MODELS AND RAINFALL - PM EDITION

Models are now starting to come into better agreement with regards to the rainfall over the southeast, there will be heavy rainfall. Now comes the tricky part of who gets what! The riverine risk is relatively high through this region later in the week.


Thunderstorms are currently producing enormous amounts of rainfall through scattered pockets of southern QLD and areas of inland NSW. The uneven distribution of rainfall set to continue with some areas being drenched and others remaining spared, but the flash flood risk is high.


The west and south seeing barely any rainfall as the main trough axis remains east and the tropics not being as active as forecast last week, means less rainfall chances for about a week to 10 days.


Lets take a look


SHORT TERM

As mentioned in the state based forecasts today and in the video, the main rainfall event is over the southeast of NSW and the ACT with a slow moving upper low. On the north of this feature storms will fire over eastern QLD and NSW as well. The tropics looking routine with the usual build up weather continuing. Inland areas of the nation, very isolated showers and thunderstorms and relatively light falls if anything in these areas.


UKMET - Rainfall Next 7 Days - HIGH CHANCE

Has been consistent for the past 3 nights and days and no change to the signal. The heavy rainfall shield will still move around the southeast but nationally this is probably a fair representation of what is to come this week.


MEDIUM TERM

The medium term is trending drier, which I have not stated for a while. A lot of what you see on the charts falls in the coming 5 days with the rainfall retreating to the tropical north and eastern QLD. The west may see a cold front pass through during mid next week introducing showers to the south of the state. This system may then introduce a thundery change to SA and VIC at the end of the 10 day period. The tropics remaining in build up mode at this time.


ICON - Rainfall Next 8 Days - MODERATE CHANCE

This has now come into line with the other models and shows the heavy rainfall through NSW more than NSW with falls of 300-400mm in a narrow strip down there. Otherwise the rest of the nation looks fairly settled and that is the right solution under the guidance across the board, though trending a little too dry in the short term. This model has another tropical feature in the Indian Ocean.

CMC - Rainfall Next 10 Days - MODERATE CHANCE

Has been consistent in the idea of heavy rainfall over the southeast and east, but moves it around from run to run so watch this space. The tropics routine weather. Isolated high based thunder elsewhere.

EURO - Rainfall Next 10 Days - MODERATE CHANCE

Very dry through much of the nation away from the northwest and southeast, perhaps a little too dry, but we will see. The rainfall over the southeast ranges from 100-300mm in some locations. The model also picking up a tropical system in the Indian Ocean which I will continue to watch as they may be singalling an increase in moisture and rainfall after this period over the north and west.

ACCESS - Rainfall Next 10 Days - LOW CHANCE

Very aggressive on the rainfall for the east and southeast hence why the BoM has followed with flood watches for northern NSW and southern QLD. I think this is too heavy for the region but the southeast could see those falls if the low stalls off the coast there into the weekend. The northwest unstable and it does see the tropical system off in the Indian Ocean.

KMA - Rainfall Next 12 Days - LOW CHANCE

Also quite aggressive on the rainfall front for the southeast and east and has the spread right. The rainfall over the north is more widespread than some other models, especially over Cape York.

GFS - Rainfall Next 16 Days - MODERATE CHANCE

Lifting this model now to a moderate chance thanks to a little more rainfall over the southeast now which is the right solution. The rest of the nation fairly quiet through to near Christmas with a hotter pattern developing with the monsoon bypassing the north. Has follow up rainfall for the east of the country as the SAM trends positive from the 20th.

ENSEMBLE DATA

The data sets becoming more aligned this evening, still have the heaviest rainfall over the east and north, but once we lose the main rainfall event over the southeast of the nation we will get a better look at the rainfall to come leading into Christmas. The MJO is pulsing through the Coral Sea and this will mean the rainfall chances are reduced nationally.


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

Has finally increased rainfall over the southeast and lowered rainfall over the north and northwest which is the correct solution on climate guide

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

Very similar to the GFS but has more rainfall for the north which I am not quite sure about given the guidance.

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

Splits the difference between the CMC and GFS and I will side with this solution. Will be watching the tropics closely in the medium term and the southeast, prepare for a deluge in the short term.

LONG TERM

The wet signals continue as mentioned in the 6 week outlook. All models strengthen the rainfall signal later December if not into January which would align with the monsoonal surge returning towards the Maritime Continent.


CFS - Rainfall Next 6 Weeks - MODERATE CHANCE

The rainfall will return across the country, as mentioned this morning, in line with the development of the monsoon in January I suspect.

More to come from 7am EDT.