April 19, 1996 modeling study - high resolution results

Beyond this preprint, which was prepared prior to the conference, we carried out further analysis and some preliminary idealized runs with the COMMAS model. With 2 km horizontal and variable (200 m near ground) vertical resolution, we noted greater storm rotation when merging occurred, and the peak vertical vorticity appears rather sensitive to the approach angle of the secondary (weaker, approaching) cell. For these coarse resolution experiments, the primary cell vorticity maximum was 0.043 s^-1; for a cell merging from the south, the magnitude was 50% greater (0.061 s^-1).

A series of higher horizontal and vertical resolution experiments are planned to further investigate the details of the merging and intensified rotation noted in these initial tests. The intensity, timing and approach angle between the two cells will be varied and the impact on FFD/RFD colocation and long-term cell behavior noted.

See also:

• domain and grid layout
• observations
• severe reports

1 km results

• White isosurface: rain water (> 0.5 g/kg)
• Color plane and contours: near-surface water vapor mixing ratio (colored from 9.5-13 g/kg - brown is drier; also contoured every 0.5 g/kg)
• Winds: every 5th vector (every 5 km)
• Time (in minutes) shown at lower right. The data shown here run from 2000 to 2248 UTC, April 19.
• Region shown is the innermost (1 km) nested grid, of the five grids used, looking north.

click for animation (QT)

Details on this work may be found here.

Also: animation of closeup on northern part of line.