Friday 1 June 2018

Day 6 - Central Nebraska

FRI 01 JUN 2018

Today was a classic case of waiting very patiently for some decent thunderstorms - very humid with dew points in the low 70s F, plenty of instability - just needed to wait for the cap to be eroded from the approaching dryline/trough out west.
SPC Forecast
SPC Tornado Probability Forecast
After lunch we headed north from North Platte (NE) to Thedford (NE), then east to Dunning (NE) where we parked up and waited for a while, noting the rapid cumulus development. The environment was extremely unstable (over 5,000 J/kg CAPE) but the deep convection was struggling to organise itself somewhat.

By late afternoon a line of thunderstorms had developed over north-central Nebraska - we nudged a little further east to Brewster (NE) then Taylor (NE) to keep an eye on a couple of developing thunderstorms - eventually we opted for the southern cell, and sat north of Burwell (NE) to let the hail core pass close to us.
The frequency of cloud-ground lightning really ramped up, and large hail began falling around us - Pete ran outside to grab the largest hail stone he could find, and we measured it using a set of callipers. It came in at 1.7 inches, or 4.3 cm - pretty sizeable!

1.7 in hail north of Burwell (NE)
By now our line of thunderstorms were beginning to back build quite some ways to the southwest, while moving to the east / northeast. In order to keep ahead of them, we had to keep drifting southeastwards, briefly stopping to watch and take photos etc.

As we approached Ord (NE) it was rapidly getting dark as the sun set, lightning flashing very frequently behind us. I noticed on radar how the low-level rotation with the storm nearest us was beginning to tighten, and we could see the cloud bases lowering and a wall cloud forming. Shortly after, a tornado warning had been issued, but we needed to keep ahead of this thunderstorm as it was fast approaching - so we drove through Ord, and parked up just SE of town looking back to the N / NW.
Our GPS location (blue circle) as the tornado warned storm approached from the west
We'd only been there for 1 minute or so before a lot of dust starting lifting from a field to our north, lit up only by lightning flashes behind. A ground circulation became evident, and eventually the dust cloud had lifted all the way to the cloud base. The tornado was moving east at a fair pace and didn't last for long - by this point the gust front / rear flank downdraft had caught up with us and slammed us with wind and rain from the west, making photographing the tornado to our north virtually impossible - especially given that it was now dark, besides the lightning.

This was the best example I've seen in reality of RFD bowing out, but also wrapping back in to the updraft area where the wall cloud had formed - almost text book!
Dust starts being picked up by a ground circulation, lifting to the cloud base
11 seconds later and the gust front hits, knocking my camera and hence subsequent photos are out of focus
We had to keep moving SE to keep ahead of this line of thunderstorms, fast becoming outflow-dominant. It essentially chased us to Grand Island (NE) where we checked in to a hotel and watched the storms as they came over us. Looking at the Storm Reports for the day, it appears we saw 1 of only 2 tornadoes in Nebraska today.
GPS tracker

No comments:

Post a Comment