MONDAY MORNING WEATHER - THE RAINFALL INCREASES OVER THE NORTHEAST OF THE NATION. COOLER OUT WEST.

The weather is starting to become volatile for the east of the nation as we start a new working week with a deepening low pressure trough tapping into a lot of moisture sitting through all levels of the atmosphere. We have seen this trough play out over the past 24hrs with a good coverage of showers and thunderstorms, some locally heavy.


But this is all ahead of a deepening upper-level low that is forecast to move in from the NT and combine with the trough in place to bring a 2-3 spell of severe weather and heavy rainfall across QLD, northern and potentially central NSW and northeast parts of SA. Along the coast, there could be some very heavy falls with some locations looking at recording some high rainfall totals, thanks to elevated SSTs and onshore winds feeding this very unstable air.


Out west, by mid-week a stronger cold front will have moved to be in position of the SWLD bringing a substantial band of rain and thunder, some moderate to possibly heavy falls are likely to occur along this feature as it moves east across the southern third of the state. The rainfall will struggle to extend further north with this system.


As the front moves into the Bight on Thursday, it will help to push out the trough over VIC, NSW and QLD where rainfall and thunderstorms will be ongoing, this system will nudge that focus of rainfall further east and by Friday that system should be on the way out of inland QLD and NSW, with the potential for heavy rainfall to linger on the coast until Saturday.


The front and trough coming through SA will bring a gusty westerly change and a band of rain but falls generally light. The system may tap into residual moisture over the southeast inland and a moderate band of rainfall could emerge for VIC and NSW through the ACT as it progresses through over the weekend.


The weekend in general once the system is on by the southeast should be settled with a large high taking over with seasonal temperatures in place.


For northern areas, the dry season has kicked in over the weekend, but it will not last long with more northeasterly winds starting to return, bringing back the humidity and the chance of showers to some parts of the Top End and persisting over northern QLD. The north of WA dry for now.


In the medium term, keeping an eye on the moisture plume coming through the jet stream to see if that can bring additional rainfall to the south and west as we tick into the 21st onwards and finish the month as it started, wet and cold for southern parts of the nation and drier weather returning to the north and east.


Let's take a look

FORECAST

Rainfall Next 10 Days

Rainfall for the east expected to become heavier and more extensive during the next day or so and become persistent over the same region over the course of the week with the risk of severe thunderstorms and flash/riverine flooding. The flooding is forecast is expected to be updated later this morning so look out for that if you are living in QLD and NSW. Showers and thunderstorms could produce heavy rainfall and flash flooding over eastern parts of SA and spread into northwest NSW mid to late week as the upper low deepens as it heads east. A trough over the east of QLD responsible for the overnight thunderstorms and heavy rainfall is expected to become more widespread from Cairns down to about Noosa with some areas within this zone getting 200-400mm in a number of days leading to flooding. The rain eases over the east from later this week. But later this week, helping to kick the rainfall out of the QLD region, a front which is forecast a widespread burst of rain to the southwest and west of the nation is forecast to move east, bringing light and patchy falls to southern SA and the front is forecast to tap into the moisture over the east and southeast inland and further moderate rainfall is likely for VIC and NSW. The weather is forecast to dry out for the south and east by the weekend. A few coastal showers will linger in a westerly wind regime and there may be another front embedded in that flow this time next week with further light falls. Into the medium term there could be another cloud band emerge ahead of the next long wave trough with moisture being drawn in from the Indian Ocean thanks to the remains of TC Karim moving through to the south of the Cocos Islands.

THUNDERSTORM FORECAST

Thunderstorm Forecast Monday

Thunderstorms are forecast to become more widespread and extend south through the day and overnight into Tuesday through to NSW with heavy rainfall leading to flash flooding the main concern over inland QLD. The rest of the nation sits in stable air.

Thunderstorm Forecast Tuesday

Thunderstorms are forecast to continue over much of QLD, with storms possibly severe with heavy rainfall leading to flash flooding and damaging winds and large hail also quite possible given the sharp upper low. Heavy rainfall along the coast with thunderstorms may also lead to flash flooding. There is the chance of thunderstorms Tuesday night with the approach of a front over the southwest.

Thunderstorm Forecast Wednesday

Thunderstorms continue over the northeast of the nation and may begin to shift southwards into NSW and eastern SA as a deepening upper low moves slowly through southern and central QLD. Storms could be severe leading to heavy rainfall and flash flooding, damaging winds and large hail nearer the centre of circulation. Dangerous thunderstorms with a tornado risk is possible in the purple zone. The new front over in WA with a trough could lead to a band of rain and thunderstorms. Some storms there could produce heavy rainfall.

Thunderstorm Forecast Thursday

Thunderstorms are forecast to impact parts of northern NSW and much of inland QLD with an upper low slowly advancing eastwards. Storms could be severe with heavy rainfall leading to flash flooding the main issue with the damaging winds and large hail risk decreasing as the air begins to warm.

Severe Weather Watch - Tuesday through Friday

Flash and riverine flooding is possible next week as widespread rainfall falls over relatively wet catchments following months of above average rainfall. Rainfall rates could be heavy enough to cause renewed moderate flooding in some of the disaster zones, though the focus of heavy rainfall has lifted back towards central and northern QLD. Storms over the inland pose the bigger threat for severe weather issues.

Severe Weather Risk - Tuesday through Friday

Significant rainfall is expected to extend over the border from the north this week, most likely it appears from Wednesday with severe thunderstorms possible ahead of the feature likely to cross the border too mid-week. Storms could be quite severe over the northeast of SA, through southwest QLD and northwest NSW closest to the upper low will all modes of severe weather possible.

Flood Risk - Tuesday through Friday

The flood risk is expected to increase through the middle to latter part of next week, especially the closer you are to the coast between Ayr and Bundaberg along the coast. A low to moderate risk extends well inland and will be connected to where heavy thunderstorms emerge.

SOUTHERN ANNULAR MODE - A SECONDARY POSITIVE PEAK NOW POSSIBLE THIS WEEK.

That could enhance rainfall once again through the east and southeast of the country with some signals that the rainfall may linger over the east and southeast of the country. Something to watch, but we are seeing the signal shift away from that neutral phase that was being slated last week for later this month.

MEDIUM TERM - May 15th-22nd 2022

Rainfall Anomalies

Rainfall anomalies continue to signal above average falls persisting about QLD and southwest and western parts of WA with seasonal weather most elsewhere. There are no drier signals present on the global modelling for this time, with forecast confidence moderate at the moment. The positive SAM potential for the east has one eyebrow cocked for QLD, where additional heavy rainfall could occur and slip into NSW. The southwest may see moisture from the decaying tropical cyclone Karim come into a front and bring widespread rainfall into the medium term. Either way the remainder of the nation should see seasonal rainfall expectations for this time.

Temperature Anomalies

A cooler bias persists for the west as conditions are set to shift from this week and continue into the medium term with the westerly wind regime impacting the area. The north of the country will return to more muggy and dry weather with temperatures reflecting the above average SSTs in place across northern Australia, so this dry season will be warmer and humid than normal. In the east, a weak signal for cooler than normal weather, but this could be increased if a positive SAM phase develops, and we see more cloud and rainfall come onto the forecast. Seasonal weather conditions are forecast elsewhere with no sign of brutally cold dry weather in the coming 2 weeks.

DATA - Refer to video for more information and the model comparison and context about all the forecast products you see from me.


12Z Euro Surface Pressure Pattern and Rainfall Distribution - Next 10 Days

As mentioned in the early start post looking at the weather for the short term, we have three events to watch with the major rainfall event over QLD into NSW the main event which I have spoken about at length for the past 10 days so will now look at the rainfall event that emerges into southeast which will ride along a weakening front. The rain not as heavy as what is going on over QLD but certainly moderate falls for parts of southern SA, through VIC and into NSW and the ACT is quite likely. The rainfall then easing over the weekend, but there are some signs that moisture may lag behind through QLD and this could lead to areas of rain coming back to inland areas of NSW and QLD and showery weather for the coast. Out west a strong cold front due on Wednesday into Thursday could see a fairly robust rain event emerge. Then another rain event could be on the cards later this weekend that will bring the chance of follow up falls across the country from next week. The remains of TC Karim offshore are now evident within the jet stream so it will flare moisture into the event over WA through this week and again in the secondary event next week.

12z Euro Precipitable Water Anomalies - Next 10 Days

The moisture is excessive over the northeast of the nation and is forecast to drift south and southeast with the chance of some record values being achieved over QLD and NSW. This will lead to some flood issues via heavy rainfall in both states. As mentioned, multiple times that this region is broad covering much of QLD and into NSW and eastern SA, but the risk is highest along the east coast where the combination of the trough and deepest moisture will stay in place longest. The drier air will hang over southern and western parts of SA before that is overrun by the moisture from the north and west. The frontal weather over the west of the nation is forecast to drag in a deep injection of moisture from the Indian Ocean spreading east throughout later this week, combining with the deep moisture in the east and southeast, making for a very soupy country for this time of year. That keeps the overnight temperatures higher and rainfall chances well above the average for many in the east, southeast and over much of the eastern inland and now it appears the southwest of the country too.

12z Euro Rainfall Accumulation - Next 10 days

Refer to video for more information

12z GFS Rainfall Accumulation - Next 10 days

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12z CMC Rainfall Accumulation - Next 10 days

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12z Euro Rainfall Accumulation - Next 15 days

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12z GFS Rainfall Accumulation - Next 16 days

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I will have further information on the severe weather in the east and the rainfall breaking out over the west this morning and more in the state-based forecasts this evening. Have a great morning.