Study of Severe Thunderstorms over Bangladesh and Its Surrounding Areas During Pre-monsoon Season of 2013 Using WRF-ARW Model

2014 ◽  
pp. 3-22
Author(s):  
Abdul Mannan ◽  
Nazmul Ahasan ◽  
Shah Alam
Keyword(s):  
Monsoon Season ◽  
Severe Thunderstorms ◽  
Arw Model ◽  
Surrounding Areas

PREDICTABILITY OF CHAOS INHERENT IN THE OCCURRENCE OF SEVERE THUNDERSTORMS

2006 ◽  
Vol 09 (01n02) ◽  
pp. 77-85 ◽  
Author(s):  
SUTAPA CHAUDHURI
Keyword(s):  
Time Series ◽  
High Frequency ◽  
Prediction Models ◽  
Monsoon Season ◽  
Weather Prediction ◽  
Deterministic Chaos ◽  
Convective System ◽  
Severe Thunderstorms ◽  
Numerical Weather Prediction Models ◽  
Meso Scale

The purpose of the present study is to investigate the existence of deterministic chaos in the time series of occurrence or non-occurrence of severe thunderstorms of the pre-monsoon season over the Northeastern part of India. Results from the current study reveal the existence of chaos in the relevant time series. The corresponding predictabilities are also computed quantitatively. The study recommends that the formulation of numerical weather prediction models for forecasting the occurrence of this high frequency meso-scale convective system must take into account the intrinsic chaos.

scholarly journals Thumb Rule for Nowcast of Dust Storm and Strong Squally Winds over Delhi NCR using DWR Data

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Kuldeep Srivastava
Keyword(s):  
Monsoon Season ◽  
Human Life ◽  
Weather Radar ◽  
Doppler Weather Radar ◽  
National Capital Region ◽  
North West ◽  
Maximum Reflectivity ◽  
Vertical Extension ◽  
Severe Thunderstorms ◽  
Dwr Data

ABSTRACTSqually winds are the natural hazards and are often associated with the severe thunderstorms (TS), which mostly affects plains of North West India during pre monsoon season (March to May). Squally winds of the order more than 60 kmph are very devastating. Under influence of these strong squally winds trees, electricity poles, advertisement sign boards fall, sometimes human life is also lost. The main objective of this study is to find out the thumb rule based on Doppler Weather Radar (DWR) Data to Nowcast the squally winds over a region. To detect thumb rule, five cases of thunder storm accompanied with squally winds ranging from (55 kmph to 110 kmph) are taken in to consideration. These TS’s occurred over Delhi NCR (National Capital Region) during May – June 2018. Maximum reflectivity (Max Z) data of Delhi DWR, Cloud Top Temperature (CTT) data from INSAT and squally winds along with other weather parameters observed at Safdarjung and Palam observatories are utilized to find out the Thumb Rule.Based on the analysis, it is concluded that presence of a western disturbance (WD), presence of East-West trough from North-west Rajasthan upto East UP through south Haryana and very high temperature of the order of 40 degree Celsius over the nearby area are very conducive for occurrence of squally winds accompanied with thunderstorms. Thumb rule find out in this study is that, squally winds of the order of 55 kmph or more will effect a station if a thunderstorm (having Max Z echo with vertical extension of cell >7 km, reflectivity >45 dBz and at a distance of more than 100 km from the station) moving towards station is present in one to two hour before images of Doppler Weather Radar.

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.

PREDICTION OF SEVERE THUNDERSTORMS WITH MINIMAL A PRIORI INFORMATION

2005 ◽  
Vol 08 (01) ◽  
pp. 75-86 ◽  
Author(s):  
SUTAPA CHAUDHURI ◽  
SURAJIT CHATTOPADHYAY
Keyword(s):  
Genetic Algorithm ◽  
Monsoon Season ◽  
A Priori ◽  
A Priori Information ◽  
Northeastern Part ◽  
Severe Thunderstorms ◽  
Suitable Combination ◽  
Quantitative Manner ◽  
Priori Information

A genetic algorithm (GA) is introduced to fix ranges of parameters, in a quantitative manner, pertaining to forecasting the genesis of severe thunderstorms in the pre-monsoon season over Calcutta (22°32′, 88°20′) in the northeastern part of India (20°–24°N latitude, 85°–93°E longitude). The results depict that definite quantitative ranges of parameters can be made available before as well as after the occurrence of severe thunderstorms using a GA. Thus, a suitable combination of these ranges of parameters before the onset can represent a possible predictor of thunderstorm genesis.

scholarly journals Simulation of severe storms of tornadic intensity over Indo-Bangla region

MAUSAM ◽  
2021 ◽  
Vol 67 (2) ◽  
pp. 479-492
Author(s):  
SOMESHWAR DAS ◽  
MD. NAZRUL ISLAM ◽  
MOHAN K. DAS
Keyword(s):  
Convective Motion ◽  
Dew Point ◽  
Wind Fields ◽  
Low Level ◽  
Westerly Jet ◽  
Severe Thunderstorms ◽  
Surface Data ◽  
Arw Model ◽  
Upper Level ◽  
Tornadic Storms

Many severe thunderstorms of tornadic intensity were reported in the northwestern parts of Bangladesh during 30 August to 14 September, 2008. Two among them occurred at Nilphamari and Kurigram districts on 30th August, and at Nilphamari district on 3rd September. The tornadic storms are studied based on a field survey, surface data, radar and satellite observations and model simulations. Low level moisture influx by southerly flow from the Bay of Bengal coupled with an upper level westerly jet stream causing intense instability and shear in the wind fields triggered a series of storms for two weeks. The exact time and locations of the storms are investigated by using the hourly precipitation data retrieved from a S-band radar of Bangladesh Meteorological Department (BMD) located at Dhaka. Subsequently, the storms are simulated by using the WRF-ARW model on double nested domains at 9 and 3 km horizontal resolutions based on 6 hourly FNL analyses and boundary conditions of NCEP.  Among the typical characteristics of the storms, the CAPE, Storm-Relative Environment Helicity (SREH), Bulk Richardson Number Shear (BRNSHR), dew point depression, and potential vorticity are studied. Results show that while there are differences of 2-3 hours between the observed and simulated time of the storms, the distances between observed and simulated locations of the storms are several tens of kilometers. The maximum CAPE is generally above 2400 J kg-1. The maximum amount of vorticity transferred by directional shear in the storm updraft (helicity) due to convective motion simulated by the model is 766 m2 sec-2, and the highest value of BRNSHR that define the region in which low-level mesocyclogenesis is more likely is 168 m2 sec-2 among the 2 cases, which is generally supposed to produce rotating storms according to the prescribed range.  

scholarly journals CAPE - A link amid thermodynamics and microphysics for the occurrence of severe thunderstorms

MAUSAM ◽  
2021 ◽  
Vol 57 (2) ◽  
pp. 249-254
Author(s):  
SUTAPA CHAUDHURI ◽  
SUCHANDRA AICH BHOWMICK
Keyword(s):  
Monsoon Season ◽  
Convective Available Potential Energy ◽  
Cloud Microphysics ◽  
Large Drop ◽  
Neutral Buoyancy ◽  
Severe Thunderstorm ◽  
Severe Thunderstorms ◽  
Cloud Microphysical Processes ◽  
Microphysical Processes ◽  
Drop Instability

Lkkj & bl 'kks/k&i= dk mÌs’; dksydkrk ¼22°32¢] 88°20¢½ esa ekulwu iwoZ _rq ¼vizSy&ebZ½ ds nkSjku xtZ ds lkFk vkus okys Hkh"k.k rwQkuksa dh mRifÙk vkSj fodkl esa lgk;d es?k dh lw{e HkkSfrdh; izfØ;kvksa dh tk¡p djuk gSA bl v/;;u ls ;g irk pyk gS fd dksydkrk esa ekulwu&iwoZ _rq ds nkSjku xtZ ds lkFk vkus okys Hkh"k.k rwQkuksa ds nkSjku rkixfrdh;] xfrdh;] es?k dh lw{e HkkSfrdh vkSj fctyh pdeus dks J`a[kykc) djus esa laoguh; miyC/k foHko ÅtkZ ¼lh- ,- ih- bZ-½ lgk;d gSA bl v/;;u ls izkIr gq, ifj.kkeksa ls ;g irk pyk gS fd dksydkrk esa laoguh; miyC/k foHko ÅtkZ 1000 twYl izfr fd- xzk- ds Hkhrj izcy ikbZ xbZ tks eqDr laogu Lrj ¼,y- ,Q- lh-½ ls Åij fu/kkZfjr nkc Lrjksa ds Hkhrj ikbZ xbZ vkSj ok;q dh viMªk¶V xfr ds ln`’k eku fu"izHkkoh mRIykodrk Lrj ¼,y- ,u- ch-½ esa yxHkx 30 - 50 eh-@ lsdsaM ik, x,A bl v/;;u ls ;g Hkh irk pyk gS fd 5 fe- eh- rd ds O;kl ds vkdkj dh c¡wns fLFkj jg ldrh gS ftlds ckn vkdkj c<+us ds dkj.k cw¡nsa VwV tkrh gSaA tc cw¡n dh f=T;k 2-5 fe- eh- ls 3 fe- eh- dh ifjf/k esa gksrh gS rc cw¡nksa dk VwVuk  'kq: gks tkrk gS vkSj 3 fe- eh- ls 5 fe- eh- dh ifjf/k esa cw¡nksa ds VwVus dh laHkkouk vf/kd gksrh gS D;ksfd bl fLFkfr esa cw¡nksa ds yxkrkj VwVus dh dkj.k mudk thoudky cgqr NksVk gks tkrk gSA  The aim of the present paper is to view the cloud microphysical processes entailed in the genesis and the development of the severe thunderstorms of pre-monsoon season (April - May) over Kolkata (22°32', 88°20'). The study shows that Convective Available Potential Energy (CAPE) is instrumental in establishing a linkage among thermodynamics, dynamics, cloud microphysics, and lightning during severe thunderstorm of pre monsoon season over Kolkata. The results of the present study reveal that for the thunderstorms reported over Kolkata, CAPE are found to be predominantly within 1000 joules per kgs within the prescribed pressure levels above the Level of Free Convection (LFC) and the corresponding values of the updraft speeds of the air are found to be nearly 30 - 50 m/s at the Level of Neutral Buoyancy (LNB). The study also depicts that the drops may grow up to the size of 5mm in diameter stably, beyond which, they tend to breakup due to the large drop instability. The breakup or splitting is observed to initiate when the drop radius is within the range of 2.5mm to 3mm and the breakup is most likely within the range of 3mm to 5mm because at this stage the lifetime of the drops are short due to the spontaneous breakup.  

scholarly journals On the tropospheric zonal and meridional fluxes of moisture in relation to nor’westers in Bangladesh during the pre-monsoon season

MAUSAM ◽  
2021 ◽  
Vol 58 (1) ◽  
pp. 67-74
Author(s):  
SAMARENDRA KARMAKAR ◽  
MD. MAHBUB ALAM
Keyword(s):  
Spatial Distribution ◽  
Monsoon Season ◽  
Lower Troposphere ◽  
Maximum Frequency ◽  
Upper Troposphere ◽  
Middle Troposphere ◽  
Surrounding Areas

Attempts have been made to study the zonal and meridional fluxes of moisture of the troposphere prior to the occurrence of nor’westers in Bangladesh during the pre-monsoon season. The study reveals that the westerly fluxes (positive) of moisture (WFM) dominate in the troposphere over Dhaka at 0000 UTC from 925 to 200 hPa level having maximum frequency of WFM from 61.68 to 96.26% in the layer from 925 to about 300 hPa level. The maximum WFM over Dhaka at 0000 UTC on the dates of occurrence of nor’westers may be more than 200 gm kg-1 × ms-1 in the lower troposphere and the maximum easterly (negative) fluxes of moisture (EFM) over Dhaka at 0000 UTC may be -128.3 gm kg-1 × ms-1 at 1000 hPa. In the upper troposphere the zonal fluxes of moisture (ZFM) become nil in most of the cases. The ZFM over Dhaka at 0000 UTC are mainly westerly and more westerly in the lower and middle troposphere on the dates of occurrence of nor’westers as compared to the fluxes on the dates of non-occurrence. The southerly fluxes (positive) of moisture (SFM) dominate in the troposphere over Dhaka at 0000 UTC from 1000 to 300 hPa level. The meridional fluxes of moisture (MFM) are mainly southerly and more southerly in the lower and middle troposphere on the dates of occurrence of nor’westers as compared to the dates of non-occurrence. In the upper troposphere the MFM become nil in most of the cases.The vertically integrated ZFM and MFM from 1000 to 100 hPa over Dhaka at 0000 UTC on the dates of occurrence of nor’westers in Bangladesh have been computed, compared and inference has been drawn. The present study also deals with the spatial distribution of the vertically integrated ZFM and MFM from 925 to 400 hPa level over Bangladesh and its surrounding areas. The range of the vertically integrated ZFM and MFM for the layer is about (2-12) × 105 and (3-14) × 105 kg × ms-1 respectively over Bangladesh in most of the cases.

scholarly journals A forecasting aspect of thundersquall over Calcutta and its parameterisation during pre-monsoon season

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 271-280
Author(s):  
G. C. BASU ◽  
D. K. MONDAL
Keyword(s):  
Potential Energy ◽  
Monsoon Season ◽  
Convective Available Potential Energy ◽  
Propagation Speed ◽  
Eastern Region ◽  
Radar Observations ◽  
Severe Thunderstorms ◽  
North Eastern ◽  
Radar Echo ◽  
Made In

Severe thunderstorms accompanied by squalls are the most hazardous weather phenomena during pre-monsoon season in north-eastern region of India. An attempt has been made in this paper to study some parameters for forecasting thundersqualls over Calcutta (Airport) during pre-monsoon season. Parameterisation of thermodynamic components alongwith the synoptic support during thundersqualls over Calcutta has been discussed here. A forecasting aspect for propagation speed of thunderstorm cell at Calcutta in pre-monsoon season has been examined with respect to radar-echo positions, mid-level winds and convective available potential energy (CAPE). Occurrences of multiple thundersqualls over Calcutta Airport within a few hours’ interval have been discussed and examined through hodograph analysis, radar observations and synoptic situations.

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