| NATS 101 Lecture 30 Hurricanes |
| Supplemental References for TodayÕs Lecture |
| Aguado, E. and J. E. Burt, 2001: Understanding Weather & Climate, 2nd Ed. 505 pp. Prentice Hall. (ISBN 0-13-027394-5) | |
| Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp. McGraw-Hill. (ISBN 0-697-21711-6) | |
| Types of Tropical Cyclones |
| Cyclone Type Winds | |
| Tropical Depression 25-39 mph | |
| Tropical Storm 40-74 mph | |
| Hurricane/Typhoon/Cyclone ³ 75 mph | |
| Most Depressions do not develop into Storms | |
| Majority of Storms reach Hurricane status |
| Some Hurricane Extremes |
| Lowest Central Pressure Pressure | |
| Pacific: Typhoon Tip 1979 870 mb | |
| Atlantic: Hurricane Wilma 2005 882 mb | |
| Costliest Hurricanes Cost-Loss | |
| Hurricane Andrew 1992 $25 billion | |
| Hurricane Katrina 2005 $156 billion?* | |
| Bangladesh Cyclone 1970 300,000 dead |
| Andrew 1992 Time Sequence |
| Katrina |
| 2005 Hurricane Summary from NASA |
| U.S. Hurricane Deaths and Costs |
| Hurricane Deaths in US |
| Hurricane Lecture Overview |
| What are the primary differences between hurricanes and extratropical cyclones? | |
| When and where do hurricanes form? | |
| How do hurricanes intensify? | |
| What is the structure of a hurricane? | |
| What kind damage do hurricanes inflict? | |
| When and where do hurricanes dissipate? |
| Differences Between Tropical and Extratropical Storms |
| Strong Fronts | |
| Cold at Storm Center Aloft | |
| Strongest Winds Aloft | |
| Forms outside Tropics | |
| Diameter of 500-1000 miles | |
| Energy Source: Horizontal Temperature Contrast | |
| No Fronts | |
| Warm at Storm Center Aloft | |
| Strongest Winds near Surface | |
| Forms over Tropical Oceans | |
| Diameter of 200-500 miles | |
| Energy Source: Energy Fluxes from Warm Ocean |
| Where Hurricanes Form? |
| Atlantic Hurricane Frequency |
| Occur in Warm Season | |
| Maximum Likelihood when Sea Surface Temperatures are Warmest-September | |
| Average of ~6 Per Year | |
| Large Yearly Variability | |
| Fewer in El Nino Years | |
| More in La Nina Years |
| Atlantic Hurricane Tracks |
| Atlantic hurricanes tend to form in the Middle Tropical Atlantic Ocean and Caribbean Sea | |
| They usually propagate westward before turning northward and then northeastward | |
| They dissipate rapidly over land |
| Hurricane Steering |
| Hurricane Necessary Ingredients |
| Warm Water with T ³ 82oF Deep Warmth > 200 ft | |
| Converging Surface Winds Seedling Low Required | |
| Conditionally Unstable Air Supports Deep Convection | |
| Widespread, Deep Humid Air Supplies More Latent Heat | |
| Weak Vertical Wind Shear Shear Shreds Storm Apart | |
| Diverging Winds Aloft |
| Where do Seedling Vortices
Come? Lots of Places and Ways |
| 3D Flow within Hurricanes |
| Thermal Structure of Hurricane |
| Radar of AndrewÕs Landfall |
| Most intense rainfall is along the eyewall. | |
| Fastest surface winds are along the eyewall. | |
| Region inside of eye is dry with light winds |
| Eye of Hurricane Luis 1995 |
| Asymmetry of Hurricane Winds |
| Hurricane Intensity Scale |
| Primary Hurricane Hazards |
| Wind Damage | |
| Large-Scale Hurricane Circulation Itself | |
| Embedded Tornadoes | |
| Flooding | |
| Heavy Rains Far Inland, 5Ó-10Ó Common | |
| Storm Surge along Shoreline |
| Hurricanes Spawn Tornadoes |
| Tornadoes embedded within an overland hurricane tend to be weak (category F1-F2) | |
| But they are embedded within an environment with 65+ kt winds. | |
| Causes hurricane wind damage to be localized. |
| Inland Flooding-Agnes 1972 |
| Even weak hurricanes can be catastrophic, hundreds of miles inland. | |
| Agnes 1972, category 1 storm for a few hours. | |
| Agnes merged with a slow-moving ET cyclone. | |
| Up to 15Ó of rain in 24 h fell over Pennsylvania. | |
| Previous flood records exceeded by 6 ft. | |
| Damage > $10B in inflation adjusted dollars. | |
| Costliest U.S. storm prior to Andrew and Katrina. |
| Storm Surge I |
| Storm Surge II |
| Storm Surge III |
| Winds and Storm Surge |
| Surge Damage |
| Hurricane Decay |
| Trends in Hurricanes? |
| Additional Hurricane Information |
| NASA hurricane images and information | |
| Fall 2005 Atmo 336 section on Hurricanes | |
| 2005 Hurricane season summary | |
| Saharan Air Layer (SAL) and hurricanes (2004) & (2006) | |
| NASA Katrina information | |
| Latest NASA Hurricane info | |
| Summary: Hurricanes |
| What are differences between hurricanes and extratropical cyclones? | |
| Many significant ones! See earlier slide. | |
| Where and when do hurricanes form? | |
| 5-20¡ latitude over oceans during warm season | |
| How do hurricanes intensify? | |
| Energy source is surface energy fluxes from the underlying warm ocean |
| Summary: Hurricanes |
| What is the structure of a hurricane? | |
| Eyewall - strongest winds, heaviest rain | |
| Eye - dry with light winds | |
| What kind damage do hurricanes inflict? | |
| Can be catastrophic due to high winds, torrential rains, and coastal storm surges | |
| When and where do hurricanes dissipate? | |
| At landfall or when they go over cold water |