Hey,

My friend just had meteorology exam.
He got 98%

His only question he got wrong was where thunderstorms are most likely to form over Australia waters.

Is it in Northern Australia during Summer
Northern Australia during Winter
Southern Australia during Winter
Southern Australia during Summer

He put the first one down.

I thought it might be the second one as the relative temperature of the ocean during winter will still be the same but there would be a colder air mass on the land.

Thanks,

alex.

I would have also said the first answer

This is a ridiculous question on so many levels. Your friend got the answer correct - evidently CASA has it wrong. Have a look at www.bom.gov.au/jsp/ncc/climate_averages/...-lightning/index.jsp

Although this map shows lightning density averages over land (rather than water) it very clearly indicates that the frequency of lightning in the north far exceeds anything in the south of the country. Almost all of the thunderstorms in northern Australia occur during the wet season (the Austral summer - but there is no 'summer' in the tropics). Thunderstorms occur all along the ITCZ, including over the oceans (particularly at night). The ITCZ lies close to, or across northern Australia during the monsoonal 'wet season'.

It is important to remember that a warm surface and a cool air mass is not sufficient to trigger a thunderstorm. An unstable air mass is also required. This occurs in northern Australia during the wet (Austral summer), and in southern Australia during winter, when the polar lows bring unstable cold air masses further north.

Southern Australian summers are dominated by the sub-tropical ridge, a stable air mass (the southerly buster phenomena is a local effect). This ridge moves northward during winter, bringing stable air over northern Australia during the dry season (Austral winter) - so thunderstorms at those times in the respective locations are far less likely.

I also feel answer 1 is right?!
An Australian summer sees the equatorial trough move south of the equator, bringing the north west monsoonal winds which collide with the northern moving south east trade winds off Australia. The Coriolis effect causes the south east wind trades to slam into the north west monsoons creating strong convergence and widespread thunderstorm activity.