16 June 2008 Severe Weather Outbreak

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Brief Description and Comments of the Event(s):

A short wave and a weak warm front/prefrontal trough moved eastward across Upstate NY and New England between 1000 UTC-1400 UTC with some showers and isolated thunderstorms. The shower activity helped moisten the boundary layer with surface dew points rising back into the upper 50s to mid 60s across much of the Albany forecast area. Pronounced clearing occurred in the wake of the morning disturbance...with significant heating occurring ahead of surface cold front and a potent short wave rotating around a cutoff low over south central Ontario.

Observational data and model guidance indicated a major severe weather outbreak was likely to occur in the Northeast. The conditional Maglenta index indicated a major severe day was going to occur with SBCAPEs of 1000-1500 J/kg...a Max sounding wind of 60 knots...0-3 SREH of about 150 m^2/s^2...storm motion of 27 knots...and EHI of 0.9. The 12Z Raob data at KBUF and KALB indicated the convective temps would be in the mid to upper 70s for convective initiation due to steepening mid level lapse rates /700-500 mb and 850-500 mb/ of around 7C/km with low wet bulb zero heights of 9-10 kft. Hail and damaging winds look to be the main threats despite bulk shear values in the 0-6 km layer of 40-45 kts. It should be noted the water vapor loop showed a mid and upper level jet streak with pronounced drying over PA and
WRN NY. The cyclonically curved jet...upper level divergence...and the SRN reaches of the forecast area being the left front quad/cyclonic exit region of the jet streak provided the upper level dynamics for the outbreak.

The VIL of the Day based on the 1200 UTC KALB sounding was 43 kg/m^2. The range was 39-45 kg/m^2. An 1800 UTC sounding was done. There was plenty of SBCAPE (in excess of 1500 J/kg) that was utilized by the cold front and its associated upper level disturbance.

Figure 1. Day 1 Convective Outlook from the Storm Prediction Center at 203 AM EDT 16 June. Note the moderate risk for much of the northeastern U.S., mainly for the potentially high number of severe hail and wind reports.

Figure 2. Area Forecast Discussion from NWS Albany at 410 AM 16 June. Note the near term discussion with the expectation of severe thunderstorms later in the day, with more emphasis on hail, and less emphasis on strong and damaging winds.

a) b)

Figure 3. Skew-T Log-P diagrams from 12Z 16 June for a) Buffalo, NY and b) Albany, NY. Note the considerable instability at 12Z in Buffalo, upstream from Albany, partially due to the cooling and drying aloft.

a) b)

Figure 4. Storm Prediction Center Day 1 probabilities for 16 June for a) severe wind and b) severe hail. Note the highest probability for wind, but still a relatively high probability for hail.

Figure 5. Area Forecast Discussion from NWS Albany at 758 AM 16 June. Note the near term discussion, referring to the Maglenta Index. Based on the observed severe weather and hail sizes (presented later), we must be careful in our use of indices and forecasted specific hail sizes, due to the micro and local scale nature to severe weather, which cannot be resolved in parameters for indices..

Figure 6. Storm Prediction Center Mesoscale Discussion from 919 AM 16 June. Note the concern for early development of severe thunderstorms and a possible watch.

Figure 7. Day 1 Convective Outlook from the Storm Prediction Center at 843 AM EDT 16 June. Note the emphasis on potential damaging winds, and little to no emphasis on large hail.

Figure 8. Note that by noon on 16 June, thunderstorms began to develop over central and western NY.

Figure 9. The Storm Prediction Center Day 1 Convective Outlook, with equal treatment of the threats of hail and damaging winds.

Figure 10. Severe Thunderstorm Watch county outline and text from the Storm Prediction center, issued at 1130 AM 16 June.

Figure 11. Area Forecast Discussion from NWS Albany at 1210 PM 16 June. Note the continued emphasis on both hail and wind damage threats, the Maglenta Index and the 1 to 1.25 hail forecasts. Also note the mention of the planned 18Z sounding. As stated earlier, specificity based on indices should be cautioned.

a) b)

Figure 12. Skew-T Log-P from a) 18Z at Albany, NY and b) 17Z at Buffalo, NY. Note the considerable destabilization that took place at Albany between 12Z and 18Z, and the considerable drying aloft that took place at Buffalo. Note also that the unidirectional winds at both sites were not very strong (>25Kt) through the boundary layer.

Figure 13. Storm Prediction Center Mesoscale Discussion at 241 PM EDT 16 June. Note the greater emphasis on hail and less emphasis on wind damage potential.

Figure 14. Radar reflectivity at 19Z 16 June. Note the bands of thunderstorms with very high reflectivities tracking through northern PA and central and eastern NY.

Figure 15. Storm Prediction Center Day 1 Outlook from 358 PM EDT 16 June. Note the continued emphasis on large hail, and just a brief mention of small scale bows with potential damaging winds.

Figure 16. Thunderstorm Watch county outline and text from the Storm Prediction center, issued at 330 PM 16 June.

Figure 17. Storm Prediction Center Mesoscale Discussion at 553 PM EDT 16 June. Note the diminishing severe weather threat.

a) b)

c) d)

Figure 18. Radar reflectivity from KENX at a) 2142Z 16 June and b) 2146Z 16 June, and radar Storm Relative Velocity Map Display from KENX at c) 2142Z 16 June and c) 2146Z 16 June. Note the reflectivities around 70 dBZ and the average rotation of >30 Kt, Tornado Vortex Signature (TVS), as well as VR Shear between 0.0331/S-0.0434/S, suggesting a potential tornado.

a) b)

Figure 19. Radar reflectivity from a)2156Z 16 June and b) 2256Z 16 June. Note the lines and clusters of high reflectivity thunderstorms consolidated into a Quasi-Linear Convective System (QLCS) in the form of a Line Echo Wave Pattern (LEWP) over southern NY and southwestern New England.

Figure 20. Storm Prediction Center Mesoscale Discussion from 618 PM 16 June. Note the shifting emphasis on heavy rain, although there is an acknowledgment of the potential for a few more potential occurrences of large hail or damaging winds.

a) b)

c) d)

Figure 21. Upper air analyses from the Storm Prediction Center, valid 00Z 17 June. Note the cooling taking place at all levels, the 50 Kt winds at 500 Mb, a threshold the Storm Prediction uses for enhanced sever weather threats, but the lack of upper jet dynamics at 300 Mb.

Figure 22. Radar reflectivity loop and progression of Severe Thunderstorm Warning and Tornado Warning Polygons on 16 June.

Color scale for hail size on images below.

Figure 23. Track of hail swath across the Capital District and Schoharie into northern Columbia Counties.

Figure 23. Hail swath from Ulster County to areas between Kingston and Poughkeepsie.

Figure 24. Hail swath from north of Poughkeepsie into Connecticut, and a separate swath in the southern Berkshires.

Severe weather reports for individual NWS offices, courtesy of The Iowa Environmental Mesonet division of Iowa State University Department of Agronomy

NWS Buffalo, NY

NWS Binghamton, NY

NWS Albany, NY

NWS Burlington, VT

NWS Upton, NY

NWS Taunton, MA

Many thanks to spotters, media and everyone who e-mailed us pictures of their hail. The severe weather reports and pictures are vital to the severe weather warnings we issue. We are always grateful for the reports and pictures that help us verify what we see on radar. The pictures are displayed below, sorted by location. If anyone would like credit for their photos, please e-mail Neil.Stuart@noaa.gov

Colonie, NY Click here for a 14 second movie of hail in North Colonie.

Guilderland, NY

Kinderhook, NY

S.U.N.Y. Albany Stuyvesant, NY - Gloversville, NY Valatie, NY

Hyde Park, NY and the NY State Thruway

Esopus, NY

What was learned from this event:

-This was a significant hail event with hail stones to 2" in diameter in Guilderland. It hailed 15 minutes at the building with 5 minutes of hail to nickel size.

-The Moderate Risk was warranted. It was not a big wind event...since the vast majority of the reports were hail.

-We had strong rotation to 40 kts with a cell in Dutchess Co. with a shear value of 0.043. It did not produce a tornado. We had a TVS for 3 scans and intermittent rotation that met the local criteria for issuing a tornado warning. The caveat was that the radar beam is at 5-5.5 kft AGL.

-Always try to generate polygons to match the counties (i.e. southern Herkimer Co saw teeth). It is recommended to use warn track or hatched track to get the output. A polygon slightly missed a warning.