High Temperatures, High Humidity and Storms 26 Feb - Mar 3

[Geoff]

I've noticed over the last few days some extensive areas of cirrus have moved over our region from the southwest and west, a particularly large one today in fact. I don't have a link to the upper atmosphere charts, and was wondering if they have cooled significantly as a result of these cloud bands, as this could increase rainfall potential a lot. Any info greatly appreciated!

[johnno]

EC Tonight still going all out for this system down here has 55mm Monday/Tuesday

http://www.yr.no/place/Australia/Victor ... /long.html" onclick="window.open(this.href);return false;

[Supercellimpact]

EC has gone for 45mm for here Monday/ Tuesday so still looking good

[Gordon]

Can I sniff a northwest cloudband on the latest Sunday/Monday BOM 4 day charts?

[johnno]

EC has up to 100mm in parts of NE Victoria

[crikey]

GEOFF
THe BOM ACCESS interactive simulation is one source of this info
According to ACCESS( the link below) there was a high velocity jetstream ( 200hpqascal upper air)down south over the bay and some of that was diverting north up over southern VIC
http://www.bom.gov.au/australia/charts/ ... fresh+View" onclick="window.open(this.href);return false;

and as to temperature at 200hpascal
The whole of the south east quadrant of OZ has upper air colder than the sub artic region atm
In your area today there was a particularly cold spot of -56 deg C over Melbourne
http://www.bom.gov.au/australia/charts/ ... fresh+View" onclick="window.open(this.href);return false;
as to cirrus clouds
google search reckons
http://en.wikipedia.org/wiki/Cirrus_cloud" onclick="window.open(this.href);return false;
wikopedia
Jet stream-powered cirrus clouds can grow long enough to stretch across continents, but they remain only a few kilometers deep

I have heard people say cold uppers can give good storms or rain but never really investigated that myself?

[Geoff]

Thanks Crikey,
Going by the 200hp chart the whole S/E of Australia is now absolutely primed for big storm potential and heavy rain!

[crikey]

Hi Gordon.
Yeah l saw that on national radar tonight. You can view its predicted path of travel usually on the 200 hpascal air stream flow fromBOM ACCESS interactive ( one source of this information)
http://www.bom.gov.au/australia/charts/ ... fresh+View" onclick="window.open(this.href);return false;



The current upper air stream from that moisture in the n/west is splitting in to 2 directions sending some of it across the northern mainland and you can see that on the national radar tonight and some is heading down south toward southern WA and then combining with the jetstream ( modified) and some entering Vic from the south
http://www.bom.gov.au/products/national ... loop.shtml" onclick="window.open(this.href);return false;

According to ACCESS from that link above.. few days later there is a strong jetstream from the Indian ocean directing potential cloud (upper/mid) toward the southern parts of the mainland and interacting and converging the boundary of the sub polar jetstream
so will be interesting to see what arrives from the s/west of WA in a few days time. In a few days it Seems a bit to far south to be a n/west in-feed. But could be fruitful coming in from The Indian ocean?

[Rhino]

EC and OCF reducing falls here mon-tue, 26mm now from 41mm, but still plenty of time yet to change and still a nice fall if we get it but may be a sign that the system may slow and develop as it travels east too. Certainly looking good east of around melb-echuca at the moment.

Rhino.

[nafets]

What does it mean if the uppers are cool - on monday morning Access is saying -58, before slightly warming to -52 on tuesday. (sorry I'm still trying to learn this stuff... )

[Geoff]

What does it mean if the uppers are cool - on monday morning Access is saying -58, before slightly warming to -52 on tuesday. (sorry I'm still trying to learn this stuff

Stefan, putting it simply, warm air rises - so if you have high temperatures at the surface with moist unstable air, this air will rise and rise fast and high to get above the cold air high above. The higher and bigger a storm cloud gets the more rain/hail it will drop as it condenses. Hope that makes sense.

[Meso]

In terms of storms it means the updrafts have greater growth potential, so bigger storms. The air keeps rising until its the same temp as the air around it. So, if the uppers are cool and the ground is hot, the air will continue to rise for quite some time as it's still warmer than the air around it. One of the key things to remember is warm air is lense dense than cold air, so it will rise through it, it has buoyancy.

My take on it anyway.

[nafets]

Thanks heaps guys! Btw is the dew point temp. the temp. at which the air cant hold anymore water therefore is condenses?

[Meso]

I think you're right there, nafets. It's a measurement of the moisture in the air. The closer it is to the actual air temp the more saturated or humid the air is. If it's the same as the air temp then you will have some form of condensation.

[AUS_Twisted]

Anyone can make their own "mini" updraft just by boiling a kettle and watching the air / steam rise fast which the steam then falls back to the ground like rain The water to surrounding air temp difference is a bit extreme to what happens with a storm but you get the idea. A volcano eruption created storm would be a bit closer to that.

[Meso]

Haha, I've actually thought a similar thing getting out of the shower and looking at all the steam. Have thought to myself "I'm basically in a cloud here". The air coming from the shower is a lot warmer and moister compared to the bathroom, so you end up with condensation.

Hmm, talk about being a weather nerd.

[TheFishmanAU]

It has been a while since we broke 35, so I am not complaining but I have a feeling that something severe is about.

Each time I see more than one contrail during the day, thunderstorms are about. I saw one and another really large one this morning.

[Jake Smethurst]

Heat does certainly appear to be a feature for the coming few days. Anticipating 35 degrees here tomorrow and then 37 degrees on Saturday, before yet another hot 34 degree day on Sunday. For Melbourne I think similar, although perhaps remaining at 35 degrees on Sunday depending on cloud cover. Moisture also increasing across the state later Saturday and during Sunday ahead of the trough which will reach the southwest late Sunday. Areas of most interest for thunderstorm development on Sunday I think will be about the ranges and in the west/southwest closer to the trigger system. I also, Fishman, have noticed very defined and long lasting contrails over the past couple of days, indicating that the upper levels are fairly moist. Further on, areas of rain on Monday as the trough moves through will occur. Thunderstorms again, mainly in the north and east and through some central parts. Will be interesting to watch. I've updated all AWF forecasts as well.

[93ben]

I wonder this is the same sort of weather pattern that we had on Christmas day. Even though there have been storms in recent days here, they haven't been really exciting. Hopefully we get something big out of this system before summer ends!

[johnno]

Yep EC and ACCESS have the heaviest falls over Central Victoria with this system which has been the trend by both these models past several runs