SCIENCE NEWS

TROPICAL CYCLONES

Weather related deaths in the u.s.

Tropical Cyclones Most violent storms on Earth Large rotating low pressure tropical storms Known as Typhoons in the W Pacific Cyclones in the Indian Ocean Hurricanes in the N Atlantic, Caribbean & Gulf of Mexico

Occurrences

Cyclone Formation Require two conditions Abundant supply of warm ocean water & Lifting mechanism

Cyclone Stages Formative Stage Energy comes from condensing water vapor Develop most often in late summer when warm water temperatures provide energy and moisture Begins as a tropical disturbance Low pressure area over warm water fueled by precipitation and latent heat Initial stage is not well understood

Developmental Stage Tropical depression Coriolis effect cause rotation, Counterclockwise in the N hemisphere Tropical depression Tropical depression – winds do not exceed 61 kilometers (38 miles) per hour

Tropical Depression

Mature Stage Air pressure at the center continues to decrease Increasing winds toward the center Tropical storm – winds between 61 to 119 km/h (38 and 74 miles) per hour Cyclone – winds exceed 120 km/h

Fully Formed Cyclone

Dissipation Stage Diminish in intensity whenever • They move over cooler ocean water • They move onto land • The large-scale flow aloft is unfavorable Can undergo several intensities

Hurricanes Profile Form between the latitudes of 5 degrees and 20 degrees North North Pacific has the greatest number per year Wind speeds reach 300 km/hr Generate 50 foot waves at sea

Parts of a hurricane Eye • At the very center • About 20 km (12.5 miles) diameter • Precipitation ceases • Winds subsides • Air gradually descends and heats by compression • Warmest part of the storm

Parts of a hurricane Eyewall • Wall of cumulonimbus clouds • Greatest wind speeds • Heaviest rainfall

Hurricane Destruction Factors that affect amount of hurricane damage Strength of storm (the most important factor) Size and population density of the area affected Shape of the ocean bottom near the shore Saffir-Simpson scale ranks the relative intensities of hurricanes

hurricane Destruction Storm surge - large dome of water 65 to 80 kilometers (40 to 50 miles) wide sweeps across the coast where eye makes landfall Wind damage Inland flooding from torrential rains

Storm Surge

Hurricane Katrina

Hurricane Katrina Of the 2005 Atlantic hurricane season was the costliest hurricane, as well as one of the five deadliest, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall.

National Hurricane Center http://www.nhc.noaa.gov/