MODELS AND ALL THINGS RAINFALL

Lots of divergence in the modelling over the coming week to two weeks which means forecasting specifics is near on impossible, which is not as a surprise in the warmer season when thunderstorms are involved.


What makes this sequence of weather really quite unusual is the moisture content in the atmosphere combining with a very energetic flow pattern which is leading to wild weather, heavy rainfall and severe thunderstorm risks more often than not for multiple states through the coming 10 days at least.


The Indian Ocean is heavily involved in pumping moisture into the nation but so is the elevated SSTs over the northern and eastern tropics. And we have the developing La Nina phase out in the ENSO with a positive SAM also underway.


All things conspiring to bring the above average rainfall with severe weather risks for northern and eastern Australia. We have seen that play out in recent days.


Lets take a look at the details.


SHORT TERM

The short term offers a soupy airmass and two troughs over the east, from tomorrow through to Wednesday with the southeast and south seeing a reduction in rainfall and thunderstorm activity. Over NSW and QLD, the rainfall and thunderstorm activity may persist in the deeper moisture profile until about Tuesday. Out west the weather is expected to turn showery and unsettled with a developing low pressure system that will then shift into SA by Wednesday and this is where the modelling as you will see below becomes low confidence. Tropical weather looks very wet with above average rainfall with troughs lingering and deeper moisture to work with leading to the wet signal.


UKMET - Rainfall Next 7 Days - MODERATE CHANCE

MEDIUM TERM

The modelling is very tricky through mid next week through to the following Monday with a low pressure system being modelled very differently by all models. Hence why you see such a variation in rainfall output across the nation. I have assigned confidence against each model based off current guidance.


ICON - Rainfall Next 8 Days

CMC - Rainfall Next 10 Days - LOW CHANCE

EURO - Rainfall Next 10 Days - HIGH CHANCE

ACCESS - Rainfall Next 10 Days - MODERATE CHANCE

KMA - Rainfall Next 12 Days - LOW CHANCE

GFS - Rainfall Next 16 Days - MODERATE CHANCE

ENSEMBLE DATA

Still the most useful data you can find through these low confidence periods with the broader data sets more consistent, and somewhat much wetter than the deterministic counterparts.


GFS - Rainfall Next 16 Days (median of 35 members) - MODERATE CHANCE

CMC - Rainfall Next 15 Days (median of 30 members) - MODERATE CHANCE

It has begun to dry a little bit for southeast inland areas.

EURO - Rainfall Next 15 Days (median of 51 members) - HIGH CHANCE

LONG TERM

The very damp signals continue into Christmas time with elevated rainfall for northern and eastern Australia and that means higher humidity, lower temperatures and severe weather risks continuing.


CFS - Rainfall Next 6 Weeks - MODERATE CHANCE

More details Saturday morning.