May 29 2012 Widespread severe weather

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This event occurred during the climatologically favored time period of late May to early June, when some of the biggest severe weather outbreaks have occurred in the past in the northeastern U.S. This event was anticipated as early as 5 days prior to the onset, as long range guidance (including the GFS, ECMWF and GFSEnsemble) showed a strong 500 hPa system tracking along the U.S./Canadian border in the 28-30 May time frame. So, although there was some uncertainty in the timing of the system 3-5 days prior to the event, the guidance was predicting respectable instability and shear ahead and along a strong cold front. The Storm Prediction Center and our office highlighted the possibility of severe thunderstorms at least 2 days in advance of the event, as well as local media.

 

The synoptic evolution is as follows: an old frontal boundary south of the region tracked north through much of New York and New England Sunday night and Monday 28 May as upper level ridging ahead of the 500 hPa system strengthened warm advection. The warm front stalled over northern New York and northern New England Monday afternoon and night, where there was an easily discernible surface temperature and dew point boundary. There was also a noticeable temperature gradient at 850 hPa. Some thunderstorms formed along the warm front in northern New York Monday afternoon and evening, some of which produced near-severe hail. Additional thunderstorms reformed through the night in northern New York and some severe weather was observed in some of the thunderstorms early Tuesday morning 29 May. Some very steep mid level lapse rates (elevated mixed layer (EML)) between 850-500 hPa (as much as -8 C/Km) tracked through the region Monday afternoon and night, which supported the thunderstorms overnight Monday night into Tuesday morning along the warm front, where the low-level forcing was weak enough that a significant outbreak was averted. The steepest lapse rates were centered over eastern New York Tuesday morning based on regional 12Z and 17Z 29 May soundings. The conditions contributing to the steep midlevel lapse rates were building east, but forecasted lapse rates and CAPEs over the northeastern U.S. through Tuesday evening were still forecasted to be @ -6.5 C/km and 2000-3000 J/Kg, respectively.

 

The potential for an EML to be over the region was mentioned 5 days prior to the event. Forecast backwards trajectories were run from HYSPLIT showing the potential for an EML to be advected into the Northeast CONUS.

 

Very strong convection was observed in the Great Lakes area Monday night into early Tuesday morning, and as is typical, our office anticipated that even with the convection expected to weaken through the overnight hours, at the very least, the convective footprint in the atmosphere would refire later in the day as it tracked through the northeastern U.S.

 

Early Tuesday morning, SPC called to request a 17Z balloon sounding. Despite recent issues with our upper air system, we were able to accommodate this request. Later Tuesday morning, our office coordinated with the Storm Prediction Center (SPC) to put our area in a moderate risk for the Day 1 Outlook. SPC called us back to coordinate a possible tornado watch, with the reasoning being the high dew points (70+ F) across the area and the possibility of localized channeled southerly flow leading to increased helicity. The staff agreed with this potential. As a result, the Storm Prediction Center coordinated a Severe Thunderstorm Watch for areas west of the WFO ALY CWA and a Tornado Watch was issued for our WFO ALY CWA. The convective footprint and old weakened convection that tracked out of the Great Lakes strengthened quite early in the morning, and additional new thunderstorms formed in central and eastern New York well out ahead of the main line of thunderstorms. Some of the storms ahead of and along the leading edge of the line of thunderstorms rapidly became severe in the early afternoon, producing significant hail and wind damage. The line of storms tracked through the region through the afternoon and evening, exiting the WFO ALY CWA by 0000Z.

 

 

Above:  Forecasts of 850 hPa theta-e from the NAM (left) and GFS (right) showing about a 15K gradient along the prefrontal trough seen in New England at 00Z 30 May, and another gradient of 10-15K along the cold front along and just southeast of the Great Lakes.  The theta-e gradient along the prefrontal trough provided sufficient forcing for initiate and sustain convection.

 

 

Above:  Storm Prediction Center day 3 outlook, probabilities and written text.  This severe weather outbreak was well-anticipated several days before it occurred.

 

 

Above:  Area Forecast Discussion and Hazardous Weather Outlook from NWS Albany, NY on 26 May illustrating the predictable nature to the potential severe weather several days in advance of the severe weather episode.

 

Above:  Area Forecast Discussions and Hazardous Weather Outlook from NWS Albany, NY on 27 May illustrating the predictable nature to the potential severe weather  in advance of the severe weather episode.

 

 

Above:  Area Forecast Discussions from NWS Albany, NY on 28 May illustrating the predictable nature to the potential severe weather  in advance of the severe weather episode.

 

 

Above:  Area Forecast Discussions from NWS Albany, NY on 29 May illustrating the predictable nature to the potential severe weather  in advance of the severe weather episode.

 

 

Above:  Soundings from 00Z 29 May from Albany NY (KALB), Buffalo NY (KBUF), Chatham MA (KCHH), Upton NY (KOKX) and Pittsburgh PA (KPBZ) showing the considerable instability and elevated mixed layer developing over the northeastern U.S. in the vicinity of the warm front and within  the warm sector south of the warm front.  This instability supported the near-severe thunderstorms during the night and early morning prior to the main severe weather outbreak during the afternoon.

 

 

Above:  Soundings from 12Z 29 May from Albany NY (KALB), Buffalo NY (KBUF), Chatham MA (KCHH), Upton NY (KOKX) Pittsburgh PA (KPBZ) and Manawaki Canada (WMW) showing the considerable instability and elevated mixed layer over the northeastern U.S. in the warm sector south of the warm front.  Note that most of the shear is deep layer 0-6km shear with relatively little shear in the 0-3km layer.  Also note the 850-500 hPa and 700-500 hPa lapse rates exceeded -6.5C/km in most areas.

 

 

Above:  Storm Prediction Center day 1 outlook and written text.  This severe weather outbreak was well-anticipated before it occurred.

 

 

Above:  Storm Prediction Center day 1 probabilities for hail, wind and tornadoes.  This severe weather outbreak was well-anticipated before it occurred.

 

Above:  Loop of Storm Prediction Center Mesoscale Page 500 hPa and 300 hPa heights, winds and divergence during the morning and early afternoon of 29 May.  Note the northeastern U.S. is in increasingly divergent upper flow and in the right entrance region of the upper jet.

 

 

Above:  Loop of Storm Prediction Center Mesoscale Page surface based CAPE during the morning and early afternoon of 29 May.  Note the increasing CAPE and values exceeding 2000 J/KG over the northeastern U.S.

 

 

 

Above:  Loop of Storm Prediction Center Mesoscale Page 0-1km shear and effective bulk shear during the morning and early afternoon of 29 May.  Note relatively low 0-1Km shear but the higher values of the deeper shear over the northeastern U.S.

 

 

Above:  Loop of Storm Prediction Center Mesoscale Page supercell composite and the significant tornado parameter during the morning and early afternoon of 29 May.  Note values above normal over the northeastern U.S., more supportive of supercells and less supportive for significant tornadoes.

 

 

Above:  Updated Storm Prediction Center day 1 outlook, written text and probabilities for wind.  Note the upgrade to a moderate risk over the interior northeastern U.S.

 

 

Above:  Storm Prediction Center mesoscale discussion 954 (left) explaining the upgrade to a moderate risk over the interior northeastern U.S. and another mesoscale discussion 956 (right) describing conditions that might require a severe weather watch.

 

 

 

Above:  Tornado watch graphic and text.

 

 

 

Above:  Storm Prediction Center mesoscale discussion 962 (left) explaining the upgrade to a moderate risk over the interior northeastern U.S. and another mesoscale discussion 968 (right) describing conditions that required the continuation of the tornado watch.

 

Above:  Loop of surface map analyses through the morning and afternoon of 29 May.

 

 

Above:  Loop of station plots and MSAS analyses through the morning and afternoon of 29 May.  Notice the increase in instability during the afternoon ahead of the front in the warm sector.

 

 

Above:  Water vapor satellite imagery loop with GFS 500 hPa heights overlayed.

 

Above:  Visible satellite imagery loop with lightning and station plots overlayed.

 

 

Above:  Radar reflectivity loop with lightning overlayed.

 

Above:  Loops of Storm Relative Velocity showing shallow rotations but vertically correlated and stronger at elevation angles above the lowest elevation angle, which illustrated potential developing tornadic activity.  Midlevel rotations and mesocyclones can suggest very efficient hail producers.  No tornadoes were reported from these thunderstorms.

 

 

Above:  Loops of Base Reflectivity and corresponding Storm Relative Velocity showing a broad appendage in the reflectivity structure and shallow rotations in the thunderstorm in the center.  The rotations were shallow but vertically correlated and strongest above the lowest elevation angle, which illustrated potential developing tornadic activity.  Midlevel rotations and mesocyclones can suggest very efficient hail producers.  No tornadoes were reported from these thunderstorms.

 

 

Above:  Loops of Base Reflectivity and corresponding Storm Relative Velocity showing a well-formed hook echo in reflectivity and shallow rotations in the thunderstorm in the center.  The rotations were shallow but vertically correlated and strongest above the lowest elevation angle, which illustrated potential developing tornadic activity.  Midlevel rotations and mesocyclones can suggest very efficient hail producers.  No tornadoes were reported from these thunderstorms.

 

 

Above:  Dual Polarimetric radar 4-panel of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  Note the values supported the presence of hail in the region of highest base reflectivity.

 

 

Above:  Dual Polarimetric radar 4-panel of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  Note the values supported the presence of hail in the region of highest base reflectivity.  3" hail was observed in this thunderstorm.

 

 

Above:  Dual Polarimetric radar 4-panel of base reflectivity (upper left), Differential Reflectivity (ZDR, upper right), Specific Differential Phase (KDP, lower left) and Correlation Coefficient (CC, lower right).  Note the ZDR column extended up above 20,000 feet which was just under the

-20C level of near 24,000 feet.  3" hail was observed in this thunderstorm.

 

Above:  Images from the 4-D Storm Investigator showing a storm over Hamilton County that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level.

 

 

Above:  Images from the 4-D Storm Investigator showing a storm over Herkimer County that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level.  Also note the low  level strong rotation supporting development of tornadic potential.

 

 

Above:  Images from the 4-D Storm Investigator showing a storm near Lake George that produced 3" severe hail.  Note the 70+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Images from the 4-D Storm Investigator showing another storm near Lake George that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Images from the 4-D Storm Investigator showing a storm in Saratoga County that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Images from the 4-D Storm Investigator showing another storm in Saratoga County that produced severe hail.  Note the 70+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Images from the 4-D Storm Investigator showing another storm in Windham County VT that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Images from the 4-D Storm Investigator showing another storm in Ulster County that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Images from the 4-D Storm Investigator showing another storm in southern Saratoga County that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Images from the 4-D Storm Investigator showing another storm in Windham County VT that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level.  Note also the bounded weak echo region and the hook echo in the reflectivity.  There is also a vertically correlated strong rotation suggesting potential tornadic development.

 

 

Above:  Images from the 4-D Storm Investigator showing a storm in Dutchess County that produced severe hail.  Note the 65+ dBZ aloft and the top of the 50+ dBZ extending well through the -20C level. 

 

 

Above:  Base Velocity images from KENX showing straight-line winds developing along the line of thunderstorms in the Mohawk Valley (left) and later in the Berkshires (right).  Peak velocity values were between 50-60 kt.

 

Above:  Plot of the verification of the Storm Prediction Center Severe Weather Outlook overlayed with the observed severe weather reports.

 

Photos below:

 

 

Above:  3+ inch hail at Bolton Landing, Lake George.

 

 

Above:  Hail at Ballston Spa, NY

 

 

Above:  Hail at Caroga Lake, NY

 

 

Above:  Wind Damage at Claverack, NY

 

 

Above:  Stormy skies at Dolgeville, NY

 

 

Above:  Hail at Niskayuna, NY

 

 

Above:  Shelf cloud seen form the Center for Emerging Sciences and Technology Management in Albany, NY.

 

 

Above:  Hail at Pine Plains, NY

 

 

Above:  Hail at Milan, NY

 

 

Above:  Hail at Bellows Falls, VT.

 

 

Above:  Hail at Great Barrington, MA.