Total Totals Index Research Articles

Dynamic and Thermodynamic Drivers of Severe Sub-Hourly Precipitation Events in Mainland Portugal

Sub-hourly heavy precipitation events (SHHPs) associated with regional low-pressure (RegL) systems in Portugal are a natural hazard that may have significant socioeconomic implications, namely in agriculture. Therefore, in this paper, their dynamic and thermodynamic drivers are analysed. Three weather stations were used to isolate SHHPs from 2000 to 2022. Higher precipitation variability is found in southern Portugal, with a higher ratio of extreme events on fewer rainy days. This study shows that these SHHP events are associated with low-pressure systems located just to the west of the Iberian Peninsula. These systems exhibit a cold core, particularly strong at mid-levels, and a positive vorticity anomaly, which is stronger in the upper troposphere, extending downward to low levels. These conditions drive differential positive vorticity advection and, therefore, rising motion to the east of the low-pressure systems. Moreover, at low levels, these systems promote moisture advection over western Iberia, also generating instability conditions, which are assessed by instability indices (Convective available potential energy, the Total-Totals index, and the K-index). The combination of these conditions drives heavy precipitation events. Lastly, the total column cloud ice water revealed higher values for the heavier precipitation events, suggesting that it may be a useful predictor of such events.

CORRELATION OF ATMOSPHERIC LABILITY INDEX TO VERTICAL WIND SHEAR AT I GUSTI NGURAH RAI AIRPORT

Wind shear is a condition that is detrimental to aircraft because it can cause the aircraft to experience lift, especially during take-off or landing, where wind shear can occur due to bad and unstable weather, so research on the correlation of the atmospheric lability index to wind shear is very important to prevent a plane crash. This research aims to determine the magnitude of the correlation of the atmospheric lability index to the vertical wind shear that occurs at I Gusti Ngurah Rai Airport, Bali. In this research, the Wind Profiler Radar (WPR) brand scintec LAP-3000 was used to obtain wind shear data in the form of wind direction and wind speed data then radiosonde to obtain atmospheric lability index data in the form of Lifted Index (LI), Total-Totals Index (TT), K-Index (KI), and Convective Available Potential Energy (CAPE) index values for each month in 2019-2020. Wind shear measurement was carried out at an altitude of 100-3000 m and data were taken on the difference in wind direction ≥ 60o and the difference in wind speed ≥ 10 knots. Meanwhile, measurement of the atmospheric lability index is carried out by a flying air balloon that has been equipped with a transmitter. All LI, TT, KI, and CAPE index value data and the number of wind shear events were analyzed with Pearson Product Moment correlation. The value of the correlation coefficient (r) between the LI, TT, KI, and CAPE indices was obtained for successive wind shear events of -0.786; 0,250; 0.738, and 0.713. These results show that the LI, KI, and CAPE index values can be used as a reference to predict wind shear events because they have a strong correlation, obtaining a correlation value between 0.60 to 0.79 compared to the TT index.

The Impact of El-Niño and La-Niña on the Pre-Monsoon Convective Systems over Eastern India

El-Niño and La-Niña are believed to change the intensity and frequencies of extreme weather events globally. The present study aims to analyse the impact of El-Niño and La-Niña on the lightning activities of cloud systems and their associated precipitation and thermodynamic indices over the Eastern India regions (Odisha, Jharkhand, and West Bengal) during the pre-monsoon season (March–May). Eastern India receives catastrophic thunderstorm events during the pre-monsoon season. The results suggest that the number of lightning flashes was higher in the El-Niño years than in the La-Niña periods, which helps convective activities to be developed over the study region. The precipitation variations showed similar patterns during El-Niño and La-Niña periods, but the magnitudes were higher in the latter. Results from the analysis of thermodynamic indices show that, during the La-Niña phase, the convective available potential energy (CAPE), convective inhibition (CIN), severe weather threat index (SWEAT), humidity index (HI), and total totals index (TTI) values increased, while the cross total index (CTI) and K index (KI) decreased. In contrast, the vertical total index (VTI) and Boyden index (BI) values showed less significant changes in both El-Niño and La-Niña periods. The anomalies of flash rate densities over most parts of our domain were positive during the El-Niño years and negative during the La-Niña years. Precipitation anomalies had a higher positive magnitude during the La-Niña phase, but had spatial variability similar to the El-Niño phase. The anomalies of most of the thermodynamic indices also showed noticeable differences between El-Niño and La-Niña periods, except for the HI index. El-Niño periods showed higher lightning and increased values of associated thermodynamic indices over eastern India, indicating more pronounced convective systems.

A Preliminary Study on the Organizational Modes of Mesoscale Convective Systems Associated With Warm‐Sector Heavy Rainfall in South China

AbstractThis work examines the organizational modes of mesoscale convective systems (MCSs) associated with warm‐sector heavy rainfall events in South China based on composite radar reflectivities during April–June from 2007 to 2020. The results showed that these MCSs can be classified into the nonlinear mode (NL) and eight linear modes: trailing stratiform precipitation (TS), no stratiform precipitation (NS), leading stratiform precipitation (LS), parallel stratiform precipitation (PS), embedded lines (EL), bow echoes (BE), training line/adjoining stratiform (TL/AS), and multiple rain bands (MRB). The NL mode accounts for 40% of the total, while linear modes account for 60%, with the TS mode being the most frequent linear mode. The detailed features of the top three most frequent organizational modes (NL, TS, and NS) were examined in this work. First, the MCSs of the top three organizational modes have different formation modes. Eighty‐four percent of NL systems and 77% of TS systems form via the broken areal mode, while 83% of NS systems form via the broken line mode. Second, relative to TS and NS systems, NL systems develop faster and have shorter lifespans but slower movements with higher 3‐h and 6‐h maximum precipitation values. Third, environmental analysis indicates that the Total Totals index (TTI) is significantly different among all the top three organizational modes, with the highest value in TS mode and the lowest value in NS mode. These features are apparently different from their counterparts in central East China due to different synoptic environments.

Impact of convection and stability parameters on lightning activity over Andhra Pradesh, India

This paper brings out the interconnection of flash rate density (FRD) with convection and stability parameters over Andhra Pradesh (AP), India. The convection parameters include rainfall, relative humidity, specific humidity, surface air temperature (SAT) and air temperature (at 850 mb). The stability parameters include convective available potential energy (CAPE), lifted index, K-index, total totals index (TTI), humidity index and total precipitable water. Both convective and stability parameters indicate good correlation with lightning activity. SAT and AT 850 mb have shown good correlations with lightning, which is a clear indication of interaction between warm air and dry air. CAPE and TTI have shown strong positive correlation with lightning activity. The correlation coefficient between FRD and CAPE is 0.81. We have also studied the influence of convective and stability parameters during lightning and no lightning activity. Later, we also attempted the estimation of lightning activity by using artificial neural network model. By using convection and stability parameters, six learning algorithms were used for training the artificial neural network. Scaled conjugate gradient backpropagation training algorithm has given the better estimation, whereas resilient backpropagation training algorithm has shown the poor estimation of FRD.

THE WAY TO DETERMINE THE APPROXIMATELY HAIL'S DIMENSIONS

To determine those storms associated with the convective clouds is necessary a good knowledge of the vertical profile of the troposphere. To determine this parameter, it's essential to make the Skew-T diagrams. From these, we can extract useful information relating to the level of free convection (LFC), the equilibrium level (EL), and the maximum speed of the updraft. The parameter brought in the discussion is handy to hail's forecast. Therefore, based on this parameter, of the ascendant airflow flux, it can determine the dimension of the hail. Besides to determine the hail's sizes, from Skew-T diagram we can find other parameters, such as the Total Totals Index (TTI), this being useful to decide on the coverage rate of the storms, the K Index (KI) - helpful in the case of convections who occur in the same air-mass. The Skew-T diagrams are useful to determine the conductor flux's speed and direction; this is situated between 700 to 500 hPa geopotential heights. Noteworthy are the synoptically materials, by analyzing the way of disposing of the isobars who can be a good indicator of the severity of the storm. Also, the synoptically materials examine at the 500 hPa, 300 hPa, and 200 hPa geopotential to notice if occur the 'cut-off low' areas in the high troposphere. To see if a cloud system is dangerous of hail will be following the cloud's top temperature.

Satellite Based Interpretation of Stability Parameters on Convective Systems over India and Srilanka

India is frequently exposed to convective systems (CS) during the hot period of pre-monsoon season. Huge thunderstorms are more often over India in the recent years. To analyze these systems, the stability parameters considered as good precursors for understanding the physics of the convective systems in prior to their occurrence. The present study is concerned about the analysis of stability parameters such as K Index (KI), Lifted Index (LI), Total Totals Index (TTI), Humidity Index (HI), Convective available potential energy (CAPE), Convective Inhibition (CIN), Lifting Condensation Level (LCL) and Level of free Convection (LFC) associated with severe convective systems over India and Srilanka during April, 2015. First, INSAT-3D satellite based brightness temperature (BT) product was used for analyzing the initial, mature and dissipation stages of the convective system at every 30 min interval. The data products from MODIS Terra satellite, MODIS Aqua satellite, Era-Interim ECMWF reanalysis satellite data and IASI satellite were used for understanding the thermodynamics related to the occurrence of these convective systems. The results of stability parameters that were derived from MODIS Terra and Aqua satellite’s data products indicated the favorable threshold values for the occurrence of convective systems. Results from Era-Interim ECMWF reanalysis satellite data also helps us to understand the dynamics involved behind the convective system. The results from IASI satellite also helped us to understand the severity of convective systems during cloudy situations. The results of this study impulse the need of satellites for analyzing the convective systems prior to their occurrence.

Long-term analysis of thunderstorm-related parameters over Visakhapatnam and Machilipatnam, India

In this present work, an attempt has been made to analyze various thunderstorm-related parameters and their influence over the two stations Visakhapatnam (VSK) and Machilipatnam (MTM). The thunderstorm-related parameters used in the present study are convective available potential energy (CAPE), lifted index, K-index, total totals index (TTI), humidity index, convective inhibition, thunderstorm prediction index (TPI), deep convective index (DCI) and updraft vertical velocity. This analysis was carried out using NCEP NCAR reanalysis monthly data for the time period from 1948 to 2012. These parameters have given good guidance for studying the thunderstorm event. We also analyzed IMD thunderstorm occurrence days reported at two stations, i.e., VSK and MTM with NCEP NCAR (daily data) calculated CAPE, TTI, TPI and DCI parameter threshold days in pre-monsoon season for every year during the time period 2010 to 2019. Out of those four parameters, TTI has shown good correlation with the IMD recorded days. So we have attempted the prediction of thunderstorms using artificial neural network (ANN) and auto-regressive moving average (ARMA) techniques for TTI parameter. While using these techniques, we have experimented in three training sets, i.e., 90%, 80% and 70%. Another attempt has been made to assess the skill of ARMA and ANN techniques in forecasting the occurrence of thunderstorm activity at VSK and MTM stations. The present study suggests that ANN has high skill than ARMA. From this study, we can understand that VSK has more chances for thunderstorms than MTM.

Impact of Atmospheric Stability Indices on Convective Systems Over India and Srilanka

Thunderstorms are real-time global phenomena, as their occurrence can take place at anytime at any place. Though their duration is less when compared to large scale processes, their damage is devastating to human life. Thunderstorms are linked with damage factors such as lightning, damaging wind, hails and rain. Real-time satellite data provide atmospheric data which is useful for prediction of thunderstorms. In this paper, an attempt is made to analyze the statistical based stability indices from INSAT-3D, MODIS and ECMWF satellites for the now casting of thunderstorms. The occurrences of severe thunderstorms over India and Srilanka during the month of October 2013, 2014 and 2015 have been analyzed. In these three years, five severe thunderstorm cases were identified using Insat-3D cloud images and thunderstorm reports. Atmospheric stability indices such as K Index (KI), Lifted Index (LI), Total Totals Index (TTI), Total Precipitable water (TPW), Humidity Index (HI) related with severe convection system over India and Srilanka during October month were identified to provide guidance for the study of convection and thunderstorm activity. These indices give us a clear indication of development of convective system before 3 to 4 hours. Results of this study indicate the importance of satellite data for studying the development and decay of convective systems.

Observed and model‐simulated thermodynamic processes associated with urban heavy rainfall events over Bangalore, India

AbstractA total of 32 rainfall events spanning the period from 2012 to 2014 over the urban Indian city of Bangalore were simulated using the Weather Research and Forecast (WRF) model. Model simulations were carried out with a four‐nested domain initialized with Global Forecast System (GFS) data and the forecast was generated on an hourly basis. The forecasted rainfall at hobli level (Bangalore has 34 hobli divisions with an area of each hobli of the order of about 10 km2) was evaluated in terms of its intensity and pattern of spatial distribution by comparing it with corresponding rain‐gauge observations. Also, the rainfall forecast skill of the model was evaluated statistically by computing root mean square error, bias and mean absolute error. Thermodynamic variables such as equivalent potential temperature, convective available potential energy (CAPE), convective inhibition (CIN), K index (KI), lifted index (LI) and total totals index (TTI) were also derived from the simulated model parameters for all the events and then verified against corresponding observations. The results showed that the WRF model could simulate the rainfall events and associated thermodynamic features qualitatively; however, there were few hoblis where the relative errors in the forecast were > 100%. The forecast errors were relatively lower for cases during the southwest monsoon season compared with other seasons. It was found that the model underestimated thermodynamic indices such as CAPE, dew point depression and the simulated LI were positive; these were indicative of the model's limitation in simulating intense convection and a possible reason for underpredicted rainfall simulations.

Study of Pre-Monsoon Thunderstorms and Associated Thermodynamic Features Over Bangladesh Using WRF-ARW Model

Thunderstorm is a mesoscale system (from a km to below thousands of km and sustaining less than one hour). Two pre-monsoon thunderstorms events are analyzed in this study which are named as event-1 (0030-0150 UTC of 19 April 2018 over Chattogram) and event-2 (0600-1000 UTC of 4 May 2018 over Dhaka). To predict these events Mean Convective Available Potential Energy (mCAPE), Mean Convective Inhibition Energy (mCINE), K Index (KI), Total totals Index (TTI), wind distribution, and relative humidity (RH) are investigated.The model simulated mCAPE and mCINE values, 18 hours before the events, are found greater than 1700 J/Kg and less than 100 J/Kg respectively which satisfies the conditions for thunderstorms to occur.The KI values are close to 400C and TTI values are greater or equal to 450C for both events. The wind patterns and the high value of mid –tropospheric RH also favors the formation of severe thunderstorm.
 Dhaka Univ. J. Sci. 67(2): 151-156, 2019 (July)

Influence of tropical-extratropical interactions on the dynamics of extreme rainfall event: A case study from Indian region

A diagnostic investigation of an extreme rainfall episode that occurred over the central and north Indian region is carried out in this study using data from a suite of observations from space-borne instruments and the reanalysis datasets. This event is unique in the sense that the organized tropical and extratropical forcing stimulated the intense rainfall on 01 Jan 2012. The WindSat (multi-frequency polarimetric microwave radiometer) observations indicate the source of the moisture flux coming from the adjoining tropical Ocean. The dynamical and thermo-dynamical contributions are evaluated based on the atmospheric instability analysis using the Atmospheric Infrared Sounder (AIRS) and reanalysis datasets by computing various stability indices such as total totals (TT) index, Potential Vorticity (PV), static stability and the Convective Available Potential Energy (CAPE). High TT index values (>40 K) are observed both in satellite and reanalysis data indicating thermodynamic instability. PV intrusion to low latitudes is also observed with extreme rainfall occurrence ahead of the PV tongue. The vertical structure of PV intrusion shows remarkable features with enhanced upward motions ahead of the intrusion representing the dynamical instability. The reduced static stability, increased CAPE and upper-level cyclonic anomalies together with enhanced moisture in the lower troposphere coming from the adjoining tropical Indian Ocean regulate the amplitude and region of occurrence of the extreme rainfall. Therefore, this study identifies the significant implications of tropical and extra-tropical influences that generate the thermodynamical and dynamical instabilities for the occurrence of the extreme rainfall event over the Central and Northern parts of India.

Toward the Operational Weather Forecasting Application of Atmospheric Stability Products Derived From NUCAPS CrIS/ATMS Soundings

Atmospheric soundings from radiosondes are critical for the weather forecasting, particularly for the diagnostic of atmospheric stability conditions that can lead to thunderstorm development. However, radiosonde observations (RAOBs) are temporally and spatially limited throughout the globe, promoting the use of satellite measurements. This paper assesses the applicability to the operational short-term weather forecasting of atmospheric stability indices and parameters (SIPs) derived from thermodynamic profiles retrieved from the National Oceanic and Atmospheric Administration Unique Combined Atmospheric Processing System (NUCAPS) using the Suomi National Polar-orbiting Partnership (SNPP) Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) radiances. For this purpose, we validated NUCAPS SIPs against SIPs derived from conventional and dedicated/reference RAOBs collocated with NUCAPS retrievals within a maximum radius of 50 km and ±1-h time difference, over midlatitudes (60°N-30°N) and tropics (30°N-30°S). Stability parameters evaluated include total precipitable water (TPW), lifted index, K-index, total-totals index, and Galvez-Davison index. NUCAPS TPW exhibited the highest level of statistical agreement with RAOBs, with the remaining NUCAPS SIPs exhibiting favorable results (linear correlations ranging between 0.65 and 0.85). Case studies over the Texas/Oklahoma region and the Northern Coast of Brazil demonstrate NUCAPS capability of generating reliable fields of atmospheric stability, as well as capturing synoptic-scale convective signatures, not feasible with RAOBs. Considering also the benefit of SNPP NUCAPS hyperspectral-infrared (IR) and microwave soundings available for both regions during critical early afternoon periods, our analysis supports the use of NUCAPS CrIS/ATMS SIPs as complementary nowcasting tools for the analysis of preconvective environments.

Assessment of Convective Activity Using Stability Indices as Inferred from Radiosonde and MODIS Data

The combined use of both radiosonde data and three-dimensional satellite derived data over ocean and land is useful for a better understanding of atmospheric thermodynamics. Here, an attempt is made to study the thermodynamic structure of convective atmosphere during pre-monsoon season over southwest peninsular India utilizing satellite derived data and radiosonde data. The stability indices were computed for the selected stations over southwest peninsular India viz: Thiruvananthapuram and Cochin, using the radiosonde data for five premonsoon seasons. The stability indices studied for the region are Showalter Index (SI), K Index (KI), Lifted Index (LI), Total Totals Index (TTI), Humidity Index (HI), Deep Convective Index (DCI) and thermodynamic parameters such as Convective Available Potential Energy (CAPE) and Convective Inhibition Energy (CINE). The traditional Showalter Index has been modified to incorporate the thermodynamics over tropical region. MODIS data over South Peninsular India are also used for the study. When there is a convective system over south peninsular India, the value of LI over the region is less than ?4. On the other hand, the region where LI is more than 2 is comparatively stable without any convection. Similarly, when KI values are in the range 35 to 40, there is a possibility for convection. The threshold value for TTI is found to be between 50 and 55. Further, we found that prior to convection, dry bulb temperature at 1000, 850, 700 and 500 hPa is minimum and the dew point temperature is a maximum, which leads to increase in relative humidity. The total column water vapor is maximum in the convective region and minimum in the stable region. The threshold values for the different stability indices are found to agree with that reported in literature.

An objective method for predicting occurrence of pre-monsoon (March-May) thunderstorm events over Delhi using stability indices

In this paper an attempt has been made to investigate different stability indices in relation to the occurrence of thunderstorms in order to determine the critical values of these indices for Delhi (28.35° N / 77.12° E) using pre monsoon data for the years 1999 - 2004. The study shows that the critical values of Showalter Index (SI), Lifted Index (LI), K Index (KI), Total Totals Index (TTI), and Sweat Index (SWI) are respectively < 2 °C, < 0 °C, > 24 °C, > 44.5 °C and > 100 for the thunderstorm to occur over Delhi. The corresponding common critical ranges of Lifted Condensation Level (LCL), Level of Free Convection (LFC), Equilibrium Level (EL) and Precipitable Water (PW) are respectively 923 hPa – 695 hPa, 856 hPa – 504 hPa, 545 hPa – 109 hPa and 18 mm – 54 mm. Testing of critical values of indices and the corresponding common critical ranges of LCL, LFC, EL and PW during pre-monsoon seasons of the years 2005 and 2006 shows that they are matching well with the respective critical values/ranges in most of the thunderstorm days.

Study of thermodynamic indices in forecasting pre-monsoon thunderstorms over Kolkata during STORM pilot phase 2006–2008

The pre-monsoon convective atmosphere over Kolkata (22.52°N, 88.37°E) during STORM field phase 2006–2008 is investigated using 12 UTC radiosonde data and thermodynamic indices. In the present study, an attempt has been made to assess the skill of various indices and parameters and to propose suitable threshold values in forecasting the occurrence of thunderstorm activity at Kolkata. The thermodynamic indices and parameters used in the present study are lifted index (LI), K index (KI), severe weather threat index (SWEAT), total totals index (TTI), convective available potential energy (CAPE), deep convection index (DCI), humidity index (HI), Boyden index (BI), dew point temperature at 850 hpa (DEW), relative humidity at 700 hpa (RH), and bulk Richardson number (BRN). Validation of the suggested threshold values of indices was conducted on the days of thunderstorm activity. It was found that one index alone cannot predict the occurrence of thunderstorm over Kolkata region. The present study suggests that the indices with highest skill for thunderstorm prediction are KI, DCI, SWEAT, DEW, HI, RH, LI, TTI, while the prediction efficiency is poor for CAPE, BRN, and BI. Observed values of these indices also reveal that scattered, multi-cellular thunderstorms are possible over Kolkata during pre-monsoon months.

Simultaneous non‐linear retrieval of atmospheric profiles and surface skin temperature from MODIS infrared radiances in Taiwan Strait

A non‐linear iterative physical algorithm that simultaneously retrieves atmospheric temperature, water vapour distribution and surface skin temperature from Moderate Resolution Imaging Spectroradiometer (MODIS) longwave infrared radiances is presented. The retrieval algorithm uses clear‐sky radiances measured by MODIS in Taiwan Strait for both day and night, and shows that it is capable of retrieving medium‐scale atmospheric temperature and water vapour. Sea surface temperature is retrieved with an accuracy similar to that achieved by MOD07 products. Evaluation of retrieval total precipitable water vapour (TPW) is performed by comparisons with retrievals from MOD07 products and data from a ground‐based sunphotometer. These show that MODIS retrieval of TPW, in general, agrees with other sounder retrievals of TPW. The total totals index (TTI) distribution retrieved from MODIS data is similar to that from MOD07 products.

Selected instability indices in Europe

A climatology of various parameters associated with severe weather and convective storms has been created for Europe that involves using radiosounding data collected at the University of Wyoming for the period from 1991 to 2005. The analysis is based on monthly means, frequency distributions of such parameters as convective available potential energy (CAPE), convective inhibition energy (CIN), KI - index, total totals index (TTI), and the severe weather threat index (SWEAT). Monthly average CAPE values exceeding 300 Jkg−1 are observed over the west Mediterranean Sea and the neighboring coastal countries. The similar seasonal cycle and spatial distributions exhibit CIN fields with summer monthly means above 100 Jkg−1 observed on the south part of the researched domain. The KI, TTI, and SWEAT indices, which assess both the lapse ratio between 850 and 500 hPa and low level humidity, show the privileged region (the Alpine area and the Carpathian Basin) with the highest instability conditions. Orography clearly plays an important role in this structure. Farther from this area, the monthly average decreases to the east, west, north, and south of the research domain. Ward’s procedure was applied to create objective regionalization according to instability conditions. This method tends to produce two regions with relatively different instability conditions and few subregions with similar conditions. The first region, covering the Alpine area, the west Mediterranean Sea, west Turkey and the southern Ukraine, is characterized by the highest instability. The rest of the investigated area is the second region with a more stable atmosphere.

Role of total-totals stability index in forecasting of thunderstorm/non-thunderstorm days over Kolkata during pre-monsoon season

The thunderstorm activity over Kolkata during pre-monsoon months (March, April and May) has been studied using the radiosonde data of Kolkata (Dumdum). The objective of the study is to examine the utility of Total-Totals Index (TTI) in forecasting occurrence/non-occurrence of thunderstorm over Kolkata. The investigation reveals that Total-Totals Index can be preliminarily used as a predictor to differentiate thunderstorm and non-thunderstorm days. The probability of occurrence of thunderstorm is higher when Total-Totals Index value is higher. While the exact prediction of thunderstorm in all the cases, using the TTI alone, is obviously not possible as TTI alone does not describe the total atmospheric conditions. However, a significant forecast can be furnished by using a threshold value of Total-Totals Index.

Forecasting thunderstorms around Delhi and Jodhpur during March and June

Total-Totals Index (TTI) has been used to explore the possibility of forecasting thunder storm activity around Delhi and Jodhpur during March and June. Higher values of TTI are associated with more favorable conditions of thunderstorm activity. Prediction of thunderstorm within a limited range of TTI IS uncertain when the chances of occurrence and non-occurrence of thunderstorm are equal.