Some murmuring surrounding rainfall chances on social media and on deterministic charts over the course of later next week into the weekend, with an upper cold pool following a strong front, moving north through NSW and into QLD, combining with onshore winds to produce rain and thunderstorms for inland QLD and northern and eastern NSW.
Rainfall numbers have been all over the shop from run to run, which expresses the high level of uncertainty as we go further out into the distance with modelling generally. In these types of situations, this point is made even more clearly with the lack of consistency from run to run making it impossible to formulate a forecast.
Rainfall for the next 7 days - Factoring in one cold pool riding through Central NSW with some slightly better rainfall later in the period below. However this forecast will likely change if the upper troughs become stronger as a solution on modelling over the weekend, seeing heavy rainfall return to the east coast and developing over southern inland QLD and northern inland NSW. Charts will be made for this event if it verifies.
So caution is needed, even though the colours are exciting.
Fast flow pattern over southeast Australia generating various solutions. Here is the latest two runs from GFS and compare the two. Rainfall outcomes underneath.
GFS rainfall for the two weeks showing reasonable rainfall in response to that cold pool moving north. This was the 00z run valid 7th May 2021.
Euro 12z run valid May 7th 2021. Shows inland rainfall and showers for the coast, with the heavier falls further west through Central QLD this morning.
This evening's run are slightly different to this morning. And the consequences and impact on rainfall coverage is quite dramatic. This will continue to chop and change dramatically as we head into next week.
GFS 00z run for this evening Valid 7th May 2021. This shows a more dynamic wavy flow but showing cold air broadly being drawn into the eastern inland from the long fetch southwesterly winds, rolling into northern NSW and southern QLD amplifying rainfall chances.
GFS going all in on heavy rainfall developing for the coast over northern NSW and extending the showers up the SEQ coast and into the inland. But once again this will definitely change next run. Accumulated rainfall for the next fortnight, after a relatively dry week, showers will increase under this scenario for northeast NSW from Thursday next week.
But the trend is not strong, with models diverging on rainfall outcomes. Even the longer term spread at towns dotted along the coastline are very large which expresses a high degree of uncertainty.
Use the green line as that is the mean of all members, but you can see the range goes from 0-140mm over the coming 2 weeks - so there is no skill in forecasting a precise forecast off that data. We have to wait and see. GFS Ensemble QPF spread for Brisbane - a reasonable example for the region along the coast. 00Z run.
So it is a wait and see game - I will have more to say about this probably tomorrow if not Sunday as we get more clarity on modelling - for now it is like chasing a weather tail. There is no skill, other than trying to make sense of crazy talk.