Teleconnections Between the Pacific and Indian Ocean SSTs and the Tropical Cyclone Activity over the Arabian Sea

Abstract

Tropical cyclones (TCs) over the Arabian Sea pose significant threats to coastal populations and result in substantial economic losses, yet their variability in response to major climate modes remains insufficiently understood. This study examines the relationship between the El Niño–Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Indo-Pacific Warm Pool (IPWP) with TC activity over the Arabian Sea from 1982 to 2021. Utilizing the India Meteorological Department (IMD)’s best-track data, reanalysis datasets, and composite analysis, we find that ENSO and IOD phases affect TC activity differently across seasons. The pre-monsoon season shows a limited association between TC activity and both ENSO and IOD, with minimal variation in frequency, intensity, and energy metrics. However, during the post-monsoon season, El Niño enhances TC intensity, resulting in a higher frequency of intense storms, leading to increased accumulated cyclone energy (ACE) and power dissipation index (PDI) in a statistically significant way. In contrast, La Niña favors the development of weaker TC systems and an increased frequency of depressions. While negative IOD (nIOD) phases tend to suppress TC formation, positive IOD (pIOD) phases are associated with increased TC activity, characterized by longer durations and higher ACE and PDI (statistically significant). Genesis sites shift with ENSO: El Niño favors genesis in the eastern Arabian Sea, causing westward or northeastward tracks, while La Niña shifts genesis toward the central-western basin, promoting northwestward movement. Composite analysis indicates that higher sea surface temperatures (SSTs), reduced vertical wind shear (VWS), increased mid-tropospheric humidity, and lower sea level pressure (SLP) during El Niño and pIOD phases create favorable conditions for TC intensification. In contrast, La Niña and nIOD phases are marked by drier mid-level atmospheres and less favorable SST patterns. The Indo-Pacific Warm Pool (IPWP), particularly its westernmost edge in the southeastern Arabian Sea, provides a favorable thermodynamic environment for genesis and exhibits a moderate positive correlation with TC activity. Nevertheless, its influence on interannual variability over the basin is less significant than that of dominant large-scale climate patterns like ENSO and IOD. These findings highlight the critical role of SST-related teleconnections (ENSO, IOD, and IPWP) in regulating Arabian Sea TC activity, offering valuable insights for seasonal forecasting and risk mitigation in vulnerable areas.

1. Introduction

The weather of tropical cyclones (TCs) represents a significant severe weather phenomenon, resulting in substantial property damage and loss of life due to their associated strong winds, intense rainfall, storm surges, and coastal flooding [1,2]. Sea surface temperature (SST) plays a fundamental role in regulating climate variability and atmospheric circulation patterns, as it influences convection, evaporation, and heat exchange between the ocean and atmosphere, thereby affecting weather systems on both regional and global scales [3,4,5,6]. The El Niño-Southern Oscillation (ENSO) is a significant mode of interannual climate variability, driven by air–sea interactions in the tropical Pacific Ocean that affect weather and climate globally through teleconnections [7]. It appears over the tropical Pacific Ocean, making a broad and significant impact on global weather and climate [8,9,10]. ENSO consists of two main phases, El Niño (warm phase) and La Niña (cold phase), that characterize SST anomalies in the central Pacific Ocean [11]. The warming of the eastern tropical Pacific frequently peaks at the end of the calendar year [12,13]. ENSO events occur every 2–7 years and last approximately one to one and a half years, with significant variations in strength [14]. One of the weather phenomena that is affected by ENSO is TCs. Several studies have investigated the relationship between TC activity (e.g., frequency, intensity, track, and genesis points) and ENSO events in different tropical oceans [15,16,17,18,19,20]. The relationship between TC activity and ENSO over the northwestern Pacific (NWP) has been extensively investigated [20,21,22,23,24] Several researchers have also focused on this relationship in the central and eastern North Pacific. During strong El Niño regimes, the duration, number of TCs, and their strength over this ocean tend to increase [8,25,26]. In contrast, the Atlantic Ocean has more activity of TCs during La Niña years (cold regime) than El Niño years [27,28]. The large-scale oceanic and atmospheric conditions are essential for the origin of TC activity over these tropical oceans [29,30].

The North Indian Ocean (NIO) is one of the favorable oceans for TC activity, which accounts for 6–7% of the global annual TC count and consists of two main basins [31,32,33]. The western basin is the Arabian Sea, and the eastern basin is the Bay of Bengal. Two of the large circulation indices that affect the NIO are ENSO and the Indian Ocean Dipole (IOD) [34,35]. Many studies concentrate on how ENSO controls the TC activity in the NIO, particularly in the Bay of Bengal [34,35,36,37,38,39,40]. The Arabian Sea, the study area for this paper, lacks sufficient research on the relationship between ENSO events and TC activity (Figure 1). As a result, this relationship is not well understood. Several studies have investigated this issue, but they have taken place over a short period or have not studied all the activities of TCs, which include frequency, intensity, track, energy metrics, and duration. The impacts of ENSO on the intensity of TCs over the NIO have been examined [41]. Based on time and location, [42] assess the large-scale parameters’ contributions to NIO tropical cyclogenesis. A comprehensive understanding of Arabian Sea TC activity in connection with ENSO is crucial for mitigating their impacts, both scientifically and socially. The primary purpose of this study is to analyze the effects of ENSO on TC activity (frequency, intensity, genesis, track, energy metrics, and duration) in the Arabian Sea from 1982 to 2021. This study aims to examine the ENSO-induced variations in oceanic and atmospheric conditions over the Arabian Sea.

The SST strongly influences the Arabian Sea climate in the Indian Ocean. The fluctuations in SST between two small rectangular areas in the western (50–70° E, 10–10° N) and eastern (90–110° E, 10–0° S) sectors of the tropical Indian Ocean are referred to as the IOD effects, which are a critical mode of climate variability over the Arabian Sea [34,43,44]. The IOD typically begins in May to June, peaks in October to November, and ends in early January. The importance of IOD in climate variability has attracted more attention lately. The impacts of SST anomaly spatial arrangement on East African rainfall have been examined [45] and the Indian summer monsoon precipitation [46]. A negative and substantial relationship has been identified between the frequency of November tropical storms in the Bay of Bengal and the IOD Mode Index from September to October [47]. With a one-month lead time, the researcher suggested that the IOD index might be able to forecast intense cyclones in November over the BoB. Using TC climatology (1982–2021), this paper investigates how ENSO and IOD affect the intensity, frequency, origin location, trajectories, energy metrics, and duration variability of TCs in the Arabian Sea. The climatic modes—ENSO, IOD, and the Indo-Pacific Warm Pool (IPWP)—are interrelated in their impact on ocean-atmosphere variability across the tropical Indo-Pacific. The distribution of SST and convection patterns is modified by the simultaneous occurrence of pIOD and El Niño episodes. Consequently, the strength and scope of the IPWP are modified by these SST anomalies. The IPWP is characterized by a mean SST exceeding 28 °C, causing an intense convection [48]. It contains the world’s most significant warm water mass. Multiple studies have shown that the IPWP directly affects the thermal and kinetic characteristics of TCs’ activity in the tropical basins [49,50].

This study examines the Indian and Pacific Ocean SST indices (ENSO, IOD, and IPWP) and their correlation with TC activity in the Arabian Sea. To achieve this objective, the study utilized a historical dataset spanning over 40 years (1982–2021) to examine this link thoroughly. It is original in that it offers a thorough analysis of the impact of three leading oceanic indicators—ENSO, IOD, and the IPWP—on various aspects of TC activity over the Arabian Sea, including frequency, intensity, genesis location, track, energy metrics, and duration. Unlike earlier studies that frequently focused on individual indices or restricted aspects of TC activity (e.g., intensity or frequency), this study provides a comprehensive and comparative assessment of multiple climatic modes. It also examines the role that the IPWP plays in the variation in TCs’ activity over the Arabian Sea, a subject that has not been extensively researched in this region. The use of long-term datasets (1982–2021) is also a novelty, as it enables decadal-scale interpretation and pattern detection, thereby overcoming the constraints of short-term or seasonal studies in previous research.

This study significantly enhances our understanding of the impact of variations in SST in the Indo-Pacific region over decades on TCs in the Arabian Sea. This is essential for the development of strategies to adjust to climate change, the enhancement of long-term predictions, and the preparation for disasters in neighboring regions. The proposed study is significant in that it advances scientific understanding and aids in the recovery of society by providing a comprehensive, current analysis of the teleconnections that influence TC activity in a region of the world’s ocean basins that is becoming more susceptible. The organization of the paper is as follows. Section 2 highlights the data and methodologies utilized for this investigation. Section 3 presents the results and discussion, while Section 4 provides the conclusions.

2. Materials and Methods

2.1. Data

2.1.1. TC Data

The India Meteorological Department (IMD) provided the best-track information for TCs, which includes the center location and intensity at every 6 h interval. This information was used in the current study. The location of the TC genesis is referred to as the first record of geographical coordinates that IMD defines as a depression (D). These events are categorized as pre-monsoon (April–May–June) and post-monsoon (October–November–December). The current investigation examined four decades of best-track TC data, from 1982 to 2021. According to IMD, CS (Cyclonic Storm), SCS (Severe Cyclonic Storm), VSCS (Very Severe Cyclonic Storm), ESCS (Extremely Severe Cyclonic Storm), and SuCS (Super Cyclonic Storm) are all terms used to describe systems with a maximal sustained wind speed exceeding 34 knots (

Table 1. Tropical cyclone (TC) classification according to the India Meteorological Department (IMD) for the North Indian Ocean (NIO).

System	Wind Speed in km/h	Wind Speed in Knots
Low-pressure area (L)	Less than 31	Less than 17
Depression (D)	31–49	17–27
Deep depression (DD)	50–61	28–33
Cyclonic storm (CS)	62–88	33–47
Severe cyclonic storm (SCS)	89–118	48–63
Very severe cyclonic storm (VSCS)	119–165	64–89
Extreme severe cyclonic storm (ESCS)	166–220	90–119
Super cyclonic storm (Sup. CS)	221 or more	120 or more

).

In this section, where applicable, authors are required to disclose details of how generative artificial intelligence (GenAI) has been used in this paper (e.g., to generate text, data, or graphics, or to assist in study design, data collection, analysis, or interpretation). The use of GenAI for superficial text editing (e.g., grammar, spelling, punctuation, and formatting) does not need to be declared.

2.1.2. ENSO, IOD, and IPWP Data

Globally, researchers have developed various methodologies and indices to identify and classify ENSO events. The Southern Oscillation Index (SOI), along with oceanic Niño 1 + 2, Niño 3, Niño 3.4, and Niño 4 sea SST indices, are utilized metrics to signify the existence of ENSO occurrences [12,51]. The most commonly used is the Oceanic Niño Index (ONI), based on the Niño-3.4 region, and it is used in the current study “https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php (accessed on 15 May 2025)”. Based on [21,51], the ONI is categorized into El Niño, La Niña, and neutral years using the Niño-3.4 SST anomalies (5 S–5 N, 120 W–1708 W) supplied by the Climate Prediction Center (CPC) at the National Oceanic and Atmospheric Administration (NOAA), as shown in Figure 2. Investigation by seasons provides information about how ENSO affects the TCs’ activity over the Arabian Sea. The pre-monsoon ONI indicates the initial or early phase of an El Niño or La Niña event. During the post-monsoon season, the ONI is higher when an event typically develops and intensifies.

The study used the Dipole Mode Index (DMI) from NOAA’s CPC [51] to look at how the IOD affects TCs in the Arabian Sea. The DMI shows how different the SST is between the western (50° E–70° E, 10° S–10° N) and eastern (90° E–110° E, 10° S–0) parts of the equatorial Indian Ocean. Positive values mean a pIOD phase, whereas negative values mean a negative phase. To classify the IOD events, we used a ±0.5 °C range in the seasonal mean DMI to sort the IOD events. When the mean DMI was ≥+0.5 °C, the seasons, which included both pre-monsoon and post-monsoon periods, were classed as positive IOD (pIOD) occurrences. When the mean DMI was < –0.5 °C, the seasons were categorized as negative (nIOD) events.

An IPWP index was made by averaging SST over the IPWP area (15° S–15° N, 60° E–180°) when SST was equal to or greater than 28 °C (Figure 3) for AMJ and OND data from 1982 to 2021. This was performed to show how the IPWP changes and how it affects TC activity over the Arabian Sea.

2.1.3. Environmental Parameters

Data concerning diverse atmospheric variables (SSTs, vertical wind shear (VWS), outgoing longwave radiation (OLR), RH, sea level pressure (SLP), and upper wind) have been acquired from the National Centers for Environmental Prediction of the National Center for Atmospheric Research (NCEP–NCAR) monthly reanalysis dataset, which has a resolution of 2.5° × 2.5° in longitude and latitude. Monthly 500-hPa OLR data have been obtained from the National Oceanic and Atmospheric Administration (NOAA) interpolated OLR dataset.

2.2. Methods

2.2.1. Calculations

• Tropical Cyclones Energy Metrics

To describe the overall TC activity over the Arabian Sea, two commonly used TC energy measures are accumulated cyclone energy (ACE) and the power dissipation index (PDI). ACE is computed by adding up the squares of the six-hourly maximum sustained surface wind speed (knots) for each TC that reaches 34 knots (18 m/s) or higher in wind speed. It is a function of the number of TCs, strength, and duration. Each unit of ACE equals and is proportional to its kinetic energy [21].

$$\mathrm{ACE}=\sum {v^2}_{max}\times {10}^4{\mathrm{kt}}^2 (\mathrm{for} v_{max} \ge 34 \mathrm{knot})$$

(1)

The PDI is the cube of the maximum sustained wind speed for each 6 h tropical storm period [52]. It is used to express the TC damage potential, which is a function of frequency, intensity, and duration [53,54,55].

$$\mathrm{PDI}= \sum {{ v}^3}_{max}\times {10}^6 {\mathrm{k}\mathrm{t}}^3(\mathrm{for} v_{max} \ge 34 \mathrm{knot})$$

(2)

2.

Duration:

To address the TCs’ duration, the total number of TC hours over the Arabian Sea was calculated and categorized based on El Niño, La Niña, pIOD, and nIOD phases.

3.

Vertical wind shear

To obtain the vertical zonal wind shear, it subtracts the monthly or seasonal mean zonal wind at 850 hPa from the overlying monthly or seasonal mean zonal wind at 200 hPa.

4.

Anomalies

To examine the impacts of various ENSO and IOD events on TC activity over AS and to compare the differences between El Niño and La Niña events, the anomaly method is employed in this study. Anomaly is the difference between the actual value in a period for any variable and the climatology value for that parameter. It can be calculated for a year, month, season, or day. For example, this study is dealing with the post-monsoon season (OND), and the anomaly for relative humidity (RH) at 500 hPa for this season in 2015 is the mean RH during that season subtracted from the climatology mean for the study period, which is 1982–2021.

5.

Correlation

The correlation coefficient is a method of statistical analysis of data, and the purpose of using it is to find or measure the strength of the relationship between two variables. In this study, correlation analysis will be used to see if there are significant relationships between TC frequency, ACE, and PDI with SSTAs in the Niño 3.4 region. We can express the equation for the simple correlation coefficient between variables X and Y as follows:

$$r_{xy}={\displaystyle \frac{\sum (x_i-\overline{x})(y_i-\overline{y})}{\sqrt{\sum {(x_i-\overline{x})}^2\sum {(y_i-\overline{y})}^2}}}$$

(3)

2.2.2. Composite Analysis of Synoptic Condition

Composite analysis (composite mean or composite anomaly) involves studying and averaging the anomalies or means of one or more categories of ocean-atmosphere variables selected according to their relationship with key conditions. The variables that will be composited—their anomalies or means—are SSTs, VWS, OLR, RH, SLP, and upper wind. It will be composited by using its values during the TC period activity for the chosen events of El Niño and La Niña years. The analysis will be conducted to determine if there is any linkage between ENSO, IOD, and IPWP events.

3. Results and Discussion

3.1. Impact of ENSO and IOD on TC Activity

A comprehensive investigation of TC data is conducted to identify possible changes in TC activity in the Arabian Sea that are connected to ENSO and IOD, based on the stated criteria. The ENSO and IOD typically start to increase before the monsoon season and reach their peak levels after the monsoon season. This means that they have a limited effect on TCs at first. This study found no clear link between climate indicators and tropical storms during the pre-monsoon period. However, the post-monsoon season, when both IOD and ENSO were more active, showed a stronger connection. This work supports the idea that their effect on TCs becomes clearer later in the year. That is why this study focuses more on the post-monsoon season, which is when IOD and ENSO are particularly relevant.

3.1.1. Frequency and Intensity of TCs

The seasonality variability of the Arabian Sea TC activity during ENSO phases initially was examined by [56] and is greatly expanded upon in this study. Over the pre- and post-monsoon seasons, the effect of ENSO phases on TC activity in the Arabian Sea considerably varies in both frequency and intensity (Figure 4). During El Niño and La Niña occurrences in the pre-monsoon season, the frequency and severity of TCs do not vary significantly. In both El Niño and La Niña, the overall count of TCs (excluding Ds) remains at seven. This accounts for 35% of the total number of intense TCs (CS and above) in the pre-monsoon season (7 out of 20). It appears slightly more frequently during El Niño years (4) compared to La Niña years (3), and no SuCS occurred in either phase. On the other hand, the overall record of TCs stays constant during the post-monsoon season—16 in both El Niño and La Niña years. This represents 64% of the total non-depression TCs (CS and above) in the post-monsoon season (16 out of 25). During El Niño, 10 intense TCs occurred, significantly higher than the six observed during La Niña. ESCSs are more common during El Niño but absent in La Niña years. La Niña years, on the other hand, show a higher occurrence of depressions (10) than El Niño years (6), therefore indicating a change toward less intense systems (

Table 2. Frequency and intensity of TCs over the Arabian Sea during different ENSO events.

Season	ENSO	Ds	CS	SCS	VSCS	ESCS	SuCS	Total
Pre-monsoon	El Niño La Niña	3	2	0	1	1	0	7
		4	1	0	0	2	0	7
Post-monsoon	El Niño La Niña	6	1	3	2	4	0	16
		10	3	2	1	0	0	16

). These proportions highlight that ENSO phases influence a greater share of post-monsoon intense TCs than in the pre-monsoon season, suggesting a stronger seasonal dependence. The absence of SuCS in both ENSO phases suggests that other atmospheric and oceanic factors, rather than El Niño or La Niña alone, may be crucial for the most extreme TCs in the Arabian Sea.

The TCs’ activity in the pre-monsoon season is relatively low, independent of the IOD events. For the pre-monsoon, the total count of TCs for both IOD events came out to be only six (Figure 5a). During the post-monsoon season, the IOD has a maximum effect on TC activity. Whereas an nIOD phase corresponds with a significantly reduced overall TCs frequency (7 TCs), a pIOD phase connects with a substantially higher frequency (Figure 5b). During a pIOD (10), the number of strong TCs (CS and above) is much higher than during an nIOD (4). Three ESCS and one SuCS have occurred more often when the IOD is positive (

Table 3. Frequency and intensity of TCs over the Arabian Sea during different IOD events.

Season	IOD	DDs	CS	SCS	VSCS	ESCS	SuCS	Total
Pre-monsoon	pIOD nIOD	0	0	1	1	0	0	2
		2	0	2	0	0	0	4
Post-monsoon	pIOD nIOD	6	1	2	3	3	1	16
		3	2	2	0	0	0	7

). Neither ESCS nor SuCS appeared when the IOD was negative.

3.1.2. Genesis and Tracking of TCs

Considerable spatial variations in genesis sites and tracks of TCs are apparent throughout distinct ENSO phases (Figure 6). Particularly between 10° N and 15° N, TC genesis sites are primarily found in the eastern and central Arabian Sea in El Niño years; this is somewhat closer to the Indian subcontinent. During La Niña years, on the other hand, the starting points of TCs are spread out more. There is a noticeable concentration in the central and western Arabian Sea, especially between 10° N and 15° N and from 55° E to 75° E, with some events close to the Arabian Peninsula. Regarding the TCs’ track characteristics during the primary TC peak season, Figure 6a–d demonstrates a difference between El Niño and La Niña years. The TCs that develop over the Arabian Sea during El Niño years follow a westward or northeastward track, with more TCs making landfall than La Niña TCs. Under La Niña, the majority of TCs move northwestward, and just a few make landfall.

In terms of the IOD effects on TC genesis and track, the years of pIOD show considerably more concentrated occurrence of TC generation, with higher density in the eastern Arabian Sea (Figure 7a,b). Conversely, during nIOD years, the distribution appears less dense, with genesis events dispersed throughout the basin. In terms of track, Figure 7c,d shows the composite paths of Arabian Sea TCs throughout the years identified by either positive or nIOD events. In nIOD years, TCs are fewer and usually follow a northwest path; in pIOD years, most TCs migrate westward.

3.1.3. Duration and Energy Metrics

This study examines the effect of ENSO and IOD on the duration of TCs (hrs), ACE, and PDI over the Arabian Sea. In terms of the ENSO relationship with TC activity over the Arabian Sea, Figure 8b shows the total duration of TCs for the pre-monsoon season and the post-monsoon season for all El Niño and La Niña years. Figure 8 and

Table 4. The total duration (hours) of different categories of TCs over the Arabian Sea during different ENSO events.

Season	ENSO	CS	SCS	VSCS	ESCS	SuCS	Total
Pre-monsoon	El Niño La Niña	108	0	153	84	0	345
		36	0	0	213	0	249
Post-monsoon	El Niño La Niña	18	141	243	447	0	876
		87	162	33	0	0	282

show that there is no significant difference between TCs’ duration during El Niño and La Niña years in the pre-monsoon season. In El Niño years, significantly above-average TC duration is observed in the post-monsoon season. The difference in TC lifetime between El Niño and La Niña phases is statistically significant in this season. This is consistent with the findings of [57,58] all of them suggest that the shift toward longer TC duration in the post-monsoon season can be attributed to the higher number of intensive TCs during that season.

In terms of the energy metrics, the yearly time series of ACE and PDI over the Arabian Sea is calculated to signify the prevailing ENSO phase (Figure 9). There are certain years when ACE and PDI are zero, either due to the absence of TCs or because the TCs that did exist had intensities below 35 knots. The annual averages of ACE and the PDI in the pre-monsoon season are 2.68 × ${10}^4$ kt² and 0.91 × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, respectively. The lowest ACE and PDI on record during the pre-monsoon season, 1 × ${10}^4$ kt² and 0.37 × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, occurred in a La Niña year (1985). The highest ACE and PDI values, 14.21 × ${10}^4$ kt² and 12.17 × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, occurred in 2001, which is a neutral year.

The correlation between ONI and TC’s energy metrics (ACE and PDI) is positive in the post-monsoon season, with values of 0.40 and 0.35, respectively. These correlations are statistically significant at the 95% confidence level with p-values of 0.013 for ACE and 0.039 for the PDI. In the El Niño years of the pre-monsoon, the average (total) of ACE and PDI values are 3.07 (24.6) × ${10}^4$ kt² and 1.97 (15.77) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, while for La Niña years of this season, they are 2.83(22.66) × ${10}^4$ kt² and 2.38 (19.05) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$ respectively (Figure 10a,c). There is a substantial increase in ACE and PDI during the post-monsoon season (Figure 10b,d), which are higher than in the pre-monsoon season. The average ACE and PDI are 3.00 × ${10}^4$ kt² and 2.25 × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, while the lowest and highest total ACE and PDI values per year are 0.64 × ${10}^4$ kt² and 0.20 × ${10}^6 {\mathrm{k}\mathrm{t}}^3$ in 2001 (neutral) and 38.92 × ${10}^4$ kt² and 35.38 × ${10}^6 {\mathrm{k}\mathrm{t}}^3$ in 2019 (El Niño), respectively. Of 14 El Niño years in post-monsoon, 7 are above the average of ACE and PDI in this season. In contrast, across 16 La Niña years in the post-monsoon, none reach the average of ACE and the PDI. In the El Niño years of the post-monsoon, the average (total) of ACE and PDI values are 5.80(81.22) × ${10}^4$ kt² and 4.68 (68.08) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, while for La Niña years of this season, 0.53(8.52) × ${10}^4$ kt² and 0.21 (03.37) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$ respectively.

The seasonal ACE and PDI in ENSO phases suggest a significant difference in the post-monsoon season compared to the pre-monsoon season. ACE and PDI in El Niño phases are significantly different from those in La Niña phases in the post-monsoon season. There are more TCs in El Niño phases compared with La Niña phases. El Niño years have above-average ACE and PDI in the post-monsoon season. This is because there are more TCs, more TC days, and stronger TCs during this phase (Figure 8 and Figure 9). In La Niña years, the opposite is true. In the pre-monsoon season, ENSO phases do not yet reach their peak values [59], so there are no apparent differences in ACE and PDI values during the different ENSO phases.

Regarding IOD impact on TCs duration over the Arabian Sea, the study indicates apparent variations in TCs length between positive and negative phases of the IOD across both pre-monsoon and post-monsoon seasons (

Table 5. The total duration of different categories of TCs in hours over the Arabian Sea during different IOD events.

Season	IOD	CS	SCS	VSCS	ESCS	SuCS	Total
Pre-monsoon	pIOD nIOD	0	48	153	0	0	201
		0	147	0	0	0	147
Post-monsoon	pIOD nIOD	48	144	312	429	156	1089
		78	114	0	0	0	192

). Under pIOD, TC activity is higher during the pre-monsoon season. With mostly 48 h of SCS and 153 h of VSCS, the overall duration of TCs in this phase is 201 h. In contrast, during nIOD periods, the total duration of TCs was 147 h, with no observable VSCS, ESCS, or SuCS categories. The TCs in this phase last exactly 147 h of SCS. Notably clear in the differences across IOD levels is the post-monsoon season. Under favorable IOD conditions, TCs have a generally much longer lifetime—1089 h. Along with 48 h of CS and 144 h of SCS, this includes significant contributions from all main TC classifications: 312 h of VSCS, 429 h of ESCS, and 156 h of SuCS. During nIOD periods, on the other hand, TCs are much shorter, lasting only 192 h. These 192 h are mostly made up of 78 h of CS and 114 h of severe SCS; no hours were recorded for higher-intensity cyclone categories.

In terms of energy metrics during different IOD phases (Figure 11), during the pIOD years of the pre-monsoon, the average (total) of ACE and PDI values are 3.35 (13.43) × ${10}^4$ kt² and 2.16 (08.65) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$. On the other hand, in nIOD years for the same season, the matching numbers are 1.21 (06.05) × ${10}^4$ kt² and 0.55 (02.74) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$. The difference in ACE and PDI values seen between pIOD and nIOD years is somewhat evident in the post-monsoon season. The average total values for ACE and PDI for the pIOD years of the post-monsoon period are noted at 09.76 (68.32) × ${10}^4$ kt² and 08.43 (58.98) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, respectively. By contrast, the nIOD years for this season reveal averages of 01.25(8.73) × ${10}^4$ kt² and 0.51 (03.58) × ${10}^6 {\mathrm{k}\mathrm{t}}^3$, respectively. Seasonal ACE and PDI analysis over different IOD phases show a clear post-monsoon season difference relative to the pre-monsoon season. These findings indicate that both ACE and PDI increase significantly during pIOD years, especially in the post-monsoon season, suggesting enhanced cyclone energy during these periods. ACE and PDI show some apparent variations between the two different IOD phases in the post-monsoon season. Their correlation with DMI was 0.56 and 0.52, respectively, with corresponding p-values of 0.0005 and 0.0002, indicating that the relationships are statistically significant at the 99% confidence level.

3.2. Climate States

3.2.1. Sea Surface Temperature

The TCs’ activity is significantly regulated by SST [60,61,62]. Figure 12 represents the SST conditions over the Arabian Sea during different ENSO and IOD phases. SST has a crucial and fundamental function in regulating TCs’ activity [60,61,63,64,65]. Figure 12a,b illustrates the composite mean of SSTs throughout the post-monsoon season under El Niño and La Niña conditions. The figure below clearly indicates that the mean SST throughout this season significantly exceeds the threshold value of 26.5 °C, which is conducive to TC activity in both regimes. SSTs in the Arabian Sea exhibit no substantial variations between El Niño and La Niña years. It is marginally higher during El Niño compared to La Niña conditions.

Regarding IOD events, the SSTs over the Arabian Sea during pIOD years show significant warming (Figure 12c,d), with high temperatures spread across the central and western areas. This general warming supports the development of more robust and long-lived systems and produces a favorable thermal environment for TC genesis at lower latitudes. More energy is available since the water is warmer during pIOD events, which results in higher TC energy readings like PDI and ACE. Especially in the post-monsoon season, the warm SSTs encourage westward-moving TCs to fit the area of highest thermal support. In contrast, when nIOD happens, there is a smaller area of warm SSTs, making it harder for TCs to grow and become stronger, leading to weaker TCs that last a shorter time and usually form at higher latitudes with less movement to the west. The different SST patterns during positive and nIOD phases are crucial in deciding how TCs behave in the Arabian Sea, including where they start, their path, strength, energy, and how long they last. The results of the study are consistent with previous findings [62]. He suggests that IOD is rising favorably and shows proof of warming in the western Indian Ocean. The study indicates that the SST and IOD have a favorable influence on the TC activities in the AS.

Figure 12. Composites of mean SSTs (°C) during post-monsoon season under (a) El Niño, (b) La Niña, (c) pIOD, and (d) nIOD events over the Arabian Sea.

Figure 12. Composites of mean SSTs (°C) during post-monsoon season under (a) El Niño, (b) La Niña, (c) pIOD, and (d) nIOD events over the Arabian Sea.

3.2.2. Outgoing Longwave Radiation

OLR anomalies are contrary to the convective activity over the Arabian Sea. The OLR anomaly pattern under ENSO and IOD phases is shown in Figure 13. ENSO and IOD significantly alter the OLR anomaly pattern over the Arabian Sea, as observed. This means that during El Niño and pIOD years, there is a noticeable drop in OLR over most of the Arabian Sea, especially in the central and eastern areas, indicating more convection. In contrast, during La Niña and nIOD years, there are higher positive OLR anomalies in the same areas, indicating less convective activity. During El Niño (La Niña) years, the ascending (descending) of the secondary branch of the Walker circulation over the western Indian Ocean creates favorable (unfavorable) conditions for convective activity and the formation of TCs in the Arabian Sea. Much research has shown how Walker circulation affects TCs’ activity in several basins [18,66,67]. These conflicting tendencies highlight the influence of ENSO and IOD phases on regional atmospheric convection, using which El Niño and pIOD develop TC-favorable conditions while La Niña and nIOD limit them. The regional distribution of OLR anomalies suggests a stronger convective response in El Niño and pIOD years, which could be linked to more TC activity

Figure 13. Composites of OLR (W/m²) anomalies at 500 hPa during post-monsoon season under (a) El Niño, (b) La Niña, (c) pIOD, and (d) nIOD events over the Arabian Sea.

Figure 13. Composites of OLR (W/m²) anomalies at 500 hPa during post-monsoon season under (a) El Niño, (b) La Niña, (c) pIOD, and (d) nIOD events over the Arabian Sea.

3.2.3. Relative Humidity

The mid-tropospheric RH is quite crucial to observe the favorability (unfavourability) of the environment for the beginning and persistence of convective activity. The development and strengthening of TCs’ activity rely on having enough mid-tropospheric RH [29,30]. A dry mid-tropospheric RH does not encourage TC’s activity. Under different ENSO regimes, Figure 14a–d shows the 500 hPa RH anomalies across the Arabian Sea. The composite anomalies for the whole season during the El Niño phase are positive, suggesting a more conducive environment for TC activity. High RH causes the release of latent heat required for TCs’ development and strengthening. The rising of the secondary limb of the Walker circulation during El Niño years over this area accounts for high moisture transfer to the mid-tropospheric level. When RH anomalies are somewhat greater over the Arabian Sea during El Niño episodes, the frequency of TCs is above average. On the other hand, La Niña events show slight positive anomalies in the middle of the Arabian Sea and negative anomalies across the entire study area, which hinder TC activity. One of the reasons is this one: most TCs during La Niña tend to disperse throughout the ocean.

Mid-level RH (500 hPa) over the Arabian Sea during different IOD events shows an apparent variation, which significantly affects TC activity. The pIOD events significantly increase moisture in the middle part of the atmosphere over the central and eastern Arabian Sea, especially between 15° N and 25° N and around 70° E–75° E, which creates good conditions for TC formation and growth. These wet conditions increase the persistence and strength of TCs. However, nIOD events are linked to dry conditions over the Arabian Sea, which reduce moisture and prevent the formation of TCs. TC’s vertical growth is limited by the dry mid-level environment, which also shortens their lifetime.

3.2.4. Vertical Wind Shear

The VWS is a significant parameter that is crucial in the TC’s activity, especially their genesis and development. While lower VWS is favorable, higher VWS negatively impacts the origin and growth of TCs [37,68,69,70,71,72,73]. It significantly influences the concentration of latent heat from convective condensation within a specific range of the air column. During El Niño (La Niña) years, the VWS is relatively low (high), which causes more (less) TC activity over the Arabian Sea. According to Figure 15a,b, in La Niña years, the weak VWS weakens and shifts upward, typically between 20° N and 11° N. For El Niño years, weak to moderate VWS over the Arabian Sea seems to be concentrated between 18° N and 5° N. This regional difference in VWS is known to impact the TC’s activity. In the case of La Niña, the pattern formed with weak VWS at higher latitudes contributes to TC activity at the upper side of the Arabian Sea. During El Niño, the pattern with VWS at lower latitudes enhances the TCs forming potential in the Southern Arabian Sea. During El Niño, weak VWS spreads over a larger area at lower latitudes, which creates better conditions for TCs to form and strengthen. These sheer distribution changes explain the noted differences in regions of TC generation and their tracks for El Niño and La Niña patterns. Figure 16c,d show that VWS tends to be somewhat weaker for pIOD events relative to negative ones. The overall pattern suggests that during pIOD phases, the Arabian Sea becomes more favorable for TC activity. This is although the alterations are not significant. However, the lack of a notable change implies that other factors probably play a part in changing the variability of TC activity in the area. As suggested by previous studies, the finding is consistent with other studies that have examined the impact of the ENSO and IOD on TC activity in different ocean basins, which have shown that while VWS is an essential factor, other variables such as SST, RH, and OLR play a more significant role [33,37,74].

3.2.5. Sea Level Pressure

The composite anomalies of SLP across the Arabian Sea reveal notable variations between El Niño and La Niña years, which strongly affect TC activity (Figure 16). Lower SLP is mainly observed in the western Arabian Sea during El Niño years, which helps to generate larger TCs by allowing more air to join and rise. This convective enhancement produces conditions conducive to stronger TCs, longer durations, and primarily westward tracks. Conversely, in La Niña years, the negative SLP anomalies are restricted to a narrower region over the eastern Arabian Sea, resulting in more constricted and relatively weaker convection. This promotes TC production in the eastern area, but, as these systems move northwestward into regions of higher SLP and lesser convection, they often weaken, resulting in shorter durations and lower intensity. While La Niña years correspond with lower and spatially restricted TC generation due to weaker and more localized convection, El Niño years tend to allow more substantial and more protracted TCs fueled by massive convective activity in the western Arabian Sea. Especially about TCs’ activity in the Arabian Sea, the change in SLP anomalies between positive and nIOD years closely mirrors the pattern of El Niño and La Niña years. In pIOD years, most of the Arabian Sea—particularly the central and western regions—shows negative SLP anomalies. Rising and gathering air, this enormous low-pressure system allows TCs to be stronger and last longer. These qualities help central or eastern TCs migrate westward toward the western Arabian Sea. nIOD years have lower SLP anomalies in the northern Arabian Sea, which results in less convection. A low-pressure region geographically constrained limits cyclogenesis, hence generating fewer, weaker, and shorter cyclones. The nIOD years have less convection and less favorable pressure systems that push TCs’ trajectories north or lead them to recurve sooner, therefore lowering westward movement and associated with lower TC activity, whereas pIOD years are linked to higher TC activity in the Arabian Sea. TC’s features are affected by the geographic extent and intensity of the negative SLP anomaly.

Figure 16. Composites of SLP (hPa) anomalies during post-monsoon season under (a) El Niño, (b) La Niña, (c) pIOD, and (d) nIOD events over the Arabian Sea.

Figure 16. Composites of SLP (hPa) anomalies during post-monsoon season under (a) El Niño, (b) La Niña, (c) pIOD, and (d) nIOD events over the Arabian Sea.

3.2.6. Upper Wind

Earlier studies have shown that, in the NIO, the TCs are guided by the atmospheric flow pattern at upper wind [41,75]. During different climate circulation modes of ENSO and IOD, Figure 17 depicts the average upper-level winds (150 hPa) in the Arabian Sea region. In El Niño years, winds blow from the southeast between 12° N and 16° N, whereas in La Niña years, winds blow from the southeast between 5° N and 17° N. There is an upper-level anticyclone over the Arabian Sea, which means that it influences weather patterns in the region. This anticyclone affects the trajectories that TCs take. When El Niño arises, the TCs that originate below 12° N move west. But anticyclonic outflow has a significant effect on TCs that form north of 12° N, pushing them northeast. Upper-wind patterns are similar during La Niña years, but TCs originate in the broader area and are moved slightly to the west, which makes the TCs drift northwest. But during La Niña events, TCs have difficulties becoming stronger because of low RH, high VWS, and unfavorable SLP. This makes them fade away over the ocean. The wind patterns during positive and nIOD years (Figure 17c,d) demonstrate increased zonal flow, notably when the IOD is positive. There are no apparent signs of an anticyclone over the Arabian Sea during pIOD. In contrast, during nIOD, an anticyclone was present, but the unfavorable conditions for TC activity resulted in very little activity. The evidence suggests that upper-level steering may not have as much of an effect on modifying TC activity during these years as ENSO phases do. However, it is essential to acknowledge that the Madden–Julian Oscillation (MJO), which can affect wind patterns and convection over the Arabian Sea, is a sub-seasonal variability that may furthermore impact TC activity during ENSO and IOD phases. It is essential to contemplate this matter. This element was not the primary focus of the current study; nonetheless, it will be investigated in future research.

Depending on the above analysis (Section 3.2.1, Section 3.2.2, Section 3.2.3, Section 3.2.4, Section 3.2.5 and Section 3.2.6), ENSO and IOD phases exhibit distinct upper-level wind patterns, shear distributions, and convective structures attributable to their large-scale atmospheric dynamics. Walker circulation, zonal SST gradients, and atmospheric reactions all affect the mechanisms. During El Niño, the Walker circulation weakens and moves eastward, which makes convection in the western Indian Ocean stronger. This change lowers SLP, increases mid-tropospheric moisture, and lowers VWS, which makes it easier for TCs to form and grow in the basin. La Niña occurrences induce less convection in the Arabian Sea because the Walker circulation in the Indian Ocean moves eastward. This makes the wind shear stronger and the mid-levels drier, which makes it harder for TCs to form over the western half of the Indian Ocean.

The IOD phases also affect the thermodynamics and dynamics of the Indian Ocean. A pIOD makes the SST gradient stronger between the west and the east of the Indian Ocean. This causes unusual convection in the Arabian Sea, convergence in the lower troposphere, and divergence in the upper levels. Increased humidity and instability in the middle levels make TCs stronger and last longer. The nIOD occurrences diminish convection and amplify wind shear, hence decreasing TC activity. These results elucidate statistical data by correlating them with synoptic-scale wind shear, moisture availability, and pressure systems, which are significant factors in the genesis of Arabian Sea TCs.

3.3. The Impacts of Indo-Pacific Warming Pool

According to [76], the Arabian Sea divides into four parts (A1 to A4), with Region A4 (southeastern Arabian Sea) being the most western part of the IPWP. The southeastern Arabian Sea, which has higher SSTs, meets a basic thermodynamic need for the formation of TCs. Along with ENSO and IOD unpredictability, the IPWP is increasingly thought to play a substantial role in long-term fluctuations in TC activity in the Arabian Sea. The IPWP’s westward expansion can significantly increase western Indian Ocean SSTs. This warming increases middle-level moisture and decreases VWS, making TCs stronger. The analysis indicates that the southeast is the most favorable area where TCs form in the Arabian Sea, accounting for more than 50% of all TCs (1982–2021). The result highlights the essential function of the IPWP in establishing a conducive environment (high convection) for cyclogenesis in the southeastern Arabian Sea. Investigating SST anomalies in the IPWP from 1982 to 2021 (Figure 18) showed the time series of SST anomalies in the IPWP. The IPWP expansion can shift the Walker circulation’s location and strength [77], affecting large-scale atmospheric circulations. A Walker cell that moves or strengthens towards the west can influence the phases and strength of ENSO and IOD [78,79,80], which in turn can affect the development of TCs over the Arabian Sea. The IPWP’s background suggests that state change may explain the recent decades’ increased SSTs, especially in the post-monsoon season. The increase in TCs’ activity and duration over this time is supported. The correlation coefficients between IPWP SST anomalies and TC frequency, ACE, and PDI in the pre-monsoon season were 0.33, 0.26, and 0.20, respectively. In the post-monsoon season, the correlations were 0.21, 0.27, and 0.30. These findings indicate that the IPWP has a positive effect, albeit smaller than the ENSO and IOD, which have a significantly greater impact on TC activity over the Arabian Sea.

Separating the IPWP data into two temporal periods—1982–2001 and 2002–2021—reveals a distinct shift. The first period shows mostly negative SST anomalies, whereas the second period shows mostly positive anomalies. It is important to note that most of the intensive TCs in the Arabian Sea (

Table 6. The number of different categories of the intensive TCs over the Arabian Sea during the periods of the negative phase of IPWP (1982–2001) and the positive phase of IPWP (2002–2021).

Period	CS	SCS	VSCS	ESCS	SuCS	Total
1982–2001	7	4	2	4	0	17
2002–2021	9	6	5	6	0	26

) have increased (26 TCs) in the past 20 years compared with less intensive TCs in the first period (17 TCs) [56,76,81]. This time-based connection suggests that the recent rise in IPWP SSTs may have contributed to intensifying TCs in the Arabian Sea; however, since SST is increasing globally (including the Arabian Sea), we cannot conclude that IPWP is the primary reason. Instead, its overall effect appears to be less significant than that of other indices like ONI and DMI.

4. Conclusions

This study investigates the influence of large-scale circulation indices, including ENSO, IOD, and IPWP, on TC activity in the Arabian Sea from 1982 to 2021, emphasizing their effects on TC frequency, intensity, genesis, trajectories, energy metrics (ACE and PDI), and duration. These variations are driven mainly by differences in ocean-atmosphere interactions during ENSO and IOD phases, which modulate regional thermodynamic and dynamic environments. The correlations in the Arabian Sea are weaker during the pre-monsoon season. In contrast, in the post-monsoon season, there are usually strong links between TC characteristics and the indices of these significant phenomena (ONI and DMI) in the Arabian Sea. This work investigates how TCs in the Arabian Sea are affected by different phases of ENSO and IOD (

Table 7. Summary of TC characteristics over the Arabian Sea during different ENSO phases in the pre-monsoon and post-monsoon seasons. The table highlights variations in TC frequency, duration, and energy metrics (ACE and PDI), showing how El Niño and La Niña events influence TCs’ behavior.

Parameter	Pre-Monsoon (All Phases)	Post-Monsoon El Niño	Post-Monsoon La Niña
TC Frequency	No consistent pattern observed due to weak ENSO signal	Higher TC frequency	Lower TC frequency
TC Duration (hours)	No apparent difference across phases	More TC days, longer-lasting systems	Fewer TC days, shorter duration
ACE (×104 kt2)	No distinct variation	Higher ACE (stronger storms)	Lower ACE
PDI (×106 kt3)	No distinct variation	Higher PDI (intense, long-lived TCs)	Lower PDI
Notes	The ENSO signal is still developing in the early season	Favors TC development and intensity	Suppresses TC strength

and

Table 8. Summary of TC characteristics over the Arabian Sea during different phases of the IOD in the pre-monsoon and post-monsoon seasons. The table emphasizes the differences in TCs’ activity, duration, and energy metrics under positive and negative IOD conditions.

Parameter	Pre-Monsoon (pIOD)	Pre-Monsoon (nIOD)	Post-Monsoon (pIOD)	Post-Monsoon (nIOD)
TC Frequency	Higher frequency of stronger TCs	Lower frequency; mostly weaker storms	Significantly higher frequency and intensity	Fewer storms with limited intensity
TC Duration (hours)	Longer-lasting TCs with multiple TC categories	Shorter-lived TCs of limited strength	Much longer TC lifespans across all types	Short-lived TCs with no intense categories
ACE (×104 kt2)	Very low	Very low	Substantially higher ACE	Very low ACE
PDI (×106 kt3)	Very low	Very low	Higher PDI (intense, long-lived TCs)	Very low PDI
Notes	Favorable for TCs’ development and strength	Suppresses TCs intensification	Creates an optimal environment for strong TCs	Inhibits TCs’ growth and duration

). With less intensive TC systems recorded in each phase, the frequency and intensity of TCs show slight variation between El Niño and La Niña years in the pre-monsoon season. While La Niña years are marked by a greater prevalence of depressions and a lower number of intense TC systems, El Niño years lead to more frequent occurrences of intense TCs, including more ESCSs, during the post-monsoon season. During the post-monsoon season, the IOD has a more noticeable effect; pIOD phases correspond with a higher frequency and intensity of TCs, including ESCS and SuCS, while nIOD phases are associated with lower TC numbers and intensity.

TC genesis sites and paths change depending on the ENSO phase, with TCs forming in different areas and taking different routes during La Niña and El Niño, which influences where they make landfall. In La Niña years, formation locations are more widespread, especially in the central and western Arabian Sea. In contrast, during El Niño years, TCs mainly form in the central and east Arabian Sea, closer to the Indian subcontinent. During La Niña years, most TCs move northwestward, resulting in fewer landfalls. In contrast, during El Niño years, they typically move westward or northeastward. The IOD affects TCs’ activity; pIOD years show higher TC density in the eastern Arabian Sea; nIOD years show fewer TCs, mostly moving northwestward.

Additionally, the impact of ENSO and IOD on TC duration, ACE, and PDI indicates that El Niño years lead to TCs that last longer and are higher energy, particularly in the post-monsoon season. In contrast, La Niña years result in TCs that are shorter and weaker. Over the Arabian Sea, the study found notable differences in TC duration and energy features between pIOD and nIOD periods. pIOD conditions increase TC activity in pre- and post-monsoon seasons with longer durations and higher ACE and the PDI, including more VSCS, ESCS, and SuCS. In contrast, nIOD years produced shorter TCs with less intensive TCs and lower energy measurements. pIOD years have more severe and longer-lasting TCs, as seen by greater ACE and PDI numbers, especially in the post-monsoon season. These differences are primarily attributed to increased ocean heat content, enhanced moisture supply, and favorable atmospheric instability during El Niño and pIOD events.

Furthermore, the role and influence of key environmental drivers affecting TCs’ activity were examined, including SST, OLR anomalies, mid-tropospheric RH, and VWS during various phases of the ENSO and IOD events, influencing TCs’ variation over the Arabian. The TCs’ development requires SST over 26.5 °C; higher SSTs are observed during El Niño and positive pIOD years, hence encouraging more severe and lasting TCs. On the other hand, nIOD years show limited areas of higher SSTs; thus, while La Niña and nIOD years are associated with dry conditions that make it harder for TCs to form, El Niño and pIOD years create better conditions for moisture in the atmosphere, which helps TCs generate and develop. While La Niña and nIOD phases are linked to dry weather that makes it difficult for TCs to grow, El Niño and pIOD years create better conditions for moisture in the atmosphere, which is needed for TCs to form. Finally, VWS patterns do not show a significant difference between El Niño and La Niña years. It is vital for TC activity, but it does not cause variability between ENSO events. In contrast, composite VWS varies between different IOD events, being favorable during pIOD events and unfavorable during nIOD events. Therefore, SST and OLR act as dominant thermodynamic regulators of TC intensity and duration, while the IOD exerts more precise control over upper-level dynamics such as VWS.

The IPWP, especially the westernmost part of it in the southeastern Arabian Sea, supports the TCs’ formation by keeping SSTs high and deep convection going. A statistical investigation of SST anomalies in the IPWP reveals a minimal connection between these anomalies and TC activity (frequency and energy metrics) during the pre- and post-monsoon seasons.

Comparing SST anomalies over time reveals that the IPWP has experienced more positive SST anomalies over the past 20 years, coinciding with an increase in the frequency of intense TCs. However, this connection does not seem to be the main one. The fact that the Arabian Sea’s SST is warming at the same time as the IPWPs and the correlations with ENSO and IOD indices show that the IPWPs’ role in TC activity over the Arabian Sea is more likely to be supportive than dominant. Thus, while global warming trends—such as those affecting the IPWP—may provide favorable background conditions, it is the regional modulation by ENSO and IOD that primarily governs TC variability in the Arabian Sea.

The insights from this work on the variability of TCs under different global circulation indices (ENSO, IOD phases, and IPWP) can help improve seasonal TC forecasting, inform disaster management plans, and support early warning systems in regions vulnerable to TC impacts.