20 June 2006 Severe Weather

 

There were some scattered hail reports this day, and one damaging wind report, for a total of 4 severe weather reports, so it was much less active than the previous day. A pre-frontal trough had passed through the region the previous day, and the cold front was forecasted to track through on this day, 20 June. There was instability present, with 1014 j/kg CAPE, and the wind profile was largely unidirectional, however, weaker than the previous day at low levels (Fig. 1). The upper plots at 850 Mb, 500 Mb and 250 Mb (Figs. 2-4) showed that temperatures had cooled at 850 Mb and 500 Mb. The winds at all levels had weakened and shifted south and east, suggesting less support for severe weather as the cooling and jet support continued to shift south and east.

 

 

Figure 1. Upper air sounding from KALB at 1200 UTC 20 June 2006. Note the instability and unidirectional shear.

 

 

Figure 2. 850 Mb upper plot with wind isotachs overlayed. Note the gradual cooling from NY through the Great Lakes and the winds ≤ 25 Kt across the region, so no strong low-level forcing was present at 850 Mb.

 

 

Figure 3. 500 Mb upper plot with wind isotachs overlayed. Note the strongest winds south and east of the region, and the winds were < 50 Kt.

 

 

Fig. 4. 250 Mb upper plot with wind isotachs overlayed. Note the upper jet segment exiting New England, and our region outside of either favorable region of the upper jet.

 

By the afternoon of 20 June, convection formed over the region along the surface cold front, seen in the Infrared satellite pictures (Fig. 5) and visible satellite pictures (Fig. 6). The surface plot showed the wind shift and dew point boundary tracking through NY during the afternoon and evening (Fig. 7). The progress of the surface cold front could be tracked in the LAPS instability display as well with the axis of instability shifting south and east with time (Fig. 8).

 


 

Figure 5. Infrared satellite picture with MSLP, 500 Mb temperatures and lightning overlayed. Click on the figure for a movie of the evolution of the convection between 2000 UTC and 2100 UTC 20 June.

 

 

Figure 6. Visible satellite pictures with lightning overlayed. Click on the figure for a movie of the evolution of the convection between 2000 UTC and 2300 UTC 20 June.

 

 

Figure 7. Surface plot with MSLP and Lifted Index overlayed with Lifted Indices above +1 shaded blue. Click on the figure for a movie showing the evolution of the surface boundary in the MSLP field and instability between 1700 UTC and 2100 UTC 20 June.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 8. LAPS display with MSLP overlayed. Click on figure for a movie of the evolution of the instability between 1800 UTC and 2100 UTC 20 June.

 

Radar base reflectivity (Fig. 9), base velocity (Fig. 10) and volume products (Fig. 11) showed the scattered nature to the convection, but it did favor eastern and southern areas, from eastern NY into the Berkshires of MA, where the severe weather occurred. Reflectivity cross-sections showed the quick pulsing of the storm that produced hail in the Berkshires (Fig. 12). Some small clusters of convection formed that produced some marginally severe hail and one damaging wind report (Fig. 13).

 

 

Figure 9. Four-panel of Base Reflectivity from KENX at the 0.5 (upper left), 0.9 (upper right), 1.3 (lower right), and 1.8 (lower left) elevation angles. Click on figure for movie showing evolution of the Base Reflectivity 2058 UTC to 2215 UTC 20 June.

 

 

Figure 10. Four-panel of Base Velocity from KENX at the 0.5 (upper left), 0.9 (upper right), 1.3 (lower right), and 1.8 (lower left) elevation angles. Click on figure for movie showing evolution of the Base Velocity from 2136 UTC to 2202 UTC 20 June.

 

 

Figure 11. Four-panel of volume products Vertically Integrated Liquid (upper left), Composite Reflectivity (upper right), Layer 2 Maximum Reflectivity (lower right), and Layer 3 Maximum Reflectivity (lower left) from KENX. Click on figures for movies showing evolution of the volume products centered at 2 different points from 2102 UTC to 2149 UTC 20 June.

 

 

Figure 12. Reflectivity Cross-Section from storm that affect eastern NY and northwest CT. Click on the figure for a movie of the evolution of the storm from 2102 UTC through 2145 UTC 20 June.

 

Map of 060620_rpts's severe weather reports

 

 

Figure 13. Severe weather reports for 20 June 2006.