Transcript nana 19
HURRICANE The ancient Tainos tribe of Central America called their god of evil “Huracan.” The Carib Indians adopted this name for the storm. At the equator, much of the sun’s energy is used in the evaporation of water, so the temperature rarely exceeds 95o F. At night, the cloud cover restricts heat loss, so the temperature generally stays above 75o F. The inter-tropical convergence zone appears as a band of clouds along the equator. Here the trade winds converge, and the air currents are generally up. This area has very little wind, and is known as the doldrums. While the equator does not have true seasons, it does have wet and dry periods as the intertropical convergence zone moves north and south following the sun. Along the equator, the wet periods occur in March and September. They coincide with the vernal equinox and the autumnal equinox (when the sun crosses the equator). “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 cyclones reach latitudes near 30 degrees North, they often move northeast.” - National Hurricane Center - A tropical cyclone is an organized low pressure area without any front attached that forms over warm tropical or subtropical water. Tropical cyclones have different names depending on where they form: Atlantic / Eastern Pacific - Hurricanes Western Pacific - Typhoons Indian Ocean - Cyclone Conditions Needed for a Tropical Cyclone # Warm ocean waters (at least 80°F / 27°C) throughout a depth of about 150 ft. (46 m). # An atmosphere which cools fast enough with height such that it is potentially unstable to moist convection. # Relatively moist air near the mid-level of the troposphere (16,000 ft. / 4,900 m). # Generally a minimum distance of at least 300 miles (480 km) from the equator. # A pre-existing near-surface disturbance. # Low values (less than about 23 mph / 37 kph) of vertical wind shear between the surface and the upper troposphere. The key is a warm ocean temperature. As water vapor rises and cools, it condenses, releasing its latent heat which powers the cyclone. The strong rotation of winds about the eye creates a vacuum of air at the center, causing some of the air flowing out the top of the eyewall to turn inward and sink to replace the loss of air mass near the center. This suppresses cloud formation, and a clear area in the center results. Trapped birds are sometimes seen circling in the eye, and ships trapped in a hurricane report hundreds of exhausted birds resting on their decks. The landfall of hurricane Gloria (1985) on southern New England was accompanied by thousands of birds in the eye. TROPICAL DEPRESSION < 39 MPH TROPICAL STORM 39 - 73 MPH HURRICANE > 74 MPH http://www.history.com/videos/science-of-ahurricane#science-of-a-hurricane Saffir-Simpson Scale CATEGORY WIND SPEED 1 74-95 mph STORM SURGE 4 - 5 ft 2 96-110 mph 6 - 8 ft 3 111-130 mph 9 - 12 ft 4 131-155 mph 13 - 18 ft 5 >155 mph >18 ft As with any low in the northen hemisphere, the winds are counterclockwise. The dangerous quadrant is the right front quadrant. Breach on Hatteras Island from Isabel, 9/13/2003 Bars depict number of named systems (open/yellow), hurricanes (hatched/green), and category 3 or greater (solid/red), 1886-2004 First storm formed May 19, 2012 Strongest storm Sandy – 940 mbar (hPa) (27.77 inHg), 110 mph (175 km/h) Total depressions 19 Total storms 19 Hurricanes 10 Major hurricanes (Cat. 3+) 1 Total fatalities 252 direct, 7 indirect Total damage > $54.98 billion (2012 USD) HURRICANE NAMES 2012 Alberto Beryl Chris Debby Ernesto Florence Gordon Helene Isaac Joyce Kirk Leslie Michael Nadine Oscar Patty Rafael Sandy Tony Valerie William 2013 Andrea Barry Chantal Dorian Erin Fernand Gabrielle Humberto Ingrid Jerry Karen Lorenzo Melissa Nestor Olga Pablo Rebekah Sebastien Tanya Van Wendy 2014 Arthur Bertha Cristobal Dolly Edouard Fay Gonzalo Hanna Isaias Josephine Kyle Laura Marco Nana Omar Paulette Rene Sally Teddy Vicky Wilfred WHAT IS THE NUMBER ONE RULE OF SAFETY IN THE EVENT OF A HURRICANE? WHAT IS THE NUMBER ONE RULE OF SAFETY IN THE EVENT OF A HURRICANE? HURRICANES MOVE SLOWLY COMPARED TO TORNADOES. WARNINGS ARE GENERALLY GOOD. SO, EVACUATE, VAMANOS, LEAVE, GET OUT OF DODGE, RUN, GET TO HIGH GROUND. REMEMBER KATRINA AND SANDY.