L7 - Tropical Cyclones Flashcards
Define a Tropical Cyclone
A relatively large and long-lasting low pressure system
- No fronts attached
- Closed surface wind circ around well-defined center
Where do Tropical Cyclones form? Why?
- Between 5-30o
- > 30o, water is too cold
- 0-5o, Coriolis too weak for spin
What are the 3 categories of Tropical Cyclone by wind speed?
Tropical depression - 74mph
What were the impacts of Hurricane Katrina (2005)?
- 18,000 people killed
- $5 billion
- > 2 inch /hour rain in some places
Why do hurricanes travel east-west and curve eastwards in the Northern Hemisphere?
- Coriolis effect
Outline Atlantic Hurricane season
- Originate further and further east from June-Sept
- Sept: Peak hurricanes, originate near Cabo Verde islands
- Oct-Nov hurricanes form mainly in Carribean
Why do hurricanes start forming further and further east?
- Rising sea temp
- > Otherwise cold current off African coast
Describe the 5 main phases of Cabo Verde hurricane
- Day 1-5: Form in east Atlantic as tropical disturbance, moving westward
- Day 7-9: Become Tropical storm off of Carribean, start curving northwards
- Day 10-15: Become Tropical cyclone, moving north-east along US Eastern Seaboard
- Day 16-17+: Water gets too cold, become extratropical cyclone, moving eastward
List 3 Mechanical factors that contribute to cyclones
- A pre-existing disturbance
- Location several degrees n. of equator
- Little change in wind speed and/or direction with height - no horizontal wind sheer
List 3 Thermodynamic factors that contribute to cyclones
- Warm sea surface temps.
- Unstable atmosphere (temps. Go down as you go up
- High atmospheric moisture content
Why is hurricane forecasting relatively easy?
- Physics well-understood
- Satellites able to detect hurricanes
- Long-record on which to base predicts
- Accurate computer models
List 5 things that would make a hurricane stronger
- Higher sea surface temp.
- More passage over ocean
- Vertical wind sheer
- Interactions with other cyclones
- Temp. and moisture patterns around storm
- Internal structural changes
List 5 hurricanes hazards
- Wind
- Waves/Rip currents
- Tornados
- Storm Surges
- Heavy Rainfall
What is the main hurricane scale called?
- Saffir-Simpson Hurricane Wind Scale
How many categories are there in the Saffir-Simpson Hurricane Scale?
5
