On the east coast of Australia, the predominant summer thunderstorm pattern seems to be the derecho variety that develops ~300-400 km inland in late morning / early afternoon, and reaches the coast by late afternoon / early evening as a squall line 100-200 km long.

Oftentimes this pattern will repeat itself over several days.

In these cases, is each day's derecho event triggered by a new moving cold front, or is the multi-day phenomenon due to a single stationary cold front which remains in place throughout the several day period, or are both scenarios possible?

  • $\begingroup$ Could you perhaps list some days when these events happen and which part of Australia? Since most of Australia is at a fairly semitropical latitude, I don't imagine there being any "true" cold fronts in summer. Usually we'd expect the opposite of your scenario, development near the coast early afternoon, then movement inland (diurnal seabreeze circulation) into the evening. Just maybe it's remnants of stronger seabreezes from other places (NZ? N Aust??), which we do see in a few areas. Repeating progressive derechos are common in the US, but more Poleward typically. So more info would help! $\endgroup$ – JeopardyTempest Dec 22 '16 at 16:37
  • $\begingroup$ Repeated derechos in the Plains/Midwest/Atlantic Coast are usually from one stationary or slowly moving front that develops new storms each afternoon which then build upscale and progress east into the next day. If we're talking true cold fronts... the scale of big synoptic systems makes it very unlikely it'd ever brand new cold fronts even in seasons more prone to cold fronts that far north (the frequency is more around a few days more typically, at least in the NHem which I'm more familiar with). So it's likely either a single front, or other more tropical features like seabreezes. $\endgroup$ – JeopardyTempest Dec 22 '16 at 16:44
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    $\begingroup$ This article is about nine consecutive days of thunderstorm activity in the Sydney area in early summer, 2014. link. These storms originated inland and moved towards the coast, which is the pattern I described in the question, and is the normal pattern on the east coast of Australia (NSW and Southern Queensland at least). Hopefully this fills in some detail? Are these associated with cold fronts? That's always been my assumption. $\endgroup$ – user2754486 Dec 31 '16 at 4:27

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