Perhaps not an inversion but an upper level convergence over the Auckland/Waikato area. Convergences at ground level have to go up because wind can't go through the ground but convergences at higher levels can go down and going by the models, chances are there will be no storms today over this area due to it surpressing activity. Clouds could get to 4 maybe 5 km in height today over this area but no higher. The upper level convergence looks likely to hang around today.
SE Waikato / SE Taranaki eastwards could get something??
Here's a nice story!
Convergence: This is air that is slowing down to reach a point, so as you progress along the direction of the wind, the wind strength may go from 100 knots to 80 knots to 60 knots and so forth. This is analogous to traffic and say roadworks. Traffic will bank up at roadworks because people have to slow down - and people behind them moving at say 110km/h have to slow down to the roadworks limit (say 60km/h). As you can see, if you timed both points, more cars could move through the 110km/h zone then the 60km/h zone per hour. This causes cars to bank up - and eventually, cars begin to find other ways of getting around the area when the build up gets too big (ie take another road). This is the same with convergence, as the wind slows down it builds a small high pressure region - air then has to move away from this point, often moving up and down. So imagine an updraft underneath a convergent zone in the upper atmosphere, it's ascending along happily but then it approaches this point, and it begins to slow down because there is pressure being forced upon it from above. For example:
More air is entering the region then leaving - so this then pushes down on the updrafts. Convergence isn't all bad - for example, it's good in the low levels (surface-850mb, even 700mb sometimes). Keeping in mind that close to the surface, air here has no choice but to go upwards because air can't go below the ground surface!
Vertical Velocities aren't negative but they aren't that positive either, so slight uncertainty there. Still, I think chances are low.
No tornadoes today, if there is they will only be of the small scale local development type...funnel clouds etc.
Cheers
Aaron Wilkinson
, so it looks like an afternoon of those flattish (but very heavy/grey looking) Cu formations with the floury edges - no definition in the cloud tops.
, I think it was convergence between an incomming Westerly seabreeze and a southerly this side of the Waitakeries + some good local heating.
