Spatiotemporal Climatology of Georgia Tropical Cyclones and Associated Rainfall

Abstract

Tropical cyclones (TCs), often characterized by high wind speeds and heavy rainfall, cause widespread devastation, affecting millions of people and leading to economic losses worldwide. TC-specific research in Georgia is scarce, likely due to the minimal geographical extent of its coast and the infrequency of direct landfalls. Research on Georgia TCs does not account for storms that make landfall in other southeastern states (e.g., Florida) and continue north, northeast, or northwest into Georgia. This study used the North Atlantic Basin hurricane database (HURDAT2) to quantify the spatiotemporal patterns of direct and indirect landfalling of Georgia tropical cyclones (>16 ms⁻¹) from 1851 to 2021. TC-induced rainfall was also quantified using rainfall data (nClimGrid-Daily and nClimGrid) from 1951 to 2021 to estimate the proportion of Georgia’s total annual and monthly rainfall attributed to TCs. A multi-methodological approach, incorporating statistics and mapping, is employed to assess the trends of Georgia’s tropical cyclones and the associated rainfall. The study analyzed 113 TCs and found that, on average, less than one TC annually ($\overline{\mathrm{x}}$ = 0.66) traverses the state. September averaged the highest percentage (25%) of TC-induced rainfall, followed by October (14%), and August (13%). This pattern aligns with the TC season, with the highest frequency of TCs occurring in September (n = 35), followed by August (n = 25), and October (n = 18). We found that 10% of tropical storms make landfall on the coastline, while the remaining 91% enter Georgia by making landfall in Florida (92%), Louisiana (7%), or South Carolina (1%) first. A threat of TCs during the peak of the season emphasizes the importance of heightened awareness, increased planning practices, and resource allocation during these periods to protect Georgia’s history and natural beauty, and its residents.

1. Introduction

1.1. Tropical Cyclone Damage in Georgia

The United States coastline stretches 5955 km (3700 miles) along the Gulf of Mexico (GOM) and the Atlantic Seaboard [1]. Within this extensive coastline, the state of Georgia accounts for 160 km (100 miles). Coastal locations throughout the GOM and North Atlantic frequently experience tropical cyclones (TCs), or low-pressure systems with strong rotating winds [2].

Georgia has experienced 107 individual billion-dollar disaster events since 1980, the most of any state in the Southeast U.S. [3]. Twenty-four of these disasters were attributed to TCs [3] experienced by Georgia and the surrounding states. These TCs were the costliest disasters in the region, with an estimated loss of USD 10–20 billion. The most recent TC was Hurricane Idalia in August 2023. Hurricane Idalia is estimated to have resulted in USD 3.5 billion in damages due to strong winds, flooding, heavy rainfall, storm surge, and downed trees [3]. Less than 24 h before landfall, Hurricane Idalia rapidly intensified, leaving residents scrambling to evacuate [4]. Rapid intensification is defined as a one-minute maximum sustained surface wind speed that increases by ≥30 knots over 24 h [5]. Hurricane Idalia was predicted to travel through Savannah, Georgia, but ultimately moved in a more northward direction. Many residents in the northern regions who were not planning on evacuating experienced heavy rainfall, flooding, and intense winds [6]. Valdosta, Georgia, experienced extensive infrastructure damage due to the lack of TC-resistant infrastructure [6].

Hurricane Irma in September 2017 caused USD 54 million in damage from falling trees, debris, strong winds, power outages, extensive flooding, and storm surge [7]. Two fatalities were reported in northern Georgia due to falling trees, with many other reports involving major injuries [7]. Rainfall across the state ranged from 30.48 mm (1.2 in) in northern Georgia to 341.9 mm (13.46 in) in the coastal area around Brunswick. Due to drier-than-normal conditions preceding the storm, the state experienced extensive flooding in multiple regions [7]. Over 900,000 residents lost power across the state, which took days to restore due to the damage around the region [8].

Hurricanes are TCs that exhibit 1-minute sustained winds of ≥33 ms⁻¹. Over half (∼60%) of all hurricanes that affect Georgia travel from the south or southeast [9]. In this paper, a Georgia hurricane is defined as a hurricane that enters the state’s boundary at hurricane-strength wind intensity, regardless of whether it makes direct landfall. TCs infrequently make direct landfall in Georgia due to the short coastline. Over 161 years, only 14 hurricanes moved directly across Georgia’s coastline without previously making landfall somewhere else along the U.S. coastline [10]. More frequently, TCs affect Georgia after making initial landfall in other states, such as Florida. A subset of storms will enter Georgia at hurricane intensity and quickly downgrade into tropical storms. These tropical storms can still cause immense damage for residents, as seen in Hurricanes Idalia, Irma, and Michael, which all became tropical storms shortly after entering Georgia. Indirect TCs entering the state at hurricane intensity through Florida should be considered part of Georgia’s historical hurricane occurrences.

1.2. Hurricane Michael in Georgia

Hurricane Michael (2018) was a Category 5 (≥69 ms⁻¹) hurricane on the Saffir–Simpson Wind Scale while in the GOM, and it made landfall just southeast of Panama City, Florida, as a Category 5 storm. The system formed in the Caribbean Sea on 2 October 2018, and by 7 October, it formed into a tropical depression off the coast of Cozumel, Mexico [11]. The system rapidly intensified before traveling off the west coast of Cuba, where maximum sustained winds reached 43.7 ms⁻¹ (85 kt; 95 mph) [11]. At landfall, Hurricane Michael exhibited maximum sustained wind speeds of 71.9 ms⁻¹ (140 kt; 161 mph) [11]. The event accelerated northeastward into Georgia as a Category 3 hurricane. Michael weakened into a tropical storm as it passed southeast of Macon, Georgia (∼265 km north of the Florida border), and continued through Augusta, Georgia, and into the Carolinas. The remnant low of Michael traveled into the Atlantic, where it dissipated off the northern coast of Portugal on 15 October [11].

Donaldsonville, Georgia, reported a maximum wind gust of 44 ms⁻¹ (85 kt; 100 mph). Hurricane Michael produced three tornadoes: Two rated as EF-0 (105–137 km/h) were recorded in Fulton and Crawford County, and one EF-1 (138–177 km/h) tornado occurred in Peach County with minor damages reported [11]. One fatality was reported due to a falling tree during the storm. Southwestern and Central Georgia reported wind damage in the agriculture/forestry sector, with Donaldsonville reporting damage to 99% of the homes and agriculture in the region. Dougherty County, Georgia, reported approximately 3000 residential structures damaged and 49 destroyed. NOAA’s National Centers for Environmental Information (NCEI) estimated USD 25 billion in damages from Hurricane Michael in the U.S. in 2018, with USD 4.7 billion occurring in Georgia from property, agricultural, and forestry losses [11].

As seen with Hurricane Michael, Irma, and Idalia, heavy rainfall is a common hazard associated with TCs. Intense, sustained rainfall can overwhelm rivers, streams, and drainage systems, leading to flash floods and the inundation of communities [12]. Rainfall and associated flood waters can lead to the failure of infrastructure, such as buildings, bridges, and roads [13,14,15] and/or cause erosion to undermine foundations and structures [14]. TC rainfall can destroy crops by causing flooding or providing excessive moisture for certain plants [16]. Soil erosion and agricultural schedules are important to obtain a yield with certain crops, and changes to these can affect the food supply chain [16].

The aftermath of TCs often results in prolonged and unexpected impacts that extend far beyond the immediate damage. For instance, Hurricane Michael’s passage through Georgia led to the downing of a vast number of trees that altered the landscape [17]. The accumulated fallen timber, which eventually dried, became fuel for a severe wildfire season the following year. The 2017 wildfire season included the devastating West Mims Fire, ignited by a lightning strike in the Okefenokee National Wildlife Refuge [18]. This fire caused mandatory evacuations in southern Georgia due to its severity [18]. Spanning approximately 140,000 acres, the fire affected not just Georgia but also reached Florida [18]. It threatened residents, firefighters, homes, Georgia’s landscape, and other species. The initial devastation caused by a TC is often the beginning, with subsequent effects impacting ecosystems and communities.

These examples illustrate that a hurricane does not need to make direct landfall on the coast of Georgia to inflict considerable damage throughout the state. Research must encompass the effects of TCs on entire states, not just on specific regions. Georgia is included in many southeastern regional studies on TCs that focus on states that experience more direct landfalls. While regional-scale research is valuable, a statewide approach is equally important.

1.3. Research Problem and Purpose

Few studies specifically focus on TCs in Georgia at a state level, likely due to the coast’s minimal geographical extent and the relative infrequency of direct landfalls. This dearth of research affects the public’s understanding of TCs in Georgia, which leaves residents without necessary planning information. TC research in the state focuses specifically on coastal Georgia [10,19,20]. Concentrating on a specific region deprives the remainder of the state of essential information needed to prepare for a severe event.

A comprehensive evaluation of the spatiotemporal characteristics of Georgia’s TCs is imperative to accurately assess and prepare for potential TCs in specific sub-regions in the state. The analytical approach enables the state to identify and prioritize regions requiring targeted assistance, resources, or disaster recovery initiatives before, during, and after the hurricane season [3]. Regions historically prone to TCs often equip their infrastructure to withstand the multifaceted impacts of such storms, including storm surges, high-velocity wind gusts, and intense rainfall [21]. However, the current lack of TC-related research within Georgia presents a substantial challenge. Without detailed knowledge of areas susceptible to TCs, there is a heightened risk of existing infrastructure that may not adequately fortify against the destructive nature of these extreme weather events [22]. While Georgia may not frequently experience TCs, closely monitoring and preparing for TCs remains critical [10]. Though less intense than hurricanes, tropical storms can still inflict considerable damage due to their potential association with heavy rainfall and strong winds [23]. Consequently, a thorough understanding of these weather events is essential for effective state-level planning and response strategies [19]. Additionally, the characteristics of TCs may change in the future [24], and it is imperative to inform communities of their historical risk and how that may change.

This research focuses on Georgia’s spatiotemporal characteristics (e.g., frequency, intensity, and location) of direct and indirect TCs exceeding 16 ms⁻¹. There is an additional emphasis on TC rainfall, showing the proportion of annual and monthly rainfall from TCs. Descriptive statistics are used to provide the spatiotemporal characteristics of Georgia TCs, including seasonality, intensity, frequency, and distribution. The research used ArcGIS Pro to aggregate monthly and annual precipitation and calculate the amount of TC rainfall in the state.

2. Materials and Methods

2.1. HURDAT2

TC data from the North Atlantic Basin hurricane database (HURDAT2) consist of data on TCs occurring in the North Atlantic Basin since 1851 [25]. HURDAT2 includes location and wind speed information at six-hourly increments for each known track in the basin. Beginning in 1961, synoptic observations at landfall were added outside the six-hour increments. Elsner and Jagger [2] provided an interpolation method that produces hourly values along the known track using the six-hourly and synoptic data. The hourly interpolated data are generated through spline interpolation [2]. This method ensures the retention of values at the designated six-hour intervals, employing a piecewise polynomial to obtain the values between the six-hour increments [2]. The geographic positions of the TCs are interpolated by using spherical geometry on the splines [2]. The data subset encompasses a comprehensive time frame from 1851 to 2021. Despite the acknowledged constraints inherent in earlier records, including the extensive historical data is vital. This approach facilitates a thorough examination of potential trends in TCs in Georgia.

HURDAT2 has limited reporting before the pre-flight (before 1944) and pre-satellite (before 1966) era [25]. This results in underestimations of storm frequency due to earlier data relying on human observations, leading to higher rates of classification or missed storms due to the lack of human presence at sea during storm occurrences [25]. TC intensities may be under-analyzed or categorized as lower than the actual event [25]. This study focuses on TCs that have crossed the Georgia border, so many concerns over the earlier records (e.g., missed open ocean storms) are less relevant here. Confidence in the estimations increases when a storm has made landfall, as land observations become more straightforward compared to open ocean observations [25].

This study only focused on TCs with sustained 1-minute wind speeds exceeding 16 ms⁻¹ within Georgia. The data were a subset to exclude storms that occurred only as extratropical cyclones, subtropical depressions, subtropical storms, tropical waves, or disturbances. Due to this, TC rainfall in this study is underrepresented. In the context of this study, the term ‘indirect’ is used to describe TCs that did not make landfall on Georgia’s coastline but entered through another location. In contrast, the term ‘direct’ defines storms that made landfall on Georgia’s coastline. We used the R Program for Statistical Computing for statistics and graphics [26]. ArcGIS Pro was used for data analysis and data mapping [27].

2.2. nClimGrid-Daily

Daily precipitation data for this study were attained from the NCEI’s nClimGrid-Daily, which consists of daily high-resolution of 0.04178° (nominally 5 km) precipitation, among other variables, from 1951 to near present [28]. The dataset includes information from the cooperative Observer Program (COOP), the Automated Surface Observing System (ASOS), and the Remote Automatic Weather Stations (RAWSs) [28]. RAWSs are only used for temperature and are, thus, not used here. The thin-plate smoothing splines method was used for a wide range of topographical and climatic features and still shows the complexity of the terrain and coastal proximity [28]. This approach collectively minimizes the likelihood of interpolation errors, making it suitable for daily temperature and precipitation at various spatial scales [29,30].

One limitation of the nClimGrid-Daily is the variation in daily observation times of stations incorporated into grid estimation. Such variations can lead to discrepancies in recorded precipitation values [31]. To minimize this impact, the dataset included daily measurements taken at midnight, 0500, 0600, 0700, 0800, and 0900 local time. These times were chosen because they are the most common for reporting [28]. Morning observations were combined with midnight observations from the previous day to align the data further. This method enhances the consistency between the two 24 h observation periods ending at these times [28].

The varying observation time of nClimGrid-Daily creates a challenge when identifying the exact dates when the TCs caused precipitation in Georgia. TCs enter Georgia at varying hours throughout any given day. To align with the nClimGrid-Daily rainfall observation times, this study reevaluated the days when TCs entered the state. If a TC entered Georgia at or after 1000 EST, rainfall data from the next day were used. If the TC entered Georgia before 1000 EST, the reported HURDAT2 date was used. This was to account for rainfall that may have been combined with the previous day’s data due to most reports coming in between 0000 and 0900.

2.3. Analytical Approach

Descriptive statistics summarize the entire database of TCs in Georgia, revealing the main characteristics. This includes determining average frequency, analyzing monthly occurrences, and identifying the weakest and strongest wind intensities recorded in the state. This study used descriptive statistics to calculate the average intensity of TCs and assess the years with the highest and lowest TC activity. This method illustrates the range and patterns of TCs in Georgia, laying a foundation for future assessments of the potential impacts on the region.

This study used a 500 km buffer (250 km buffer on each side of the track’s center point) around the interpolated HURDAT2 tracks to isolate the TC rainfall from any influences from other meteorological systems [32]. Any buffers intersecting with the Georgia state border were used in the rainfall portion of this study [33].

From 1951 to 2021, the total rainfall that occurred on the days of each TC was aggregated annually. The start date for each storm was the first day that the storm buffer intersected Georgia, and the end date was the last day of the intersection. Statistical summaries for months and years are provided. Some storms have rainfall spanning over two months. For example, Hurricane Ernesto in 2006 entered Georgia on 31 August and departed the state on 1 September. Both days were included for aggregation, and each monthly summary was considered separately.

The rainfall data were clipped to the Georgia state boundary. The rainfall from each TC was then summed to find the total rainfall in Georgia from these events. The TC rainfall was next divided by the annual rainfall from 1951 to 2021. The daily rainfall grids were used to calculate each TC’s rainfall and then compared to the annual rainfall grids (e.g., from all sources of precipitation). The annual grids were calculated by summing the monthly gridded rainfall. The monthly gridded rainfall data were extracted from the sister dataset—nClimGrid-Daily. The nClimGrid-Daily dataset was standardized with nClimGrid-Monthly to ensure consistency across various products and applications [28].

The procedure applies to both annual and monthly rainfall averages. First, the annual TC gridded rainfall total was determined by summing the precipitation from each TC and clipping it to Georgia’s state boundary. To determine TCs’ contribution to the state’s precipitation, the sum was divided by the total rainfall from 1951 to 2021. Precipitation data were averaged by month. TCs affecting Georgia across two months were divided to ensure accurate attribution to the correct month. For accurate monthly rainfall estimates, the total precipitation and TCs affecting Georgia were both divided by 71 years to account for months with no precipitation in the dataset. Finally, TC monthly averages were divided by the total monthly rainfall.

3. Results

3.1. Descriptive Statistics

This study analyzed 113 tropical storms and hurricanes occurring within the boundary of Georgia from 1851 to 2021 (

Table 1. Tropical cyclones in Georgia from 1851 to 2021 separated by landfall intensity and direct/indirect landfall. Percentage of total TCs relates to Georgia’s total.

Event Type	Total Count	Hurricanes	Tropical Storms	Percentages of Total TCs
Direct Landfall	10	4	9	9%
Indirect Landfall	103	19	83	91%
Total Impact	113	24	89	100%

). The classification of storm type was based on the intensity of the TCs when the storm entered the state’s boundaries either on the coast or through another state, reflecting the varied intensities experienced throughout the state.

Figure 1 depicts the 10 direct landfalling TCs in Georgia categorized by storm type. Figure 1b shows the 103 indirect landfalling TCs in Georgia categorized by storm type. These indirect TCs form within the Atlantic Basin, Caribbean Sea, and Gulf of Mexico, and the tracks make initial landfall in Florida (92%), Louisiana (7%), or South Carolina (1%).

Figure 2 and Figure 3 are heat maps highlighting the specific locations where TCs have entered and exited the state. The first entrance of each TC track into the state is considered. One track from an unnamed TC in 1947 entered the state multiple times due to the track’s curvature but only the initial entrance is considered. Two TCs only had one track segment enter the state before leaving the state. These two storms (Unnamed 1874 and Eta 2020) are included in both the entrance and exit maps. Each TC’s point of entry or exit is marked with a black dot. Each point has a buffer with a 40.3 km (25 mi) radius to determine the overlap among points, indicating areas where multiple buffers intersect. On the maps, red areas indicate regions with the highest density of entry points, while green represents the areas with little TC activity within a 40.3 km radius. Regions without color signify the sparsest areas, where TCs have not directly entered or exited. However, this does not imply that these areas have been completely unaffected by TCs. The densest entry area is along the southern border, where most tracks made landfall in Florida from the GOM and then continued into Georgia, followed by the sparsest area along the western border.

Figure 3 is a heat map for the exit points of TCs in Georgia from 1851 to 2021. There are nine TCs not considered in this map as they became tropical depressions ≤ 16 ms⁻¹ within the state’s borders. These storms were all unnamed systems (1871, 1873, 1875, 1887, 1916, 1917, 1933, and 1966) except for Florence in 1953. Most storms exited on the eastern edge of the state, with the densest area along the southeastern border. This is because most TCs entered from the south and traveled eastward; however, some TCs continued north into Tennessee or North Carolina. TCs that made direct landfall on the coastal area tended to move westward exiting along the state’s western border.

Table 2. Category distribution of tropical cyclones in Georgia, 1851–2021.

Tropical Cyclone (16–32 ${\mathbf{ms}}^{-1}$)	Category 1 (33–42 ${\mathbf{ms}}^{-1}$)	Category 2 (43–49 ${\mathbf{ms}}^{-1}$)	Category 3 (50–58 ${\mathbf{ms}}^{-1}$)	Category 4 (59–70 ${\mathbf{ms}}^{-1}$)	Category 5 (≥70 ${\mathbf{ms}}^{-1}$)
89	15	7	2	0	0

shows the distribution of annual Georgia TC counts categorized by the Saffir–Simpson Hurricane Wind Scale (NOAA 2020). Category 4 and Category 5 hurricanes have not occurred in the state’s known history. Hurricane Michael in 2018 and the Unnamed 1898 hurricane both maintained Category 3 hurricane status as the tracks entered Georgia but decayed as the storms traveled further inland. The Unnamed 1898 hurricane made landfall on 2 October from the Atlantic Ocean on the southern coastline of Georgia with an estimated wind speed of 57 ms⁻¹. The Unnamed 1898 hurricane decayed and downgraded into a tropical storm around 201.1 km (125 mi) in Georgia. Hurricane Michael entered the southwestern corner of Georgia from the GOM with a wind speed of 53 ms⁻¹. Hurricane Michael decayed and downgraded into a tropical storm around 144.8 km (90 mi) from the state’s border.

Figure 4 illustrates the time series of annual Georgia TCs over the 171-year period. When considering all TCs, the average rate is 0.66 TC/yr, with a ${\sigma }^2$ of 0.65. When considering only tropical storms, the rates are 0.52 TS/yr (${\sigma }^2$ = 0.56) and hurricanes and 0.14 hur/yr (${\sigma }^2$ = 0.145). Most of the hurricanes (27%, $\mathrm{n}=21$) occurred in the first one hundred years of the dataset. Only three hurricanes occurred after 1950.

3.2. Tropical Cyclone Seasonality

TC seasonality in Georgia is shown in Figure 5. The most active months of the hurricane season were August, September, and October [34]. September was the most active month for TCs in Georgia (n = 40; 35%), followed by October (n = 27; 24%). August was the most active hurricane month (n = 8; 7%). May had two recorded tropical storms outside of the official hurricane season. This is not uncommon, and further analysis of the storms is included below. June experienced a high number of TCs (n = 15; 13%).

3.3. Wind Intensity

Figure 6 illustrates the maximum wind speeds (ms⁻¹) of TCs in Georgia. Most TCs decayed upon entering the state’s boundaries. However, five TCs increased wind speed as they moved further into the state. Two TCs reached their peak wind speeds approximately 50 miles north of the southern border of Georgia, with the intensity of a tropical storm and tropical depression. Another two storms originating from the GOM passed through Florida and into Georgia, achieving their maximum wind speeds as tropical storms at the Georgia–South Carolina border. These storms traveled nearly 225 km (140 mi) northeast from their entry point into Georgia while increasing in intensity. Additionally, Hurricane Dora (1964) made landfall in Florida from the Atlantic, moved west, and then turned northeast through western Georgia, covering about 410 km (260 mi) of the state before its highest wind speed was recorded as it crossed into South Carolina. The maximum wind speed was 54.6 ms⁻¹ by an unnamed Category 3 hurricane in 1898. The mean wind speed was 27.2 ms⁻¹ with a ${\sigma }^2$ of 75.8.

3.4. Annual Average Rainfall

The study analyzed 119 storms occurring between 1951 and 2021 based on the available rainfall data. Figure 7 shows the TC tracks when rainfall data were available. A 500 km buffer was added around each track to determine the area where rainfall might have occurred from the TC. When the buffer intersected Georgia, the TC and associated rainfall were included. TCs were, again, categorized into tropical storms and hurricanes based on the highest maximum sustained wind recorded within the buffer area. There were 42 (35%) hurricanes and 77 (65%) tropical storms. Across the 119 TCs, there were 295 days of observed precipitation within the state’s border, equivalent to roughly 1% of all days during the period of study (1951–2021).

Georgia is divided into five distinct regions, including the Appalachian Plateau, the Ridge and Valley region, the Blue Ridge Mountains, the Piedmont region, and the Coastal Plain (Figure 8). The Coastal Plain can be divided into the upper and lower regions. When discussing the rainfall in this study, the regions will be referenced to provide spatial context regarding where rainfall occurs within the state.

Figure 9 shows the rainfall attributed to TCs across the state by percent of total Georgia annual rainfall. Along the coastline, approximately 5–6% of annual rainfall is attributed to TCs. This value gradually diminishes moving toward the northwest. The Piedmont and Upper Coastal Plain regions receive an average of 2–4% of annual rainfall from TCs. The northwestern portion of the state receives $\le 1\%$ annual rainfall from TCs.

3.5. Monthly Tropical Cyclone Precipitation and Tracks

Understanding the distribution of TC rainfall across months of the TC season and the proportion of annual rainfall is important for planning purposes. May is not considered a part of the North Atlantic TC season, but of the 119 TCs in this portion of the study, 7 TCs occurred in May (Figure 10a). Five of these pre-season May TCs (all tropical storm strength) have occurred since 2012. May has a high precipitation concentration from TCs in the Lower Coastal Plain, 3–5% (Figure 11a). The rest of the state has an average of 0–2% annual precipitation from TCs.

In total, 19 TCs have occurred in June since 1951 (Figure 10b). Of these, 3 were hurricanes, and 16 were tropical storms. Most of the June tracks form in the GOM. The western Caribbean is known for retaining its warmth well into the later part of the hurricane season. However, Figure 10b suggests that this region starts to warm up earlier in the season than previously thought, potentially indicating a longer period of elevated temperatures [35]. Most of the TCs travel into Georgia from the GOM, traveling northeast into the Atlantic.

In June, the highest precipitation concentration is along the southeastern border with 4% of its annual precipitation from TCs (Figure 11b). The Lower Coastal Plain receives 3% of average annual precipitation from TCs. The Upper Coastal Plain and Piedmont region receive 2%, with the remainder of the state receiving 0–2%.

July observed 13 TCs with 5 hurricanes and 8 tropical storms, as shown in Figure 10c. Three TCs formed in the Southern Atlantic, six in the GOM, and four east of Georgia’s border in the Atlantic.

July has a high precipitation concentration from TCs in the western Piedmont region, around 4% (Figure 11c). This is surprising as most of the tracks travel near the state’s southeastern region (Figure 10c). This could be because the tracks closest to this region did not produce much rainfall. The southeast and northern regions receive an average of 0–4% of their annual rainfall from TCs.

Figure 10d depicts the tracks that occurred in August. Three tracks in Figure 10d are also shown in September’s (Figure 10e) track map because the storms spanned the two months. There were 25 TCs that occurred in August, with 6 hurricanes and 19 tropical storms. Twenty of the August TCs formed in the Atlantic, with seven forming near the coast of Florida and/or South Carolina.

August has a high concentration of TC rainfall along the eastern border of Georgia (Figure 11d). This is likely due to the number of storms traveling through Georgia and South Carolina. The southwestern portion of the state has a range of 2–3% on average TC precipitation per year. The northeastern region has the highest annual average concentration of rainfall, with an average range of 4–5%.

There were 35 TCs in September (Figure 10e). September experienced the highest number of hurricanes, with a total of 19. In addition, there were 16 tropical storms in September. There is one TC that is also represented in October’s (Figure 10f) track map because it spanned the two months. Most of the storms formed in the Atlantic, with only six TCs forming in the GOM.

Figure 11e shows that September had the highest average rainfall compared to all other months. The highest concentration of precipitation is attributed to TCs along the eastern border moving inland within the Coastal Plain and Piedmont regions. This could be due to the high-traffic area of TCs that traveled specifically in that area (Figure 10e). Most of the state receives an average of at least 3% of its annual rainfall from TCs in September. The only exception is along the eastern border, which receives 20–25%, and this is the highest concentration of rainfall averages for this region compared to the other months.

Figure 10f shows that October had 18 TCs with 8 hurricanes and 10 tropical storms. One TC formed in the middle of the Atlantic Ocean while the rest formed in the GOM, Caribbean Sea, or the southern portion of the Atlantic Ocean. Figure 11f shows that the highest concentration of 10% of rainfall in October occurs along the eastern border within the eastern border of the Coastal Plain. The rest of the state sees varying concentrations of around 1–4% of its rainfall from TCs.

Figure 10g shows that November only had two TCs with one hurricane and one tropical storm. Hurricane Kate (1985) traveled through Georgia from the GOM, and it formed in the Atlantic Ocean. Tropical storm Juan (1985) formed in the GOM and traveled within the buffer, so it never moved over any part of Georgia. The majority of the rainfall this month is attributed to Hurricane Kate.

Figure 11g shows that the highest concentration of precipitation was due to Hurricane Kate. The rainfall was highest as the hurricane entered the southwest region and exited along the middle of the eastern border. This precipitation was mainly concentrated in the Upper Coastal Plain. The southern coastline and the northern portion of the state received no rainfall from TCs during this month.

4. Discussion

This research focused on the spatial characteristics of tropical cyclone (TC) frequency, intensity, and rainfall in Georgia, USA. The study found that 113 TCs entered the state of Georgia from 1851 to 2021. Previously, the authors of [10] found 14 hurricanes that made direct landfall on Georgia’s coast from 1851 to 2014. Of the 113 TCs in this study, 24 were categorized as hurricanes, and 89 were categorized as tropical storms as they entered the state’s borders. Consistent with the established patterns of activity, Georgia’s TC season was most active during the months of August, September, and October [34]. September had the highest TC frequency ($\mathrm{n}=40$; 35%), October had the second highest TC frequency (n = 27; 23%), and August had the highest frequency of hurricanes (n = 8; 7%). A surprising early batch of May (n = 2; 2%) and June TCs (n = 15; 13%) was seen within the data. The early occurrence of TCs in June and May may be attributed to the position of the Bermuda High, which increases the likelihood of landfall in the Gulf of Mexico earlier in the TC season [36]. The maximum wind speed observed was 54.6 ms⁻¹ by an unnamed hurricane in 1898. The minimum wind speed observed was 16.3 ms⁻¹ by an unnamed storm in 1904. The mean wind speed for indirect and direct landfalls in GA observed across the dataset was 27.2 ms⁻¹. A study found that Georgia’s coastline experiences TCs with an average of lower wind speeds compared to the coastline of South Carolina [37].

Another study revealed that all category hurricanes in Georgia have decreased over time [10]. Many studies primarily concentrate on the assessment of lifetime maximum intensity over the open ocean, rather than the intensity when a TC reaches land and moves inland, which complicates making direct comparisons [37]. Bettinger et al. (2009) and others found that TCs making landfall on the Gulf of Mexico coast decrease in intensity more quickly than similar storms making landfall on Georgia’s coastline [37]. These findings challenge prevailing assumptions about the impact of changing climate conditions on hurricane behavior in the North Atlantic Basin. In the Georgia TC dataset, most hurricanes (87%) occurred in the first 100 years of the data. This is likely causing the decreasing trend in intensity. Another probable factor contributing to the decrease in TC intensity is the transformation of Georgia’s landscape. The region’s transformation has been shaped by a confluence of factors, including natural processes, natural disasters, demographic changes, and economic developments. Georgia has continually increased in urbanization, which can disrupt the essential conditions required for a TC to maintain or increase in intensity. Severe storms still existed in the later years, including Hurricane Michael in 2018. Further statistical analysis should be conducted to focus on the modern (flight/satellite era to the present) tropical cyclones in Georgia [25]. This will assist in seeing what the trends and characteristics of modern TCs are. Georgia TCs occur most often in September, which aligns with the most active month for TCs throughout the basin [34]. This has implications for disaster preparedness and resource allocation, emphasizing the importance of heightened vigilance and readiness during September. On average, Georgia experiences 0.66 TCs (0.52 tropical storms and 0.14 hurricanes) per year. While it is not expected to be an annual occurrence, the threat of TCs remains within Georgia and is heightened in the middle of the season.

TC-induced rainfall was observed at high percentages across the Coastal Plain and the Piedmont region when compared to annual rainfall totals. Other studies have conducted similar TC rainfall research on the east coast [32,38,39]. The differences between this study and the previous studies include the time span, study area, and rainfall dataset. The studies found similar results for Georgia while having a lower resolution [32,38,39]. Similar to this study, there is little variability in the Appalachian Plateau and the Ridge and Valley regions of Georgia. This study had a higher resolution and found that 1–5% of TC-induced rainfall occurred on average along the coastline. The 3% or lower TC-induced rainfall was seen in the northwestern portion of the state. Figure 9 and Figure 11, showing the Piedmont region, as well as Upper, and Lower Coastal Plains, indicate more variability in the amount of rainfall compared to Nogeuria and Keim’s study [32,38,39].

May and November had the lowest TC-induced rainfall amounts, with 3% and 1%, respectively. Only two TCs were recorded in November. The most TC-induced rainfall occurred in September and October, with 25% and 14%, respectively.

The impact of TCs on regions in Georgia can vary based on whether the landfall was direct or indirect. Nonetheless, both scenarios entail considerable risks of flash floods and intense winds. This study also acknowledges indirect TC-related impacts not previously or extensively mentioned, such as tornadoes and wildfires. Furthermore, a severe hurricane is not limited by whether a TC makes direct or indirect landfall in a region.

5. Conclusions

The spatial and temporal patterns of TC-induced rainfall further emphasize the varied impacts these storms have across different regions of Georgia. The coastline and the Piedmont regions experienced a higher percentage of TC-induced precipitation. This variability in impact allows for an approach to disaster preparedness and response that is tailored to the specific vulnerabilities of each region.

Rainfall during September occurs across the entire state, regardless of the region. The emphasis on September as a peak month for TCs underscores the need for targeted preparedness efforts during this period. The provided annual averages contribute to a comprehensive characterization of Georgia’s tropical weather patterns, providing valuable insights for future research and policy considerations. This research aims to represent the people who are underrepresented in the literature and in planning practices to create a safer environment and to spread information to better protect the public. Hurricane Idalia and Hurricane Michael prove that hurricanes make their way into Georgia and have a major impact on the region, yet the public focuses on hurricanes’ impact in Florida, South Carolina, and North Carolina. Hurricanes and tropical storms continue to impact Georgia, and this research serves as an updated climatology to help protect Georgia’s history, natural beauty, and the people within.