MORNING WEATHER WRAP - THE MODEL MADNESS CAUSING HAVOC WITH RAINFALL FORECASTING

The joys of spring time and weather forecasting, it is as tricky as it gets. High sum game for many out there at the moment harvesting through central and eastern areas. Some expecting 100mm one run, to then see it reduced to 5mm the next. The weeping and gnashing of teeth continues this morning.


Flood zones need to be on alert, especially areas that have already seen moderate to major flooding with some guidance suggesting a further 100-200mm of rainfall in these areas, but other models not agreeing on that and placing the flood risk further south and east. This morning we now see the northward shift of the rainfall in the east.


It is a dog's breakfast to forecast through SA, NSW and VIC at the moment and forecasts will once again change dramatically for those further south. But this can still change so stay tuned to the guidance.


The unsettled and humid weather over the northern tropics is back and over the eastern inland too, north of this feature. The weather out west is drying out and warming up, that carries higher confidence in the forecast package today.


A secondary feature is expected to develop from a trough through WA which may bring further storms later in the weekend into early next week, that system then floats across and meets the left over moisture from the lead system. This feature will also be carrying deep amounts of moisture from the northwest. BUT where it goes, remains up in the air however as mentioned in recent days, it does look to favour QLD and NSW, basically the further east you are the wetter you will be with that feature.


A very tricky and volatile period of weather to come.


Lets take a look

FORECAST

Rainfall Next 10 Days - GFS vs EURO Forecasts.

The rainfall in this first system coming through the nation is becoming clearer as we track the low pressure trough and deepening low pressure system from SA through to NSW and VIC over the weekend. This system has been awfully hard to forecast and now we are seeing the bulk of the rainfall shift into central NSW which is a cause for concern for flood zones. The rain leaves the east early next week with the showers easing. The tropics is expected to see an increase in showers and thunderstorms this weekend into next week with moisture increase and a trough developing over the Base of the Top End. A secondary system is likely to develop over eastern WA and move into central Australia and meet the moisture creeping south through the NT. This system is expected to run into the moisture via easterly winds over the eastern seaboard and more widespread rainfall is expected to develop for southeast and eastern Australia, once again the heaviest falls likely over NSW and QLD. The far west of WA is expected to remain dry though watching tropical moisture offshore the coast.


My forecast based off GFS data - I am still leaning with this solution. Sees the next week as just wet with persistent troughs and easterly winds.

My forecast based of Euro data - has been most inconsistent but this is now gathering pace as being a likely outcome with two systems on the board.

Thunderstorm Forecast Friday

A broad area of thunderstorm potential for the eastern seaboard but the storms like previous days mostly under severe thresholds (the storm warnings were very trigger happy). Gusty winds the main risk today over southeast NSW and heavy rainfall in pockets of QLD and back over SA.

Flood Risk This Week - Broad forecast risk with 2 systems on the board.

This is shifting north with the guidance, as mentioned yesterday and last night there has been a creep north with the heavy rainfall shield and that continues. Though watch carefully in the next day with heavy rainfall possibly wiggling further north or creeping back south. But be aware and prepare for the worst and hope for the best.

DATA


12Z Euro - Surface Pressure Pattern and Rainfall - Next 10 Days

I have more analysis in the video on this. But the high pressure system to the south will play the part of distributing the rainfall over the east this weekend. If it ridges further north, the further north the heavy rainfall will be through NSW even into southern QLD. If the ridge is flatter, the rain will sink further south through southern NSW and northern VIC. Either way if you are living in Central NSW, the risk of heavy rainfall is high. For the remainder of the nation it is fairly settled this weekend, but next week a secondary low forms and this is also being poorly modelled so pay attention to the forecasts. Finally, the tropics are active, after a dry week, the moisture is surging in from the north and east.

12z Euro - Precipitable Water Values - Next 10 Days

You can see the role of the high pressure system for the weekend system during the weekend, note that ridge bumping the low north and as high the moves east under the low, it propels the low pressure system further west and merges this into the secondary feature out of Central Australia. With the available moisture, I suspect rainfall will change rapidly through the outlook period so stay tuned. The wettest weather, the further east and north you go.

12z GFS - Rainfall Accumulation - Next 10 Days

Refer to video for more details

12z Euro - Rainfall Accumulation - Next 10 Days

Refer to video for more details

12z CMC - Rainfall Accumulation - Next 10 Days

Refer to video for more details

Your latest 6 Week Outlook coming up mid morning and I will try and tackle this rainfall event during the weekend and next week. I think we will have a better idea on the rainfall spread this afternoon. If it is heading south, we will know by this afternoon, if it is heading north we will know by this afternoon. This is where you need the analysis, not just the modelling.

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