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

MAUSAM ◽  
2021 ◽  
Vol 62 (3) ◽  
pp. 329-338
Author(s):  
M. DURAISAMY ◽  
S.K.ROY BHOWMIK ◽  
B.K. BANDYOPADHYAY
Keyword(s):  
Free Convection ◽  
Precipitable Water ◽  
Critical Values ◽  
Objective Method ◽  
K Index ◽  
Equilibrium Level ◽  
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.

scholarly journals A synoptic and thermodynamic analysis for forecasting of squalls at Agartala

MAUSAM ◽  
2021 ◽  
Vol 72 (4) ◽  
pp. 791-802
Author(s):  
RANJAN PHUKAN ◽  
RAKESH KUMAR ◽  
M. CHANDA ◽  
RANA DAS ◽  
D. SAHA
Keyword(s):  
Thermodynamic Analysis ◽  
Wind Direction ◽  
Monsoon Season ◽  
Critical Values ◽  
Wind Pattern ◽  
K Index ◽  
Synoptic Conditions ◽  
Stability Indices

Thunderstorms accompanied with squalls cause a serious damage in Agartala and its neighbouring areas in the pre-monsoon season. In this paper, the synoptic conditions, stability indices and lower level wind pattern associated with squalls at Agartala (23.90° N, 93.25° E) during 2011 - 2020 are analysed to obtain their percentage contributions and critical values in occurrence of the events. Five major synoptic conditions are found to have contribution to the events, with varying percentages. The critical values of Showalter Index, Lifted Index, K-Index, SWEAT Index, Total Totals Index are obtained based on their contribution for at least 80% of the events. Wind direction at 925 hPa and 850 hPa with southerly component is found to be another important precursor for occurrence of the squalls.

scholarly journals THE WAY TO DETERMINE THE APPROXIMATELY HAIL'S DIMENSIONS

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Nicolae Ilie ◽  
Liviu Apostol ◽  
Aurel Danut Axinte
Keyword(s):  
Free Convection ◽  
Vertical Profile ◽  
Good Knowledge ◽  
Cloud System ◽  
Maximum Speed ◽  
Air Mass ◽  
Convective Clouds ◽  
K Index ◽  
Equilibrium Level ◽  
The Way

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.

scholarly journals Modified instability index of the troposphere associated with thunderstorms / nor'westers over Bangladesh during the pre-monsoon season

MAUSAM ◽  
2021 ◽  
Vol 62 (2) ◽  
pp. 205-214
Author(s):  
SAMARENDRA KARMAKAR ◽  
MD. MAHBUB ALAM
Keyword(s):  
West Bengal ◽  
Monsoon Season ◽  
Critical Values ◽  
Spatial Distributions ◽  
Instability Index ◽  
K Index ◽  
Severe Thunderstorms ◽  
Total Index ◽  
Stability Indices ◽  
Instability Indices

The present study is an attempt to study different Modified Stability Indices in relation to the occurrence of severe thunderstorms/nor’westers in order to find out the critical values of different modified indices favorable for the formation of thunderstorms in Bangladesh. Computations have also been made for the stations in and around Bangladesh for studying the spatial distribution of the modified stability indices. The Modified Instability Indices such as Modified Cross Total Index (MCT), Modified Vertical Total Index (MVT), Modified Total Totals Index (MTT), Modified SWEAT Index (MSWI), Modified K-Index (MKI) and Modified Energy Index (MEI) show greater instability of the troposphere in the morning as compared to CT, VT, TT, SWI, KI and EI. The critical values of different modified instability indices at 0000 UTC over Dhaka are: MCT >= 20° C, MVT >= 26° C, MTT >= 46° C, MSWI > 300, MKI >= 40° C and MEI < -6 joules/gm respectively for the nor’westers to occur in Bangladesh. The spatial distributions of modified stability indices have revealed that maximum instability lies over the area of surface low pressure especially over Bihar, West Bengal and adjoining Bangladesh at 0000 UTC on the dates of occurrence of nor’westers. Nor’westers occur at theeastern end of the maximum instability. For severe nor’westers of tornadic intensity, the critical values of different modified instability indices at 0000 UTC over Dhaka are: MCT >= 20° C, MVT >= 28° C, MTT >= 50° C, MSWI >= 500, MKI >= 42° C and MEI < -8 joules/gm respectively for the nor’westers to occur in Bangladesh.

scholarly journals MENGINTIP KONDISI CUACA PENYEBAB BANJIR BESAR DI DKI JAKARTA TANGGAL 25 OKTOBER 2010

2011 ◽  
Vol 12 (2) ◽  
pp. 43
Author(s):  
Mimin Karmini ◽  
Findy Renggono
Keyword(s):  
Rainfall Intensity ◽  
Heavy Rain ◽  
Rainfall Amount ◽  
Western Region ◽  
Convective Activity ◽  
Stagnant Water ◽  
Standing Water ◽  
K Index ◽  
Convective Process ◽  
Stability Indices

DKI Jakarta dikejutkan dengan hujan deras pada jam 16:00 WIB. Genangan airlangsung terjadi akibat derasnya hujan. Hujan berlangsung sampai sekitar jam 20:00WIB. Dari data AWS di Jatiwaringin, curah hujan tertinggi sebesar 230 mm tercatatpada jam 16:00 WIB. Curah hujan sampai jam 19:00 WIB tercatat sebesar 650.60 mmatau intensitas 216.87 mm/jam untuk periode jam 16:00 s.d. 19:00 WIB. Beberapaindeks stabilitas, yang dihitung dari data rawinsonde jam 07:00 WIB, menunjukanpotensi terjadinya aktivitas konvektif yang bisa menghasilkan hujan deras. Beberapaindeks stabilitas yang menunjukan potensi terjadinya proses konvektif kuat adalah: LI(Lifted Index) = - 06; SI (Showalter Index) = - 0.7; K Index = 36.7; TT (Total Totals) =43.9. Kejadian hujan paling deras di kawasan barat DKI Jakarta sampai Tangerang.Genangan air hampir merata di DKI Jakarta dan Tangerang dengan ketinggian yangbervariasi antara 20 cm – 100 cm.Jakarta was struck by torrential rain at 16:00 pm. Standing water caused by heavy rainoccured immediately. The rain lasted until around 20:00 pm. From the AWS measurement at Jatiwaringin, highest rainfall of 230 mm was recorded at 16:00 pm. Rainfall amount until 19:00 pm was recorded of about 650.60 mm, in other words rainfall intensity was about 216.87 mm/hour for the period of 16:00 – 19:00 pm. Some stability indices, which is calculated from rawinsonde at 07:00 am showed the potential for convective activity which could produce heavy rain. Some stability indices that show strong potential for convective process are: LI (Lifted Index) = - 06; SI (Showalter Index) = - 0.7; K Index = 36.7; TT (Total Totals) = 43.9. The heaviest rainfall occured in the western region of Jakarta until Tangerang. Stagnant water is almost evenly in Jakarta and Tangerang with varying heights between 20 cm - 100 cm.

scholarly journals A comparison of stability indices and precipitable water derived from radiosonde data collected at two nearby locations and weather radar data in Brazil

2020 ◽  
Vol 13 (3) ◽  
pp. 1280
Author(s):  
Mauro Angelo Alves ◽  
Inácio Malmonge Martin ◽  
Fernanda Lyra Alves ◽  
Ivan Dos Santos Muniz ◽  
Cássia Solange Lyra
Keyword(s):  
Weather Radar ◽  
Precipitable Water ◽  
Radar Data ◽  
Radiosonde Data ◽  
Stability Indices

A Graphical Technique of Forecasting Overcast Skies and Precipitation with Central Weather Facility Products

1961 ◽  
Vol 42 (2) ◽  
pp. 110-117 ◽  
Author(s):  
James P. Jenrette
Keyword(s):  
Vertical Motion ◽  
Precipitable Water ◽  
Critical Values ◽  
Motion Field ◽  
Water Field ◽  
Graphical Technique ◽  
Thickness Field

Practical procedures for forecasting areas of overcast skies and precipitation are presented. The forecast thickness field is relabeled as a forecast maximum precipitable water field. A forecast actual precepitable water field is then graphically subtracted from this field to derive a forecast saturation chart. The forecast saturation chart is then adjusted with the forecast vertical-motion field. Isopleths of critical values on the adjusted saturation chart outline forecast areas of overcast skies and areas of probable precipitation.

Sensitivities of Simulated Convective Storms to Environmental CAPE

2011 ◽  
Vol 139 (11) ◽  
pp. 3514-3532 ◽  
Author(s):  
Cody Kirkpatrick ◽  
Eugene W. McCaul ◽  
Charles Cohen
Keyword(s):  
Free Convection ◽  
Three Dimensional ◽  
Environmental Parameters ◽  
Precipitable Water ◽  
Relative Strength ◽  
Convective Storms ◽  
Low Level ◽  
Reduced Height ◽  
Character Feature ◽  
Lapse Rates

Abstract A set of 225 idealized three-dimensional cloud-resolving simulations is used to explore convective storm behavior in environments with various values of CAPE (450, 800, 2000, and 3200 J kg−1). The simulations show that when CAPE = 2000 J kg−1 or greater, numerous combinations of other environmental parameters can support updrafts of at least 10 m s−1 throughout an entire 2-h simulation. At CAPE = 450 J kg−1, it is very difficult to obtain strong storms, although one case featuring a supercell is found. For CAPE = 800 J kg−1, mature storm updraft speeds correlate positively with strong low-level lapse rates and reduced precipitable water. In some cases, updrafts at this CAPE value can reach speeds that rival predictions of parcel theory, but such efficient conversion of CAPE to kinetic energy does not extend to all storms at CAPE = 800 J kg−1, nor to any storms in simulations at lower or higher CAPE. In simulations with CAPE = 2000 or 3200 J kg−1, the strongest time-averaged mature updrafts, while supercellular in character, feature generally less than 60% of the speeds expected from parcel theory, and even the strongest updraft found at CAPE = 450 J kg−1 fails to reach that relative strength. When CAPE = 2000 J kg−1 or more, updrafts benefit from enhanced shear, higher levels of free convection, and reduced precipitable water. Strong low-level shear and a reduced height of the level of free convection correlate closely with low-level storm vertical vorticity when CAPE is at least 2000 J kg−1, consistent with previous findings. However, at CAPE = 800 J kg−1, low-level vorticity shares the same correlations with the environment as updraft strength. With respect to storm precipitation, in simulations initiated with only 30 mm of precipitable water (PW), all of the storms that last for an entire 2-h simulation tend to produce liquid precipitation at roughly similar rates, regardless of their CAPE. In environments where PW is increased to 60 mm, storms tend to produce the most rainfall at CAPE = 2000 J kg−1, with somewhat lesser rainfall rates at lower and higher CAPE. Nevertheless, over the simulation domain, the ground area that receives at least 10 mm of rainfall tends to increase as CAPE increases, owing to a greater number and size of precipitating updrafts in the domain.

scholarly journals A statistical analysis of sounding derived indices and parameters for extreme and non-extreme thunderstorm events over Cyprus

2010 ◽  
Vol 23 ◽  
pp. 79-85 ◽  
Author(s):  
K. Savvidou ◽  
A. Orphanou ◽  
D. Charalambous ◽  
P. Lingis ◽  
S. Michaelides
Keyword(s):  
Statistical Analysis ◽  
Potential Energy ◽  
Convective Available Potential Energy ◽  
Radiosonde Data ◽  
Available Potential Energy ◽  
K Index ◽  
Upper Limits ◽  
The Stability ◽  
Simple Statistical Analysis ◽  
Stability Indices

Abstract. The main purpose of this study is to provide a simple statistical analysis of several stability indices and parameters for extreme and non-extreme thunderstorm events during the period 1997 to 2001 in Cyprus. For this study, radiosonde data from Athalassa station (35°1´ N, 33°4´ E) were analyzed during the aforementioned period. The stability indices and parameters set under study are the K index, the Total Totals (TT) index, the Convective Available Potential Energy related parameters such as Convective Available Potential Energy (CAPE), Downdraft CAPE (DCAPE) and the Convective Inhibition (CIN), the Vorticity Generator Parameter (VGP), the Bulk Richardson Number (BRN), the BRN Shear and the Storm Relative Helicity (SRH). An event is categorized as extreme, if primarily, CAPE was non zero and secondary, if values of both the K and the TotalTotals (TT) indices exceeded 26.9 and 50, respectively. The cases with positive CAPE but lower values of the other indices, were identified as non-extreme. By calculating the median, the lower and upper limits, as well as the lower and upper quartiles of the values of these indices, the main characteristics of their distribution were determined.

scholarly journals Global Positioning System (GPS) Precipitable Water in Forecasting Lightning at Spaceport Canaveral

2008 ◽  
Vol 23 (2) ◽  
pp. 219-232 ◽  
Author(s):  
Kristen Kehrer ◽  
Brian Graf ◽  
William P. Roeder
Keyword(s):  
Logistic Regression ◽  
Global Positioning System ◽  
Binary Logistic Regression ◽  
Precipitable Water ◽  
Forecast Model ◽  
Predictor Variables ◽  
Positioning System ◽  
K Index ◽  
Global Positioning ◽  
New Models

Abstract This paper evaluates the use of precipitable water (PW) from the global positioning system (GPS) in lightning prediction. Additional independent verification of an earlier model is performed. This earlier model used binary logistic regression with the following four predictor variables optimally selected from a candidate list of 23 candidate predictors: the current precipitable water value for a given time of the day, the change in GPS PW over the past 9 h, the K index, and the electric field mill value. The K index was used as a measure of atmospheric stability, which, of the traditional stability measures, has been shown to work best in the area and season under study. This earlier model was not optimized for any specific forecast interval, but showed promise for 6- and 1.5-h forecasts. Two new models were developed and verified. These new models were optimized for two operationally significant forecast intervals. The first model was optimized for the 0.5-h lightning advisories issued by the U.S. Air Force’s 45th Weather Squadron. An additional 1.5 h was allowed for sensor dwell, communication, calculation, analysis, and advisory decision by the forecaster. Therefore, the 0.5-h advisory model became a 2-h forecast model for lightning within the 45th Weather Squadron advisory areas. The second model was optimized for major ground processing operations supported by the 45th Weather Squadron, which can require lightning forecasts with a lead time of up to 7.5 h. Using the same 1.5-h lag as in the other new model, this became a 9-h forecast model for lightning within 37 km (20 n mi) of the 45th Weather Squadron advisory areas. The two new models were built using binary logistic regression and a list of 26 candidate predictor variables: the current GPS PW value, the K index, and 24 candidate variables of the change in GPS PW levels over 0.5-h increments up to 12 h. The new 2-h model found the following four predictors to be statistically significant, listed in decreasing order of contribution to the forecast: the 0.5-h change in GPS PW, the 7.5-h change in GPS PW, the current GPS PW value, and the K index. The new 9-h forecast model found the following five independent variables to be statistically significant, listed in decreasing order of contribution to the forecast: the current GPS PW value, the 8.5-h change in GPS PW, the 3.5-h change in GPS PW, the 12-h change in GPS PW, and the K index. In both models, the GPS PW parameters had better correlation to the lightning forecast than did the K index, a widely used thunderstorm index. Possible future improvements to this study are discussed.

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