06-01-10 CHASE LOG: NE
This chase consisted of MaryLynn and I, and eastern NE looked like the place to be as a Slight Risk was in place for the area with the SPC issuing a 10% hatched area for tornadoes by the 1630Z update.The upper flow was fairly zonal but there was a shortwave trough forecast to swing through the region later in the day that would initiate convection on a stalled boundary that eventually evolved into a cold front.This front was enhanced by a convective complex that moved across the NE/SD border during the morning, which spit out an outflow boundary that intersected the boundary.The plan was to leave Sioux City, IA early in the morning and head south to Lincoln, NE to get ahead.The airmass ahead of the boundary was becoming quite unstable during the afternoon with SB CAPE values of 2000-3000 j/kg with higher pockets of instability.Moisture was not an issue with dewpoints in the upper 60’s, while inflow winds were from the south-southeast at around 15-20 mph.The idea was that any storms that fired in this airmass ahead of the boundary would be supercells with tornado potential due to bulk shear values of 40-50 kts and decent low level shear as well.Storms did not end up firing in this airmass ahead of the boundary due to the lack of any large scale forcing.Storms did fire on the boundary to the north around 1pm and did not look impressive at first and were taking their time to mature/intensify.One storm finally took on supercell characteristics around 3pm near Stanton, NE and this is the storm we went after, traveling north on Hwy 77.As we traveled up 77, the storm was reported to have produced a 5 minute tornado near West Point, NE.We were too late for this tornado, but we did intercept the cell near Oakland, NE.At this point, the storm began to move to the east rather quickly so, to stay out ahead, we progressed on Hwy 32 to Craig, NE and then stair-stepped south and east on some gravel roads.All the while, the storm had cycled with a new, rotating wall cloud.South of Craig at around 4:20pm we observed a large funnel that was moving rapidly northwest to southeast.This funnel got very close to the ground at this point, but we could not confirm that it touched down until a report came in from another storm chaser in the area that a tornado had truly been observed.We were quite a distance away at this point and the reason why we could not tell for sure if it was down or not.Thereafter, the storms began to congeal into a line but our storm continued to show strong signs of rotation embedded in the heavy rain and hail on the line as it crossed I-29 into western IA.Here is where we let the storm core us near Missouri Valley, IA as we were right in the notch and observing a lot of rising motion and several areas of rotation.Thereafter, we attempted to get ahead of the line, traveling south on I-29 through extremely heavy rain, high winds, and small hail, eventually calling it a day as storms had gone completely linear at this point.
Suspicious lowering looking west from Oakland, NE.
Blocky non-rotating wall cloud near Oakland, NE.
Fuzzy picture of reported tornado near Craig, NE.
Our position around the time the picture above was taken near Craig, NE.
Another radar grab from near the time of the tornado and the approximate location of our position as noted by the arrow.
View of the storm on I-29 near Missouri Valley, IA with continued, well defined mesocyclone.
More photos from this day can be found here: http://www.flickr.com/photos/39991047@N02/sets/72157624131398817/