2 Tropical CyclonesThese are the greatest storms on Earth and are among the most destructive of natural disasters.They are know by several names, depending on where they form.HurricaneUsed in the Atlantic and eastern and central Pacific and is derived from the Carib Indian word “huracan” for the Carib god of evil.TyphoonUsed in the western PacificCycloneIndian Ocean termWilly WillyUsed in Australia (also “tropical cyclone”)
3 Naming Hurricanes Starting in 1953 Prior to 1953 Starting in 1979 NWS started using female namesPrior to 1953Only the most severe hurricanes were given namesThey were often namedFor the place they did the most damage . . .Galveston Hurricane of 1900Or the time they hit . . .Labor Day Hurricane of 1935Hurricane of 1938 (Also called “The Long Island Express” or the New England Hurricane of 1938Starting in 1979Male and female names were included in lists for the Atlantic and Gulf of Mexico
4 Tropical Storm and Hurricane Names for the Atlantic, Gulf of Mexico, and Caribbean Sea Letters Q, U, X, Y, and Z are not used becausethere are few common names starting with these letters
5 Six Separate ListsThe names are used over again at the end of each six-year cycle.Each calendar year starts with the next list, even if all the names weren't used the previous year.One list is repeated every seventh year.For example, in 2012 the 2006 list will be used again.The exception will be if any names have been retired. The names of storms which have been extremely deadly and costly aren't used again.
7 More on Naming Hurricanes If more than 21 named tropical cyclones occur in the Atlantic basin in a seasonAdditional names are taken from the Greek alphabet (Alpha, Beta, Gamma, Delta, Epsilon, Zeta, etc.)If a storm forms in the off-seasonThe name used is based on the calendar yearRetiring NamesWhenever a hurricane has had a major impact, any country affected by the storm can request that the name of the hurricane be “retired” by agreement of the World Meteorological Organization (WMO)This means it can’t be used for at least 10 years
8 Tropical Cyclone Characteristics Form over tropical oceans between 5o and 20o latitude (except the South Atlantic and eastern south Pacific)By international agreement, a storm is classified a hurricane if wind speeds are 74 mph (119 km/hour) and has a rotary circulation.
9 Hurricane FranVisible Image 9/5/96FLCubaMature hurricanes average about 600 km (372 miles) across but can be up to about 1500 km (930 miles).Pressure drops as much as 60 millibars from the outer edge to the center.Steep pressure gradient generates rapidly spiraling winds which increase as the center of the storm is approached (due to conservation of angular momentum).Duration: A week or more
10 The Structure of a Hurricane: Convective Rain Bands Tropical moisture spiraling inward creates rain bands that pinwheel aroundthe storm center
11 The Structure of a Hurricane: The Eye Wall As the inward rush of warm, moist surface air reachesthe center of the storm it rises in a ring of cumulonimbus towers.It’s a doughnut shaped wall of intense convective activity.
12 Produces the most intense rainfall and greatest wind speeds The Eye WallProduces the most intense rainfalland greatest wind speedsKatrina Eye WallHurricane Charley
13 The Structure of a Hurricane: Outflow Outflow prevents the convergent flow at lower levels from “filling in” the storm.
14 The Structure of a Hurricane: The Eye Average Diameter is20 to 30 miles (32 to 48 km)A quasi-circular or quasi-oval region of light winds and skies that are clear to partly cloudyand free of rain.Caused by descending air that heats by compression, making it the warmest region of the storm.
15 Can you identify when the eye passed? Wind speeds recorded by a data buoy in the easternGulf of Mexico during the passage of Hurricane Kate (1985)
16 Hurricane Wilma October 2005 EyeThe record for the lowest surface air pressure for an Atlantic Hurricane,882.0 mb, was recorded in the eye on Oct. 18
17 Vertical Section and Associated Patterns of Wind, Pressure, and Rain
18 Hurricane Formation and Decay Cooperative Program for Operational Meteorology, Education and Training
19 Hurricanes are Huge Heat Engines Fueled by latent heat released when huge quantities of heat are released by condensation.Released heat warms the air making it buoyant (unstable).Results in lower surface air pressureInitiates a rapid inflow of airRequires a large quantity of heat to get started.Develop most often in late summerOcean temperatures 27o C (80o F)
20 Hurricanes Form in the Tropics Often form in the ITCZ.Few form poleward of 20 degrees latitudeWater isn’t warm enoughNot within 5 degrees of the equatorCoriolis force is too weak to initiate rotary motion
21 Tropical Disturbances AfricaS. AmericaOriginate in Africa as disorganized arrays of clouds and thunderstormsWeak pressure gradient and little or no rotationMost die out but some will develop rotation
22 Disturbances Can Become Easterly Waves Streamlines (arrows) show low-level airflow.East of the axisWinds turn slightly poleward and converge forming cloudsTropical Disturbances are associated with this side of the waveWest of the axisWinds divergeClear skiesCan develop into a tropical depression
23 Trade Wind Inversions Prevent Development into a Tropical Depression Subsiding air in a nearby subtropical highTurbulence near the surface prevents lower level air from sinkingAn inversion develops between the lower zone and the subsiding warmer layers aboveThis reduces the ability of the air to rise.
24 When Conditions Favor Hurricane Development . . . No inversion exists and upper-level winds are not too strongA Tropical Depression FormsPressure drops at center with a steep gradientSurface winds strengthen and bring in additional moistureCondensation releases heat and air risesFurther adiabatic cooling forms more cloudsCondensation releases more latent heatHigher pressure develops aloft resulting in outflowThese processes continue and the storm forms.
25 Hurricane Allen (1980) loses strength as it moves over land. Hurricane Decay(1)(2)(3)Hurricane Allen (1980) loses strength as it moves over land.Hurricanes diminish in intensity wheneverThey are deprived of the warm moisture needed for the source of latent heat byMoving over land (roughness of surface also rapidly reduces wind speeds)Moving over cooler ocean waterLarge-scale flow aloft is unfavorable
26 Storm Tracks For 2005 - 28 Named Storms! Influenced byTrade WindsPrevailing SouthwesterliesJet StreamOther Highs and Lows
27 Hurricane Destruction Depends onStrength of the StormSize and population density of the area affectedNearshore bottom configuration
28 Damage to the roof of the Superdome from Hurricane Katrina Wind DamageHurricane AndrewHurricane WilmaThe most obvious type of damageDebris becomes flying missilesMobile homes are particularly vulnerableHigh rise buildings, especially upper floors,areVulnerableTornadoes that are produced by somehurricanes contribute to the storms damageDamage to the roof of the Superdomefrom Hurricane Katrina
29 Hurricane Winds Storm surge will be greatest along the coastline hit by the right side of the hurricane
30 Storm Surge The dome of water 65 to 80 km wide that sweeps across the coast near the landfall position of the eyeThe most devastating damage in the coastal zoneResponsible for 90% of hurricane-caused deathsCause:Strong onshore winds push water towards the shoreWinds also create violent wave activity.Low pressure on ocean surface is relatively insignificant
31 Storm Surge of the Galveston Hurricane of 1900 An unexpected Category 4 storm
41 Saffir-Simpson Scale Based on study of past storms Ranks the relative intensities of hurricanesEstablished based on observed conditions.Scale of 1 to 5Category 1 is least severeCategory 5 is most severeRareNot likely in the northeast because water temperatures are too cool.
43 Category One Wind speed: Storm surge: Central Pressure: 980 mb Damage: 74-95 mph ( km/h)Storm surge:4-5 feet above normalCentral Pressure: mbDamage:Damage primarily to unanchored mobile homes, shrubbery, and trees along with some coastal road flooding and minor pier damageExamples:Allison, 1995; Danny, 1997
44 Category Two Wind speed: Central Pressure: Storm surge: Damage: mph ( km/h)Central Pressure:mbStorm surge:6-8 feet above normalDamage:Roofing, door and window damage to buildings; Considerable damage to shrubbery and trees, mobile homes, poorly constructed signs, and piersExamples:Bonnie, Georges, 1998
45 Category Three Wind speed: Central Pressure: Storm surge: Damage: mph ( km/h)Central Pressure:mbStorm surge:9-12 feet above normalDamage:Structural damage to small residences and utility buildings; foliage blown off trees and large trees blown down; mobile homes destroyedExamples:Roxanne, 1995; Fran, 1996; Rita, 2005.
46 Category Four Wind speed: 131-155 mph (210-249 km/h) Central Pressure: mbStorm surge:13-18 feet above normalDamage:Extensive damage to doors, windows and lower floors of shoreline houses; total roof failures on small residences; shrubs, trees, and all signs blown down; mobile homes completely destroyedExamples:Hugo, 1989, Luis, Felix, Opal, 1995, Emily, Katrina, Wilma 2005.
47 Hurricane Katrina A Category 5 over the Gulf of Mexico August 18, 2005 Came ashore as a category 4 stormand 8 hrs later was still a Category 1
48 Category Five Wind speed: Central Pressure: Storm surge: Damage: Greater than 155 mph (249 km/h)Central Pressure:<920 mbStorm surge:generally greater than 18 feet above normalDamage:Complete roof failure on many buildings and some complete building failures with small utility buildings blown over or away; severe and extensive window and door damage; mobile homes completely destroyedExamples:Camille, 1969; Gilbert, 1988; Andrew, 1992; Mitch, 1998
49 Atlantic Hurricanes that made Landfall as Category 5 Storms 1NameDateLandfall locationFatalitiesDeanAug. 21, 2007Near Majahual, MexicoAt least 13GilbertSept. 1, 1988Cancun, Mexico327EdithSept. 9, 1971Nicaragua30CamilleAug. 17, 1969Mississippi, USA256JanetSept 28, 1955Chetumal, Mexico>600UnnamedSept. 16, 1947Bahamas54Labor Day HurricaneSept. 3, 1935Florida Keys408Sept 5, 1932No RecordsSan Felipe-Okeechobee HurricaneSept. 13, 1928Puerto Rico2,1661 Since records began in 1886
51 1938 New England Hurricane – (The Long Island Express) The storm was tracked as it moved west from Africa and toward the Bahamas Islands.The U.S. Weather Bureau (now called the NWS)Knew it was a powerful stormIt had reached category 5 strength on September 19It was believed the hurricane would curve out to sea before reaching the Northeast.The Bureau tracked the storm on the 21st as it was off the coast of Norfolk, V.ANow a category 3 storm.
52 A large area of high pressure Was located over the Atlantic Ocean just east of the coastKept the storm close to the coast and moving northeastward.Charlie Pierce, a young research forecaster for the BureauConcluded that the storm would not continue to move northeast and curve out to sea but would instead track due north.He was overruled by more senior meteorologistsThe official forecast was for cloudy skies and gusty conditions –but no hurricane
53 Instead of Curving Out to Sea… The storm moved due north and accelerated in forward speed to 70 mph.In the history of hurricanes, this is the fastest known forward speed recorded.The incredible forward speed of the storm was 70 mphWinds to the east of the eye are moving from south to north.The same direction as the forward speedAdded to the already powerful winds. Eastern Long Island and New England would later be hit with wind speeds that exceeded 180 mph!
54 Landfall on LI on Sept. 21The eye was about 50 miles across and the hurricane was about 500 miles wide.3:30 PM which was just a few hours before astronomical high tide.High tide was even higher than usual because of the new moon (spring tides).Storm tides of 14 to 18 feet across most of the Long Island and Connecticut coast, with 18 to 25 foot tides from New London east to Cape Cod.Caused enormous storm surgeHigh tides combined with winds gusting over 180 mphWaves between 30 and 50 feet pounded the coastline with millions of tons of sea water, sweeping entire homes and families into the sea.The impact of the storm surge was so powerful that it was actually recorded on the earthquake seismograph at Fordham University in New York City.Downtown Providence, Rhode Island was submerged under a storm tide of nearly 20 feet.Downtown Westhampton Beach, a mile inland, was under 8 feet of water!Sections of Falmouth and New Bedford, Massachusetts were also submerged under as much as 8 feet of water.Rainfall resulted in severe river flooding across sections of New York, Massachusetts, and Connecticut
55 Total Estimated Damage 700 deaths (50 on L.I.), 708 injured4,500 homes, cottages, farms destroyed; 15,000 damaged26,000 destroyed automobiles20,000 miles of electrical power and telephone lines downed1,700 livestock and up to 750,000 chickens killed$2,610,000 worth of fishing boats, equipment, docks, and shore plants damaged or destroyedHalf the entire apple crop destroyed at a cost of $2 million