Harald Richter

Synoptitians et al.,

For a third day in a row the cutoff over NW NSW/SE QLD is facilitating deep
convection in NSW and QLD. The cutoff has a very nice symmetric appearance, in
particular in the IR imagery.   YBCV, close to the low centre, shows a
low tropopause around 350 hPa. YCBT has northeasterlies througout the column,
and parcels taken from the shallow moist layer near the ground yield LIs
just shy of -4.  Despite yesterday's convection in the area, YMOR also
shows LI=-5 using the shallow moist layer near the surface as the parcel
origin.  Good stuff for day 3!

The main convective activity at 3:10 LT stretches from Nyngan (NSW)
through Moree into QLD.  A secondary area is centred around Williamtown.
On the surface the very light ENE flow turns into a southerly W of the line
in NE NSW.  This type of surface flow creates problems for good low-level
shear needed for storm organisation.

W.r.t. reports, was there a small tornado near Coonamble yesterday?

NSW/QLD ROs -- are you out there?

Harald

John McBride
Ah... Harald,  I wish you hadn't sent that message out -- I was actually
getting some of my other work done today..... but, being the way I am, I
couldn't resist having a look at the current cut-off low.

                    Satelite image                                                                            500 hPa analysis

As you point out, its a beauty.  It stands out nicely on the new NMOC/GASP 200 hPa
jet-stream analysis that I have referred to in earlier emails.  The
windspeeds in the  subtropical jet has increased dramatically, almost
doubling over eastern Australia in the last couple of days (see images below).
According to my observations of a week ago (synoptic discussion 15 march) that
the sub-tropical jet at this time of year seems to lie up with the surface thetae front /dry-line, the
magnitude of the dry line should have increased dramatically in that
region  also, and looking at the GASP thetae charts, sure enough it has (see images below).
The IPV  loop for the past few days as the cut-off came up from higher
latitudes is  interesting also - revealing a strong tropopause dip and
lots  of  polar/stratospheric air in the cut-off (links to IPV sequence below).

JMcB

Jet Stream 200 hPa flow
                                25th 1200 UTC                                                                                                27th 1200 UTC

Corresponding Thetae analyses (colour-scale the same as per usual)

Links to sequence of 350K IPV analyses:  All 11 UTC;  24th March,   25th,   26th,   27th,   28th
 

John Colquhoun
Harald,

The severe weather forecasters are rather busy in NSW RO.

There was a damage report from Coonamble on Tuesday indicating that the
roofs of the motel and scout hall had been blown off. However, we did
not receive a tornado report.

Yesterday afternoon was interesting as there were a couple of supercells
to the east and SE of Moree that were the left movers of split pairs.

Sincerely,

John Colquhoun

Milton Speer
John/Harald:
There is a good subtrop jet over QLD but it's the line on the radar near Sydney
that is flash flood material for Sydney (see attached radar gif file ) and is
currently our concern up here..
This is a good example of a significant flash flood event in Sydney (flash flooding
reported from Windsor in Sydney's NW suburbs). With these type of events in Sydney
it's the mid-level vertical motion induced by uplift of moist east or
northeasterlies with drier northerlies or westerlies undercutting to produce a band
oriented NE/SW as indicated in the following figure:

A web description of Severe Sydney Flash Floods is given here:
http://www.nsw.bom.gov.au/web/rfc/servdev/syd_ffs_web.htm

Cheers,
Milton