Not very often we have such a broad risk of severe weather over a large part of one state simultaneously and that is exactly what we have this week with a sharp trough over the east and an upper low deepening over the southwest from tomorrow into Thursday feeding off the very deep moisture profile, this resulting in flash flooding, riverine flooding and severe thunderstorms.

The wet phase is forecast to be fairly long duration in some locations resulting in a few places exceeding 500mm for the week along the coast.

Across tonight into Tuesday, areas of rain and local thunderstorms are forecast to continue with moderate falls in some areas. The rainfall is forecast to become more widespread during Tuesday afternoon in advance of the upper low that will waft into the southwest during the evening. Severe thunderstorms are also forecast to form in areas that see some breakthrough sunshine west of the rain band, but to the east and north of the upper low.

The thunderstorm activity over southwest areas overnight Tuesday into Wednesday will form another rain band while heavy to very heavy rainfall will be ongoing with another rain band over the eastern regions of the state from Cairns south to about Noosa. This will be where we find the larger rainfall totals.

More rain and thunderstorms forecast to continue on Thursday but the focus of the heavy rainfall will begin to move east and south with moderate to heavy falls extending over much of the state. Some local flooding possible in many locations as well.

Friday, the rain and thunderstorms continue to move east, helped along by a strong cold front over the Bight which will see drier air move into the west of the state. A low may form along the trough during Friday which could enhance rainfall rates along the SEQ coast and extend up to the Wide Bay. This could create some dangerous flooding potential.

The weather eases during the weekend with drier weather forecast for most of the inland during Saturday into next week.

Some evidence we may see showery weather continue for the coast post the rainfall event with moderate falls for coastal areas. Another trough over the inland could see showers increasing once again next week with potential for heavy rainfall once again if a positive SAM unfolds.

Let's take a look at the latest information.


Rainfall Next 10 Days

Rainfall is forecast to become more widespread overnight with thunderstorms also expected to become scattered, providing the heavy rainfall potential for inland areas. Note that the rainfall guide provided below is a guide, especially when thunderstorms are in the mix, meaning some areas could see well above what is forecast and a few seeing less than what is shown, but overall, most areas should see above average rainfall through this sequence. The heaviest and most widespread rainfall potential is likely to be found along the coast from Cairns through to Noosa, with some areas possibly seeing record May rainfall. The rainfall may lead to dangerous flash flooding and riverine flooding. The showers and storms may increase over the southwest during Tuesday night into Wednesday morning with the risk of heavy falls leading to flash flooding between Thargomindah to Moomba and north to Windorah. This will help form a rain band that moves south into NSW. The rainfall will begin to ease from northwest to southeast through Thursday and Friday with the trough moving east and the upper low weakening. The rainfall rates could be enhanced by a small low that forms over the southeast inland of QLD which could see some dangerous flash flooding before full statewide clearance of this event during Friday night. The weekend much drier but there is some evidence now supporting a return to widespread showers and thunderstorms over the coastal areas next week.

The rainfall gradient for the southwest is very tight and with thunderstorms in the mix, the rainfall guide is uneven too, so be aware that your numbers will change for this region on the data sets, but the rainfall guide should remain stable here.

Rainfall totals may be understated in comparison to some models and some agencies but remain weather aware as some areas in this zone could see falls over 400mm through the period along the coast and up to 200mm inland.

Thunderstorm Forecast Tuesday

Thunderstorms are forecast to continue over inland areas overnight into Tuesday with these largely non severe but with the moisture levels high, heavy rainfall is possible at any time with thunderstorms anywhere through the state. The thunderstorms may turn severe during Tuesday afternoon in advance of the upper low. All modes of severe weather possible with these storms, mainly overnight into Wednesday but important to point the risk out. Thunderstorms up over Central QLD could produce heavy rainfall leading to flash flooding here.

Flash Flood Risk Tuesday (Thunderstorms)

The thunderstorms are expected to be prolific rainfall producers throughout the state with the most intense rainfall likely about the Central QLD coast and adjacent inland. Thunderstorms over the far southwest may also produce heavy rainfall leading to flash flooding tomorrow night into Wednesday

Damaging Winds Risk Tuesday

The risk of damaging winds is low tomorrow through the day but increases in risk at night into Wednesday with the approach of an upper low. Thunderstorms may produce wind gusts of 100km/h

Large Hail Risk Tuesday

Large hail is a low to moderate risk over the southwest near the upper low. This risk looks to unfold from the evening into Wednesday.

Severe Weather Risk - Tuesday through Friday

The severe weather risk is largely unchanged with a broad area of unstable and irritable weather with high moisture, deep instability and dynamic support for widespread heavy rainfall leading to flooding potential, the highest risk along the coast. Inland and over western QLD, northeast SA and northwest NSW, there is the chance of severe thunderstorms leading to all modes of severe weather mid-week before that risk translates east and eases as the trough begins to weaken. So, we will have a high to very high risk of flooding over the coastal areas of QLD and into NSW and a high to very high risk of severe thunderstorms over broad areas of the inland.

Riverine Flood Risk - Tuesday through Friday

We are looking at enhanced rainfall beginning from later tonight through Tuesday and extending further south and east as we move through mid-week before the system contracts towards the coast later this week. Between now and then, most areas should see 50mm or so but many of you in QLD and northern NSW should see more than that, especially along the coast. Some areas in QLD could see 500mm for the week, that focus area between Cairns and Bundaberg but that focus area will narrow further. Thunderstorms over southwest QLD, northwest NSW and northeast SA could drop 50-150mm of rainfall as well in quick time increasing the risk of flooding in these remote areas. Remain weather aware and stay up to date with forecasts.

Flash Flood Risk - Tuesday through Friday

The flash flood risk is broad, and that is in part due to the very large upper-level trough and low-pressure system which will combine with the moisture that has been propelled west over the weekend through much of QLD into the eastern NT and northern SA. This will start to become more apparent today and tonight and you will start to see the rainfall unfold in a very large way Tuesday through Friday. The flash flood risk is more likely about the coast where rainfall is expected to be more extensive, but with thunderstorms over the inland, especially that tri state region, we could see some very heavy rainfall rates with severe thunderstorms. The risk is not uniform across the state at all times, so please remain weather aware and across the warnings as they pop up. But I am covering a broad area to give you the heads up to pay attention to the weather this week.

MEDIUM TERM - May 16th-23rd 2022

Rainfall Anomalies

The SAM remaining at positive values should continue to pump easterly winds through this period with showery air and a moderate chance of further above average rainfall likely. With moisture streaming in via the jet stream, this could feed a trough over the eastern inland leading to widespread inland rainfall developing. That same cloud band and moisture plume may deliver widespread rainfall over inland WA with some moderate falls and the potential of this falling over the same area for a number of days. This rainfall may extend into western SA but the high pressure over the southeast may erode the heaviest of the rain making it through to Ag Areas of SA.

Temperature Anomalies

A very strong signal for above average temperatures and humidity over northern Australia with that warmer air extending southwards with northeast winds over the tropics. The east warmer than normal with a northwest to northerly flow early in the period but then that easterly flow with higher humidity will bring rainfall and milder weather. Cooler over the west of the nation under persistent cloud and rainfall potential. Near seasonal most elsewhere in white.


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

A very dynamic week of weather over the east and southeast plus out west with the break in the dry spell and warm weather there. More high humidity and unsettled weather is expected into the medium term as well with a deep moisture profile likely to link up with low pressure over the nation. The positive SAM phase if it emerges in the medium term could once again propel easterly moisture through the nation, opening the door for more heavy rainfall over QLD and NSW.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture levels are rising throughout the nation as the easterly winds propel moisture into an upper trough that is positioned through the interior of the country. The trough in the east is already lifting the moisture into widespread areas of rain over QLD and showers into NSW. The humidity will be lifted by the upper low over SA during Tuesday and extend that heavy rainfall risk right through QLD and into NSW mid to late week as the moisture is swept eastwards by the trough and front pushing through WA which too will have deep moisture attached. Note the moisture coming through the medium term via the remains of Karim coming into the jet stream. There may be some excessive moisture once again over the nation into the medium term, well above average moisture usually means we see well above average rainfall chances and that is likely once again as we track through the back of the month. So there is more potential follow up rainfall for large areas of the nation following the rainfall expected and high humidity over the nation this week.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - the rainfall comes in heavy in many locations this week with the upper trough over the east. Another event is likely to come through next week with another system in the medium term as well so there is quite a bit of weather for the second half of May on the way it appears.

I will have more weather information this evening and from early on Tuesday morning.

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