NSW - SHOWERS INCREASING WITH INLAND THUNDERSTORMS DEVELOPING

The weather turning sharply wetter across the next few days with the chance of locally heavy falls developing along parts of the coast and with thunderstorms across the inland.


A humid and unsettled spell courtesy of the positive SAM phase projecting unstable easterly winds and deepening moisture levels being drawn in from the Coral Sea and Pacific Ocean.


There is the chance of a low forming within the trough which will align itself over the east coast later this week. That may see heavy rainfall develop for coastal areas and those on and east of the divide. The risk remains low and undermined at this time, but modelling has supporting some locations seeing torrential falls along the coast given the elevated SSTs presently in the region.


Lets take a look

FORECAST

Rainfall Next 10 Days

Rainfall remains most widespread for those in central and eastern areas of the state but the further west you go from a line from Bourke south through Hay to about Swan Hill, conditions turn sharply drier for now through this week. Will have to watch how far west the trough retrogrades during the latter part of the week into the weekend. Some chance we could start to see moisture begin to be drawn in from the northwest tropics as the monsoon deepens over northern Australia. Overall the sequence is wet with some areas likely to see 1-3 months worth of rainfall with flooding a risk through the period.

Thunderstorm Forecast Monday

Thunderstorms are forecast to redevelop along parts of the Central NSW coast and extend northwest over the Central Tablelands through the Central West and up to the Upper Western. The thunderstorms coverage will also extend over much of northern inland NSW and may dip as far south as Canberra during the afternoon and evening. Thunderstorms may turn severe with heavy rainfall and damaging winds. Large hail is a very low risk but may be observed in the larger clusters of thunderstorms. Thunderstorms should diminish by evening.

Flash Flood Risk Monday

Thunderstorms carry a moderate chance of producing flash flooding over a broad area during the afternoon and evening. Some locations may see 50mm in an hour with the precipitable water values/moisture content very much supportive of high rainfall rates. Slow storm motion will also assist in larger accumulations.

Damaging Winds Risk Monday

Damaging winds also a low to moderate risk of a broad region on Monday. This will be mainly associated with strong outflow/downbursts from the higher precipitation thunderstorms.

DATA - Refer to video for further analysis and guidance relating to the forecast charts above and the movement on the data sets.


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

Not much change from this morning for the short term, but from later in the outlook period, the spread, depth and scale of the monsoonal weather over northern Australia will have consequences for the nation's weather. There is likely to be tropical low pressure form or cyclone activity form over northern parts of the nation. Classically, as we move into early March, the traditional format for rainfall spreading across the nation is from northwest to southeast from WA, through central interior and SA and then into NSW and VIC. This is a decent chance. Across the east of the nation, onshore winds for the coming week will see frequent showers for the NSW and QLD coast, locally heavy with cooler temperatures. The onshore flow will feed the trough over the inland producing showers and storms on a daily basis for much of QLD, NSW and into the ACT and northern VIC. Overall the nation will turn wetter as we go through the outlook period. Once we get to the end of the first week of March, we could have a neutral SAM, reducing rainfall risks along the east coast and bringing back the frontal waves for southern Australia, helping to bring in more moisture from the north and northwest so that is something to watch. Not an overwhelming signal but is there.

00Z GFS - Precipitable Water Anomalies - Next 2 Weeks

Moisture spread across the nation remains unchanged, it has been building in recent days and is likely to increase further then drift south through to VIC by the middle to latter part of the week. The moisture over northern Australia rising sharply as the trough north of the nation deepens and a monsoonal westerly flow moves closer to the nation. If we have a low pressure system developing north of the nation as the GFS says this week (has picked the tropics reasonably well this week), then we could see widespread rainfall develop earlier than what other models are suggesting. Refer to the rainfall and models post this evening.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to video for further guidance

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to video for further guidance

00Z GFS - Rainfall Accumulation - 2 Weeks

Refer to video for further guidance and a state based fly around.

A closer look in - the wet weather is expected to increase throughout this week.

More weather information coming up later this evening with the models and rainfall wrap and as mentioned in the email agenda today, plenty on the board to cover off this week.




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