May 16, 2000

GUERNSEY, WYOMING TORNADOES CAPTURED

Chase Account by: Scott Blair.

Chase Team: Scott Blair, Chris Bannan.

The chase day started around 6:30am at the Comfort Inn in Colby, KS. A quick look at data suggested the target area would be across Eastern Wyoming. There were several varibles coming into play. SPC had picked up on the situation, but highlighted the greatest threat a little to the east of our target area. We left Colby just after 9am heading north on Hwy25.

Skies were overcast with a few breaks during the early to mid morning hours. (Note- for rest of the account, Mountain Daylight Time will be used) We arrived in Sidney, NE at 12:30pm. We stopped at the local Mc Donald's for some hot food and made a trip to the local library for some updated discussions and surface obs. We ran into Gilbert Sebenste gathering data as well. Moisture advection had done its part by sending decent moisture into the high terrain of Wyoming. I decided it would be best to catch the storms at initiation, so we left Sidney at 2pm.

We headed north on Hwy71, then east on Hwy88 into Wyoming. At 3:45pm, we briefly pulled off south of Hawk Springs on Hwy313 to view the sky and listen to NWR. By 4:00pm, skies were mostly clear with a few cumulus dotting the sky. A cirrus shield was visible to the west. In the vicinity of the cirrus, a few towers developed around 4:17pm. The towers were organizing and rapidly building.

At 4:40pm, we took I-25 northbound at the Chugwater exit. By 5:15pm, we arrived in Wheatland. The NWS in Cheyenne issued a severe t-storm warning for NW Platte County. Topping off with gas, we continued north. Just after 5:20pm, a new rain shaft developed to the NW of our location. We left the interstate at exit 92 and setup outside of Dwyer on Hwy26. By 6:00pm, we were in good position. The precipitation core became very strong and well defined. A severe t-storm warning was reissued for this core over NW Platte County. After a dozen minutes, we decided to find better contrast. We bumped east and stopped outside of Guernsey on a hill. The terrain was absolutely picturesque. This added to the serine scene. The only other car on top of this hill was Dave Hoadley. I must say Dave is a great person and a fantastic chaser. We chatted and admired the many inflow bands that flowed into the core of the storm.

The rain free base was visible and became rapidly better structured and defined. A little precipitation began to fall around the base. Shortly after around 7:00pm, a wall cloud developed and a large funnel protruded toward the ground. The funnel was sustained for nearly five minutes with a tornado touching down for about half the time. A small needle would occasionally be seen dancing around the base. I was amazed due to everything developing so rapidly. The tornado apparently lifted back up with no real lasting signs of a funnel. We decided to head slightly west to get a better view. After three minutes, a rope tornado quickly developed. The tornado was almost a horizontal tube as it clearly touched down. After two minutes, the tornado lifted and the condensation broke apart. Beautiful contrast existed with both tornadoes.

We found a good place to pull off and watched the meso. An obvious clear slot associated with the RFD had developed. This filtered in golden sun along the base of the storm. Decent cyclonic rotation persisted just to the north. A small anticyclonic swirl in the clouds passed the road to the west. Within seven minutes, the RFD quickly advanced towards us with a large plume of dust following. In approach of the RFD, the temperature dropped a good ten degrees. As we pushed east, precipitation wrapped around the meso. We received hail up to 1.25" for a few minutes before the winds abruptly shifted back to the southeast and all precip ended.

The sun was beginning to fall close to the horizon. The end result provided a plethora of colors across the storm. The supercell appeared now outflow dominated. A new storm appeared south of the meso. We shot a few more pictures and called it a day. We stopped in Torrington at the local Pizza Hut. We met a few other chasers including one group from Colorado that had their window busted by hail plus Jim Leonord, RJ Evans, and Charles Edwards associated with Cloud 9 Tours. After eating and visiting, we arrived at 1am and stayed the night in Ogallala, NE. What a classic High Plains event! -Scott Blair


***Local Storm Report from NWS CYS***
LSRCYS PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE, WY
0707 PM 3 NE GUERNSEY WY TORNADO
05/16/00 PLATTE
TORNADO ON GROUND FROM 707-710 PM NO DAMAGE

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