MODELS AND RAINFALL - THE DRIER PERIOD CONTINUES. NOW WE HAVE GOOD VISION ON WHEN A SHIFT DEVELOPS.

The drier spells can be frustrating for areas that have missed out on reasonable rainfall of late, that being parts of QLD and SA/VIC. But in these cases, it is a very useful time to track weather systems that are brewing into the short and medium term, without contamination from too much high impact weather.


I firmly believe that once we lose the last of the wet season rainfall up north and the sub tropical ridge breaks down into the medium term as well, that we will have better vision on what is likely to occur from ANZAC Day onwards.


It is a time that most people use as a benchmark for planting crops and starting to organise stock etc for the cold season ahead.


There is a lot of weather in the cooler season for Southern Australia to come. That may even persist into Spring so the decisions made now are critical based off the best data and analysis available.


This is why I work so hard for you.


Lets take a look


SHORT TERM

The short term offers a big bag of nothing for inland areas of the nation. We could see a few showers about southern coastal areas of the country with a weak cold front over Easter Monday. Light showers in onshore winds are expected for parts of the QLD and NSW coasts. The higher concentration of rainfall is forecast to be found over the southwest of the nation with another wave of low pressure next week and moisture streaming in from the Indian Ocean. There is likely to be very high rainfall rates over northern Australia which could lead to some records being broken in some spots over the NT and QLD.


UKMET - Rainfall Next 7 Days - LOW CHANCE.

Keeping the tropical wave amplified over FNQ and then into the Coral Sea with another burst of moisture developing over the northern Indian Ocean and could spread southeast into the jet stream next week. For now not much once we clear the rainfall off WA's south coast with ridging in place. Rain may develop for southern SA later Sunday and move into VIC Easter Monday. That idea is starting to appear back on charts.

ICON - Rainfall Next 8 Days - VERY LOW CHANCE

This model is suggesting the tropical low rotates through the Indian Ocean and then turns south and southeast into WA with significant rainfall through Easter and then coming into SA from next Wednesday. Unlikely.

MEDIUM TERM

The medium term offers not a whole lot for inland areas but I do fully expect the ridge over Australia to break down from around ANZAC Day and this may open the door for rainfall to return from the west with jet stream cloud cover. We are likely to see the SAM mode remaining positive and I do expect rainfall to increase for NSW and QLD before that phase resolves back to neutral. Rainfall over the northern tropics should start to ease as the wave weakens but there could be small scale low pressure systems developing through a weak trough over open waters. If we can get a circulation northwest of WA then we may see better rainfall chances spreading through the continent later this month into May.


CMC - Rainfall Next 10 Days - VERY LOW CHANCE.

Looking very disorganised and not worth mentioning. It is the outlier of the group.

EURO - Rainfall Next 10 Days - MODERATE CHANCE

Latest Euro brings back the rainfall to the southeast with a change late Easter Sunday into Monday but I am not sure on this but will keep watching. This is a timing issue and whether we will see the ridge break down and allow for moisture to escape in the gap from northwest to southeast and feed the trough over the southeast early next week. Heavy falls in the Gulf of Carpentaria with the tropical system but that moisture looks to go east. More moisture building in the Indian Ocean should be watched by all of you in the southern, eastern and even western Ag areas of the nation as we move out of Easter and approach ANZAC Day.

ACCESS - Rainfall Next 10 Days - LOW CHANCE

Noting the moisture over the Gulf of Carpentaria. That is in good agreement with the other models but what this model does is shift the moisture eastwards and not westwards. A separate tropical system may emerge on the other side of Easter over the Indian Ocean and feed into the jet stream. Maybe some light to moderate rainfall coming into the southeast towards Easter Monday but this also is low confidence forecasting. Dry interior

GFS - Rainfall Next 16 Days - LOW CHANCE

Very wet over the northern tropics and probably a little too dry for the eastern inland given the data sets from other agencies, but the better rainfall chances away from the tropics will be found along the east coast and over the southwest of the country.

ENSEMBLE DATA

The ensemble data in reasonable agreement with the upper ridge being forecast in the same place. The issue that the models have in the medium term is how long does the upper ridge stay in force for and when will it open the gate for moisture to stream into the jet stream and frontal weather bringing rainfall chances back over inland and southeast/eastern inland Australia.


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

Similar spread to the CMC and noting the rainfall over the tropics is heavy but no where near the volume as per the deterministic data above meaning that even though the rainfall is excessive up north, it is still highly volatile in terms of volume of wet weather hitting the coast so keep watching. Moisture in the medium term increasing through the Indian Ocean separate to the NT and QLD moisture plume may increase rainfall chances into the end of the month from northwest to southeast across the country but dry through interior.

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

Rainfall numbers are coming up over the western interior and that does seem to spread along the southern coastline of Australia through the medium term. Until then light falls for the southeast and southern areas. The bulk of the showers over the east coast will be light but could reach an accumulation of up to 50mm and the northern tropics seeing well above average rainfall but not as amplified as the deterministic data.

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

The Euro starting to increase the risk of moisture spreading southeast from the Indian Ocean in the medium term. That will likely be disconnected from the tropical weather over northern areas in the short term. Rainfall numbers also increasing through the south and southeast at the end of the period, beyond ANZAC Day more likely with the moisture and instability meeting in the Bight and bringing about better rainfall chances to end the month. Moderate accumulation over the east coast in onshore winds off and on through the period should be well below severe thresholds and not impact flood zones with any additional issues at this time.

LONG TERM

More details on this forecast was posted today with the latest 6 week outlook. Conditions will shift and it could do so with a bang for some areas of the nation.


CFS - Rainfall Next 6 Weeks

Note that we are moving into a time of not IF we will see the seasonal shift, but WHEN. And all models are signaling that will take place but it is now WHEN.

More coming up from 8am EST on Wednesday - have a good night.