MODELS AND ALL THINGS RAINFALL - THE DIVERGENCE IN GUIDANCE MAKING THE FORECASTING TRICKY.

The guidance is simple in that we know it is humid, it is likely wetter than average over many areas away from the far SW of WA, but who actually gets the heaviest of the rainfall in these set ups are not easy to discern ahead of time. I really want to point out once again, your numbers will vary with thunderstorms in the play, which you have seen today through parts of VIC, NSW and SA. This will be repeated time and time again through the next few days.


Lets get into it.


SHORT TERM

The short term dominated by the trough in the east and southeast, the monsoon trough and developing low pressure system within the trough over the NT and WA this weekend which then becomes slow moving and the potential developing trough on the east coast with onshore winds, driving showers and storms mid to late next week. The southern areas may begin to dry out from mid next week as a southerly flow develops.


UKMET - Rainfall Next 7 Days

The Uk is quite generous taking the rainfall through the northern tropics southwards to the Central NT and interior of WA with flooding potential. Otherwise monsoonal over the north of the nation with the westerly flow and squalls. The eastern inland seeing showers and thunderstorms with uneven distribution of rainfall. The east coast not seeing much in the way of rainfall nor is south and west WA.

ICON - Rainfall Next 8 Days - MODERATE CHANCE

Signals are for the monsoon to ramp up in the short term with a tropical low over the northwest producing significant heavy rainfall around the Kimberly and down to about Broome inland to Derby, with falls of 400mm possible. Inland flooding through the NT quite possible with a deep trough with heavy falls daily until the end of this period. The weather over the southeast is dictated by the placement of troughs and interaction with moisture and this will lead to uneven distribution of rainfall.

MEDIUM TERM

The medium term, models go off in tangents. I will leave the commentary at that and let you see the data below, overall all of these carry a low chance except the Euro and CMC which have been running more consistent from run to run with the placement of the rainfall bearing systems.


CMC - Rainfall Next 10 Days - MODERATE CHANCE

Very heavy rainfall with the tropical low and monsoon trough over northwest Australia stretching through the monsoon to another tropical low over the Gulf leading to extensive heavy falls. Flooding is however contained to the northern tropics and not so much Central Australia as other models suggest. The east wetter with that trough in the middle of next week with onshore winds. Overall the remainder of the southeast and south will see uneven distribution of rainfall.

EURO - Rainfall Next 10 Days -HIGH CHANCE

Probably been the most consistent out of the bunch, not much change from this morning with the uneven distribution of rainfall for the south and east. The heavy tropical rainfall contained to the monsoon and a westward moving tropical low bringing up rainfall chances for interior WA. Then watching the east coast for the potential of a trough producing showers and storms mid to late next week, whether that be over QLD or NSW, or maybe both.

ACCESS - Rainfall Next 10 Days - LOW CHANCE

Still similar in the idea of taking the tropical moisture through northern and western parts of the nation but is the only model to take heavy rainfall into the Wheatbelt of WA. Otherwise uneven distribution of rainfall related to the trough with tropical downpours most elsewhere through the short term.

KMA - Rainfall Next 12 Days - LOW CHANCE

Most aggressive in spreading the monsoonal moisture across the country lifting rainfall chances over much of the continent next week and removing the chance of the humidity clearing out of the nation.

GFS - Rainfall Next 16 Days - VERY LOW CHANCE.

This will change, the short term as per above, but anything from day 7 will be treated as very low chance.


ENSEMBLE DATA

The ensemble data also a little divergent, mostly thanks to the GFS going a little bit off the rails, which is normal ahead of cyclone formation in the data sets and in response to the SAM moving more neutral in the medium term for a period.


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

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

Falls are increasing over the northern tropics which is suggesting we may be dealing with tropical lows in the outlook period.

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

Probably closest to the post in the medium term due to consistency, the area to watch is the NSW coast and into southeast QLD in the medium term.


LONG TERM

Wet weather signal continues, there is no end to the above average rainfall signals as we move into March.


CFS - Rainfall Next 6 Weeks

The north is wet but the numbers throughout the nation generally indicate for the coming 6 weeks or so, the tropical influence is high as will be the SAM in a positive phase.

More coming up from 8am EDT Thursday.