cyclones Flashcards
what conditions are needed for cyclones to form?
where SST are greater than 26.5 degrees c and a depth of 60m, with a significant Coriolis effect, most form 5-20 degree latitude
max speed of a cyclone?
119km/hr
how do they develop?
in a uniform mass of very warm and humid air without associated fronts
size of a tropical cyclone?
about 1/3rd the diameter of an extra tropical cyclone, central pressure lower and horizontal air pressure gradient much greater
where do they form?
on easterly waves (10 to 20 knots), also called tropical easterly waves
what is the eye?
clear skies, area of subsiding air with light winds, ranges from 20-65km across
what is the eye wall?
circle of cumulonimbus clouds, associated with strong winds and precipitation, most `dangerous part
what causes most destruction?
90% fatalities caused by coastal and inland flooding, eddy circulation near eye wall responsible for most serious wind
what happens when hurricane makes land fall?
looses warm water energy source, weakens rapidly so most damage at the coast, heavy rains carry inland
how are hurricanes rated?
saffir simpson scale, range of central air pressure and wind speed, potential for storm surge and property damage
what was hurricane katrina?
Cat 5, 1833 people died, hit 29th august 2005, there was around $100 billion damage, hit coastline as a cat 3.
what did Davis and Bosart say in 2004?
nearly half of the Atlantic tropical cyclones from 2000 to 2003 depended on an extratropical precursor, this change caused Tropical transition, to be contrasted extratropical transition, resulting in ET becoming a tropical cyclone
what did Nyberg say in 2007
hurricane activity in North Atlantic Ocean has increased significantly since 1995, reliable observations only cover last few decades, proxy records of wind shear and seas surface temps go back 270 years, records indicate frequency decreased from 1760s - 1990s, enhanced activity in 1995 not unsual compared to other high periods
