Topic: Saturday 25th February 2006 Sunday 26th February 2006 storms

[Jimmy Deguara]

Hi,

Once again the Sydney region is in for some action. Instability ofr Saturday is marginal but sufficient for some strong storms moving near or into the Sydney region from the west. Perhaps some lightning and rain during the night.

Sunday is looking better with cloud band clearing and storms developing behind. Instability is sufficient for strong to severe storms given model CAPEs of 1100J/kg based on the 12Z GFS data. The latest 00Z data has dropped this to 600J/kg but this still is suffucient for strong to severe storms. Being local activity, it should provide some action for those storm starved Sydney siders!

The focus for development is a combination of an approaching upper trough and southerly change.

Regards,

Jimmy Deguara

[Beatart]

Hey Jimmy,

At around 6pm today (Sunday), there appeared to be a small storm heading North East towards (or just to the south) of Camden. A few rumbles were heard but has now died out. There now appears to be a line heading North East stretching from just South of Jenolan to Nowra. I hope this bring some well needed rain (and of course some action!!!!!)

My AVN plotten program has somehow been lost in the computer upgrade so I can't tell the Cape & LFTX but here's hoping it's good!

Justin.........


P.s. Just got some more rumbles as I went to submit, which I gather are from the new line approaching!

[Jimmy Deguara]

Hi Justin,

I got some timelapse from the earlier storms near Richmond and then this developed further due to interaction of the SE to NE convergence line! Quite impressive as we had NE winds there and storms backbuilding though other storms to the S were slowly moving NE. I saw several cloud to ground lightning bolts decend from the anvil that was hidden by clouds - quite impressive.

Now we are in rainfall with the storms from the SW and another from the north colliding in the western suburbs.

An interesting day!

AvnPlotter is online now:

http://www.australiasevereweather.com/links/gfs_avn_help.htm

Regards,

Jimmy Deguara

[Jimmy Deguara]

Hi,

This is a more detailed chase plan.

I chased locally - I waited until late afternoon as was the plan. An interesting base developed near Richmond which acted odd compared to other activity or let's say anticipated activity based on the models. This was the key that set the scene for conditions we experienced. After a little timelapse of this I headed into the mountains Bell Line of Road briefly but no opportunities to film the nice base and updraft west of Mt Tomah so I headed back immediately near the Sydney Basin.

I saw an impressive line of convergence. I timelapsed the same storm from the back which was slowly intensifying but also backbuilding to a stationary position in the area. With the storm raining on me from the west, I headed down to near Richmond. The storm here was quite impressive so I began to film briefly.I noted NE winds at my location knowing that winds on the other side would have been SE.

Whilst filming, a double major bolt descended through the cloud from the top of the updraft and most likely the anvil. The danger in these bolts is they seemed to come through the mid-level cloud. I set up tripod and captured some impressive video of multiple bright bolts coming from this now impressive updraft and anvil through the mid level cloud as well. The upraft gradually became obscured by the mid-level cloud so I aimed for the southwestern activity.

I knew we were in for flash flooding rain rates from this event based on the behaviour of the cells being slow moving. More lightning bolts to the south and I headed for those storms but they were sparse. Finally I set up for the region near Agnes Banks where heavy rain hugged the mountains. From here I headed home.

During the night we had heavy rain for about an hour which is definitely the heaviest rain we have had for about a year! Cell upon cell developing rapidly overhead. We were always situated near the convergence line with a few cells to the west of the convergence moving south early on and colliding with the line from the southwest. I suspected a surface low may have developed.

2 maps below showing most of rainfall fell during the night period. Maps courtesy fo the Bureau of Meteorology.

My official reading this morning for the previous 24 hours is 91.6mm which is in agreement with the 90mm I think which was Quakers Hill rainfall pluviometer. [Correction Jeff Brislane was correct in suggesting Box Hill rather than my thoughts on Quakers Hill. There is a pluviometer here but not included in the map].

Regards,

Jimmy Deguara

[Jeff Brislane]

I witnessed some serious flash flooding in Penrith last night as a result of the storms. High st was flooded up and over the footpaths on both sides as were many other local streets. Plus many of the canals in south penrith were at full capacity. I saw quite a few roads that had at least a foot of water over them.

[Jimmy Deguara]

Hi Jeff,

Being so flat, and I suspect due to some drains not being totally cleared, that region can flood quite easily. But it was fairly extensive flash flooding around western and northern Sydney. I would like to see some of your pictures Jeff as that would have been spectacular!

Grange Avenue also went under as one would anticipate. It had subsided by this morning of course.

Come to think of it, rainfall of the order of yesterday and last night would have a return period of approximately 1 in 2 to 3 years. I suspect that in such a short period though 1 to 2 hours which is where most of the rainfall was dumped, the return period must at least be 1 in 5 years! Last time we had rainfall total of that amount I think dates back to May 1997. I may require to check records.

Regards,

Jimmy Deguara

[Beatart]

Couldn't get out last night, but from home we only received 22mm. The light show to the North, North West was impressive but covered by low cloud from my point of vision making it near impossible for photo's.

I gather the Penrith area has power again Jeff? The reports on the news this morning said there was still local flooding and power black outs around the area.

Justin......

[Jeff Brislane]

Powers back on now. I couldn't get any pics as it was too dark and the street lights in Penrith were all out. Werrington creek at werrington flooded up to 2 feet above victoria st and 3 cars who tried to cross got stranded! They were still there this morning. Emu plains also had flash flooding with some homes inundated with stormwater.

I'll be interested to see how much rain Matt's guage recieved as I recorded a substantially higher total than Penrith AWS.

Penrith AWS got 54mm but Glenmore Park got 94mm. Box Hill also recorded a reading higher than nearby guages. I recorded a whopping 117mm which is double the AWS. This can happen though as a couple of kilometers can make a huge difference in rainfall sometimes.

[Matthew Piper]

I only received 68mm here, however Id say Glenbrook would have received a lot more as the highway was almost totally covered with water near the information centre. Whilst I was at church a number of close lightning strikes hit between 7 and 8pm with one particular one producing a deafening bang.

[Jimmy Deguara]

Hi Matt,

I like the way after this whole drought we are sugegsting "only received 68mm" haha That still is a significant fall of rain.

Regards,

Jimmy Deguara