16 May 2012 Severe Hail

(Click on any image for larger image)

 

The synoptic set up was conducive for severe weather in the Northeast, with a strong mid/upper level disturbance moving eastward across the eastern Great Lakes during the day/evening. A strong mid level wind max, with the core positioned just to the northwest of our area, was associated with this upper level disturbance and was mainly responsible for the large magnitude of deep layer vertical wind shear of 40-50 knots.

 

At the surface, as is typical for this area, there were at least two distinct boundaries present. One was a pre-frontal trough that progressed eastward from central NY during the morning/early afternoon. Dew points dropped in the upper 40s to lower 50s to the west of this boundary, which to the east in our area dew points were in the upper 50s to lower 60s. Convection was initiated along this boundary, over the western Adirondacks and Mohawk Valley early to mid afternoon and progressed eastward. The second boundary was a cold front over western NY.

 

NWP model guidance showed instability and shear supportive of severe weather during the afternoon of 16 May.  The mid-level lapse rates (850-500 hPa) and CAPE forecasts from both the NAM and GFS showed considerable instability.  The 850 hPa predictions indicated a respectable theta-e gradient associated with the advancing cold front which suggested good low-level forcing that could initiate and sustain convection.  Winds at 850 hPa were strong as well suggesting enhanced low-level forcing.  Upper level dynamics were pushing into the region as well, seen in upper plots and satellite imagery as an upper-level vorticity center tracked east, through southern Canada along the U.S./Canada border.  The high resolution WRF provided good guidance as to the areal extent, timing and mode of the convection in its predicted reflectivity field.

 

 

Above:  Loop of 500 hPa heights forecasts from the NAM, GFS, ECMWF and GFSEnsemble showing the upper-level energy tracking through southern Canada.

 

 

Above:  Loop of 850 hPa winds forecasts from the NAM, GFS, ECMWF and GFSEnsemble showing the increasing boundary layer winds and increasing low-level forcing.

 

 

Above:  Loop of surface winds forecasts from the NAM, GFS, ECMWF and GFSEnsemble showing the directional convergence along the surface cold front.

 

 

Above:  CAPE forecast from the NAM (upper left), GFS (upper right), ECMWF (lower left) and GEFSEnsemble probability of 0.05" of rain in 6 hours (lower right).

 

 

Above:  Loop of 850-500 hPa forecasts from the NAM (left) and GFS (right) showing the steepening mid-level lapse rates (-6 C/Km to -7.5 C/Km).

 

 

Above:  Loop of 850 theta-e forecasts from the NAM (left) and GFS (right) showing the tight gradient, supporting strong low-level forcing.

 

 

Above:  Loop of layer composite reflectivity forecasts from the high resolution WRF initialized at 00Z 16 May (left) and 12Z 16 May (right).

 

 

Above:  16 May 12Z upper plots at 250 hPa (left), 500 hPa (center left), 850 hPa (center right) and 925 hPa (right).  Note the advancing upper short wave and the upper jet energy along with the increasing 850 hPa winds and thermal ridge.

 

 

Above:  12Z 16 May soundings from Albany, NY (KALB, left), Buffalo, NY (KBUF, center) and Upton, NY (KOKX, right).  Note the instability and shear present in the 12Z soundings across the region.

 

 

Above:  18Z 16 May sounding from Albany, NY (KALB, left).  Note the increased instability and shear present in the 18Z sounding at KALB.

 

 

Above:  Day 2 Storm Prediction Center outlook issued 15 May highlighting the severe thunderstorm potential for 16 May.

 

 

Above:  Day 1 Storm Prediction Center outlook issued the morning of 16 May highlighting the severe thunderstorm potential for 16 May.

 

Above:  Mesoscale discussion issued by the Storm Prediction Center highlighting severe thunderstorm potential and the potential need for a Severe Thunderstorm Watch.

 

 

Above:  Areal outline of the Severe Thunderstorm Watch and overlay of radar.

 

 

Above:  Mesoscale discussion issued by the Storm Prediction Center discussing the convective parameters supporting the continuation of the Severe Thunderstorm Watch.

 

 

Above:  Mesoscale discussion issued by the Storm Prediction Center discussing the convective parameters supporting the continuation of the Severe Thunderstorm Watch.

 

 

Above:  Loop of surface maps showing the passage of the cold front.

 

 

Above:  Loops of water vapor satellite imagery prior to and during the event.

 

 

Above:  Loop of visible satellite imagery during the event.

 

 

Above:  Loop of radar reflectivity and severe thunderstorm warning polygons during the event courtesy of Iowa State University.

 

 

Above:  Loops of radar reflectivity and severe thunderstorm warning polygons during the event.

 

 

Above:  Loops of vertically integrated liquid during the event, with the highest values highlighting where the greatest potential for large hail was tracking, including parts of the Capital District (right panel).

 

 

Above:  Four panel Dual Polarimetric Radar image of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  The values of each product suggest hail as one of the precipitation types in the area of the highest base reflectivity.

 

 

Above:  Four panel Dual Polarimetric Radar image of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  The values of each product suggest hail as one of the precipitation types in the area of the highest base reflectivity.  The 3 body scatter spike extending northwest of the high base reflectivity core suggests large hail.

 

 

 

Above:  Four panel Dual Polarimetric Radar image of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  The values of each product suggest hail as one of the precipitation types in the area of the highest base reflectivity.

 

 

Above:  Four panel Dual Polarimetric Radar image of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  The values of each product suggest hail as one of the precipitation types in the area of the highest base reflectivity.

 

 

Above:  Four panel Dual Polarimetric Radar image of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  The values of each product suggest hail as one of the precipitation types in the area of the highest base reflectivity.

 

 

Above:  Dual Polarimetric Radar Hydrometeor Classification Algorithm (HCA) output for 4 thunderstorms hat produced hail.  The HCA indicated rain and hail mixed.

 

 

Above:  Dual Polarimetric Radar ZDR columns extending upward about 13,000 feet to 18, 000 feet, which is well above the freezing level of around 11, 000 feet but not quite to the -20C level, which was around 23,000 feet.

 

 

Above:  Severe weather reports (courtesy IEM Iowa State)

 

Photos of thunderstorms and observed hail

 

 

 

Above:  Pictures of a mesocyclone to the north of the Center for Emerging Sciences and Technology Management (CESTM).

 

 

Above:  Severe hail observed in Herkimer County (left), including the town of Ilion (right).

 

 

Above:  Non-severe hail observed near Glens Falls airport.

 

 

Above:  An unusual cloud base or low hanging scud cloud in Saratoga County.

 

 

 

Above:  Chaotic base of the thunderstorm as seen from Albany (top 3) and rainbow (bottom 2).

 

 

 

Above:  Developing mesocyclone as seen just northwest of North Colonie (top left), and observed severe hail in North Colonie (remaining 4 panels).