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Evan Lowery Dr. Eric Hoffman Northeast Regional Operational Workshop IX

Using the wsr-88d storm structure product to develop a climatology of northern new england thunderstorms as a function of large-scale flow. Evan Lowery Dr. Eric Hoffman Northeast Regional Operational Workshop IX. MOTIVATION. Northern New England thunderstorms pose a forecasting challenge

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Evan Lowery Dr. Eric Hoffman Northeast Regional Operational Workshop IX

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  1. Using the wsr-88d storm structure product to develop a climatology of northern new england thunderstorms as a function of large-scale flow Evan Lowery Dr. Eric Hoffman Northeast Regional Operational Workshop IX

  2. MOTIVATION 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. Scientific Question 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. Background AND METHODOLOGY How does large-scale flow affect the development and intensity of northern New England thunderstorms? 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?

  5. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background AND METHODOLOGY 1. How can thunderstorms be identified and monitored? “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? FIG 1: Miller (2007)

  6. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background AND METHODOLOGY 1. How can thunderstorms be identified and monitored? 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? 25 km 25 km 125 km 125 km FIG 2: Miller and Sirvakta (2007) FIG 3: Brown (2000)

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

  8. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background AND METHODOLOGY 1. How can thunderstorms be identified and monitored? 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)

  9. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background AND METHODOLOGY 1. How can thunderstorms be identified and monitored? 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)

  10. 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) Background and METHODOLOGY FIG 4: NCDC Java NEXRAD Viewer (Short range reflectivity 06/19/2006) FIG 5: NCDC Java NEXRAD Viewer (Short range reflectivity 06/19/2006) FIG 6: NCDC Java NEXRAD Viewer (Storm structure product 06/19/2006) FIG 7: NCDC Java NEXRAD Viewer (Storm structure product 06/19/2006) FIG 8: NCDC Java NEXRAD Viewer (Storm structure alphanumeric table 06/19/2006) FIG 9: NCDC Java NEXRAD Viewer (Storm structure alphanumeric table 06/19/2006)

  11. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background AND METHODOLOGY 1. How can thunderstorms be identified and monitored? 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

  12. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background AND METHODOLOGY 1. How can thunderstorms be identified and monitored? 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

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

  14. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background 2. How can the pre-convective environment be analyzed? 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)

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

  16. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Background 4. How can results be objectively analyzed? Radar Data Objective Analysis Interpolation Method: Isotropic Barnes Analysis wq = exp(-r’2/k) k = k*[(2Δaz)2max] Trapp and Doswell (2000) R = 232 km

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

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

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

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

  21. Northern New England Terrain Map

  22. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Thunderstorm cells (VIL ≥ 23 kg m-2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan) Results 925 hPa SE Flow Storm Density [count / area * 100] 49 events 274 thunderstorm cells

  23. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Thunderstorm cells (VIL ≥ 23 kg m-2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan) Results High Storm Density 700 hPa SW Flow Storm Density [count / area * 100] 150 events 1921 thunderstorm cells

  24. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Thunderstorm cells (VIL ≥ 23 kg m-2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan) Results High Storm Density 700 hPa W Flow Storm Density [count / area * 100] 79 events 651 thunderstorm cells

  25. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Thunderstorm cells (VIL ≥ 23 kg m-2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan) Results 700 hPa NW Flow Storm Density [count / area * 100] High Storm Density 73 events 599 thunderstorm cells

  26. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Thunderstorm cells (VIL ≥ 23 kg m-2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan) Results CAPE(J/kg) 0 Stable 0-1000 Marginally unstable 1000-2500 Moderately unstable 2500-3500 Very unstable ≥3500 Extremely unstable Stability Assessment 700 hPa Flow CAPE [ J / kg ] Highest CAPE values south of mountains and away from coast FIG 15: Avg CAPE per 700 hPa Flow Regime 79 events 651 thunderstorm cells 73 events 599 thunderstorm cells 150 events 1921 thunderstorm cells

  27. How does large-scale flow affect the development and intensity of northern New England thunderstorms? Thunderstorm cells (VIL ≥ 23 kg m-2, Ref ≥ 50 dBz, Range ≥ 25 km and ≤ 125 km, > 1 Volume scan) Results Total Totals Index 44 Thunderstorms 50 Severe thunderstorms possible ≥ 55 Severe thunderstorms likely, tornadoes possible 43 53 TT = (T850 + Td850) - (2 * T500) Stability Assessment 700 hPa Flow Total Totals [-] FIG 15: Avg. TT per 700 hPa Flow FIG 26: Total Totals Histogram (700 hPa SW Flow)

  28. How does large-scale flow affect the development and intensity of northern New England thunderstorms? summary SW Flow has the largest number of thunderstorm cells 925 hPa SE Flowthunderstorm 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

  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. REferences

  30. Questions or comments?

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