Hi, Michael. Ground to cloud lightning. Whereby strong negative (positive return stroked) strikes initiate upward lightning that return stroke positively (confusing aint it!) They are pretty rare I agree but in the US they are prevalent. Whether or not it has to do with atmos conditions or storm types is something to be investigated. I've only got one image of upward leaders and that was by accident photographing a big CG..was only after viewing the image that I went whoa!
You can see the upward leaders streaming up - they were unseen by the naked eye and were simultaneous as the CG hit. Because this one did not hit anything high was even more surprising..
Storm report 10/10/2010
I had always planned to chase today (Sunday) as the CAPE was a little better. Although the scenarios have been somewhat 'wet' storm wise there have been brief moments of anticipation seeing flashes here and there but electrification was always going to struggle a bit given the low storm tops. Many of the storms failed to anvil and they remained average in height, so chasing the ones that did get decent lift still proved a pain the neck given a lot of low cloud surrounding them. Rather than being able to pick something that was going to produce lightning of some depth became akin to finding a target, waiting...more waiting and then moving on again. So no success over the last couple of days or nights.
GFS was okay for energy but I don't beleive good enough for decent cells to remain high and charged. Whilst the lightning trackers were showing some decent amount of hits, the reality is that most, if not all of them were totally hidden behind heavy precip curtains.
We had targeted east toward Jabiru, about 90km short of the town. We did see only one large CB that anvilled twice with overshooting tops, but if there were bolts then we were obviously too late. We decided to keep to the Annaboroo area and wait for things to happen. There was no shortage of cells meandering and grouping and as it panned out - as you will see by the radar loop - a long line of cells converged into a line and kept on going. No strong winds or torrential downpours, just a grandmother paced moderate rain borne line that just took its time to the coast. Which made chasing something easy...just stay ahead of it and she'll be right!
I had planned to chase to Adelaide River some 70km south of Darwin, which going by the GFS models was a little less in CAPE, but from what we saw on radar and visually had probably the larger storm sets as our line east merged with it. So William and I headed out east in the hope of lightning...alas not to be, but got some nice structured shots and the like.
Sounding for today was pretty average but showed a lot of moisture and a dreaded cap that was really hard to break. Only a few discreet cells found locations in which to get some distance aloft, all the others remained under the cap, which would have inhibited electrification of any worth or timeframe.
Radar loop for the day..
http://radar.strikeone.net.au/?fuseaction=loops.main&radar=633&numberofImages=10&dateStart=1286683200&dateFinish=1286712000You will see the cells starting to form at the beginning of the loop, this is when we headed out east. The line behind at the final run time was heading toward Darwin as I posted the reply here...so more wet stuff about to come.
Images from today's chase:
On the highway going east...the line starts to begin.
William, who is traditionally a landscape and bird snapper...and an NT policeman who likes storm shots...! The storm behind is off to the NW...a beastie that was!
Various shelf cloud shots on the way back toward Darwin. It rained from here on in!
The line of cells flanking towards the south-west on their journey to something...
There's a low progged for this week to the NW of the NT...no rublings of anything yet as it's a bit weak, but most of the authorities overseas have picked up on it. Early monsoon? Looks ominous with the amount of thunderstorm activity in the Timor and Arafura seas....
Cheers all!