**3. Data and methods**

Edwards [14] studied a TC-tornado dataset dating from 1995 to 2009 from which various graphical and statistical analyses were generated. He conducted a detailed analysis of the position and intensity of 1139 tornadoes that occurred in association with TCs during this 15 year period as shown in **Figure 3**. One revealing result was that the 1139 tornadoes broke down such that there were 722 F0-tornadoes (63.39%), 339 F1-tornadoes (29.76%), 75 F2-torndaoes (6.58%), and 3 F3-tornadoes (0.26%). This statistical breakdown revealed that an overwhelming percentage of the TC-induced tornadoes were characterized by a weaker intensity (i.e., winds of 63 kts or less). The aforementioned TC-induced tornado distribution is comparable to tornado statistics from 1970 to 2002, which were compiled by McCarthy and Schaefer [15]. Within the aforementioned 32-year tornado climatology, the following intensity percentage distribution was found: 39, 36, 19, 5, and 1% for F0, F1, F2, F3, and F4 tornadoes, respectively [15]. The second finding was the apparent peak hours of TC-induced tornado occurrence between 18:00 UTC and 00:00 UTC as reflected in **Figure 4** [14]. This 6-h window in which TCinduced tornadoes occurred most frequently provided evidence for the strong influence of the diurnal cycle on these times of tornadogenesis. This highlighted the importance of diabatic

56 Recent Developments in Tropical Cyclone Dynamics, Prediction, and Detection

heating and its influence on convective available potential energy (CAPE) values.

**Figure 4.** TC-tornado events by UTC time, in 3-hourly groupings. Yellow bars correspond to the local diurnal cycle 19 along the Gulf and Atlantic Coasts, while dark blue bars correspond to the nocturnal cycle. Purple bars correspond to the period of transition between the maximum diurnal cycle impacts and the overnight hours. Periods end in the mi-

Edwards et al. [16] studied a 2003–2011 subset of the Storm Prediction Center (SPC) TC tornado records dataset in conjunction with environmental convective parameters derived from the SPC's hourly mesoscale analysis archive. A key difference observed between TC and non-TC tornado environments was that TC-tornado environments exhibited deeper tropospheric moisture coupled with the reduced lapse rates (near moist adiabatic) and lower CAPE. There was also a proposed objective, which is to study TC-tornado environments more consistently

nute 20 before the labeled times, e.g., "21–00" covers 2100–2359 UTC [4].

A core element of this chapter was analyzing 44 potential TC-tornado events between 2001 and 2015 across the Tropical Atlantic basin. An event was designated as any 24-h period in which a TC was near (within ∼160 km) or making landfall along the United States Gulf Coast or East Coast. The critical part of the data collection involved differentiating TC tornadoes vs. tornadoes associated with other mesoscale and/or synoptic-scale systems. This was accomplished by comparing the location and track of a given TC with the positions of reported tornadoes. The final step was analyzing the evolution of available radar data to confirm or reject the validity of reported tornadoes based on the timing of the reports with respect to TC progression.

The first major component of this work was conducting comprehensive synoptic analyses of the lower, middle, and upper levels (as well as an array of model-derived products). These synoptic analyses focused on specified mandatory levels (i.e., 300, 500, 700, 850 mb, and the surface) in conjunction with several model-derived products (see below) from the SPC's hourly mesoscale analysis archive. It is important to note that these model-derived products became fully available from 18 October 2005. Between 3 May 2005 and 17 October 2005, data were only available from 17:00 UTC to 03:00 UTC on the following day (11 out of 24 h per event), limiting the number of consecutive hours available for assessment during that 5-month timeframe.

The model-derived products being analyzed include 0–1-km energy helicity index (EHI), 0–3 km EHI, 100 mb mean parcel lifted condensation level (LCL) height (meters AGL), 300 mb height/divergence/wind, 500 mb height and vorticity, 500, 700, and 850 mb heights/temperatures/winds (measured in decameters, degrees Celsius, and knots), 850 mb moisture transport vector (measured as the product of the wind speed (m/s) and the mixing ratio (g/g) at 850 mb), 850 mb temperature advection (measured as the increasing or decreasing temperature trend) (i.e., positive values indicative of warm-air advection vs. negative values indicative of cold-air advection)), Bulk Richardson Number (BRN) shear (m2 /s2 ), effective bulk shear (kts), mean sealevel (MSL) pressure, and precipitable water (inches). Among the 44 events, only 26 events have near/fully complete data sets (June 2005 through June 2015). In addition, some data were missing for 12 events between June 2005 and June 2007, limiting data analysis somewhat during that timeframe.
