Cold air funnels develop in our area at times & occasionally there are many of them.  An example would be an "outbreak" of funnels July 19, 2009 & September 25-26, 1994-both associated with cut-off or nearly cut-off, cold, occluded upper lows.  However, neither of these produced confirmed touchdowns.  These funnels very rarely touchdown & are not associated with a intense, rotating t'storms, but rather spotty showers or just cumulus clouds. 

A cold, often cut-off, upper low that tends to sit & spin for many days often leads to these funnels.  The spin day after day creates lots of vorticity & with cold air aloft & a bit of heating, tubes of spinning air parcels can be turned vertically via rising air.

You combine this with moist lower levels, the low air pressure anyway & then the small, localized pressure drops of cumulus-towering showers & you get a funnel to develop.  It develops right as that pressure drops more under the rising air of that cumulus tower or cumulus tower & shower.  The lower pressure causes the condensation (especially in the moist airmass) of the funnel that spins faster as it tightens up.  Again, the funnel is turn vertically as some heating & rising air turn the rolls of vorticity upward.

A show of the rarity of actual touchdowns, in the past 55 years I have found only 5 verified, official touchdowns from cold air funnels in the viewing area.  One nearly touched down back the summer of 2014 in the Wea Plains area in southwestern Tippecanoe County.  This report is thanks to Meteorologist Tyler Snider of Attica (now NWS Meteorologist in Tulsa).  He shared pictures of the cold air funnels that day.

June 25, 2006

Funnel briefly touched down  south-southeast of Odell (Tippecanoe County) on June 25, 2006 at 2:10 p.m.

It tracked about 1050' through a corn field & farm, but was only 225' wide at its peak width.  It did knock door off quonset hut on a farm & broke a couple of branches.

Here is a radar image near the time of the landspout tornado:

Temperatures were 75-80 over the area with dew points 58-63.

Upper low was rolling like a bowling ball southeastward out of eastern Iowa with spokes of showers & t'showers developing & pivoting around it.

You can see the upper level feature at 500 mb:

June 11, 2003

The others were actually two brief funnels in the Greater Lafayette area on June 11, 2003.

One touched down between Poland Hill Road & Old US 231 on June 11, 2003 at 1:47 p.m.

Some tree branches were snapped down by the very brief touchdown behind modern-day Purdy Concrete

The other occurred at 2 p.m.  It was only 120' wide at its peak width, but tracked 0.5 mile through a corn field & knocked a few tree branches down at the end of the track.

It touched down southeast of the Tippecanoe County Amphitheatre Park, crossed north 9th & lifted just before reaching the CSX railroad tracks.

Radar image around the time of the cold air funnels & landspout tornadoes:

It was not particularly warm by June standards.  Temperatures were 67-74.

There is spiraling, bowling ball upper low pivoting into Illinois toward Indiana.

Note the lack of a surface features, indicating it was an upper level system.  Winds in the upper low from 2,500 to 30,000' were exceptionally light.

Vorticity max pivots from southern Illinois to central Indiana with upper low:

May 24, 1988

This set-up is very similar to what occurred in June 2003.

Note the cold upper low in a vorticity-rich environment & the frontal boundary with low-level wind shift.

It was not overly warm with 60s to 70.

Numerous cold air funnels were reported with the greatest number in the eastern Illinois.

Brief touchdown was reported 1 mile north of Otterbein in a corn field.  A narrow 150' wide, 400' path of flattened/swirled corn plant damage was reported. 

May 29, 1973

A funnel briefly touched down in an open field at the time at 1:20 p.m. on a day with temperatures only in the 60s in Tippecanoe County.

This F0 touchdown was reported from just east of modern-day Robin Hood Lane in West Lafayette & then lifted over the modern-day US 231/around where McCormick Road ends (INDOT maintanence facility).

NOAA NCDC records incorrectly indicate that it had a 15-mile path, which would have taken it through West Lafayette to Buck Creek to Carroll County.  However, other funnels sighted were likely incorrectly reported as the same funnel & assumed to be touching down.  There were multiple cold air funnels that day & NOAA record indicate them as "funnels aloft". 

An F0 with path at only 60' would not make for a 15-mile tornado track & no damage was reported from West Lafayette.  This track would have taken it right through Bar Berry Heights & right over the top of WLFI studios (we had no building damage from storms in 1973).  This path would have also have taken it across Cumberland right by Henderson Street.

The damage path was 60' wide & after touchdown moved northeastward as a "funnel aloft".  Damage was reportedly (inflation-adjusted) $1700 to corn crop.

There is the cold, spinning upper low with highs in the 60s & 1:30 a.m. temperatures 48-54 over the region.