1. Evan Lowery Dr. Eric Hoffman Northeast Regional Operational Workshop IX

2. - Northern New England thunderstorms pose a forecasting challenge - Large-scale flow has often been used as a forecasting tool - Few thunderstorm climatologies have been completed across northern New England

3. How does large-scale flow affect the development and intensity of northern New England thunderstorms during the warm-season months April – September (2003 – 2007)?

4. Questions 1. How can thunderstorms be identified and monitored? 2. How can the pre-convective environment be analyzed? 3. How can large-scale flow be identified for each thunderstorm cell? 4. How can results be objectively analyzed? How does large-scale flow affect the development and intensity of northern New England thunderstorms?

5. “ Vertically integrated liquid (VIL) water content of thunderstorms has been shown to be a good indicator for the potential of severe weather.” Winston and Ruthi (1986) Grasso and Hilgendorf (2001) a. cell-based or gridded VIL? b. VIL limitations c. VIL threshold for thunderstorms? d. Which radar product will be used? How does large-scale flow affect the development and intensity of northern New England thunderstorms? F IG 1: Miller (2007) 1. How can thunderstorms be identified and monitored?

6. a. cell-based or gridded VIL? (VIL: cell-based) b. Limitations of VIL c. VIL threshold for thunderstorms? d. Which radar product will be used? How does large-scale flow affect the development and intensity of northern New England thunderstorms? 1. How can thunderstorms be identified and monitored? F IG 2: Miller and Sirvakta (2007) 25 km125 km F IG 3: Brown (2000) 25 km125 km

7. 25 km from RDA 125 km from RDA How does large-scale flow affect the development and intensity of northern New England thunderstorms? F IG 4: VIL sampling region (25 – 125 km from KGYX)

8. a. cell-based or gridded VIL? (VIL: cell-based) b. VIL limitations? (Range: 25 – 125 km) c. VIL threshold for thunderstorms? d. Which radar product will be used? “VIL values in organized convective cells usually exceeded 10 kg m -2.” Kitzmiller et al. (1995) Brimelow (2006) “A VIL threshold of 25-30 kg m -2 was effective at correctly identifying those storms associated with the severe hail over central Alberta.” Brimelow (2006) How does large-scale flow affect the development and intensity of northern New England thunderstorms? 1. How can thunderstorms be identified and monitored?

9. a. cell-based or gridded VIL? (VIL: cell-based) b. VIL limitations? (Range: 25 – 125 km) c. VIL threshold for thunderstorms? (Threshold: 10 kg m -2 ) d. Which radar product will be used? WSR-88D Level III Storm Structure Product (Gray/Portland, ME) How does large-scale flow affect the development and intensity of northern New England thunderstorms? 1. How can thunderstorms be identified and monitored?

10. F IG 4: NCDC Java NEXRAD Viewer (Short range reflectivity 06/19/2006)F IG 5: NCDC Java NEXRAD Viewer (Short range reflectivity 06/19/2006)F IG 6: NCDC Java NEXRAD Viewer (Storm structure product 06/19/2006)F IG 7: NCDC Java NEXRAD Viewer (Storm structure product 06/19/2006) F IG 8: NCDC Java NEXRAD Viewer (Storm structure alphanumeric table 06/19/2006)F IG 9: NCDC Java NEXRAD Viewer (Storm structure alphanumeric table 06/19/2006) How does large-scale flow affect the development and intensity of northern New England thunderstorms? WSR-88D Level III Storm Structure Product (Gray/Portland, ME)

11. a. cell-based or gridded VIL? (VIL: cell-based) b. VIL limitations? (Range: 25 – 125 km) c. VIL threshold for thunderstorms? (Threshold: 10 kg m -2 ) d. Which radar product will be used?(Storm Structure) WSR-88D Level III Storm Structure Product (Gray/Portland, ME) How accurately can the storm structure product track storms? “The results show that cells above 40 dBz have a 68% of being detected and that cells with reflectivities above 50 dBz have a 96% chance of being detected.” Johnson et al. 1998 How does large-scale flow affect the development and intensity of northern New England thunderstorms? 1. How can thunderstorms be identified and monitored?

12. CRITERIA VIL: cell-based Range: 25 – 125 km from GYX Min VIL: 10 kg m -2 Min Reflectivity:50 dBz Min Duration:> 1 Volume scan WSR-88D Product: Storm Structure How does large-scale flow affect the development and intensity of northern New England thunderstorms? 1. How can thunderstorms be identified and monitored?

13. NLDN Lightning strikes Vs. VIL values June – August (2005) How does large-scale flow affect the development and intensity of northern New England thunderstorms? 1. How can thunderstorms be identified and monitored? F IG 10: VIL (kg m -2 ) Vs. Lightning Count (%)

14. Proximity Soundings a. Def. proximity sounding? “Proximity refers to events which are required to occur within 3 h of the sounding time and within 100 nautical miles (185 km) in space. Craven (2001), Craven et al. (2002a,b), and Brooks (2003) b. Which Reanalysis dataset should be used? “It is expected that the NARR data set will show the mesoscale detail in weather systems, particularly severe weather, that the coarser NCEP/NCAR GR would miss.” Grumm (2005) How does large-scale flow affect the development and intensity of northern New England thunderstorms? 2. How can the pre-convective environment be analyzed?

15. 700 hPa is “the first mandatory pressure level that is clearly above the underlying terrain.” Wasula and Bosart (2002) How does large-scale flow affect the development and intensity of northern New England thunderstorms? 3. How can large-scale flow be identified for each thunderstorm?

16. Radar Data Objective Analysis Interpolation Method: Isotropic Barnes Analysis w q = exp(-r’2/k) k = k*[(2 Δ az ) 2 max ] Trapp and Doswell (2000) How does large-scale flow affect the development and intensity of northern New England thunderstorms? 4. How can results be objectively analyzed? k32.8 k*0.5 2 Δ az 232km [ 1 o ( π /180)] grid spacing4 km radius of influence3 * grid spacing min. # obs3 R = 232 km

17. - Find radar indicated start time - Find location of Max intensification ( Δ VIL/ Δ t) - Find location of Max intensity (VIL) - Find location of Max Weakening ( Δ VIL/ Δ t) - Find radar indicated end time - Download relevant NARR data - Identify large-scale flow (925, 700 hPa) per storm - Stratify results by large-scale flow Monitoring Storm Cell Intensity How does large-scale flow affect the development and intensity of northern New England thunderstorms?

18. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) - 231 events - 3238 thunderstorm cells meet criteria - 700 hPa Flow: (SW=1921, W=651, NW=599, SE=45, NE=22) F IG 11: Thunderstorm cells per flow regime (700 hPa) How does large-scale flow affect the development and intensity of northern New England thunderstorms?

19. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) Yearly, Monthly, and Diurnal distribution F IG 13: Monthly distribution of thunderstorm cellsF IG 14: Diurnal distribution of thunderstorm cells How does large-scale flow affect the development and intensity of northern New England thunderstorms? F IG 12: Yearly distribution of thunderstorm cells

20. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) Focus on 4 Flow Regimes How does large-scale flow affect the development and intensity of northern New England thunderstorms? Level, Flow# Events# Thunderstorm cells 925 hPa, SE49274 700 hPa, SW1501921 700 hPa, W79651 700 hPa, NW73599

21. Northern New England Terrain Map

22. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) 925 hPa SE FlowStorm Density [count / area * 100] How does large-scale flow affect the development and intensity of northern New England thunderstorms? 49 events274 thunderstorm cells

23. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) 700 hPa SW FlowStorm Density [count / area * 100] How does large-scale flow affect the development and intensity of northern New England thunderstorms? High Storm Density 150 events1921 thunderstorm cells

24. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) 700 hPa W FlowStorm Density [count / area * 100] How does large-scale flow affect the development and intensity of northern New England thunderstorms? High Storm Density 79 events651 thunderstorm cells

25. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) 700 hPa NW FlowStorm Density [count / area * 100] How does large-scale flow affect the development and intensity of northern New England thunderstorms? High Storm Density 73 events599 thunderstorm cells

26. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) Stability Assessment700 hPa FlowCAPE [ J / kg ] How does large-scale flow affect the development and intensity of northern New England thunderstorms? CAPE(J/kg) 0Stable 0-1000Marginally unstable 1000-2500Moderately unstable 2500-3500Very unstable ≥3500Extremely unstable 150 events1921 thunderstorm cells79 events651 thunderstorm cells73 events599 thunderstorm cells Highest CAPE values south of mountains and away from coast F IG 15: Avg CAPE per 700 hPa Flow Regime

27. Thunderstorm cells ( VIL ≥ 23 kg m -2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan ) Stability Assessment700 hPa FlowTotal Totals [-] How does large-scale flow affect the development and intensity of northern New England thunderstorms? Total Totals Index 44Thunderstorms 50Severe thunderstorms possible ≥ 55Severe thunderstorms likely, tornadoes possible TT = (T850 + T d 850) - (2 * T500) 4353 F IG 15: Avg. TT per 700 hPa Flow F IG 26: Total Totals Histogram (700 hPa SW Flow)

28. SW Flow has the largest number of thunderstorm cells 925 hPa SE Flow thunderstorm cells develop along mountains 700 hPa SW, W, NW Flow localized concentrations of thunderstorm cells Total Totals low variability across all flow regimes Ongoing Research - Compare: Severe Vs. non-severe days Short, medium, long duration storms - Generate soundings Severe Vs. non-severe days Short, medium, long duration storms How does large-scale flow affect the development and intensity of northern New England thunderstorms?

29. AMS Glossary (2007). Definition of Vertically Integrated Liquid (VIL). Retrieved February 9, 2007 from http://amsglossary.allenpress.com/glossary/search?id=vertically-integrated-liquid1 Brimelow,C.,G.W. Reuter,2006: Spatial Forecasts of Maximum Hail Size Using Prognostic Model Soundings and HAILCAST. Weather and Forecasting, 21, Issue 2, 206-219. Brooks,H.E,J.W. Lee,J.P. Craven,2003: The spatial distribution of severe thunderstorm and tornado environments from global reanalysis data. Atmospheric Research., 67-68, 73-94. Brown, R. A., V. T. Wood, 2000: Improved WSR-88D Scanning Strategies for Convective Storms. Weather & Forecasting, 15 Issue 2, 208-220. Johnson, J. T., P. L. MacKeen, 1998: The Storm Cell Identification and Tracking Algorithm: An Enhanced WSR-88D Algorithm. Weather & Forecasting, 13 Issue 2, 263-276. Kitzmiller, D. H., W. E. McGovern, and R. F. Saffle, 1995: TheWSR-88D severe weather potential algorithm. Wea. Forecasting,10, 141– 159. Miller, S. T. K., Class Lecture (28 Mar 2007) Trapp, R.J., C.A. Doswell: Radar Data Objective Analysis. Journal of Atm. Sci., 17, 105-120. Wasula, C. W., L. F. Bosart, 2002: The Influence of Terrain on the Severe Weather Distribution across Interior Eastern New York and Western New England. Weather & Forecasting, 17 Issue 6, 1277-1289. Winston H. A., L. J. Ruthi, 1986: Evaluation of RADAP II Severe-Storm-Detection Algorithms. Bulletin of the American Meteorological Society, 67 Issue 2, 145-150.