Topic: NSW/Qld Severe Hailstorms then Cold/Snow: 19 to 22 of October 2008

[nmoir]

i chased the cells which formed west of lithgow and headed east and dropped 3-4cm hail (report from michael bath) in blackheath.
i lost site of them as the high based storm passed over the boundary of cool moist south easterly cloud

pictured firest is the anvil in top of frame , in lower part you can see the edge of the low cloud and cells to my south
second is the storm when it was around bell

[James]

Blackheath Storm - 20 Oct, 2008

Went for a chase on the Central Tablelands this afternoon. Based myself between Lithgow and Bathurst from around 3pm expecting a late starting day.

Some nice cells formed over the Wollemi NP however no chance of chasing them. I was hoping to catch a storm from near Bathurst back home. At around 4pm things started to shape up nicely. The dry’ish high based trough line was now closing in on Bathurst and low level moisture seemed to be increasing.

   

Sure enough some bases started to get their act together over Bathurst. I knew I had to head east quickly if I was to stay ahead of it.

   

Heading east it became obvious that the southern portion of the storm was becoming dominant. A lovely rippled base with nice towers above raced its way east gaining size and momentum the further it went.

   

   

The cell was now moving to the right indicating good organisation and most likely some rotation. I realised I was coming across the Blue Mountains with no chance of keeping up with it. South of Lithgow I encountered 1cm hail from the main core. Once past the trees and now in Little Hartley I was astonished to see a RFD on the south-western edge heading just south of the main highway.

   

At this point I called off the chase and positioned myself for the RFD expecting some ok hail. Majority of the stones were 1-2cm with the odd bigger one amongst them.

   

The storm continued on through the Blue Mountains and seemed to gain some size (Blizz's pics confirm this). Whilst looking for larger hail I noticed the continuous roar coming from above. The structure was now pretty impressive from the back end however there was no way of catching it.

   

[Jimmy Deguara]

Very nice James. That was where I was headed but I remained near Richmond and Kurrajong refusing and too lazy to budge until some interaction with moisture occurred. I was chatting to Nick on and off before I alerted him to watch that particular cell. But the speed it was travelling you need to be in Blackheath for a dead hit.

I took interest in the cell I had pass over Kurrajong area simply because of its crisp side anvil. You will see below that they were definitely too high!

The last picture shows my view of the Lithgow/Blackheath cell but it seemed to go downhill at this point onwards.







All photos for 20th October 2008

Regards,

Jimmy Deguara

[Steven]

Hi Steven,

No you are not missing anything really. I slipped Qld in to the title as I would guess there is a chance of storms in SE Qld on Tuesday and/or Wednesday. Latest GFS run actually looks a bit more promising in my opinion with a nice mid level jet (50knot max) nosing into the mid north coast and northern rivers areas. I expect some activity could spill over the border ranges into S Qld. Here's a forecast sounding from the Brisbane valley area-

http://soundings.bsch.au.com/skew-t.html?source=ncep&lat=-27.65&lon=153.1&date=2008102106&gribdate=2008101900

Not much CAPE but I think the temp and dew point temp will be higher the 23/15 plotted.

Michael

Hello Michael T,

From what I've seen in the latest GFS, things look far more promising for SE QLD on Tue/Wed. Seems GFS can never make its mind up ha ha. (Considering it was a different story on the last run)

I'm still learning about Skew-T's, but its all Greek to me mate. lol

[Michael Thomas]

I must say that I wrote yesterday off a little early before, that Blackheath storm was actually quite interesting. Some pretty solid hail there from such a small storm. The Sydney sounding is unusual, the coming off the tablelands must have really been elevated since the boundary layer was stable and strongly capped.

It seems that things are lining up quite nicely today. Mid-level flow should be around 30 to 40 knots over much of the northern rivers and S Qld. I expect NE winds should develop along the coast and into SE Qld. Therefore shear should be quite adequate for organised storms including supercells. Interestingly, the moisture has been quite poor in NE NSW and SE Qld with dp's struggling to get past 10C despite the onshore winds. Fortunately, in the 12Z Brisbane sounding dp's had increased about 5C to 15C. Also, last night dew points along the coast in the northern rivers were getting up around 16C. This is great news since it shows that the moisture is returning in time for today's storms. I suspect we should see some additional moistening tomorrow. Temps are forecast to approach 30C tomorrow away from the coast. Plotting on a forecast sounding for 30/16 gives around 2000 j/kg of CAPE and LI's around -7. In short if we see dp's in the mid teens or greater with good heating there should be plenty of instability. My guess for today is that we should see a couple of strong storms firing on the southerly change. I also think there's a good chance of a nice storm or two coming of the northern tablelands and border ranges. With the solid instability, steep mid level lapse rates and adequate deep layer shear I think that large hail will be quite probable with and any dominant storms.

Good luck to those heading out, hopefully today doesn't disappoint.

Michael

[Macca]

Hi all,

With the upper trough approaching today and the upper levels cooling, I cannot see the 50-100km coastal strip remaining as dry as it has over the last 24hrs.  I think we'll see the NE'ly pick up nicely late this morning as the (inland) trough deepens in response to the upper trough and drag moisture inland.  The vis sat pic currently shows a convergence line sitting off the coast - i'm wondering if that is possibly where the moisture is (east of that line).  Will watch it this morning and see what happens. 

Shear is definitely better in the NR's this afternoon with 15-20knts from the N-NNE at the surface swinging around to 15-20knts from the WNW at 850mb, 20-30knts at 700mb and 40knts at 500mb.  Concern is that the 850mb level is drying out (moreso over the NRs than SEQ) but given that 850mb is roughly 1450m ASL, even if the moisture was only 100mb deep (ie up to 900mb), it would be plenty on the coastal plains of the NR's and could give some beautifully structured storms, especially with the winds in the mid levels being half decent (first time this year).  As for the hail, if something can tap into that coastal moisture, look out!  As others have suggested, with quite cold upper level temperatures, very large hail is a definite possibility with any of the strong storms.

My current thinking is that storms will develop both on the S'ly change (near/off the coast) and along the ranges.  As the storms on the ranges move east, I would suspect they will only get better the closer to the coast they get given the increasing moisture in the lower levels (and hence increasing energy).  My play today will probably be the NR's.  Although the shear is better down there, it also runs the risk of drying out in the low levels. 

I think Brisbane will get a pretty decent show again tonight but probably not until later.  But with the cool upper levels, it should be quite a show. 

Macca

[Michael Bath]

Aside from the storms, there is a reasonable chance of some snow Wed evening on parts of the tablelands including southern parts of the Northern Tablelands and the Barrington Tops.  Walcha area and even up to Guyra is possible according to the latest GFS. 850 temps will be around zero and with some decent moisture into the forecast period.

[David C]

a similar storey has appeared in the Brisbane Times too 20/10/2008 under the heading "Supercells spark tornado fears", Brisbane times by Andrew Wight - 6.48 am.

I don't recall seeing storey headlines warning the public of the potential for supercell thunderstorms. The article takes it one step further by stating that supercells are expected to sweep into Brisbane tomorrow from the Darling Downs and Northern New South Wales bringing torrential rain and strong winds.

The article similar to the one posted above states that conditions will be right for formation of supercells and even states that there is the possibility of tornadoes.

It's great to see the BoM slowly getting the correct terminology out there, although 'SUPER'cell is a potentially very tantalising term for the media and begets sensationalism!

Just on today, the mid-level lapse rates are around  7.6°C/km (GFS forecast sounding that is)-- sustained updrafts, supercells,  that develop in relative isolation would be expected to produce some very large to giant hail.

 

[Jimmy Deguara]

David,

Just on today, the mid-level lapse rates are around  7.6°C/km (GFS forecast sounding that is)-- sustained updrafts, supercells,  that develop in relative isolation would be expected to produce some very large to giant hail.

I guess you could be correct but the storms would have to develop explosively and tap into the low level moisture. West winds at 850 and even lower are depleting moisture levels in the Northern Tablelands. This was the issue yesterday and the moisture in the Northern Rivers seem to be relatively lower than normal for this time of the year and with such systems. I bet there will be an LP or two if something can sustain themselves along a boundary.

The best conditions seem to favour the critical time around sunset.

Regards,

Jimmy Deguara

[Ben]

Yet another day where I would have loved to have chase., but again university is in the way (couldnt chase yesterday either). I would have personally picked the Kempsey/Coffs Harbour region today, due to distance generally.. otherwise I would have like the Evans Head/Lismore region later this afternoon. At any rate, Kempsey and Coffs seem to be getting a hammering. Crescent head probably just got thwarted by large hail. Look forward to seeing pics/reports by people!

[Macca]

Hi all,

Currently in the NR's (20km N of Ballina) heading S to somwhere...hehe.  Massive cells to the south - HUGE overshoot on the storm just north of Coffs (although its flattened out over the last 5 minutes - actually its just gone nuts again - massive dome on the back end of it...I mean MASSIVE).  Weaker stuff (visually and per radar) north and west of that stuff but I think that will intensify over the next few hours as it moves into the areas east of the ranges. 

I think the Lismore corridor will play out nicely later on in the day (2 hours time) and I can see us (myself and AC) playing around down here for the rest of the afternoon and hopefully then following storms back up to Brisbane later this evening!

Macca (& AC)

[Richary]

Had just noticed the storms there on the radar. The one off the coast of Nambucca looks nasty indeed. Also just got a picture message from Woolgoolga and spoke to someone there. Lots of golf ball sized hail with some larger. One schoolkid got knocked out apparently and at least one car window shattered. Also punched a hole in her outside table.

[David C]

Good luck Macca and Anthony.

I like the positioning of the cell NW of Grafton atm, but still early days


Anyway,


For people in the
NORTHERN RIVERS,
NORTHERN TABLELANDS and parts of the
MID NORTH COAST Forecast Districts.

Issued at 3:20 pm Tuesday, 21 October 2008.

Severe thunderstorms are likely to produce giant hailstones, (hail upto the size of Golf Balls), very heavy rainfall, flash flooding and damaging winds in the warning area over the next several hours. Locations which may be affected include Lismore, Grafton, Coffs Harbour, Armidale, Tenterfield, , Guyra, Casino, Kyogle, Yamba, Maclean, Woolgoolga, Sawtell and Dorrigo.

Golf Ball sized hail was reported from Woolgoolga just after 3pm, and large hail from near Crescent Head just after 2pm.

[David C]

New spotter report in and warning text amended. See below....

Issued at 4:05 pm Tuesday, 21 October 2008.

Severe thunderstorms are likely to produce giant hailstones, (hail larger than the size of Golf Balls), very heavy rainfall, flash flooding and damaging winds in the warning area over the next several hours. Locations which may be affected include Lismore, Grafton, Coffs Harbour, Armidale, Tenterfield, Guyra, Casino, Kyogle, Yamba, Maclean, Woolgoolga, Sawtell and Dorrigo.

Giant hail in the 6 to 7cm range, (Tennis Ball size), was reported from Woolgoolga, and large hail from near Crescent Head just after 2pm.

[Steven]

Indeed, very nasty cell. BOM is classing it as very dangerous.