Biitter disappointment - 8th April 2015
 
After waiting patiently from the buzz and excitemnt of my first chase, the second opportunity to chase extreme weather came at the beginning of April. This day began very differently to the first chase day in March. Convection from the previous day had continued through the night and into the following morning and afternoon, instead of dying off as it was preidcted to. It had left a veil of mid-level cloud hanging across the land, which restricted the solar heating to the surface and ultimately prevented supercells developing here. The SPC had initially issued an enhanced risk of severe weather, but this was upgraded to a moderate risk across northern Oklahoma, south western parts of Kansas and central Missouri by the mid afternoon. 
SPC convecive outlook issued at 10:30 am local time. The moderate issued was a bit of a surprise because cloud cover looked like it would inhibit any convection. The moderate was issued due to confidence of a high probability of tornadoes. The enhanced area was for hail, severe wind and to a lesser extent, tornadoes. 
Credit: Storm Prediction Center
For this storm chase we were much better prepared, having bought a verizon mifi for mobile internet access whilst on the road, and also using better radar software that used direct feeds from the SPC to update the conditions and weather reported with various storms. We also had the RadarScope mobile radar app on our smartphones, which was a useful back up whenever signal failed for the mifi. With a storm chase already under our belts and better hardware and software to work with, I felt quietly confident that we would be able to intercept a great storm. Living in central Oklahoma, we drove for two hours to the far northeast of the state, arriving by mid-afternoon and made our second plan of attack here. I was surprised to see the moderate probability of severe weather issued by the SPC, since thick cloud and elevated thunderstorms were already in place over much of Oklahoma. In any case, we had to chase near to Oklahoma, since we needed to be back for lectures the next day. This meant having to sacrifice chasing further into the moderate zone in southeastern Kansas. 
Surface weather map, valid for 6pm on the 8th April. All of Oklahoma and parts of Kansas and Missouri are in the warm sector of an apporaching cyclone, positioned over Colorado. Significant moisture return from the Gulf of Mexico had been occuring for several days prior to this event. 
Credit: NOAA/Weather Prediction Center 
Storms were forecast to develop in the warm sector through the late afternoon and early evening. They were not forecast to form in a long line initated by a front, so there were likely to be discrete supercells than developed. The warm front was also forecast to provide a small focus for storm initiation. Along with deep-layer wind shear present over this region, low level shear was forecast to be especially favourable for a few strong tornadoes to develop. The atmospheric setup was a classical Great Plains supercell and tornado setup, with a significant amount of low-level moisture, allowing surface dewpoints to reach into the mid-60s °F. A nose of warm air, advected from the high deserts of Arizona and New Mexico provided a cap which inhibited convection until it could explode in late afternoon. As a result, 2-3000 J/kg of surface-basd CAPE became available over a wide area. 
6pm sounding from Topeka, Kansas. Around 2000 J/kg of CAPE is available here, with values increasing further south towards the Kansas/Oklahoma border. Deep-layer wind shear in this event was especially high, with over 60 knots available in the first 8km. 
From http://weather.uwyo.edu/upperair/sounding.html
We decided to drive to north east Oklahoma to catch any storms that developed earlier in the day and moved northeast into the zone of more favourable conditions for tornado development. If a decent storm that was producing tornadoes developed, we said that we would chase it into Missouri! As it turned out, very little initiated in the moderate zone through the afternoon, and we were left looking at a non-severe thunderstorm that did not produce any severe weather as it trundled northeast through Kansas. The reasons for the lack of severe thunderstorm development during this time are interesting, but will not be explained here. 
 
We made the tough (and frustrating) decision to drive due west, parallel to the Kansas/Oklahoma border to intercept a supercell that developed close to the Oklahoma panhandle. This storm was a strong supercell that probably developed along the warm front and was moving east (towards us) at around 40 mph. We were moving towards it at around 70 mph, along the main roads, but it still took over 2 hours to drive that distance of 200 miles. Along the way, we anxiously watched as the supercell produced several tornadoes and was constantly dropping funnel clouds. It had a great radar signature, with a hook echo and all the other classic features of a supercell. Unfortunately, we arrived only about 45 minutes before dark and so many of the features of the storm were not easily visible. However, we did witness some incredible lightning, a rotating wall cloud and possibly a funnel cloud. The supercell produced several EF-0 tornadoes, even after dark, and passed to the north of Witicha, Kansas. This was too far north for us to chase, so we turned around and headed for home. 
Some mammatus clouds from a supercell to the south of the storm we were chasing in Kansas. This supercell formed in west-central Oklahoma and produced another EF-0 tornado. 
Unfortunately, I don't have any more worthwile photos to share, but there is a video of the Kansas supercell on my
 
After it got dark and we began the long drive back home, an intercept of a squall line with strong straight line winds looked tempting. We ended up sitting in the car, eating pizza and watching the lightning show and torrential rain. The strong straight-line winds had died down by this stage, but we witnessed some greating night-time lightning, including some strikes that were less than 100 metres away! This storm chase was a dissapointment and a bust, however. It seemed like a bit of a waste of time, driving around 500 miles and barely seeing a supercell as night fell. I think this can partly be blamed on our own lack of judgement of where to head to wait for the storms (that wrong call we made, driving to north east Oklahoma, cost us most of the day and hundreds of extra miles), and partly on the SPC. Their convective outlooks issued in the morning and afternoon of the 8th of April were, unfortuntely, mostly wrong. However, if this chase taught me anything, it was to never expect the forecast to be perfect and to always expect something different and unexpected to happen.                      
YouTube channel.
Storm Prediction Center forecast verification for 1630Z, or 10.30 am local time. The moderate risk, which was mainly issued for tornadoes, lacked any and was mostly battered by strong straight-line winds instead. Most tornadoes developed well to the west of this region, in the slight and enhanced risks of severe convective weather. The supercell we chased in southern Kansas can be spotted by the long line of red dots (tornadoes).
Credit: Storm Prediction Center