2010-05-19

Northern Oklahoma Boundary

Mapped GPS Log
Quick Overview
Chase Region:Northern Oklahoma
Forecast Target:Fairview, OK
Realized Target:Watonga, OK
Mileage (from GPS):279.6 miles
Crew:
  • Robert Fritchie
  • Rachael Sigler
Significant Events:
  • Three Tornadoes
  • 4 minutes of sustained Severe RFD Winds
  • Transects of Boundaries and a Meso-Low
  • Photos of Storm Structure
Chase Forecast

A 500mb trough, with its axis in the Texas panhandle on the 18th, was forecast to move out over the southern plains during the day on the 19th. A mid-level and upper-level jet streak was associated with this feature and aided in creating a sheared environment supportive of rotating storms. Additionally, the indirect thermal circulation below the jet core's exit region set the stage for rapid moisture transport and subsequent destabilization of the low-levels.

Convection from the previous evening and the morning left a strong outflow boundary that merged with a warm/stationary front along the I-40 corridor. By late morning, clouds were eroding and surface heating began warming the low-levels along and north of the boundary. Forecast storm vectors were Northeast at 30 knots, which left the chance that a right-moving storm could attach itself to the E-W boundary and product significant tornadoes as the storm tracked Eastward.

Forecasts were for a strong dryline bulge to form during the afternoon, with the enhanced convergence to be the initiation point for storms. I was planning to let the storms fire along this feature, but stick near the boundary so that when the storm finally met up with it, we would be in perfect position. this wasn't quite the way things initiated (storms went up right along the boundary independent of any dryline feature), but the boundary was indeed the big focus for tornadic activity.

Chase Description

Rachael and I left OUN around 1645, and made our way west to Weatherford while evaluating targets along the way. As we progressed, we noted the clearing trend north and south of the boundary (yay!) and also adjusted our target further south as we realized the boundary was not lifting as far north as we had anticipated. Once we moved north out of Weatherford, we noticed a quickly developing, localized surface low along the boundary just southwest of Watonga. We used the instrumentation to transect the low and the boundary several times and finally caught up to some convection localized just northeast of the low near Hitchcock, OK. We noticed an interesting rain-free base and some rotation.

At 2018, we observed a clear-slot and strong rotation, followed by a long, snake-like and mostly-horizontal funnel that protruded from the updraft and eventually oriented itself in the vertical. We did not see any rotation at the ground. After about 10 or 15 minutes, the funnel disappeared and we repositioned north and east.

From 2148 to 2155, we observed a large cone tornado about 5 miles west-northwest of Hennessey. The tornado eventually roped out and we repositioned east.

From 2215 to 2217, we observed a short-lived tornado with intermittent condensation north of Hwy 51, and just south of Marshall, OK. After getting blasted by severe RFD winds, we again repositioned east and took a final dive north near Orlando, OK.

In Orlando, we observed a tornado that formed just south of town and crossed 77. The condensation was again intermittent, but a circulation was observed at the ground from 2308 to 2310. Later, as we repositioned south, we could see the tornado come closer to fully condensing. this was observed around 2312 and was the same tornadic circulation.

We then dropped off our first storm at I-35 and picked up the storm approaching Guthrie, OK. We noted several funnels and lots of rotation, but never observed any tornadic activity. We quickly gave up on that storm as well, ending the day at an Olive Garden (classy!) with Amos Magliocco, Scott Blair, Lauren Hill, Jason Levit, Katie Burtis, and Derek Deroche.

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