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High Precipitation Supercell with Spectacular Mothership Mesocyclone Structure - NSW North Coast: Sunday 30th March 2003
Report by Michael Bath

On Chase: Michael Bath, Dave Ellem and Rodney Wallbridge.

Video clip by Rodney Wallbridge of the HP mesocyclone at its peak intensity [1.00 min - 3.59mb WMV]

Saturday evening I received an SMS from Anthony Cornelius asking if I was going to be chasing the next day. Prior to this message, and an earlier message from Jimmy about a likely chase, I had not even checked the AVN forecasts for Sunday due to other commitments on the day. It got me thinking that something big was likely, so I made sure it was going to be ok to head out for at least part of the afternoon.

Sunday morning revealed the extent of the setup: a very cold -43 C at 300 hPa and -17 to -14 at 500 hPa across the Mid North Coast and Northern Rivers. It was a little warmer in the Northern Rivers than the Mid North Coast at 850 hPa, which would help inhibit convection occurring too early there, however the MNC looked certain to fire early. Lifted Index was about -4 to -6 and CAPE about 1500, but these values were not representative of the situation. Strong SW shear would enhance updrafts, a triple point from the surface trough was working its way up the coast, and reasonable turning was evident in the lower levels. Winds were pushing 30 knots at 700 hPa from the SW, and 45 knots by 500 hPa from the SW. Higher up, the winds were tending WSW at 80 knots. Morning satellite imagery revealed large thunderstorm clusters in the Tasman Sea, an axis for the SE - NW or perhaps SSE - NNW aligned trough across NE NSW. DPs were in the high teens along the coastal plains and mid teens on the Northern Tablelands. AVN plots of relative humidity revealed plenty of moisture till about 600 hPa, then dry above that - another indicator of strong updrafts, and likely hail. I forecast that storms would head NE today, with stronger cells moving NNE. This steering flow is ideal if strong storms form near the coast, but difficult if the only activity remains on the eastern slopes of the Great Divide.

Jimmy Deguara had headed out on chase from Sydney to the Mid North Coast, so I was checking observations out of interest. I suspected Anthony had headed south, but had not heard from him. My usual chase partners in the Northern Rivers Dave Ellem and Rodney Wallbridge were available for chasing, though at this stage I was unsure what time I could head out, and hoped activity in the Northern Rivers would be late.

By 1pm strong thunderstorm cells were active in the Mid North Coast district and a Bureau of Meteorology severe thunderstorm advice was current. An isolated cell had developed NE of Tenterfield and looked set to track northeast into Queensland. Elsewhere in the Northern Rivers it was fairly clear of cloud, which helped give a beautiful view of the storm to my northwest. It exhibited some strong features at times, with some solid anvil backshearing, but probably did not go much higher than about 11 or 12 kilometres into the atmosphere.

Wollongbar 1.29pm Wollongbar1.53pm Wollongbar2.11pm Wollongbar2.17pm Wollongbar2.30pm

The next couple of hours were like torture for me, stuck at home and only being able to check radar and worry about missing the action. Very large cells were tracking generally NE and NNE on the Grafton radar and spreading into the Northern Rivers region from the south. A very obvious supercell with hook echo was just west of Coffs Harbour and Woolgoolga. I was hoping Anthony had headed down from west of Brisbane and would be observing its features. Another strong storm had developed SW of Grafton and there was another further SW behind it. Dave and Rodney headed off about 3.45pm. I was fortunately able to leave just 20 minutes behind them.

Woodburn 4.20pm Woodburn 4.32pm Woodburn 4.39pm Woodburn 4.42pm Woodburn 4.45pm

We met up at South Woodburn about 4.30pm. Rodney immediately said a report of 130km/h winds had been observed near Grafton. Two very large storm cells were to our south and south-southwest. The anvil from the westernmost cell was almost overhead and was incredibly high and thick, as well as being beautifully illuminated. Tops of this storm were quite obviously around the 15km mark, probably higher. The think anvil spread off towards the ENE with bubbles of mammatus. There was a little haze near the surface and a moderate inflow wind from the N or NE. We could not see any base features at this time, but some lightning and thunder was observed. It was a little unclear whether we were observing the Woolgoolga supercell mentioned earlier which had travelled up the coast, or another one or two cells which had come up from Grafton. I suggested that it was not a good day to encounter the weather this storm was producing ... the setup was likely to give large hail and violent winds, and the Pacific Highway south of Woodburn goes though a heavily forested area.

Woodburn 5.06pm Woodburn 5.06pm

We obtained a radar update via UHF CB, then went to view it ourselves at one of Rodney's friend's house on the outskirts of Evans Head (about 6km SE of Woodburn). I took one look at the display and said we must go west to remain on the NW flank of the storm. We raced back to Woodburn then along the Coraki Road which heads generally northwest. As soon as we passed Woodburn the base of the westernmost cell came into view ! I can still hear the expletives and excited cries !! Unbelievably, this storm was able to be immediately classified as an HP supercell with "mother ship" type mesocyclone. It was just so obvious, beautiful curved base with multiple striations, lowerings, powerful lightning strokes, and thick massive anvil streaming overhead.

Woodburn 5.05pm

NW of Woodburn 5.13pm NW of Woodburn 5.13pm NW of Woodburn 5.14pm NW of Woodburn 5.16pm NW of Woodburn 5.17pm NW of Woodburn 5.18pm NW of Woodburn 5.18pm NW of Woodburn 5.18pm NW of Woodburn 5.19pm NW of Woodburn 5.19pm NW of Woodburn 5.19pm NW of Woodburn 5.19pm

Video stills by Rodney Wallbridge:

Video stills from Michael Bath (one sequence):

At our first vantage point stop for the two chase vehicles, we were only about 10 kilometres from the meso. It was incredible to watch this structure become clearer each minute as it advanced NNE at about 60 km/h. Dave and I were comparing it to the Casino supercell of 17th January 2001. The Casino one was larger overall, but this storm had such a well defined mesocyclone that in the end, it was hard to compare. The three of us watched in awe as the lightning punched through the lowered base and off towards the NE. There was still an inflow wind into the storm.

It was hard to get into the cars and move on, but I knew we had to otherwise we'd get slammed by the severe weather. The road briefly headed SW round a bend in the Richmond River at Swan Bay. This was rather freaky at the time as we were heading right towards the meso ! I knew the road would go nearly north shortly, so it was only a brief worry. We stopped again a couple of ks SE of the Bungawalbyn turn off. It was so close now, the motion, the evolving striations, the hail shafts, the thunder, and outflow spreading north to our west ... we could not stay long, but left it perhaps one minute too long. The scene was breathtaking, so beautiful, so photogenic, and a structure not witnessed before.

S of Coraki 5.24pm S of Coraki 5.25pm S of Coraki 5.25pm S of Coraki 5.27pm S of Coraki 5.27pm S of Coraki 5.27pm S of Coraki 5.27pm S of Coraki 5.28pm

S of Coraki 5.29pm

Video stills by Rodney Wallbridge:

Some anvil structure taken from McLeans Ridges by Alison Bath:

McLeans Ridges 5.05pm McLeans Ridges 5.05pm McLeans Ridges 5.05pm

Some photos taken from Wollongbar by Owen Ellem, first three looking SSW, last two looking NW.

Wollongbar Wollongbar Wollongbar Wollongbar Wollongbar

The following photographs were taken by Ray Mullens from Goonellabah.

5.51pm 5.51pm

The following photographs were taken by Reg Yager from Goonellabah.

This photograph was taken at Tregeagle looking SE by James Whyte


These 2 photographs was taken at Modanville looking SE towards Lismore by Dan Slattery

These 2 photographs was taken at Woodlawn looking SE by Jen James

Crunch time came and I yelled at the others - again :) - to get in the cars and go ! It was a race to get out of there now, the road headed NW then N towards Coraki. The gustfront caught up with us near Bungawalbyn. The winds whipped up dirt from nearby fields and drove it horizontally across the road. Trees were bending over. Bursts of rain and a few hailstones battered the cars. We had to briefly slow down as visibility became quite poor and the cars were buffeted from the south. It was almost a case of stop and ride it out, then the road veered from NW to N ... we floored it and just escaped the fury. It was a relief but it wasn't over - the storm was still powering up from the south and spreading towards the NW - complicated by another storm that had formed west of the high precipitation supercell.

NW of Coraki 5.36pm NW of Coraki 5.37pm

I made a decision to go WNW towards Casino rather than north towards Lismore, even though more severe weather was approaching from the SSW. We managed to keep out of the storm, stopping near Tatham and ESE of Casino. Light was reducing as the sun was quite close to setting. Lightning was constant and base lowerings to our NE, E and SE exhibited features consistent with a very strong thunderstorm. The meso was now approaching the eastern parts of Lismore and the Alstonville Plateau. A wall cloud had formed on the new western cell to our S, and a lowering appeared like a tornado for a while, but unfortunately was not. We were in an excellent position if it had. ESE of Casino we stopped for a while to observe the show, the outflow winds were amazing, picking up dirt and reaching about 80 to 90 km/h - it was hard to stand, let alone hold the video steady !

SE of Casino 5.42pm SE of Casino 5.51pm

SE of Casino 5.54pm SE of Casino 5.54pm

SE of Casino 6.15pm SE of Casino 6.15pm SE of Casino 6.15pm

After the winds abated, we quickly drove to Casino for fuel then back down the Coraki Woodburn Road to try and find any hail and damage. It was almost dark, though the constant lightning was keeping the entire storm structures ahead illuminated. We passed through some rain and debris from trees across the road, and then some low fog from the hail near Coraki. In the dark we found large quantities of 1 to 2 cm hail in the grass, but it was hard to see. It also looked like about 50 millimetres of rain had fallen as the fields and drains were awash.

near Coraki 6.51pm near Coraki 6.51pm near Coraki 6.54pm

We then proceeded to Broadwater national park to watch lightning out to sea for about 40 minutes. The storms were moving so quickly that the lightning soon became too distant to photograph. Lightning photos by Michael Bath.

Broadwater Broadwater Broadwater Broadwater Broadwater Broadwater

Another small storm with a few cloud to air lightning bolts was active to the north when I got home to Mcleans Ridges:

McLeans Ridges McLeans Ridges McLeans Ridges McLeans Ridges McLeans Ridges McLeans Ridges

The Bureau of Meteorology issued a special warning for this storm:


Issued at 6:24 PM Sunday 30 March 2003.
The Bureau of Meteorology in SYDNEY has issued a Severe Thunderstorm Advice
for people in the following weather forecast districts: 
Northern Rivers and 
Northern Tablelands north of Glen Innes.
This advice is valid until 11 PM and should not be used after this time.
Thunderstorms are forecast within the advice area. Some of these are
expected to be severe, bringing large hailstones, destructive winds and
very heavy rainfall.
At 6:25pm, a number of particularly large thunderstorms are located near
Lismore and Casino. These storms are moving north to northeast and are
likely to affect townships including Mullumbimby, Byron Bay and Nimbin.
Hailstones large enough to damage car windscreens and damaging wind gusts
in excess of 100km/h have been reported with these storms.

Dave Ellem also took some pictures of the damage and hail the next morning in the Newrybar area.

Some aditional observations:

Observations by Stuart MacDonald from Alstonville:


If you (or someone you know) have any photographs or video of this event, please feel free to contact Michael Bath. Your contributions are very welcome.

Media Reports

  • The Northern Star 31st March 2003
  • The Northern Star 1st April 2003
  • Coffs Harbour Advocate 2nd April 2003
  • The Northern Star 3rd April 2003
  • The Northern Star 9th April 2003
  • Rivertown Times 10th April 2003 [Page 01][Page 04]

    Video clips and stills

  • Video clip by Rodney Wallbridge of the HP mesocyclone at its peak intensity [1.00 min - 3.59mb WMV]
  • Video Stills by Michael Bath


    From Bureau of Meteorology.

  • High resolution interactive Grafton loop 0350z to 0820z 30/03/2003 (1.50pm to 6.20pm local - images courtesy Sydney BoM)
  • Grafton local scale loop 0200z to 1030z 30/03/2003 (noon to 8.30pm local)
  • Grafton medium scale loop 0130z to 0730z 30/03/2003 (11.30am to 5.30pm local)
  • Brisbane medium scale loop 0300z to 1200z 30/03/2003 (1pm to 10pm local)

    Some frames showing a hook echo from the earlier Woolgoolga supercell SE and E of Grafton (3.40 to 4.10pm):

    3.40pm 3.50pm 4.00pm 4.10pm

    Some frames showing the HP supercell during the intense part of the chase (5.10 to 5.50pm) - six level web radar on left, 16 level BoM radar on right:

    5.10pm 5.10pm
    5.20pm 5.20pm
    5.30pm 5.30pm
    5.40pm 5.40pm
    5.50pm 5.50pm

    Satellite Images

    From TWC Weatherzone at 1pm and 3pm local.

    1pm local 3pm local

    From Bureau of Meteorology at 1pm, 3pm & 4pm and 7pm local.

    1pm local 3pm local 4pm local 7pm local

    From Land rapid Response System

  • 250 metre resolution image at 0335z (1.35 local) This corresponds closely with this radar image. You can see a developing supercell southwest of Coffs Harbour, the supercell near Nambucca Heads, then further south the supercell Jimmy Deguara was chasing and just about to be bombarded with hail located northwest of Port Macquarie. The southern end of this complex was near Taree. Other activity west of Coffs Harbour eventually became part of the storm discussed in this report.

    Analysis Chart

    From Bureau of Meteorology.

    30/03/2003 06z

    AVN Model Analysis

    From NOAA 30/03/2003 06z analysis run

  • Liftex Index
  • CAPE
  • Relative Humdity surface
  • Relative Humdity 850 hPa
  • Relative Humdity 700 hPa
  • Relative Humdity 500 hPa
  • Relative Humdity 300 hPa
  • Temperature (C) 850 hPa
  • Temperature (C) 500 hPa
  • Temperature (C) 300 hPa
  • Winds (knots) surface
  • Winds (knots) 925 hPa
  • Winds (knots) 850 hPa
  • Winds (knots) 700 hPa
  • Winds (knots) 600 hPa
  • Winds (knots) 500 hPa
  • Winds (knots) 300 hPa

    Document: 200303-01.htm
    Updated: 9th August, 2005
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