Lecture 18: Hurricanes

Question 1

what are hurricanes

Answer 1

• tropical cyclones
• exporting heat from tropics to mid latitudes
• ocean heat is the primary energy source, hurricanes gain energy as they travel over the ocean
• rain is the hurricanes release of energy

Question 2

pressure gradient

Answer 2

• eye of hurrivane is a low pressure region

Question 3

coriolis effect

Answer 3

in the northern hemisphere
- the impact of earth’s rotation on winds
- in the NA winds are deflected to the right when flowing towards the eye

Question 4

centrifugal force

Answer 4

• pull to the right

Question 5

friction

Answer 5

slows down the wind

Question 6

birth ingredients

Answer 6

• water temperature > 27 C
• warm humid unstable air
• in northern hemisphere surface winds rotating counterclockwise
• significant Coriolis effect to sustain rotating surface winds
• weak high-altitude winds

Question 7

tropical disturbance

Answer 7

• poorly organized cluster of thunderstorms
• weak surface winds
• diameter 200-600 km
  frequent in tropical regions

Question 8

tropical depression

Answer 8

• clearly defined low pressure central area
• organized wind circulation initiated
• vertically: strong winds lift warm and moist air upwards in the central area

Question 9

tropical storm

Answer 9

• classical hurricane structure but no eye
• counterclockwise winds (64-118 km/h)
• storms are names

Question 10

hurricane

Answer 10

• classical hurricane structre with a well-developed eye
• eye forms wehn wids > 118

Question 11

decline

Answer 11

• hurricanes decline rapidly after they make landfall

Question 12

rainbands

Answer 12

• dense clusters of thunderstorms spiraling slowly counterclockwise
• hurriane diamter ~500 km
• most intense rainfall

Question 13

eye

Answer 13

• similar to a chimney
• area of lowest pressure
• surface wind converge
• winds spiral up along eye wall
• high altitude winds diverge

Question 14

vertical movements of air

Answer 14

• air must overcome gravity
• rising air loses energy and becomes cooler
• sinking air gains energy and becomes warmer
• cool air sinks inside the eye
• warm air

Question 15

storm surges

Answer 15

through succion, low pressure below eye creates a mound of water
- winds deform and push mount towards land
- in northern hemisphere: surge and strongest winds on the right side of the advancing storm

Question 16

cape verbe type hurricanes

Answer 16

• thunderstorms forming in the sahel
• intensity increases above atlantic
• approaching north america, path curves to the right

Question 17

ITCZ (intertropical convergence zone)

Answer 17

• sone near equator where northern and southern hemisphere trade winds converge
• exact location varies throughout the year
• storms frequent when ICTZ above caribbean sea

Question 18

post tropical transition

Answer 18

• in north atlantic hurricanes venturing north of 30-40 degrees latitude might experience post tropical transition
• move into cooler and faster air streams
• accelerate
• deform
• hurricanes experiencing post-tropical transition might merge with an existing depression and regain strength