The weather starting to shift in the west, the end of a long hot spell is forecast this weekend with a heat trough moving inland over the SWLD. So refreshing conditions forecast for the west of the nation which will be welcome after a shocking period of heat.
Northern Australia remains in the seasonal routine of showers and thunderstorms, but there is evidence we could see the rainfall increase next week and into the end of the month with the approach of the MJO through the Eastern Indian Ocean and that could proceed through to northern parts of Australia.
Looking over the east, the onshore winds are likely to continue with the moisture being drawn into a trough over inland QLD and NSW leading to scattered showers and thunderstorms redeveloping and a humid airmass emerging, so back to those tropical vibes for large areas of the southeast and east next week.
The ingredients are there for a robust weather event mid to late next week, starting out near SA and then moving into the eastern inland next weekend and then beyond there, it could be another case of an ECL forming off the NSW coast. In my 25 years of watching weather, this is how these events emerge. They develop in the fashion of running over SA as an upper entity and then move east over the eastern inland before surfacing off the east coast of QLD but more regularly off NSW. We will watch that trend. The models are a hot mess.
For now the driest part of the nation is over in the west, but conditons could start to shift with the moisture streaming in from the Indian Ocean out of the monsoonal weather way up north, but that jet stream can drag the moisture from a long way away and feed it into troughs and fronts passing south of the nation. This is where Northwest Cloud Band Season develops. So that will be another feature to watch.
Finally some areas in FNQ have had a failed wet season despite the La Nina, but the later season rainfall from March into May can be very productive and there is evidence we start to see more seasonal to above seasonal rainfall for these locations and farming communities.
Lets take a look
Rainfall Next 10 Days
Rainfall is still very tricky to pin down with poor guidance from about day 5 onwards. In the short term, we will see scattered showers and thunderstorms over inland NSW and QLD this weekend, but with the trough broadening, the coverage will spill over into Eastern SA and through VIC and into the southeast of NSW by early next week as the humid warm airmass expands across the southeast states. The onshore east to northeast winds will produce moderate to heavy showers along the NSW coast with southeast winds producing light to moderate showers over SE QLD, more heavy near the trade wind convergence over the FNQ coast with flooding possibly developing. All those onshore winds will continue to spread moisture over the eastern and southeast inland and meet the trough near the SA border. The weather over the west and northwest of the nation is expected be seasonal, but the moisture over the Indian Ocean in association with the MJO is likely to lead to the increase of the showers and storms and then this activity will run through the NT and Cape York next week. That moisture also needs to be watched as troughs push through the Southern Ocean. Any northern front that emerges could see widespread showers and storms developing throughout the nation in the form of a northwest cloud band, and there is some chance of that developing. But as I mentioned, anything beyond 5 days nationally, is poor guidance.
Thunderstorm Forecast Saturday
Thunderstorms are forecast to spread through western parts of QLD and into northwest NSW with the chance of thunderstorms turning gusty through Central and Northern NSW and into Southern and Central QLD. Thunderstorms continuing to be gusty over the NT and parts of the Kimberly. Storms also developing in the SWLD of WA or continuing from Friday over the region with the chance of gusty winds, but most storms should be below severe thresholds in this area.
Thunderstorm Forecast Sunday
Thunderstorms will continue to move westwards through the eastern inland with a trough. Thunderstorms may become severe through southwest QLD and northwest NSW with heavy rainfall and damaging winds. Damaging winds also possible with thunderstorms over the NT. Thunderstorms increasing in coverage over the eastern inland as the trough broadens through the day and that could see storms impact eastern SA and into VIC but the coverage fairly isolated but worth mentioning for those travelling for the long weekend.
Thunderstorm Forecast Monday
Thunderstorms are forecast to move further west through NSW and into SA through Monday with the chance of storms becoming severe over inland SA, with damaging winds and heavy rainfall a chance. Thunderstorms also likely to develop over elevated terrain through VIC but no severe weather expected. Thunderstorms will extend back northwards through the NT into the tropics where storms may be gusty with damaging winds and heavy rainfall leading to flash flooding. Storms over WA will be confined to the Kimberly region and in QLD, confined to western areas and through the Gulf Country and Cape York where heavy rainfall may lead to flash flooding.
Thunderstorm Forecast Tuesday
Thunderstorms will continue from overnight and into Tuesday for large parts of Central Australia extending south into the Ag areas of SA and through to the Southeast where thunderstorms may turn severe with heavy rainfall and gusty winds. Thunderstorms over the tropics also increasing in coverage and extending southwards into the outback where storms could be severe with damaging winds. The thunderstorm risk over eastern parts of the nation low with the main lifting trigger sitting over western VIC, NSW through SA and into the NT. That looks to be the focus for now and the risk of severe weather is moderate.
DRIVERS TO WATCH
SOUTHERN ANNULAR MODE - SOUTHERN OCEAN
The SAM is set to move back to neutral values from today through the weekend and we could see a negative phase develop next week for a period but once again, with La Nina waning, may not be a large period of neutral or negative values. We have seen in recent days that the negative signal next week is softening which is what you expect in the broader climate situation and that looks to shorten the life of the negative movement next week, so if you are living over the eastern parts of the nation, we could see more wet weather events into the medium term and the easterly winds to return, meaning drier warmer weather over the west and south. When the SAM in this place, it opens the door for further ECL development.
MJO - TROPICS
No change to the guide from the last week, though the speed of the MJO rotating through the nation's north is slower it appears, but the impact will be the same with increasing showers and thunderstorms for the north of the country. And we could see the late season cyclone activity across the northern waters as well which act as wildcards and they are also the key to many Autumn Breaks across the nation, not always, but certainly play a part of fanning moisture throughout the nation, especially WA and SA through the southeast inland.
DATA - Refer to video for more information and the model comparison and context about all the forecast products you see from me.
00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks
The pressure pattern as mentioned in the video remains complex and low confidence with a lot of moving pieces in terms of troughs of low pressure, upper level disturbances and moisture also deepening over vast areas of the nation meeting at times on some of the models but then moving around from run to run, so the consistency and quality of the forecasts over the coming days are poor and will remain poor for this weekend. In the short term, unsettled weather will remain a feature for scattered pockets of the western interior, northern tropics, central and eastern inland and along the east coast. Most other areas should be fine and partly cloudy. It is from next week, once we get a better grip on the evolution of the upper trough/low near SA and whether it amplifies over the country or is absorbed into the westerly flow will have major implications on the rainfall and temperature spread. For now watching the SAM and MJO very closely as these will determine the rainfall spread and the temperature spread across the nation. I think we will have a better idea on the weather beyond the middle of next week on Sunday evening if not Monday morning. Already we have seen adjustments with the unsettled weather now covering SA in coming days where that didn't seem likely day ago. So the weather will continue to be volatile and your forecasts will change.
00Z GFS - Precipitable Water Values - Next 2 Weeks
Deeper moisture is moving west from the eastern inland on Saturday into the Central parts of the nation, especially over SA with moderate rainfall likely from thunderstorms, but the coverage scattered and random and no one can tell you anywhere, whether you will get precipitation this weekend. The broad moisture coverage will linger for a good portion of the week ahead with the chance of more unsettled weather building for northern and eastern Australia as the MJO rotates around. Drier air should dam over in the west near high pressure ridging in. The MJO up in the Indian Ocean may override this, if the jet stream can bend and tilt, allowing the northwest winds aloft drag in the moisture and there is a slim chance of cloud and rainfall returning next weekend, but for now thinking it stays dry. Along the east coast, the deeper moisture profile will be found over QLD with heavy precip possible for the FNQ Coast. Otherwise the moisture levels will remain higher than normal for the tropics and over the east coast, drier weather for the southwest of the nation and changeable conditions elsewhere with mixed odds moving forward regarding rainfall.
00Z GFS - Rainfall Accumulation - Next 10 Days
Refer to the video for further information
00Z GFS - Rainfall Accumulation - Next 2 Weeks
Refer to the video for further information - no need for a state by state fly around as the pattern is very low confidence.
More coming up from Saturday morning with the next National Wrap but I will be having a little more down time over the next 2 days just to reboot my batteries and to see my family who have been neglected due to the severe weather. Next update tomorrow morning from 8am EDT.