Unseasonal Severe Hailstorm Chase!
May 1, 1999

For the previous week, the models had been forecasting a very intense upper level trough, and cold pool of air above SE QLD.  So intense and cold, that in fact, severe thunderstorms developed over some parts in May!  This is a fairly significant event, in the fact that SE QLD thunderstorms generally need days of high  temperatures, high DP’s and low pressures.  And certainly, 23C, DP of 12C and 1020hPa does not classify into any of these.  However, today was certainly a day  that proved that weather has no restricted boundaries, and certainly does not follow any unbreakable universal laws.

The day before (Friday, April 30th) there were some storms that formed in NW NSW during the evening.  This was certainly encouraging to see, as it helped outline  the cold pool’s potential of thunderstorms.  These thunderstorms continued out through the night and moved fairly rapidly eastwards, before weakening into showers.  However, that morning (Saturday May 1st) there were some small storms that formed near Moree, that had pink on radar between 5:50am and 6:30am, and it was only 14C in Moree at that time! 

Unfortunately, these thunderstorms dissipated into showers, however the satellite pictures still showed plenty of potential.  Not to mention the forecasted cold air, at 06Z, Brisbane was forecasted to be –21C at 500mb. Just after 6am though, I spotted some very welcome Altocumulus Castellatus, despite the fact that it was not there for very long, it was still welcoming.  During the QLD ASWA meeting, we made periodic examinations of the sky, at 11am, it certainly was not looking very hopeful, however the cold air wasn’t forecasted until the afternoon, and certainly, with the combination of low temperatures and DP’s, the air would need to be atits coldest before any decent convection could occur.  From midday until 1pm, the sky began  to improve dramatically, very soon towers begun to spring up everywhere, and energex lightning tracker showed some lightning about 300km W of Brisbane, and radar observations showed weak t’storms beginning to form about 80km W of Brisbane.  We also noticed a severe thunderstorm advice for the SE QLD district, this was certainly very encouraging to see!  We left soon after 1pm to chase, we had to pick up some extra film first though.  After this we set out for the Warrego Highway to head west.

We were watching a very nice precipitation free base on the  NW side of the storm with hope, however apart from a slow moving, yet obvious inflow band, it was relatively unexciting.  It was very cold where we were, the  temperature would have been around 18-19C, and this was the first storm chase I had ever been on where I was shivering! 

We soon had to move out of the area due to rain, we traveled a little further east on one of the side roads and observed a very strong rainfoot beginning to develop.  It was only short lived, but the  precipitation curtain was very thick and solid, and the rain-foot was very well defined.  Unfortunately, by the time we could find a suitable place to pull over, the rain-foot became less pronounced.  With no more suitable roads to the east, we were forced to quickly head back for the highway and to head east to have another look at the storm.  We sat there for a few minutes, however soon it began to rain again, so we had to find another place to observe the storm from.  However, 3cm splats on the windscreen from raindrops (while stationary!) worried us about the possibility of hail.  Hail was already probable in any thunderstorms that formed (regardless of height) because of the fact that the air was so cold above us, because of this, we made a quick dash to the nearby service station that we noticed.  We had to drive towards the storm though to get there, and although the rain was not very intense, the drops while driving were huge, and reduced visibility greatly.  Fortunately, we soon came to the service station and pulled in for temporary shelter.  At this stage, winds were gusting to 20 knots, and the rain was still fairly heavy.  We were waiting for hail, it was allowed to hail now that we had got the car under shelter!  Of course, mother nature was not so obliging, and we only ever had  heavy rain.  The rain was never very intense, however the large drops of rain made up for this greatly, and still caused a large amount of water washing down the road across the highway.  Winds continued to get stronger, gusting to 25knots at times, sitting on about 20knots sustained, rain was nicely almost horizontal at times, we were standing at the corner of the service station, we couldn’t even poke our heads around the corner, as the wind was blowing the rain under the eaves, and we were getting soaked!  We could see the shrubs and bushes being blown madly in the wind, and a nice mist was being whipped up on the road.  Winds continued to get stronger, and my estimate would be between 30-33kn gusts, with 22kn sustained.  Certainly, it was a nice thunderstorm, however it was not severe.

There was heavier rain coming, and we knew the thunderstorm was moving slowly, if we were to stay where we were, we’d have been stuck for another thirty minutes.   Spotting a small break in the thunderstorm, we decided to try and get out of the position we were in.  We had thought that the worse of the storm had moved to the north of the highway, however we may have slightly misjudged this.  We noticed some very nice little hail drifts on the side of the road, and that kept us alert to the possibility of hail.  Rain was only moderate at this stage, however sure enough, we heard the dreaded loud “clonk” on the car roof!  We slowed down when we  heard this, and continued slowly, the hail was only relatively small (pea to marble size) at this stage.  However, when we observed cars pulled over with tarpaulins and blankets over them, we thought “oh f___” and quickly pulled over! Fortunately for the car, there was only infrequent hail, and it did not appear to ever be larger  than marble hail.  After most of the hail had cleared, we continued again, however a little further up the highway there were some nice hail drifts again!  Not being  able to resist looking at all the hail, we turned north onto a road that appeared to be covered in hail, it looked like snow at times!  Along the side of the road, there  were some nice hail drifts, this also blocked some of the water.  As we drove over some of the puddles, you could hear the hail underneath bouncing and hitting the car!  We quickly took some more pictures of the hail, before setting off further east to catch up with the storm.  Fortunately, it was still only moving relatively slowly.

However, a call from Chris who told us that although the cell to our north was small, it had maximum intensity for the past hour quickly helped  assist us in that decision!  And it was well worth it, it had a VERY nice rounded base, it looked awesome!!!  However it was difficult to tell if there was rotation in it,  if you looked at it one way, it appeared to have rotation, then if you looked at it from another angle, it didn’t appear to have any.  This cell, however was going to  move into a horrible area for chasing, full of hills and trees, however we spotted some excellent mammatus and could not resist continuing to chase this cell.  There  was some very nice CG’s and CC’s in the storm, a few of the CC’s were pink, there was also a nice crawler!  Certainly, this storm was still worth it.  However, it was now 5:30pm and was getting dark, so we thought we’d still try and follow it north to get a nice advantage point for some lightning.  At around 6pm, Chris rang  again and informed us that the storm we were chasing had sparked a severe thunderstorm warning for the sunshine coast.

We thought we’d try and get on top of the ranges to a good look out point, there was some absolutely blinding CG’s!  And at times, the rain was still quite heavy, and the added combination of fog and mountainous, windy roads certainly didn’t make it the ideal situation to be in.  Unfortunately, this meant that we had to drive very slowly, and by the time we got over the range, we never found a look out point, and the storms had moved further north.  At this point, we decided that we should call off the chase, as we couldn’t spot too much more lightning as it had appeared to die down a bit.  Considering it is May, this was certainly an excellent chase, I had never expected anything like this to ever happen in May!  I’m not complaining though!