Andrew Watkins

G'day john,

Matt Wheeler said you might have been interested in the email I sent
to him and others earlier - please see below and the attached image
for Fawkner Beacon.

Also..
According to Ken Dickenson (sp?) in the Age online, max
gusts on "the bay" (don't know where) were 122km/h.
According to Blair.. Melbourne was the only site in the
western 3/4 of the state (ie west of East Gippsland)
NOT to receive rainfall last night!
The 22.9 I mention below is from my records, gained from
grabbing the public obs ever 10 minutes. A check of ADAM
shows 23.1, so yes, it did spike higher momentarily.
Doesn't change the timing much though.. see the attached image
of the temp trace for yesterday. And notice the diff between
the mean and median..

Andrew.
---
Dr Andrew B Watkins
Climate Analysis and Prediction
Australian Bureau of Meteorology

-----Original Message-----
From: Andrew Watkins
Sent: Tuesday, 3 September 2002 9:02
Subject: winds

G'day All,

Anyone who thought it was windy last night is right... Fawkner Beacon had a peak 1-min gust of 52 knots, and
a 10-min av peak of 46 knots, at around 11:15 last night, at least according to my 10-min grabs. See attched wind
graph,

or go to the bay page of course... http://www.earthsci.unimelb.edu.au/~awatkins/bay.html

Also...
No rain for the Melb gauge (but would we expect otherwise this year??), however there was some rain about as my car in
Parkville (~4km from city gauge) was covered in red-dirt mud (and not from a recent mountain bike trip either, for a change,
rather from the dirt in the precip). Melbournes max temp looks like it occurred at around 11:10pm, with a 22.9.
Melbounre eh.. cant beat it!

Cheers,
Andrew
 

John McBride
Subject: [synoptic_discussion] Back on board: fronts, dust and seafog

Gedday all,
 I am back at work after a a little over two weeks' off and raring to get back at my old adversary, the atmosphere.  It had a bit of a victory
during my holiday as the rain managed to follow the lovely Patricia and I up through central NSW, sit over us  as we looked at it through the window
of a Surf Club on the beach at Surfers; then follow us down through Coffs Harbour to Sydney.

Anyway, a couple of interesting things going on.

1.  We had a terrific front through Melbourne last night, with a 52 kt gust at Fawkner Beacon and a 10 minute average peak of 46 kts (thanks
Andrew Watkins for the info).  There was a truck blown over on the West Gate Brdige and I had trouble getting back from my brother's place in
North Melbourne.  He only lives a few blocks away from me but there was a tree down in Molesworth Street and another one in Chapman St, both
blocking the road.  I'll put some charts up on my web-page tonight; but one interesting aspect is that the cars in the Streets of Melbourne today
have a layer of red-dust on them This was presumably deposited in the cold air after the initial change.  The last time we saw that was in the two
consecutive fronts (dust storm and Ash Wednesday) of the 82-83 El Nino.... anyone know anything about soil moisture out there?

2.  At morning tea this morning Peter Steinle mentioned he was out sailing on Sunday and experienced another sea fog over the Bay....... Hopefully he
will write a paragraph or so on it for this discussion.

 Talk to you later

John McB

The promised charts:
24 -hour wind-temp (maptool loop) over Victoria:  maptool_loop.gif

Blair Trewin

1.  We had a terrific front through Melbourne last night, with a 52 kt gust at Fawkner Beacon and a 10 minute average peak of 46 kts (thanks Andrew
Watkins for the info).  There was a truck blown over on the West Gate Brdige and I had trouble getting back from my brother's place in North Melbourne.
He only lives a few blocks away from me but there was a tree down in Molesworth Street and another one in Chapman St, both blocking the road.
I'll put some charts up on my web-page tonight; but one interesting aspect is that the cars in the Streets of Melbourne today have a layer of red-dust
on them This was presumably deposited in the cold air after the initial change.

*****

It was actually a bit earlier than this - I drove through a brief shower in the Fairfield area around 9.30 (a couple of hours before the frontal
passage) and my car had a substantial dust cover afterwards.

*****

The last time we saw that was in the two consecutive fronts (dust storm and Ash Wednesday) of the 82-83 El Nino.... anyone know anything about soil
moisture out there?

*****

I've seen dust on cars somewhat more regularly than this (probably about once a year), although last night's deposits were probably the heaviest I've
seen since moving here in 1994. (Also not quite sure how much of the major Mallee duststorm of Easter Thursday 1997 - which I got to experience in its
full glory en route to Mildura - found its way as far south as Melbourne).

Blair

John McBride

On Tue, 3 Sep 2002, Blair Trewin wrote:

>
> I've seen dust on cars somewhat more regularly than this (probably about  once a year), although last night's deposits were probably the heaviest I've
> seen since moving here in 1994. (Also not quite sure how much of the major  Mallee duststorm of Easter Thursday 1997 - which I got to experience in its
> full glory en route to Mildura - found its way as far south as Melbourne).
>
> Blair
>
>

This is interesting.  In the 82-83 events, the dust layer was definitely in the cold air, as can be seen in the pictures of the clear visualisation
of the density current structure, the cold air being marked by the dust.
I have seen the same thing since: Some years ago (in the 90's sometime)  I was driving back down the Hume Highway on a Sunday afternoon and saw a
summertime front come in over the ci ty below me: F rom the distance and perspective of the hills above the city, I could see a clear
density-current type dome of thin dust coming in with the summer-time front.

>From Blair's evidence, last night's dust deposition was actually before the front.  Still, the question is: where does the red dust come from?  In
the case of it coming with the northerlies, it is blown down from northern Victoria: In the density current/cold-air situations, presumably it is
picked up in the cold air directly west of us, and advected along in the air immediately behind the frontal boundary.  It is possible it is picked
up in the northerlies ahead of the front back in the Mallee (northwest Vic) and somehow entrained into the cold air through the frontal boundary.
This seems unlikely simply by analogy with haboob type outflows of thunderstorms which visually are very similar.

Anyway... here is something for us to watch for and keep records of..... From now on, let us know whenever you get a layer of red dust on your car
in Melbourne.

Cheers

John McB

Bill Wright

One report...

Three years ago (Sept 1999) I was in Tasmania with the family. On the east
coast, near Freycinet Peninsula, we experienced light rain that was heavily
laced with red dust, leaving a good coverage on exposed surfaces. There was
a strong northerly wind blowing, and I presume the dust came from the
mainland, where much of South Australia had experienced a very dry nine
months prior to September.

By the way, there was a very good map of dust-storm frequency published in
"Search" by an N.J. Middleton in 1984.

Cheers

Bill W.

Harald Richter

Hi folks,

Here's my take on the MEL dust:  Soil moisture upstream of the pre-frontal MEL
atmosphere (NW VIC) is very low giving us a dusty (powdry) top soil layer.
Strong surface winds picked up the powder, distributed it mechanically
througout a deepish boundary layer, and advected that BL with
the mean NW BL flow over MEL.  There, our standard high-based showers
rained very few raindrops through a BL with plenty of dust, giving us
a proficient dust/water ratio.

Does this fantasy paragraph square with the FIRST observation of
dust-on-cars?

Harald

John McBride

Date: Thu, 5 Sep 2002 00:41:21 +0000 (GMT)
From: John McBride <jmb@BoM.GOV.AU>
To: synoptic_discussion@BoM.GOV.AU
Subject: [synoptic_discussion] Melbourne wind event of 2 September
 

Walking to work from Nth Melbounre this morning provided a strong visual
reminder of just how major an event last Monday night's wind storm was.
All along the streets on the way in we passed cordoned-off areas around
downed trees; and on four or five occasiosn we were passed by trucks with
their trays loaded up with downed trees and branches.

John McB

Elly Spark

Date: Sun, 08 Sep 2002 13:19:46 +1000
From: elly spark
Subject: Re: [synoptic_discussion] Dustt-on-Snow

Hi all,

While at Persisher Valley last week, strong to gale force northerly
winds on Tuesday, Very obvious dirt-on-snow Wednesday morning. I assumed
it would have been blown in from the NSW Upper Western, ie back of
Bourke. Very dry up there, with blowing dust being reported fairly
regularly of late. Looking at last Monday's charts, your Victorian dust
may also have originated there in the northerlies ahead of the previous
front on Monday.

Be interesting to find out if any red dust was reported on the NZ
snowfields?
 
 

--
Elly Spark