Download Exempla hurricanes

Exempla
Cyclones and Hurricanes are Natural Hazards created by a sequence of atmospheric
conditions. The two most important conditions are heat created by the sun and the
movement in which air undertakes from low to high pressure. Cyclones are extremely
destructive when they come into contact with Humans and tour land however to be formed
they have to follow a number of processes.
Cyclone Heta and Hurricane both saw warm ocean temperatures before they
formed into tropical storms. Before Katrina the ocean was recorded at 27 degrees and Heta
recorded ocean temperatures even warmer than this. The ocean was so warm due to the
sun being directly ahead at this time of year. Katrina formed in August which is when the
sun is hottest in the Northern hemisphere and it formed over the Bahamas which provide a
large supply of water. The Bahamas are located around 10-15 degrees north which is where
Hurricanes form. Due to the force of the earths rotation (Coriolis force) being able to spin
them from storms into something more devastating here. Cyclone Heta formed December
25th 2003 which is the middle of the cyclone season in the Southern Hemisphere it to
formed around 10 degrees south of the Equator on the edge of the inter-tropical
convergence zone (ITCZ). Heta formed just south of Tokelau which is a small pacific island
nation. Katrina formed from a large storm which began over Africa. This warm ocean
temperature formed an initial tropical storm which is large depression before the constant
supply of warm moist air along with a jet stream which is a current of extremely low
pressure which circles the air at 10-30 increased the rate in which they were spinning by
acting like a vacuum and sucking air out the cyclone due to its lower pressure and upgraded
these storms into class five hurricanes. Heta reached Cyclone strength on New Years day
2004, Katrina reached hurricane strength on August 23rd 2005. The mass of low pressure
created by these natural events saw extremely low pressure zones formed. Heta was
recorded to have air pressure of only 915hpa and Katrina had an even lower pressure of 902
hpa. To be classed as a hurricane/cyclone a air pressure of 970hpa or less is needed which
shows that these storms were very large. This low pressure meant high pressure was
rushing in to replace the void left this resulted in winds of 250km/h for Heta and 280 km/h
for Katrina both storms had gusts of well over 300 km/h. The high pressure rushing in goes
for the eye of the storm where it gets converted into latent heat keeping the cyclone warm
and spinning Katrina’s eye was 46.3 kilometres in diameter this area would have seen calm
clear conditions when it passed over head. However the area around the calmer eye is
extremely windy and provides the worst weather conditions. Katrina provided to be such a
strong hurricane it dropped 200-250mm on New Orleans as it passed over. Heta died out
after causing substantial amounts of damage to Niue among other island in the South pacific
as it headed south and therefore could no longer keep itself warm. Katrina died out as it
passed over the USA and couldn’t fuel itself with water anymore.