Albany area thunderstorms - local chase

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Pete
Cumulonimbus
Posts: 470
Joined: Mon May 30, 2011 9:02 pm
Location: Albany, Western Australia

Mon Oct 17, 2011 11:02 pm

The GFS models had shown promising signs for potentially severe thunderstorms for Sunday night for most of the week. Consistent runs showed LI's of -6 to -9 around the Albany area for Sunday night with CAPE of nearly 2000j/kgs. The BoM predicted a very deep surface trough to develop rapidly during Saturday and combine with a mid-level disturbance during Sunday. Models also showed a sharp surface convergence line to the west of Albany Sunday night. The only thing I had in doubt was the cap, it was a strong cap! The BoM predicted 27 degrees for Sunday, which I also doubted would eventuate because of the thick mid-level cloud accompanying the trough on Sunday morning. Therefore the cap would of been about 4 degrees and CIN around 176j/kgs.

Sunday morning came and skies were overcast and E/NE'lies were gusting to 50km/h in the morning. Pressure was dropping and dew point was rising. By 10am skies were starting to clear from the north and small cumulus towers began bubbling up to the north of Albany. Convection was shallow but promising.

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Soon after they abruptly collapsed and were replaced by thick alto-cumulus once again. Temperatures were struggling to rise, only 18 degrees at 11:00am! The cloud cleared out to sea once again and heating really started - until the sea breeze hit. I was really starting to lose hope about the day and getting ready to write it off as a bust. Temperature climbed to 23.7 degrees at 1:30pm despite the sea breeze and cumulus began trying again, collapsing again and again. By 4pm the dew point was up to 15 degrees thanks to the moist onshore breeze and the temperature sat on 22 degrees. I went in and watched the Rugby until about 5pm, I was convinced by then that us Kiwis would win. :P So I went out and glanced to the north where towers were exploding upwards. Dad and I decided to head out north to get a better look. Cells were heading south/south-eastwards at a fairly decent pace, when they collapsed again. We headed further west to the local shopping centre and took some photos of the less than promising sky.
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By then it was nearly 5:30pm and still no N'ly change as forecasted. We decided to head back, deciding our only hope was with the trough moving inland. I headed out again about 6pm and the north was looking a lot more promising. Cumulus towers were pushing up fairly quickly to the northeast.
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Not long later a cumulus exploded up rapidly to the north. I took a photo of it in its early stage.
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A small fire to the north of Albany was fueling the cumulus and lightning was flickering about beneath them despite no anvil and the fact that they had quite low tops.
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The line of storms became more organised, still low tops but a small flanking line was visible as they headed further south to the east of my place. See left of photo.
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Lightning was very infrequent but the radar showed promising development to the north. By 8pm the N/NE change had arrived and distant lightning was becoming more frequent to the north. The sky overhead was clear and I could make out an enormous cell to the north complete with crisp anvil and overshooting top. Cell became close enough for me to capture lightning. The storm produced some epic crawlers. :D
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This shot was amazing. :o
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Looking at the soundings I have no idea what broke that cap. At 8pm the temperature was 15.7 degrees and dew point of 14.5 degrees. I assume that surface convergence, maybe forced lifting from the Porongurups and the low to the north all helped. Surface heating was marginal. Synoptic at the time of the storm.
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Still a welcome start to the spring storm season. :)
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Rivergirl
Admin/Moderator
Posts: 3672
Joined: Sun Nov 22, 2009 6:04 pm
Location: Ferny Creek VIC
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Tue Oct 18, 2011 9:52 am

Great report and photos Pete. Love the lightning one. Yes that last one would have been intense :o
Lily
Supercell
Posts: 4014
Joined: Wed Nov 25, 2009 10:29 pm
Location: Rowville/Lysterfield

Tue Oct 18, 2011 3:04 pm

Nice one, Pete, thanks so much for sharing, glad you had some fun with it too, and yay to your dad for getting out amongst it lol :D
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