Interesting jet streams over eastern Aus tomorrow.

[Capt NG]

Not unusual.. But can get quite choppy.. Salty, discovered a tip, look for the temp variation to ISA on FMC. If it changes more then 2 degrees over 60 seconds it indicates a shear zone.. More inclined to get moderate CAT in this case..and of course on the pole ward side of the jetstream..

[Nillus]

Oooo...good to know!
Ta!

[Adam the Akrodude]

So what we're looking at is a jetstream looping around southern Australia? That does look weird! You've got some Cb action as well huh? Obviously I've never seen a weather chart like this, never getting anyway remotely near even 10k feet! Fascinating to see the sort of weather you guys need to contend with and plan for.
Think I'd be passing on the in flight coffee!

Cheers

Adam

[Capt NG]

The Cbs don't have allot of vertical development because the level of the tropopause at this time of year is lower. The west to east jetstream is pretty common for this time of year and will stick around for most of he the winter period now. The jet stream coming up from the south and looping around probably has something to do with the cold front passing the region as we speak..

CAT is more pronounced on the poleward side of a jet stream due to the flow around the core. The shear zone is typically indicated by changes in temperature as warm air from below the core gets brought up in rotation to the higher part of the core, that was what I was telling salty about.. But he probably already knows this anyway. Progress page 2 of the 737 FMC displays temperature and ISA deviation. Hence can be used to predict areas where CAT is encountered. Salty check your ISA deviation next time your in CAT.. It'll be up and down.

[Nillus]

We have a continual Delta ISA/SAT/TAT readout on the Engine/Warning Display.
I was in +\- 400 fpm standing wave activity west of Mumbai the other night. SAT was varying -49 to -51.
I use SAT for the same purpose as you. If I see a rapid change(4 degrees) I put on the signs.