When is Australia’s wet season?
October to April.
When is Australia’s dry season?
May to September
In which season does most hazardous aviation weather in the tropics occur?
Wet
When is Australia’s tropical cyclone season?
November to April
What are the ingredients for cyclone formation?
1) warm sea-surface temps greater than 27°C
2) deep moisture at low levels
3) light winds throughout troposphere
4) need convergence as a trigger
Between which latitudes doe the ITCZ typically form?
5-20 degrees
True or false. The tropics generally oppose the movement of Hadley cells.
False. The tropics generally follow the movement of Hadley cells.
What are tropical cyclones?
- Intense depressions forming over tropical oceans with surface temps > 27°C
- Starts as a tropical disturbances and require Coriolis force to develop balanced circular flow
How long do tropical cyclones typically last
Last on average 6 days.
What are the stages of formation of a cyclone?
- Formative stage
- Immature stage
- Mature stage
- Decaying stage
Elements of a cyclone’s formative stage?
- Convergence causes a deepening of pressure towards 1,000 hPa
- Winds reach gale force (34 knots or more) in one quadrant
- Eye forms
Elements of a cyclone’s immature stage?
- Central pressure below 1,000 hPa and continues to fall
- Winds reach hurricane force (64 knots or more)
- Spiral bands start forming
Elements of a cyclone’s maturing stage
- Central pressure very low and steady’s, 950 hPa in eye
- Bad weather extend to approx. 150 NM from centre
- Strongest winds in left forward quadrant
- Eye: clear sky and light winds
Elements of a cyclone’s decaying stage?
- Cyclone moves into area where energy supply is interrupted either by moving over land or if sea temperature decreases.
- Becomes sub-tropical depression of considerable intensity when moving inland or proceeding to higher latitudes.
—– Winds decrease in strength
—– Wide-spread flood-rains may continue
True or False. During the wet season the ITCZ moves south to latitudes over northern Australia
True
