Our second chase of the 2011 storm season focused around a Moderate Risk for severe thunderstorms over much of easterm Missouri and central and southern Illinois. Forecasts were prediciting the most severe storms to fire along the warm front as it lifted north through Missouri and Illinois. The Storm Prediction Center posted their 1630 UTC Day 1 Outlook which showed and enhanced area of tornadic development into south central and central Illinois. Here is a graphic of that specific outllook.
A very strong mid-spring low pressure system was moving out of the southern Plains. A warm front was draped along the low and was poised to lift northward through the St. Louis area leaving it in the warm sector. Dewpoints rose into the 60′s and CAPE (Convective Available Potential Energy) values were in the 3000 to 4000 j/kg (joules per kilogram) range. We had moisture in place with the dewpoints and we had the lifting mechanisms with the warm front moving through the area, although initially the atmosphere was capped, but the ingredients were in place for a severe weather outbreak.
Barb and I prepared to depart as i got off an hour early from work to get our drive in to our target area which was Whitehall Illinois. I was in contact with P.D.S. Chase Forecaster Colt Forney as he and fellow Basehunter chasers Scott Peake and Kevin Rolfs came up from Norman to chase along with us. Storms began to fire to the west around 4:30 pm and we had not yet reached our target area. We ere expierencing some connectivity issues with our mobile broadband device due to lack of service in west central Illlinois. As we reached Whitehall, we staged in the Fire Department parking lot. This parking lot was on the south side of town and gave is a great view to the west and south.
We re-established connection and spoke with Colt. They were looking to head a bit more west and attempt an intercept to our immediate west. at this time, the Storm Prediction Center issued a MD (Mesoscale Discussion) regarding the potential for tornadic activity. The Mesoscale Discussion is shown below:
As you can see by the arrow indicated on the map, we were in the greatest area for tornadic development. A Tornado Watch had been previously issued. Colt and his group advised us that there were expierencing strong winds as they intercepted the cell that was moving northeast our of Missouri and into our area. A tornado had already been reported in Pike County, Missouri and was captured on video by Reed Timmer and the TVN crew.
The Fire Chief came out to ask us what the status of the storms were. We showed them the cell that was approaching and that it had been previously tornado warned and did produce a tornado in Missouri. They decided to activate their sirens as a precaution. Colt contacted us to advise that they had 70 mph wind gust accompanying the storm they were on, but it appeared to be losing some of its severity. We decided to abandon this storm and we picked out another one to our southwest that looked promising. As we departed Whitehall we did get into a small hail core area and noted 1′ hail as we drove south towards Carrollton, Illinois. Colt and his crew also bailed out on this storm and chose to drive northeast out ahead of it again in the event that the storm recycled. The northern storm did begin to recycle and looked very promising as we drove east on Ruote 108 towards Carlinville.