Friday, March 12, 2010

How to go from late summer to winter in less than 30 minutes

Listening to: Metallica - Reload

My fair city of Wellington got a big old can of weather whupass opened up on it this afternoon.
Story links here (via Stuff) and here (via This was the first big storm of he year, and while it is technically early autumn, storms like this don't usually turn up for another month or two, and are generally not as psychotically intense. This thing inflicted the sort of damage in an hour or so that the regular southerlies take a day or two to manage.

Being an interested weather watcher (some may have noted numerous previous weather related posts (link)), I had an idea that we may get some interesting weather this afternoon, so took my camera to work on the off chance there might be something worth photographing. As the day progressed I periodically checked the metservice website (including their wonderful rain radar) as well as looking out the nearest window to see how things were developing. As it turned out, things got interesting right when I finished for the day, so I headed down to Petone Beach at the northern end of Wellington Harbour to watch the expected southerly arrive. I was hoping to get some cool cloud shots, and maybe some lightning if I was really lucky. As it happened I got a little more than I bargained for. Apologies to those who have already seen these on facebook. And a big shout out to my 16 year old nephew who got caught by the storm and rode it out (for about 10 miles worth) on a pushbike during his regular training ride.

Click on any pic to enlarge

Thanks to the timestamping on my camera images, I can give an exact timeline for just how fast this thing descended. I got to the beach at about 1620, just as the storm was starting to engulf the city. This is from Petone, looking across the harbour to Wellington about 10 kilometres away. Matiu/Somes Island is on the left about 2 kilometres away. Where I am standing the sun is still shining, and there is a warm northerly breeze...
Looking out south to the harbour entrance, Seatoun on the right is still in the sun, but the imminent storm is apparent.
By 1625, the inner harbour and central city are disappearing into the gloom.
Looking back at the harbour entrance at 1627 it is becoming clear that this isn't your average southerly change.
Matiu/Somes Island at 1628. The normal backdrop of the city and eastern suburbs is entirely obscured.
Possibly the largest whirlwind I have ever seen (est 1-200m across) under the squall line as it advances across the harbour at 1629. This got me wondering if I was about to see an actual tornado for the first time, and was somewhat intimidating given the bigger picture I was seeing.
At 1631 the storm has hit the other end of the beach, and although I didn't see them at the time, there are actually people still swimming in the picture. If you look closely you can see them, as well as the sand the wind is picking up. The white line on the water is where the wind shear is. Where I was the wind was no longer out of the north, but shuffling confusedly. When the shear hit it was like a bomb. The wind went from confused shuffling to 100+kph gale in few seconds.
Here is the same view five minutes later at 1636. I had retreated to my car at this point, althought the car was being bounced around by the gale so much I moved it to point into the wind to lessen the feeling I was going to be rolled (the MX-5 is not particularly noted for its weight...). I was also wondering if I was in over my head a bit with this storm. I bailed for a slightly less scary location a few minutes later.
Looking back toward Matiu/Somes at 1641. You can just see the island. The sea state makes an interesting comparison with the shots from less than 15 minutes earlier.
These are typical scenes around Lower Hutt tonight.

The worst of the storm had passed by 1830, and by 1930 it was almost like nothing had happened, albeit much colder.
Just for comparison, this is what dawn looked like from my lounge (looking northwest) this morning.
Interesting day.


Maureen said...

Weather is so weird. Yesterday morning when I left for work there was...umm...converting to metric... about 4-5 cm of snow and by the time I got on the freeway it was raining and the snow had completely melted. And by the time I left work it was sunny and warm.

Awesome storm pics!

2treesandahorse said...

dudue that so makes me home sick in a weird sort of way. Love them quick storms. sweet photos as usual.

missrabbitty said...

i watched that thing roll in. it went from blue to storm in the time it took me to get from the new world to my home (about four minutes cos the traffic was good). and then it lasted less than an hour and i was underwhelmed. but the unusual wind direction intrigued me. it was from the northwest. but the later reports of 'tornados' answered that observation.

missrabbitty said...

so now i've read the first part of your post...and as a scientist i should be whipped cos i just let weather happen...was this thing predicted? (excuse my a scientist.) and great pics...glad someone listened.

d3vo said...

Awesome photoblogger and weather blogging, all in one!

Off-Black said...

Thanks all.

Missrabbity, Metservice was predicting hevy showers with thunder for the afternoon, but not having checked the marine forecast or wind warnings, I'm not sure to what extent the supercell we got was anticipated. I like thunderstorms as notice any possible forecast for them. I had no idea the storm we got was coming in terms of intensity.