MODELS AND ALL THINGS RAINFALL - LOOK AT THE DIFFERENCES A TROPICAL SYSTEM MAKES

This is a great time to show you what the wiggling and wobbling of a tropical system can do to modelling rainfall for the nation. I say it time and again, you do not have to live in the tropics to be impacted by tropical weather! This is a great example and many are wanting rain, many are not, so lets see where the agencies lay as we go through Monday evening.


SHORT TERM

The short term, totally dictated by Tiffany up to the north and the deep trough with weak steering currents over the eastern inland of the nation. Upper troughs running over this unstable airmass will flare up the storm coverage for VIC, NSW and southern QLD throughout this week. Otherwise the west is dry as is much of SA.


UKMET - Rainfall Next 7 Days - MODERATE CHANCE

Keeps the tropical system up over the eastern Top End. Not much impact further south as yet.

MEDIUM TERM

The remains of Tiffany are likely still on the board next week, now below you can see the different directions the models take her by the spread of rainfall. Some leave her up in the NT, some take her through QLD, some take her through WA. The bottom line is, it is too early to call where she goes, but it is useful to see the data sets as a whole and recognise there are similarities amongst them, but it is harder to pick than a broken nose at the moment so it will take time to settle down.


ICON - Rainfall Next 8 Days - MODERATE CHANCE

Like UKMet - keeps the Tropical system up over the NT for much of the next week.

CMC - Rainfall Next 10 Days - HIGH CHANCE

This is probably more in line with the right solution - given the consistency across the data sets this evening. Would likely shear off the moisture into QLD leaving WA out of the heavier rainfall opportunities which would then mean no impact for SA.

EURO - Rainfall Next 10 Days - VERY HIGH CHANCE

This is the likely outcome based off the latest observations and data sets I have seen.

ACCESS - Rainfall Next 10 Days - MODERATE CHANCE

Brings the tropical system into the heart of the NT and then pushes her southwards into the southwest of the NT. No moisture impact from her just yet through the southeast, keeps it in QLD. Most of the rain you see there is from storms in a stagnant pressure trough over the southeast.

KMA - Rainfall Next 12 Days - MODERATE CHANCE

Shows excessive rainfall of over 25 inches for the NT which is not impossible if the system stalls out, but this model has a lower skill score. But in agreeance, showing the moisture sweeping south from the tropics, favouring a run through the eastern states rather than south or southwest.

GFS - Rainfall Next 16 Days - LOW CHANCE

Been very inconsistent in it's idea and has not performed well with this feature so still rendering this a low chance. This morning it had 1.5m of rain for the west coast of the NT.

ENSEMBLE DATA

These are useful guides in times like these where the broader data sets give you and idea of where the heaviest of the rainfall will go. They are more broad and have less detail, but they are more accurate in terms of forecasting in these challenging times.


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

Similar to the other models on the boarder data sets suggest some wild weather coming into the NT. To what scale as you can see above, remains to be seen and that will be refined out over time

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

Showing the wet signal more for northern and eastern Australia, especially around the Top End.

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

This data set offers more rainfall beyond the 10 day forecast above, so the moisture will eventually creep south, for now the tropical moisture will stay in place up over the NT before shifting southeast and east.


LONG TERM

And you guessed it, even more to come beyond the short and medium term.


CFS - Rainfall Next 6 Weeks - MODERATE CHANCE.

A very wet signal continues for the outlook period and this model does not handle tropical weather well so the fact it has that much rainfall up north is of concern regarding flooding.

More details coming up from around 8am EDT.