MODELS AND ALL THINGS RAINFALL - THE MJO IS COMING TO THE NORTH AND THE SAM HAS REACHED POSTIIVE

The first positive peak in the phase of the SAM has unfolded and as a result the coming 3-4 days are expected to turn more damp and humid for the east, but there could be several more positive peaks in the phase over the coming short and medium term outlook which could see larger waves of rainfall and moisture emerge on the forecasts for QLD, NSW and VIC in particular.


The impacts of the SAM may be carried into SA with troughs in the medium term as well as a persistent and long fetch easterly flow develops.


Over the north, the MJO moves through phase 3, 4 and 5 bringing the monsoonal trough back into play and the risk of tropical depression and cyclone formation increases through the outlook, thus increasing the chance of enhanced rainfall which may spread inland depending on the track of these features.


The southwest and central areas of the nation look dry for now but watch these tropical features closely in the coming week to two weeks as things can change quickly and it takes one system to bring a seasons worth of rainfall in a sitting with these events.


Lets take a look


SHORT TERM

The short term is dominated by the positive SAM phase which has been covered off well with the MJO over the tropics. Now we are looking for the low pressure over the nation in relation to the moisture to find the heavier rainfall events that may emerge through this time. The higher chances of widespread meaningful rainfall will be found over the north and east of the nation and drier weather continuing for the south and southwest and central areas.


UKMET - Rainfall Next 7 Days - LOW CHANCE.

Shows the upper disturbance over QLD through NSW and stalling out with a trough leading to heavier rainfall for NSW and parts of QLD. The tropical weather is starting to increase as well. Dry weather most elsewhere.

ICON - Rainfall Next 8 Days - LOW CHANCE

Showing the upper disturbance over the outback of QLD and the positive SAM and the MJO rolling through northern Australia. Overall the rest of the nation quiet, but this is probably too dry.

MEDIUM TERM

The persistent positive SAM signals are expected through the medium term and this will keep the rainfall chances going over the east coast and that moisture spreading through the inland areas of the east. Over northern areas, the MJO is expected to run through phase 4 and 5 and then slow down in the Western Pacific and when it gets there, higher rainfall chances over northern and northeast areas of the nation are expected and better odds of moisture running southwards through the nation is likely when the MJO is there. Moisture has a better chance of producing rainfall over central Australia under this guide.



CMC - Rainfall Next 10 Days - MODERATE CHANCE.

Also showing the positive SAM and the MJO rolling through a little later than other models for northern areas. The upper disturbance for QLD tapping into tropical moisture is a feature to watch in the coming days as that may produce severe weather. The west and southwest looking settled for now.

EURO - Rainfall Next 10 Days - MODERATE CHANCE

Probably a little too dry for the west and central parts of the nation. Rainfall clearly connected to the SAM and the MJO moving through the north, note the tropical system over the Gulf. Will be somewhere else tomorrow.

ACCESS - Rainfall Next 10 Days - MODERATE CHANCE

Very similar to the Euro in it's spread but more generous with the heat trough out west. More widespread heavier rainfall for the east as it picks up the upper system mid week like the GFS and CMC where heavier rainfall is pulled onto the east coast of NSW and more particular QLD.

KMA - Rainfall Next 12 Days - LOW CHANCE

The rainfall over the nation clearly picking the MJO and the SAM, but the KMA amplifies the MJO over QLD and into the Western Pacific which I am not so sure about.

GFS - Rainfall Next 16 Days - LOW CHANCE.

This is suggesting a large influence from the tropical northwest to the southeast and highlights what that will look like in the medium term. The east has a higher confidence forecast along with the far north and watching very closely the upper level disturbance over QLD combining with tropical moisture in the short term.

ENSEMBLE DATA

Showing the bias of the rainfall connected to the SAM being positive and the MJO moving through phase over northern Australia and the drier bias as the moisture starts to seep south and west through the nation.


GFS - Rainfall Next 16 Days (median of 35 members) MODERATE CHANCE (I do expect more rainfall for the interior and back through the southeast.

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

It is picking up the monsoonal activity over the north, the widespread rain in the east and with the SAM and also suggesting moisture may sweep south through the tropics over the interior with improving rainfall odds into early March.

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

The Euro ensemble vs the single unrendered data set below still very wet for the north and the east and the spread of moisture as per the guidance in other models will come down to the tropical systems and their tracks as we move through the medium term and that is yet to be determined, but as you can see from the above and below there are many different options on the table.

EURO Single Data Set - Rainfall Next 15 Days

Note the two tropical entities in the north and the large amount of rainfall over the southeast of the nation as well. This model run does see the upper system mid week.

LONG TERM

The strength and length of the monsoon is expected for 2 weeks and ease through mid March with monsoonal break conditions developing as the MJO moves into the Central Pacific. The SAM is expected to remain positive for a while but likely to turn back neutral through mid March. I would anticipate a wet start to the month then a quiet phase and a wet end to March and start of April. Frontal weather may begin to get involved in bringing moisture out of the Indian Ocean into WA and SA through the latter parts of March into April as well.


CFS - Rainfall Next 6 Weeks

The wet season continues up north and prolonged easterly winds may drive heavy rainfall for eastern areas of the nation which may rival the falls over the northern tropics! Mixed odds elsewhere. I will have more on the 6 weeks tomorrow.

More coming up from 8am EDT pending no more severe weather knocking out the power. Thanks for your patience this morning.




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