The Outlook | Severe heat of summer may have passed

Severe heat of summer may have passed


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The weather patterns for the rest of the month are likely to be quite different to those of last month.

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THE active phase of the northern monsoon which brought flooding rains to northern parts of Queensland earlier this month has passed and the semi blocking Tasman sea high which directed hot air over NSW day after day in January has now moved on as well, so the weather patterns for the rest of the month are likely to be quite different to those of last month.

This will mean fewer very hot days, but still warmer than normal weather can be expected overall.

It may also mean extended dry periods as no moisture from the tropical north-eastern Queensland area has found its way south during this recent event.

The tropical pulse (known as the Madden-Julien Oscillation) has moved out into the Pacific and with stable weather now across the tropical areas, a further pulse is unlikely for at least a few weeks, meaning more stability for the north and north-west areas.

The longer term climate indicators are continuing to be a little confusing.

The weak El Nino that was developing at the end of 2018 has faded and a neutral pattern has returned across the Pacific.

The atmospheric response to the sea surface temperatures returning to neutral has been mixed.

The Southern Oscillation Index has fallen in recent weeks but is still around zero – the middle of the neutral range.

Cloudiness has decreased in the central Pacific and the south-eastern trade winds in the tropical western Pacific have weakened again - and this often indicates the potential for an El Nino returning in the coming month.

A few of the international models are indicating at least a 50 per cent chance of an El Nino event returning by the end of winter or into spring but the majority still believe neutral conditions will persist throughout the year.

Either way, a significant break to the current drought in many parts of south-eastern Australia seems unlikely as rainfall will continue to be variable and good falls will depend on the occasional and scattered “one of” event that often occurs in a neutral pattern.

From April onwards, the trends in the Indian Ocean Dipole will become of greater importance. It has fallen a fraction and is a little under zero.

A negative IOD would be helpful if it continues into April and May, when the effects of the tropical monsoon have passed.

Finally, well above average SSTs persist over the Tasman Sea and into the Great Australian Bight.

There are minimal areas of cooler than average water anywhere around the continent and this will be a contributing factor in keeping temperatures mostly above normal for the first half of the year. 

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