AUSSKY  - 'Going to Extremes' 2013 - Chasing the Weather USA

First chase of 2013 to Lawton, Oklahoma

30th March 2013

Report: Clyve Herbert

Photography: Jane ONeill & Clyve Herbert 

Its 3am..KABOOM!!!! there's nothing quite like a plains night thunderstorm.

After one of the coldest March's in 100 years across the plains of the USA, it was finally warming up. A line of storms had developed over western Kansas the previous evening responding to a split jet and an increase in surface moisture from the Gulf. The synoptic pattern was complex...a series of troughs across western Kansas and the Texas Panhandle, most of which were quasistationary. Meanwhile in the upper levels, a shortwave was advancing from the Rockies across the western plains area and introducing colder uppers. The squall line was moving through central Kansas around 3am, a narrow meandering band of storms showing signs of weak bowing. The thing about Plains storms at night is that you can hear thunder for a long time before the storm gets to your location, but the return of moisture and temperatures in the mid 50's in the early hours was a welcome change to the mid teens and low 20's (F) that had lingered through virtually all of March. As the squall line moved through Hillsboro accompanied by strobe lightning and occasional close cg's, there was a burst of hail and heavy rain lasting about 5 minutes. If you're a weather nut like me, when storms are pending at night, you experience a restless sleep... Gradually the squall line recedes away to the southeast and thunder wanes. With the light rain tippling on the verandah, eventually I'm lulled to sleep only to be jerked awake around 4,30 by an almighty crash and a BANG! probably caused by a rogue positive stroke from the back of the receding storm band.

Our plan today (after breakfast), is to head south along a boundary expected to move through central Kansas and western Oklahoma. There is an off-chance of isolated storm in the late afternoon and evening particularly in southwestern Oklahoma. We were keen to find some decent storms after weeks of snow and blizzards. A moist tongue of air from the Gulf was streaming north across Oklahoma and Kansas ahead of a slow moving frontal boundary. We leave Hillsboro in the drizzle and murk and head south then west of Wichita to pass through Kingman and onto Manchester, Oklahoma. By this time, we are in clear sunny air with dew points in the high 50's. We are heading south and paralleling the frontal boundary that separates dry air with dew points in the high 30's from an area of modest moisture through Oklahoma. The line is only marked in the late afternoon by a narrow band of relatively low topped cumulus. We eventually line up at Watonga to watch a couple of crappy multicells mature to our southwest. Although these are the first storms to materialise along the boundary they are in relatively dry air. Instead, we head south to better moisture. On crossing the I-40, we tag onto a line of deep cumulus developing along another boundary. They rapidly develop into strong cells.Eventually a dominant cell grows NW of Lawton, and quickly splits into left and right movers. The left mover is closer and we pursue and pull over to photograph and video. The left move split eventually takes on the persona of a LP supercell and rotates anticyclonically. We drive near to the core and are pummelled by golf ball to tennis ball sized hail...its time to try the hard hat!!! and we successfully measure the hail. The left mover though is dying quite quickly and we head south through Lawton to chase the right mover......the right mover is no slouch and puts on a brilliant evening display with stunning colours in the setting sun. We turn north and head back to Kansas..our first storm chase for 2013 is done!

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What a surprise, thousands of the shape of a horiontal vortex...Cherokee Oklahoma.Photo: Jane ONeill

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For some reason Cherokee attracted not thousands but tens of thousands of starlings...Photo: Jane ONeill

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Pyrocumulus north of Lawton OK..Photo: Jane ONeill

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Here we are closing in on the Lawton cell Oklahoma, at this stage the storm had not split,condtions were marginal for supercells with temps around 80F and dew points near 60F...increasing cold aloft and an approaching frontal boundary are helping destabilise the local environs.Photo: Jane ONeill

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Photo: Clyve Herbert

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The left mover split takes on the look of an LP storm, very little rain mainly large hail..Photo: Clyve Herbert

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The left moving cell retains a prong lowering.Photo: Jane ONeill

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After the Lawton cell split the primary cell became the left mover which develops anticyclonic rotation..Photo: Jane ONeill

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The actual updraft core of the left mover cell is relitivley small. Photo: Clyve Herbert

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The last gasp of the left mover cell drops golf ball hail north of Lawton.Photo: Jane ONeill

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The bulk of hail is golf balkl sizes however there were a couple of tennis balls as well..Photo: Jane ONeill
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Clyve tries out our new hard hat!! A success! Photo: Jane ONeill

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In near end stage of the left moving LP a horiontal vortex appears...The left mover split retained a prominant anticyclonic rotation.Photo: Jane ONeill

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Horizontal vortex spins around the decaying left moving split...

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The final stages of the left moving split and it was still dropping golf ball hail.Photo: Clyve Herbert

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The final phase in the left mover is a narrow rotating updraft...Photo: Clyve Herbert

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A large turkey cumulus erupts and blocks the setting sun...Fort Sill Photo: Jane ONeill

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Almost a beaver structure under the right split moving cell.Photo: Jane ONeill

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These sequences show the right split Lawton cell which became the primary cell after the left split decayed..Photo: Clyve Herbert

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Thick outflow anvil of the right split cell..Photo: Clyve Herbert

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Thick anvil streamer of the right moving Lawton cell still showing growing tops above the snow fallout..Photo: Jane ONeill

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The main updraft core of the right moving Lawton cell split lifts a veil of pileus..Photo: Jane ONeill

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Photo: Clyve Herbert

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We rated the Lawton cell as a splitting low end supercell that produced golf ball to tennis ball haill Photo: Clyve Herbert

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There is nothing as specill as a sunset storm glowing like this image...note the overshooting top appearing in the brighter sunlight at that altitude.Photo: Jane ONeill

Stay tuned for the next episode...

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