Tropical Cyclone Ingredients• Light winds ⇒ instability along I.T.C.Z.• High humidity (oceans) ⇒ fuel (latent heat)• Warm surface waters over a vast area (at least 26ºC / 76ºF ⇒ tropics, < 25 ºN or S)• Will not form within 5 o of equator (no Coriolis )
Tropical Cyclone Features• Spiral bands• No Fronts• Eye wall cloud• Eye• Size: 100-600 miles, but can be larger Death Toll: 12,000
Tropical Cyclone Formation• Easterly waves (fig. 8-24) – vertical perturbations within the trade winds – about 10% intensify and rotate• Tropical depression (winds < 63 kmph, 39 mph)• Tropical storm (63-118 kmph, 39-73 mph) – naming of the storm• Cyclone (winds > 119 kmph, 74 mph) – Saffir-Simpson scale (Table 8-1) – ranks 1 to 5 (5 is “catastrophic”)
Saffir-Simpson ScaleCategory Winds Effects No real damage to building structures. Damage primarly to unanchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier One 74-95 mph damage Some roofing material, door, and window damage to buildings. Considerable damage to vegetation, mobile homes, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of center. Small craft in unprotected Two 96-110 mph anchorages break moorings. Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating Three 111-130 mph debris. Terrain contin More extensive curtainwall failures with some complete roof strucutre failure on small residences. Major erosion of beach. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet ASL may be Four 131-155 mph flooded requiring mass Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet ASL and within Five greater than 155 mph 500 yards of the sh
Hurricanes, Typhoons & CyclonesWorld Map shows locations of Hurricanes,Typhoons &CyclonesNamesReflectLocationsAll are theSame typeOf storm
Paths of Hurricanes: North AtlanticNorth Atlantic hurricanes develop 5 to 10 degrees north ofThe equator & travel to the west, yet as they move fartherNorth theychangedirections& moveeastwardMost donot makelandfall
Hurricanes:Coastal Damage/Death Coastal damage can be extensive as high winds, high Tides And ‘storm surges’ push ocean water far inland Galveston, Texas Was struck in 1900 & 6,000 were killed In 1970 a Hurricane Hit Bangladesh & Killed 300,000 in 1991 200,000 died(Note that many people in Australia, Mexico, and S.E. Asiadepend on the hurricanes for live-giving moisture each year.)
Tropical Cyclone Hazards• Storm surge (up to 20 feet) – pressure (1 cm rise per 1 mb drop in pressure) – winds / friction• rain / flooding causes most damage!• winds• tornadoes
• Power Tropical Cyclone Power – one hour = total USA electricity for one year – one day = nuclear arsenals of USA and Russia• Highest U.S.death toll: Galveston, TX, 1900 - 20 ft. storm surge killed 6,000 (1/6 the population)
2005 Atlantic Hurricane Season• Most named tropical storms in history (28); including most intense ever (Wilma: 882 millibars; 185 mph sustained winds) and most Category 5 storms (4) ever• New Orleans destroyed; worst U.S. hurricane damage ever. Cost estimated at: $100,000,000,000• Death toll: at least 2048 confirmed dead as of 4/2006; most were among poorest elderly people.
Forecasting and Safety• Tracking – satellites – coastal radar• Prediction – computer modeling• City evacuation plans
Extratropical v. tropical cyclones Midlatitude cyclone • Forms outside the tropics. • Largest diameter of all storms • No eye • Has distinct fronts.Tropical cyclone• Forms over a tropical ocean.• Eye and dramatic pressure drop (900 mb or lower)• Has no fronts.• Smaller average size, but much higher winds.
Hurricane LinksHurricane & Storm Tracking for the Atlantic & Pacific Oceans - Showsall current hurricanes and their tracksUS National Hurricane Center - North Atlantic, Eastern PacificThe Hurricane Hut - Information on all past storms to 1950, along withimages and individual storm summaries.Create-a-Cane Interactive fun site from NOAA, allows to specifyconditions and see how they impact storm formationNASA Hurricane Web Page - Data, research, science & multimediaresources from NASAWMO guide on cyclone terminologyNOVA scienceNOW: Hurricanes