Gedday,
I feel we should discuss Wednesday's record rainfall event. I haven't had much of a chance to look at the structure yet. I'll do that this afternoon.
To get the discussion going,
I'll make a call here for people to report significant aspects of the event.
From the TV news, I know
it was a record 24 hours rainfall for Melbourne, with 120 mm being recorded
for the 24 hours ending 9am Feb. 3. I also hear it is the coldest
Melbourne February day for so-many years (more info please?)
Again from the TV news, I hear it is the first February hail event in Adelaide for 27 (?) years... more info?
There was a major dust storm
in Brisbane following the front (same front?)...... any info on visibility,
how widespread... how unusual etc on the dust storm./... I assume it was
a cold-air dust-storm that came in with the density current nose structure
of the front... Is this true?
As I said, I haven't had a chance to look at the structure yet... I'll do that this afternoon. Still, I'll put up a couple of interesting things on the web-page:
First, some F160's. The F160 for Melbourne at 2300 2 Feb UTC has the tropopause at 500 hPa. This is almost certainly associated with the tropopause dip in the centre of the system. Associated with this, the system has a warm core above that level, between the warm (in potential temperature terms) stratospheric air inside the tropopause fold/dip and the surrounding colder (potential temp) tropospheric air. This is consistent (thermal wind) with the winds you see along the right-hand side of the F160, with fairly rapid decrease with height above about 400 hPa.
I have also put up the My Gambier sounding which is pretty interesting. Look at the sharp inversion of about 15 degrees potential temp depth between 700 and 780 hPa. Yet the wind structure is fairly smooth and non-changing through those depths. Does any one who was on shift that day or who has looked at the system have any understanding of this feature.
I have put up a 24-hour loop of the temperature and windfield over Victoria from the automatic weather station obs.
loop1 On that you can see consistent 40 kt southerlies over the Melbourne/Port Philip Bay region through the night from about 1200 UTC 2 Feb to about 2100 UTC. Late in that period there are 30-40 kt northerlies over north-eastern Vic, showing both the strength and the small scale of the circulation.
Lastly, some rainfall analyses and model progs for the event (also on the web-page):
In general they underestimated the intensity of the event; but they weren't bad... you would have been expecting heavy rain over a large area.
This afternoon/Monday I'll pore over the charts and give a little web-page synoptic_discussion email as to why it happened. Though if any out there already understand it well, write us an email.
A couple more requests: in the corridors I have heard chat that the rapic images on Wednesday were such that Melbourne looked like it was in the middle of a tropical cyclone. That is interesting. A lot of what you see when you see the curved cloud bands on the radar screen for a TC is bright-band (I think.... Pete May, Jeff Kepert... correct me if I'm wrong???) Anyway... did anyone save the images or know how to extract them? Please send me a loop of Melbourne radar images.
Second request: tell us a bit about what happened in the other States: South Oz, New South, Qld. Damage/impacts plus meteorology.
Cheers
John McB
Rain graph for melbourne (ctsy Andrew Watkins)
Date: Fri, 4 Feb 2005 15:07:17 +1100
From: Brian
Taylor
Subject: RE: [synoptic_discussion] 3 February 2005:
South- East Australia record rainfall
event
John
I believe Blair Trewin has found that Melbourne was not
a record
unrestricted 24 hour rainfall (129mm?) but a record 9am
to 9am (1-day)
record. Whatever.
Brian T
Robin Hicks
Date: Fri, 4 Feb 2005 16:20:01
+1100
From: R.Hicks
Brian, Blair,
If you are trying to compare unrestricted 24 hour periods,
the 6am to 6am
rainfall was 124.6mm and 7am to 7am 127.4mm
More detailed analysis between 6am and 7am might get
a peak that gives the 129mm a nudge.
Robin Hicks
a/National Manager, Fire Weather and Air Quality Services
WOSPB, Bureau of Meteorology
Date: Fri, 04 Feb 2005 15:19:11 +1100
From: Paul
Fox-Hughes: Tasmanian severe weather
Hi John
v. quickly, cos I'm late for various things,
very sig wx day Tas Wed. night into Thursday due the low,
as well.
I'll put some documentation up, prob Monday, wx permitting:
damaging winds n/ne Tas Wed night/Thur morning (Devonport
Apt @5:523 am Thu was sse 46/59 kt,
etc) and sig flash flooding e/se coasts during Thur,
due the rainband
Cheers
Paul
From: "Mike Willmott" Storms, Dust and Lake Eyre
>Hi Again,
>
>Lee has provided some more imagery. If you go
to
>http://image.ho.bom.gov.au/apps/sigevents/current/
(internal Bureau only) you will note
>that the passage of the frontal system which produced
all the weather in
>SE Australia also produced quite a bit of dust in Queensland.
>
>Regards,
>
>Mike
Date: Fri, 04 Feb 2005 15:53:22 +1100
From: Milton
Speer
John,
Looks like the duststorm was mainly a postfrontal
event (quite spectactular really over Lake
Eyre almost emanating from a point source there).
I've put together a loop of images based on the GOES9
volcanic dust enhancement algorithm of
Andrew Tupper/Rod Potts at http://www.nsw.bom.gov.au/web/rfc/servdev/dust_2feb05.htm
(just
click on 'first' at bottom to bring up first image then
click 'play' ).
Milton
Date: Fri, 04 Feb 2005 14:55:54 +0930
From: Andrew
Tupper
Milton, that's a heck of a sequence - there are some false
alarms caused by low level
temperature inversions, but the Lake Eyre dust storm
is amazing. I wonder how far afield Lake
Eyre salts can be found?
Andrew
Date: Fri, 04 Feb 2005 17:11:45 +1100
From: Milton
Speer
Andrew,
Washington, Todd, Middleton and Goudie 2003: Dust-Storm
Source Areas determined by the
Total ozone Monitoring Spectrometer and Surface Observations,
Annals of the Association
of American Geographers, 93(2), pp. 297-313,
mention that the area of greatest duststorm frequency,
as determined from met. station
data, has been shown to be broadly coincident with the
huge (1.3 million km**2)
internal drainage basin of Lake Eyre.
I'd guess the raised dust would actually be a mixture
of salt and other drainage basin
fine sediment.
Material raised by the frontal systems is occasionally
transported as far as New
Zealand (pre-frontal) according to ,
Collyer,Barnes,Churchman, Clarkson and Steiner 1984:
Trans-tasman dust transport event,
Weather and Climate 4:42-46.
Dust haze from the Lake Eyre basin in the southeasterlies
over the Kimberly is quite
believable.
Date: Fri, 4 Feb 2005 16:01:27 +1100
From: Robin
Hicks
One interesting feature was the rapid deepening of the
low over East
Gippsland on the Wednesday evening that best shows up
in the hourly obs for
Bairnsdale Airport. Pressures fell by nearly 8hPa in
two hours and the
marked change in direction of the strong winds suggests
the centre moved
westwards over the site between 9 and 10pm, and
then over Sale after 10pm
Bairnsdale
03 01:00 12.0 7.5 74 N 24 13 33 18 988.9 61.0
03 00:00 13.1 9.2 77 NNW 22 12 31 17 989.6 60.8
02 23:00 13.7 11.8 88 N 26 14 35 19 989.4 60.4
02 22:01 14.6 14.1 97 N 35 19 54 29 987.7 60.4
02 21:00 16.1 15.3 95 S 59 32 81 44 987.4 59.6
02 20:00 14.6 14.3 98 S 61 33 81 44 990.1 59.4
02 19:00 14.0 13.7 98 S 44 24 57 31 995.1 56.0
02 18:00 14.2 13.9 98 S 35 19 52 28 996.4 50.0
02 17:00 13.5 13.2 98 SW 17 9 22 12 997.5 38.8
02 16:00 13.4 13.1 98 WSW 20 11 30 16 998.8 22.6
02 15:00 12.4 12.1 98 SSW 20 11 26 14 999.0 18.8
East Sale
03 01:00 13.1 9.9 81 N 18 10 26 14 988.1 42.4
03 00:00 - - - - - - - - - -
02 23:00 - - - - - - - - - -
02 22:02 14.9 14.7 99 SSE 63 34 76 41 987.9 37.0
02 21:00 14.3 12.7 90 S 52 28 74 40 990.6 32.0
02 19:58 14.0 12.9 93 S 41 22 59 32 993.5 31.0
02 19:04 14.2 12.9 92 S 33 18 57 31 996.4 27.8
02 18:00 14.3 13.2 93 S 28 15 43 23 997.8 24.2
During this time of intensification, the SE winds at Hogan
Island (In Bass
Strait E of Wilsons Prom) picked up markedly, reaching
sustained mean speeds
of 63kts and at 3am the wind was gusting to 76kts
Hogan Island
03 05:00 11.7 11.3 97 NE 46 25 54 29 988.9 39.4
03 04:00 14.4 14.3 99 ESE 105 57 128 69 984.9 37.8
03 03:00 15.8 15.7 99 SE 117 63 141 76 984.2 28.8
03 02:00 14.6 14.5 99 SE 117 63 139 75 984.2 27.2
03 01:00 14.3 14.0 98 SE 111 60 131 71 986.1 24.0
03 00:00 15.0 13.1 88 SE 113 61 137 74 988.6 22.6
02 23:00 14.4 13.8 96 SE 105 57 133 72 990.9 22.6
02 22:00 13.8 13.5 98 SE 91 49 113 61 992.9 22.2
02 21:00 13.5 13.1 97 SSE 91 49 115 62 995.3 18.4
02 20:00 13.0 12.3 96 SSE 80 43 96 52 997.1 14.2
02 19:00 12.9 11.5 91 SSE 76 41 87 47 997.9 12.8
Re the radar imagery, as the rain band cleared Melbourne
to the west on
Thursday morning there was a marked line of intense echoes
on the rear edge
forming an arc.
Robin Hicks
a/National Manager, Fire Weather and Air Quality Services
WOSPB, Bureau of Meteorology
John McBride: radar imagery.
Courtesy of Tim Hume, I have the Melbourne radar imagery for that day: Now on my web-page, at the bottom
Melbourne radar movie loop
Date: Fri, 04 Feb 2005 13:09:48 +0800
From: Noel
Puzey : Yellow Fog in the Kimberley
For those interested, much of the Kimberley yesterday
(3rd Feb) and this morning have reported
"yellow fog", "smoke haze but no smell of smoke" or "dust"
. I think it is likely to be the
suspended dust from inland Australia raised by the cut
off event travelling in the SE flow
over northern WA - looks like about half of Oz was affected
by the dust.
Noel
Peter May: Bright bands on
radar
Date: Fri, 04 Feb 2005 16:19:50
+1100
From: p.may
Subject: Bright bands in TC's
John,
as we discussed, because the fereezing level is
so high (~ 4 km or more)
in a TC, most of the radar images you see are not affected
by bright band
that much. For a 1 degree beamwidth radar, you
wan't have any part of the
main lobe of the beam intersecting the bright band until
the range is ~ 150
km or more (for wider beamwidths its a bit closer).
For the storms here in Melbourne over the past few days,
the freezing level
and therefore brightband were much lower, with brightband
evident down to
about 1 km so the radar images (particularly on
the public web) were very
affecteded by the bright band,
regards,
peter
Rob Webb: Radar-derived rainfall
accumulation
Hi John
Not sure if this has found it to you yet but attached
is the 24hr
radar-derived accumulation from Alan Seed's Rainfields
system. There are
some problems there that Alan Seed might like to comment
on (some bright
band contamination?)
Melbourne to 9am 3 February
Sydney 2 Feb
There should be some interesting applications, particularly
when we run the
system on the new Dopplers. As a contrast I attach the
accumulations from
the Sydney supercells of this week.
For info, realtime images can be found at
http://comms2.bom.gov.au:880/radar/rainfields/
(Internal Bureau only)
Thought you might be interested.
Rob
Alan Seed re: Rainfall accumulations:
Date:
Sat, 5 Feb 2005 11:33:35 +1100
From:
Alan Seed
Rob, John
The very high accumulations
in the west are likely to be due to bright band-
radar returns from melting
snow. The problem came about because there was
very little rain close to
the radar which I use to estimate the magnitude of
the artefact so I was not
able to correct for a period of about an hour.
The high returns are the
hills, this should be fixed with the new radar but
in the mean time and in
a parallel universe where I have more time I will
need to finish the QC for
the existing radar.
Alan
Satellite loops:
Gedday again,
I have put on the web-page
(about half-way down) an enhanced IR loop of the event grabbed
from the realtime DIFACS.
A couple of comments:
a) One thing that is impressive
is the blow-up of convection along the east coast at about
1000 2 Feb UTC. It looks like some
sort of interaction whereby a dry adiabatic layer
over-rides a warm-moist boundary
layer. I haven't had a chance to look at the flow fields
yet; but no doubt, those on the
bench in NSW (using the Meso-viewer) already have a good
knowledge of this aspect of the
event. Could someone send us a couple of graphs and a
paragraph on what happened here?
(Harald?)
b) I was a little late getting to
DIFACS, so my loop begins at 03Z on the second; so I miss
the genesis or development.
Did anyone save same enhanced images for the previous couple of
days (Tim Hume?) or know how to
quickly extract them?
Thanks
John McB
Satellite Loops:
Victoria
Australia
Date: Fri, 04 Feb 2005 15:51:44 +1030
From: Jenny
Dickins
At 03:51 4/02/2005 +0000, John McBride wrote:
> Again from the TV news, I hear it is the first February
hail event in Adelaide for 27 (?)
> years... more info?
Always risky to believe everything you hear on the TV!
Yes, the cold air Cb produced a number of hail showers
in various Adelaide suburbs during
Wednesday (2/2/05), although not here at the Regional
Office (Kent Town). Cold air hail in
Adelaide in February is pretty rare, but it is very hard
to determine just how rare.
Our records show that the last time hail was observed
at Kent Town during February, was 28
years ago, ... 21 February 1977 ... a warm 30C day with
afternoon thunderstorms with very
heavy showers and hail ... definitely not cold air hail!
Interestingly, this day was just a
couple of weeks after the office moved from the West
Terrace building.
People have already pointed to some spectacular images
of the dust ... here is a loop of
visible images showing the beginning of the event on
Tuesday afternoon (1/2/05) ... put
together by Martin Crowe.
http://www.sa.bom.gov.au/~mcrowe/animate/DU010205.html
My overwhelming impression from sitting on the periphery
of this system, was that the NWP
guidance has been excellent, and from 4-5 days out, right
through the event and in the
aftermath, Bureau services have been top class.
regards
Jenny
*************************************************
Jenny Dickins
Meteorologist, Radar Services and Training
Bureau of Meteorology, Adelaide
Jon Gill
Hi John,
there were lots of very interesting aspects to this event
and I'm not sure
where one could start in discussing it. Some of the records
broken are
provided at
http://aifsa-vic.bom.gov.au/rgn/vccs/special_events/feb2_3records.html
put together by colleagues in the Qld Climate section.
Melbourne's official
maximum ended up above the record lowest due to the temperature
rising prior
to 9am. Certainly, all through the previous day, a new
record was looking
good with the temperature hovering around 12-13C. See
the attached graphic
from Andrew Watkins' site.
A notable feature evidenced by the radar imagery was the
uniformity of the
returns over a vast area. In fact, I recall noticing
that the echoes formed
a continuous sheet over the entire radar range, with
the extremities of the
precipitation field beyond the range of the radar in
all directions. In
otherwords, a solid disk across the whole display. This
was on the 256km
range setting. There was little evidence of significant
embedded convection
anywhere, although there was some lightning activity.
The main source of
inhomogeneity in the radar pattern was the bright banding
that painted a
yellow circle around Laverton. The whole thing looked
like a giant blue and
yellow fried egg.
Cheers...Jon
John McBride_ airline chaos
> Date: Fri, 4 Feb 2005 15:34:00 +1100
> From: a.wain
> hi john
>
> I'm still in sunny Qld, you obviously got your flight
home OK. A freind of my wifes was
> travelling back from Sydney to Melb around the same
time you were heading back. After a 3
> hr delay they were on descent into Melb when they got
diverted to Adelaide. He got home at
> 11 am the next morning!........[SNIP]
>
In case anyone is wondering... YES: I/we did make it home
on Wednesday night. My initial
email was from the Qantas Club lounge at Coolangatta,
where I was trying to figure out what
was going on by plugging my laptop in to the phone/internet
line in the Qantas Club and
looking at the Bureau external web-site.
After that, I went for a walk and saw an attractive Qantas
female employee sitting at the
Q-club reception desk. She, being attractive, and
me being me... I stopped and chatted. When
talking about the weather and why our plane wasn't there
yet, I mentioned the radar images.
It was then I learned something about the Qantas club
that you should all take note of.
The attractive female (Hence known as AF) had the current
rapic loops for Sydney, Melbourne
and Brisbane available in open windows on her desktop.
I wandered around behind her desk and
we looked and discussed and had a great time while I
explained the images to her and showed
her where the time stamps are so that for line convection
she can extrapolate the past
movement to forecast where the system will be and
so on and so on. We were sitting there
almost on one another's knees having a great time with
the radar until the lovely Trish
wandered around looking for me... and that as the end
of that.
Our plane did take off at about 8.30 Coolangatta
time. We landed in Melbourne around 11.40
pm Melbourne time in heavy rain and with a 35 knot westerly
at the ground. The landing was
actually pretty smooth; so I was quite impressed by the
skills of the pilot, as I was by the
skills of the taxi driver who subsequently got us along
the rapidly flooding Tulla Freeway to
our home in North Melbourne.
So: remember that tip about the Qantas Club.
cheers
John mcB
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