EARLY EDITION - WEDNESDAY MORNING - QUIET TODAY BUT THE WEATHER ACTIVE FROM THE WEEKEND TO NEXT WEEK
It is looking relatively benign for most of us today as weak cold fronts provide the only real chance of rainfall for southern coastal areas of the country with the high-pressure ridge over the country set to hold firm and keep conditions dry for most of us.
But things are set to shake and bake through the west of the nation from later this week into the weekend and next week. The largest wave of Winter weather spreading through the nation from west to east looks to tap into the deeper moisture that is also wafting through the country from the northwest.
The combination of both of these elements leading to widespread rainfall chances spreading throughout the country with a great chance of above average rainfall for many areas which will be welcome in southern and western areas.
Let's take a look
Upper Air Pattern
The fast flow pattern is currently emerging under a high-pressure ridge over SA. The full appearance of the fast flow pattern won't be seen until the weekend where we see the first of two major long wave troughs passing through the country. The first of which will impact WA more than the remainder of the nation, but it will set up the secondary wave in the fast flow pattern and you can see that peaking over WA and then moving throughout SA and into the southeast inland from next week. That system has the potential to deliver widespread severe weather. Into the medium range, the wind fields ramping up over the Southern Ocean which is an indication that the fast flow pattern is moving north in response to the SAM trending negative. The further negative it is forecast to become, the further north the frontal weather will impact into mid-month. So certainly, lots to watch.
Simulated Satellite Imagery
The cloud bands continue to stack up in the medium range and the amount of moisture surging southwards into frontal weather will continue to dictate who gets exactly what in terms of rainfall. There are signals for a major cloud band early next week that may spread the breadth of the nation from west to east, quite possibly the biggest rainfall event of the season thus far. The weather over the north quiet for now but note the upper-level northwest winds shearing moisture southwards over the tropical areas, so even though it looks cloud free for now, your moisture levels may increase enough for afternoon convection to return in scattered pockets along the north coast.
Once again, the moisture distribution through the medium term remains of low confidence as we try to see what the models do with the wavier flow and the major elements in place being the moisture surging through the jet stream and feeding into the frontal weather. Do we see the negative SAM unfold? Well, the GFS is recognizing that tonight but not printing out the frontal weather and that is why you see the moisture staying further north and not much rainfall coming through the nation into the second week of August, where 6hrs ago it showed a wetter outlook. The relationship between the moisture and the frontal weather is key to rainfall increasing.
Not much of a change throughout the coming 2 weeks, with the temperatures likely to remain above average throughout large sections of the nation with the heat engine responding to the elevated SSTs surrounding the nation. The temperatures are expected to increase further as we move further into August, but the shift is already on, something that people do not track religiously like here. It is always about rain rain rain, well you need the warmer weather to see rainfall increase further.
Quite clearly looking wet next week as the major weather event sweeps the nation from west to east but as the ridge flattens out into the medium term and the SAM tends more negative and we see a break between fronts, things settle down a bit rainfall wise perhaps by mid-month if this is right. BUT the confidence the further you get out is lower and weather events proceeding ones down the line are usually poorly charted. Good signs for southern Australia though in the coming week.
More coming up from 8am EST with a look in greater detail at the short and medium term.