MODELS AND ALL THINGS RAINFALL - THE MONSOON DRIVES THE HEAVY RAIN UP NORTH. STORMY EAST AND SOUTH

The weather truly has been anomalous entering into the driest time of the year as a continent with a deep trough over the southeast and east and the monsoon trough south of the tropics also pumping moisture and rainfall chances southwards.


Heavy rainfall and flash flooding has appeared daily in many areas during the past week and this may continue over the coming 3-4 days. Next week, there is some chance we will have a drier southerly push into southern parts of the nation while the monsoon continues over the north.


Along the east coast, the wild card system to watch is the stalled trough interacting with the onshore easterly flow which may lead to showers/rain becoming heavy and thundery at times for NSW and/or QLD.


Lets have a look at all the data sets.


SHORT TERM

As mentioned above, the monsoon trough a couple of tropical lows will dictate the heavy rainfall and flood risks over the northern third of the nation, the trough over the southeast and east will drive the uneven distribution of rainfall leading to some copping a month to four months worth of rainfall in a sitting. A drier airmass may move into southern SA and VIC next week while moisture may move south into southern interior parts of WA.


UKMET - Rainfall Next 7 Days - MODERATE CHANCE.

The monsoon drives the heavy rainfall chances beyond the storm outbreak across the southeast and east of the nation. The east coast is too dry. The north has the heaviest of the rainfall with the monsoonal low staying over the Kimberly. Note that it does not come southwards like other modelling I showed you earlier. That changes the rainfall distribution downstream.

ICON - Rainfall Next 8 Days - MODERATE CHANCE.

The wet weather continues over much of the north and note the difference in the placement of the tropical lows, how that impacts the moisture across the inland and how it sweeps eastwards rather than south or southwest. I am leaning to this solution as well. The east coast is too dry.


MEDIUM TERM

The monsoon continues over the north as we move through the medium term and there is a high chance of tropical lows in the mix as the monsoon trough sits over the region. The easterly winds are likely to dominate once again following a brief southerly flow mid to late next week. The humidity and rainfall chances then begin to increase as we move into the second week of February. Out west, the moisture may increase further over the course of the first week of February lifting rainfall chances for the SWLD.


CMC - Rainfall Next 10 Days - MODERATE CHANCE

Monsoonal trough is king in terms of rainfall over the north and northeast of the nation. The east coast is wet with the onshore wind flow which is probably the right solution. The hit and miss showers and storms over the remainder of the nation would continue with the troughs under this guide for a large parts of the nation. The west is dry.

EURO - Rainfall Next 10 Days - HIGH CHANCE.

Has been the most consistent model in handling the tropical moisture and the placement of the tropical low over the northwest. From there you can see the monsoon trough over the north and the moisture is shearing east and southeast from the tropics. So that will dictate rainfall. The southwest would be dry, this is in stark contrast to GFS below.

ACCESS - Rainfall Next 10 Days - MODERATE CHANCE

The KMA and Access sit in between the Euro and the GFS showing you a blend of the two, but do not force the moisture as far south as the GFS through WA but not as far east as the Euro. Under this solution, most of the inland of the NT and northern WA would be under water. The east of the nation is damp and the threat of the onshore winds combining with a trough is gaining momentum. Heavy falls with the storm outbreak for VIC.

KMA - Rainfall Next 12 Days - MODERATE CHANCE

The KMA and Access sit in between the Euro and the GFS showing you a blend of the two, but do not force the moisture as far south as the GFS through WA but not as far east as the Euro. Under this solution, most of the inland of the NT and northern WA would be under water. The east of the nation is damp and the threat of the onshore winds combining with a trough is gaining momentum. Heavy falls with the storm outbreak for VIC.

GFS - Rainfall Next 16 Days - VERY LOW CHANCE

The modelling is poor and very inconsistent. This usually means that the tropics are going to get even more active and impact rainfall across the nation into February.

ENSEMBLE DATA

No real change to the overall broader guidance. I would like to see these by Sunday once we lose the thundery mess over the south and east for better guidance into the medium term. For now the wettest weather over the medium term will be over the north and along the east coast and perhaps developing over the western interior.


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

Remains very low confidence based off the deterministic this evening and I expect changes related to the tropical weather that emerges in the medium term. Note it does not have a strong bias in taking the tropical moisture with the low southwards towards inland WA.

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

Better accuracy with the CMC on this one, has been most consistent with the Euro, so will stick with that data set.

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

No real change from last night on the guide.

LONG TERM

Still no signal of the drier signal coming back.


CFS - Rainfall Next 6 Weeks - MODERATE CHANCE

Monsoon rules up north and that impacts the rest of the nation. With the potent moisture supply the rainfall should be above average in many areas, especially interior, southeast and eastern parts.

More coming up from 8am EDT.