1. Methods and Definitions Three primary databases were used for this study: the NHC-HURDAT database was used to identify the track and intensity of all landfalling tropical cyclones during 1997-2008; the SPC-ONETOR database was searched to identify all tornadoes reported within 800 km of each TC center; and the ESRL-RAOB database was searched to identify all rawinsondes launched within 800 km of each TC. These data were further quality-controlled and analysed in the following manner: 1.A total of 60 TCs were identified – only periods when a system was classified as either a tropical storm or a hurricane are included. 2.A total of 958 TC tornadoes were reported with these systems. A cursory examination of available surface analyses was performed to ensure the tornadoes were embedded within the TC environment. 3.A total of 5601 TC soundings were identified. Soundings with either (a) missing data at mandatory levels, (b) large dewpoint spikes, or (c) super-adiabatic layers >100 m in depth were discarded 4.In a few cases, soundings did not reach 12 km AGL or exhibited sensor wetting errors in their boundary layer data. Sounding tops and wetting errors were removed following Bogner et al. (2000). 5.All soundings & tornadoes were placed in a TC-relative framework (azimuth/radius) as function of either (a) true north (earth–relative), (b) the storm motion (storm–relative), and (c) the 850-200 hPa vertical shear (shear –relative) derived from the SHIPS database. 6.All sounding winds were converted to their cylindrical components relative to the moving storm center. 7.A large number of instability (CAPE, CIN, LCL, LFC, EL, LI), moisture (RH, θ v, θ e ), vertical shear (mean, bulk, helicity), and composite (BRN, EHI, VGP, SCP, STP) parameters were computed for each sounding. Shears were computed through a multitude of layers and in the cell-relative framework following McCaul (1991). 8.TC-relative composite maps were constructed for each sounding parameter and tornado EF-Sum (McCaul 1991) using an objective analysis with the Cressman weighting function and a 200 km cut-off on a 800×800 km horizontal grid with 50×50 km grid spacing. Discriminating between Tornadic and Non-Tornadic Soundings in Tropical Cyclones Matthew D. Eastin, Brian M. Hays, and M. Christopher Link Department of Geography and Earth Sciences, University of North Carolina at Charlotte Motivation and Objectives Landfalling tropical cyclones (TCs) regularly spawn tornadoes, with the majority of events occurring within 100 km of the coastline as the outer rainbands (>200 km from center) of major hurricanes, but the threat can persist for 2-3 days after landfall (Schultz and Cecil 2009). Many tornadoes are spawned by “miniature supercells”, which are often shallower, less intense, and shorter-lived than their midlatitude counterparts (Eastin and Link 2009, and references therein). Moreover, sounding-based composite parameters such as SCP and STP (see Thompson et al. 2003) – designed to enhance the situational awareness for midlatitude severe weather forecasting – have shown limited success in TCs (Baker et al. 2009), perhaps in part, due to significant physical differences between the respective supercells and the stability and vertical shear profiles in their local environments (e.g., McCaul 1990, Spratt et al. 1997; Bogner et al. 2000; Curtis 2004; Molinari and Vollaro 2010). Such differences would suggest that forecasting TC tornadoes may require a unique set of forecasting tools and conceptual models. The objectives of this study are to first discriminate between tornadic and non-tornadic soundings associated with U.S. landfalling TCs based on a comprehensive review of stability and vertical shear parameters; and second, develop a new composite parameter, called the Tropical Cyclone Tornado Parameter (TCTP), which effectively identifies regions within the TC environment most conducive to miniature supercell formation and tornadogenesis. We anticipate that such a parameter will enhance the situational awareness for those severe weather forecasts unique to tropical cyclones. TC Tornadoes (1997-2008) Climatology of Onshore TC Environment – Earth - Relative EF-Sum W E S N Earth-Relative from TC Radius from storm center (km) EF-Sum Motion-Relative from TC Radius from storm center (km) EF-Sum Shear-Relative from TC Radius from storm center (km) ML-LCL m Radius from storm center (km) ML-CAPE J/kg Radius from storm center (km) RH-46km % Radius from storm center (km) SCP Radius from storm center (km) 03km-SHR m/s Radius from storm center (km) BRN-SHR m/s Radius from storm center (km) 01km-CRH m 2 /s 2 Radius from storm center (km) STP Radius from storm center (km) TCTP Radius from storm center (km) BRN TC Tornado Proximity & Non-Proximity Soundings Proximity Soundings Launched within 185 km and 3 h of at least one reported tornado Must exhibit non-zero ML-CAPE (located along/on the warm side of any pre-existing boundary) Total = 184 Non-Proximity Soundings No tornado reported within 185 km and 3 h of launch location/time Must exhibit non-zero ML-CAPE Total = 3956 Proximity Soundings Radius from storm center (km) Composite Proximity Altitude (km) & Pressure (hPa) Composite Non-Proximity Altitude (km) & Pressure (hPa) SB-CAPEML-CAPEMU-CAPEMLCAPE03 USED ML-LCLML-LFCRH-24kmRH-46km USED 01-SHR03-SHR06-SHRBRN-SHR USED 01-CRH02-CRH03-CRH06-CRH USED SCPSTPTCTPBRN TC Tornado Parameter (TCTP) Initial Formulation & RationaleInitial Performance References and Additional Reading Baker, A. K., M. D. Parker, and M. D. Eastin, 2009: Environmental ingredients for supercells and tornadoes within Hurricane Ivan. Weather and Forecasting, 24, 223-244. Bogner, P. B., G. M. Barnes, and J. L. Franklin, 2000: Conditional instability and shear for six hurricanes in the Atlantic Ocean. Weather and Forecasting, 15, 192-207. Curtis, L, 2004: Midlevel dry intrusions as a factor in tornado outbreaks associated with landfalling tropical cyclones from the Atlantic and Gulf of Mexico. Weather and Forecasting, 19, 411-427. Doswell, C. A. III, and D. M. Schultz, 2006: On the use of indices and parameters for forecasting severe storms. Electronic Journal of Severe Storms Meteorology, 1(3), 1-22. Eastin, M. D., and M. C. Link, 2009: Miniature supercells in an offshore outer rainband of Hurricane Ivan (2004). Monthly Weather Review, 137, 2081-2104. Edwards, R. and A. E. Pietrycha, 2006: Archetypes for surface baroclinic boundaries influencing tropical cyclone tornado occurrence. 23 rd AMS Conference on Severe and Local Storms, St. Louis, MO, P8.2. Markowski, P. M., E. N. Rasmussen, and J. M. Straka, 1998: The occurrence of tornadoes in supercells interacting with boundaries during VORTEX-95. Weather and Forecasting, 13, 852-859. McCaul, E. W. Jr., 1991: Buoyancy and shear characteristics of hurricane-tornado environments. Monthly Weather Review, 119, 1954-1978. Molinari, J., and D. Vollaro, 2010: Distribution of helicity, CAPE, and shear in tropical cyclones. Journal of the Atmospheric Sciences, 67, 274-284. Rasmussen, E. N., and D. O. Blanchard, 1998: A baseline climatology of sounding-derived supercell and tornado forecast parameters. Weather and Forecasting, 13, 1148-1164. Schultz, L. A., and D. J. Cecil, 2009: Tropical cyclone tornadoes, 1950-2007. Monthly Weather Review, 137, 3471-3484. Spratt, S. M., D. W. Sharp, P. Welsh, A. Sandrik, F. Alsheimer, and C. Paxton, 1997: A WSR-88D assessment of tropical cyclone outer rainband tornadoes. Weather and Forecasting, 12, 479-501. Thompson, R. L., R. Edwards, J. A. Hart, K. L. Elmore, and P. Markowski, 2003: Close proximity soundings within supercell environments obtained from the Rapid Update Cycle. Weather and Forecasting, 18, 1243-1261. Future Work 1.Stratify the proximity soundings with regard to their relative time and location to the reported tornadoes (before/after and upwind/ downwind). 2.Perform a comprehensive statistical assessment of TCTP using the classic 2×2 contingency table and its associated metrics. 3.Explore additional (more effective) formulations of the TCTP within the context of the contingency table analysis. 4.Explore the role of dry air intrusions in TC tornado outbreaks and how to include their impact in the TCTP formulation. 5.Assess TCTP performance using an independent dataset derived from the 2009-2011 landfalling TC cases (may need more cases). 6.Complete a climatological assessment of the near-shore (but offshore) environment to determine the spatial evolution of those regions most conducive to miniature supercell formation and tornadogenesis as storms transition from offshore to onshore. Use the instability, shear, and helicity parameters that best discriminate between tornado proximity and non-proximity soundings in tropical cyclones Following methods outlined in Thompson et al. (2003), we develop a single, normalized, non-dimensional parameter An additional criteria is that the sounding must exhibit non-zero ML-CAPE, or the TCTP is set to zero. As any one component decrease to zero, the TCTP → 0 TCTP > 1.0 suggests the local environment is supportive of TC tornadoes The TCTP outperforms SCP, STP, and BRN within the developmental dataset, and it exhibits a strong spatial correlation within the climatological assessment