MAY 27, 2001 TORNADIC SUPERCELL AND
WALL CLOUD OVER HAMILTON, NJ
  
1630Z SPC Convective Outlook Risk Map
(same as 20Z output.)
2000Z CONVECTIVE OUTLOOK:
...NORTHEAST U.S...
A LINE OF STRONG TO OCCASIONALLY SEVERE THUNDERSTORMS HAS DEVELOPED THIS AFTERNOON ALONG AN ADVANCING SURFACE BOUNDARY ACROSS WESTERN NEW YORK INTO CENTRAL PENNSYLVANIA. SURFACE OBSERVATIONS IN THIS AREA SHOW A CLOUDY AND COOL AIR MASS IN PLACE ACROSS THE NORTHEAST

...BUT VERY COLD MID LEVEL TEMPERATURES /-20 TO -25 DEG C AT 500 MB/ ARE ALSO PRESENT /AS NOTED ON MORNING SOUNDINGS THROUGHOUT THE GREAT LAKES AREA/. THERE IS SUFFICIENT SURFACE BASED NSTABILITY
/SURFACE BASED CAPE VALUES TO 1000-1500 J/KG/ TO SUPPORT ADDITIONAL THUNDERSTORM ACTIVITY. THE COLD MID LEVEL AIR WILL HAVE THE POTENTIAL TO SUPPORT LARGE HAIL WITH THE STRONGEST ACTIVITY THROUGH THE REMAINDER OF THE AFTERNOON AND EVENING.

00Z Surface Analysis for May 28, 2001
PA Thunderstorms formed ahead of the surface warm front asscoiated with the developing wave in Michigan. This is the situation as the tornadic cell cloud is passing through central NJ. (Image at left from Severe Thunderstorm Event Index; analysis by C. Crisp , SPC.)
GIF animation of KDIX 0.5 deg reflectivity scans from 21Z to 23Z. (Click on thumbnail for larger animation.) The leading cell splits, with the LH storm following the top fork and the RH storm following the bottom. It is the latter cell that passes over Mercer County, NJ.
Once the cell reaches the Delaware river, set up camera on vacant lot in Robbinsville, NJ. The intent was to test a variable ND filter consisting of crossed polarizers for daytime lightning, but this storm did not present much lightning. (Right: Google Earth image of camera location.)

(BTW, the idea of using crossed polarizers as a variable NDF idea did work, but naturally could not overcome reciprocity failure in the film, and was eventually abandoned. Also, it was not truly neutral density owing to the strong spectral dependence of the resulting image.)
In 2008, the site is heavily developed, and no longer suitable for viewing storms.  The camera was located in what is now a parking lot for a local multistory business and the effective horizion is elevated to about 40 degrees (or more.)
 
 
Time: about 2230Z (~6:30 PM) Looking approximately WNW. The wall cloud is rotating and has just cleared the clump of trees at the left edge of the field of view. The blue tint is due to the wavelength dependence of the polarizers being used to attenuate the ambient light.
 
 The cell was moved a bit further ENE. The lack of distinct outlines is caused by poor contrast in the scene itself, but also due to motion of the cell during the 2-3 minute exposures.
 
Last good view on the roll. The cell continued off to the ENE and out of view, lost in the treeline N of the camera site. A short inflow tail is visible, although this feature seemed to rotate with the wall cloud. 
 
 
KDIX 2.42 deg Reflectivity at 2237Z. A slight hook-shaped echo has developed over central Mercer county. A strong mesocyclone is associated with the inflow notch (see right.) The trailing (left-moving storm) is due west of the right-moving cell. KDIX 2.42 deg Radial Velocity at 2237Z.The mesocyclone--not so visible in the lowest elevations at this (close) distance from the radar--is obvious even in this thumbnail sketch..
 
 
KDIX 3.34 deg Reflectivity at 2237Z. The storm quickly moves off to the NE and into an area of congested roads and poor visibility
KDIX 3.34 deg Radial Velocity at 2237Z.
Later, this storm spawned an F2 tornado in Gordon's Corner. The NCDC Storm Events database lists this event as well.
 
The Severe Thunderstorm Event Index (SPC) records a sequence of Tornado, hAil and Wind events associated with this storm (which are not listed in the LSR, for some reason.)  
 
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