historical Storm Information

 National Climatic Data Center:

www.ncdc.noaa.gov

 NOAA Coastal Services Center:

www.csc.noaa.gov

Emergency/Preparedness Information

 American Red Cross:

www.redcross.org

 FEMA:

www.fema.gov

Mobile NHC and NWS Information 

 Mobile NHC website in basic HTML: 

www.nhc.noaa.gov/mobile

 Mobile NHC website in WAP format:

www.nhc.noaa.gov/index.wml

 Mobile NWS website in basic HTML: 

mobile.weather.gov

 Mobile NWS website in WAP format:

cell.weather.gov

Other Information

 NHC advisory emails:

www.nhc.noaa.gov/signup.shtml 

 CPHC advisory emails:

www.prh.noaa.gov/cphc/pages/signup.php

 Audio Podcasts:

www.nhc.noaa.gov/audio/index.shtml

 Geographic Information System Data: 

www.nhc.noaa.gov/gis/

 NOAA Weather Radio All Hazards: 

www.weather.gov/nwr

 Hurricane Tracking Charts:

www.weather.gov/os/hurricane/ 
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What To Listen For

 HURRICANE/TROPICAL STORM WATCH: Hurricane/tropical storm conditions are possible in the 

specified area of the watch, usually within 48 hours of the onset of tropical storm force winds. During 

a Watch, prepare your home and review your plan for evacuation in case a Hurricane/Tropical Storm 

Warning is issued. Listen closely to instructions from local officials.

 HURRICANE/TROPICAL STORM WARNING: Hurricane/tropical storm conditions are expected in 

the specified area of the Warning, usually within 36 hours of the onset of tropical storm force winds. 

Complete storm preparations and immediately leave the threatened area if directed by local officials.

 EXTREME WIND WARNING: Extreme sustained winds of a major hurricane (115 mph or greater), 

usually associated with the eyewall, are expected to begin within an hour. Take immediate shelter in 

the interior portion of a well-built structure.

 Additional Watches and Warnings are issued to provide detailed information on specific threats such 

as floods and tornadoes. Local National Weather Service offices issue Flash Flood/Flood Watches and 

Warnings as well as Tornado Warnings.

National Hurricane Center and Central 

Pacific Hurricane Center Products 

PUBLIC ADVISORIES offer critical hurricane 

watch, warning and forecast information.

FORECASTS/ADVISORIES provide detailed 

hurricane track and wind field information.

PROBABILITIES OF HURRICANE/TROPICAL 

STORM CONDITIONS offer locally specific 

chances of experiencing tropical storm, strong 

tropical storm and hurricane force winds out to 

5 days to better know if one will be impacted and 

when these conditions may occur.

Local NWS Office 

Products

HURRICANE LOCAL STATEMENTS

give greater detail on how the storm will impact 

your area.

NON-PRECIPITATION WEATHER 

PRODUCTS provide High Wind Watches and 

Warnings for inland areas that could experience 

strong winds.

Use all of the above information to make an informed decision on your risk and what actions to take. 

Listen to recommendations of local officials on TV, radio and other media and to NOAA Weather Radio 

All Hazards for the latest tropical cyclone information.
10

Are You Ready?

Before the Hurricane Season

FEMA

9 Determine safe evacuation routes inland.

9 Learn locations of official shelters.

9 Check emergency equipment, such as 

flashlights, generators and battery-powered 

equipment such as cell phones and your 

NOAA Weather Radio All Hazards receiver.

9 Buy food that will keep and store drinking water.

9 Buy plywood or other material to protect your 

home if you don’t already have it.

9 Trim trees and shrubbery so branches don’t 

fly into your home. 

9 Clear clogged rain gutters and downspouts.

9 Decide where to move your boat.

9 Review your insurance policy.

9 Find pet-friendly hotels on your evacuation route.

When in a Watch Area... 

9 Frequently listen to radio, TV or NOAA Weather 

Radio All Hazards for official bulletins of the 

storm’s progress.

9 Fuel and service family vehicles.

9 Inspect and secure mobile home tie downs.

9 Ensure you have extra cash on hand.

9 Prepare to cover all windows and doors with 

shutters or other shielding materials.

9 Check batteries and stock up on canned food, 

first aid supplies, drinking water and medications.

9 Bring in light-weight objects such as garbage 

cans, garden tools, toys and lawn furniture.

When in a Warning Area...

9 Closely monitor radio, TV or NOAA Weather 

Radio All Hazards for official bulletins.

9 Close storm shutters.

9 Follow instructions issued by local officials. Leave 

immediately if ordered!

9 Stay with friends or relatives at a low-rise inland 

hotel or at a designated public shelter outside the 

flood zone.

9 DO NOT stay in a mobile or manufactured home.

9 Notify neighbors and a family member outside of 

the warned area of your evacuation plans.

9 Take pets with you if possible, but remember, 

most public shelters do not allow pets other than 

those used by used by people with disabilities. 

Identify pet-friendly hotels along your evacuation 

route.

During the Storm

Plan to Leave if You...

9 Live in a mobile home. They are unsafe in high 

winds no matter how well fastened to the ground.

9 Live on the coastline, an offshore island or near a 

river or a flood plain.

9 Live in a high rise building. Hurricane winds are 

stronger at higher elevations. 
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What to Bring to a Shelter

REMINDER: If you are told to leave 

your home, do so immediately!

What to Bring to a Shelter

 First-aid kit

 Medicine, prescriptions

 Baby food and diapers

 Games, books, music players with headphones

 Toiletries

 Battery-powered radio and cell phone

 Flashlights

 Extra batteries

 A blanket or sleeping bag for each person

 Identification

 Copies of key papers such as insurance policies

 Cash, credit card

If Staying in a Home...

9 Turn refrigerator to maximum cold and keep 

it closed.

9 Turn off utilities if told to do so by authorities.

9 Turn off propane tanks.

9 Unplug small appliances.

9 Fill bathtub and large containers with water in 

case clean tap water is unavailable. Use water in 

bathtubs for cleaning and flushing only. Do NOT 

drink it. 

If Winds Become Strong...

9 Stay away from windows and doors, even if they 

are covered. Take refuge in a small interior room, 

closet or hallway.

9 Close all interior doors. Secure and brace 

external doors.

9 If you are in a two-story house, go to an interior 

first floor room.

9 If you are in a multi-story building and away from 

water, go to the 1st or 2nd floor and stay in the 

halls or other interior rooms away from windows.

9 Lie on the floor under a table or other 

sturdy object.

Be Alert For...

9 Tornadoes—they are often spawned by 

hurricanes.

9 The calm “eye” of the storm—it may seem like 

the storm is over, but after the eye passes, the 

winds will change direction and quickly return to 

hurricane force.

After the Storm

9 Keep listening to radio, TV or NOAA Weather 

Radio All Hazards.

9 Wait until an area is declared safe before 

entering.

9 Watch for closed roads. If you come upon a 

barricade or a flooded road, Turn Around 

Don’t Drown!TM

9 Stay on firm, dry ground. Moving water only 

6 inches deep can sweep you off your feet. 

Standing water may be electrically charged from 

power lines. 

9 If using a generator, avoid carbon monoxide 

poisoning by following the manufacturer’s 

instructions.

9 Avoid weakened bridges and washed out roads.

9 Once home, check gas, water and electrical and 

appliances for damage.

9 Use a flashlight to inspect damage. Never use 

candles and other open flames indoors.

9 Wear proper shoes to prevent cutting feet on 

sharp debris.

9 Do not drink or prepare food with tap water until 

officials say it is safe.

9 Avoid electrocution by not walking in areas with 

American Red Cross downed power lines. 
12

NOAA PA 201152 

Gather information about hazards. Contact your local National Weather Service office, emergency 

management office and American Red Cross chapter. Find out what type of emergencies could occur and 

how you should respond. Learn your community’s warning signals and evacuation plans. Assess your 

risks and identify ways to make your home and property more secure.

Meet with your family to create an emergency plan. Pick two places to meet: a spot outside your 

home for an emergency, such as fire, and a place away from your neighborhood in case you can’t return 

home. Choose an out of state friend as your family’s point of contact for everyone to call if the family gets 

separated. Discuss what you would do if advised to evacuate.

Implement your plan. 

1. Post emergency telephone numbers by the phone.

2. Install safety features in your house, such as smoke alarms and fire extinguishers.

3. Inspect your home for items that can move, fall, break or catch fire and correct them.

4. Have your family learn basic safety measures, such as CPR and first aid, how to use a fire

 extinguisher, and how and when to turn off water, gas and electricity in your home.

5. Teach children how and when to call 911 or your local emergency number.

6. Keep enough supplies in your home for at least 3 days. Assemble an emergency supplies kit. Store

 these supplies in sturdy, easy-to-carry containers, such as backpacks or duffle bags. Keep important

 documents in a waterproof container. Keep a smaller emergency supplies kit in the trunk of your car.

Family Emergency Plan

Practice and maintain your plan. Ensure your family knows meeting places, phone numbers and safety 

rules. Conduct drills. Test your smoke detectors and NWR monthly and change the batteries at least once 

each year. Test and recharge your fire extinguisher(s) according to manufacturer’s instructions. Replace 

stored water and food every 6 months. 

9 At least a 3-day supply of water 

(one gallon per person, 

per day)

9 At least a 3-day supply of 

non-perishable food

9 At least, one change of clothing 

and shoes per person

9 One blanket or sleeping 

bag per person

9 First-aid kit

9 Battery-powered NWR 

and a portable radio

9 Emergency tools

9 Flashlight, extra batteries

An Emergency Supplies Kit Should Include:

9 Extra set of car keys

9 Credit card and cash

9 Special items for infant, elderly or 

disabled family members

9 Prescription and non-prescription 

medicines 

Everyone needs to be prepared for the unexpected. You, as well as your family and friends, will most 

likely not be together when disaster strikes. How will you find each other? Will you know if your children or 

parents are safe? You may have to evacuate or be confined to your home. What will you do if water, gas, 

electricity or phone services are shut off?

Steps to Take

I

II

III

IV

Safety and preparedness material is online at:

Federal Emergency Management Agency: www.ready.gov

American Red Cross: www.redcross.org

NOAA National Weather Service: www.weather.gov/safety.php