Investigating a Concentrated Tornado Outbreak in Southeastern Florida Preceding Hurricane Ian's Direct Impact

Present water bodies and atmospheric mechanisms heavily influence the weather phenomena that occur in Florida. One of the most impacted areas includes the East Coast, specifically the southeastern region, as severe thunderstorms and seasonal tropical cyclones frequent this location. In 2022, as Hurricane Ian approached the West Coast, a tornado outbreak produced 14 tornadoes from the Miami area to Delray Beach. Characteristics of this event matched patterns that occur when tropical cyclones approach Florida from the Gulf Coast on a northeastern track, placing South Florida in a highly favorable sector for tornadic events (Hagemeyer, n.d., pp. 1-2). Suggestions of diurnal implications of sea and land surface temperatures on tornado incidents (Hagemeyer, 1997, p.405) from supplementary research showed prevalence in this outbreak as the event occurred between 7 pm (EDT) on September 27th and the following morning at 10 am (EDT) on September 28th. Correlation testing was conducted with ASOS data near KMIA to incorporate reanalysis data from the ECMWF ERA5 collection. The variable investigated was “average monthly precipitation” accrued during 2022. Once completed, additional variables gathered included surface latent heat flux (SLHF), divergence, sea-surface temperatures (SST), and the ‘u’ and ‘v’ wind components. The areas analyzed with reanalysis ranged from 90°W to 75°W and 20°N to 35°N. Skew T’s and reports from the Mesoscale Discussion provided by the Storm Prediction Center explained the energy source for supercell production. Products identified rising warm air and advection of 4.3°C/km to 0.2°C/km from 1-15 km, CAPE of 3285 J/kg, DCAPE of 624 J/kg, CIHN of -6 J/kg, SARS analog of 60% TOR, and LowRH of 87%; reports also showed effective wind shear of 35-50 kt. However, surface observations have limited capabilities and must be corroborated with reanalysis data to fully explain meteorological phenomena at different scales. As a result, an R2 value of 0.873 and a CORREL function value of 0.934 were discovered from correlation testing. The following results were then obtained: SLHF values from -2e06 J/kg to -2.6e06 J/kg, counterclockwise circulation from 0-24 kt at the surface, SST of 304 K (about 88°F), and divergence values from 0.0001s-1 and 0.00025s-1 at 250 mb. The influence of storm tracks and diurnal impacts, previously suggested in prior research, was confirmed, and the importance of divergence was proven. The significance of divergence lies in the understanding that meteorologists often analyze areas of positive vorticity advection and rising air to identify areas of severe weather events. Thus, the values obtained helped demonstrate the favorable conditions that allowed the outbreak, as the locations with the highest calculated divergence coincided with the locations of tornado reports. Intended future analysis will include storm-relative helicity and hodographs.