Characteristics of severe thunderstorms over Bangladesh and neighborhood: Observations & WRF- ARW...

Characteristics of severe thunderstorms over Bangladesh and

neighborhood: Observations & WRF-

ARW model simulations

Senaka Basnayake

Asian Disaster Preparedness CentreThailand

WRF Lecture Series, 20 – 24 September 2010 @ BCCR - Norway

“Safer communities and sustainable development through disaster risk reduction”

History of ADPC• Established in 1986, at the initiative of WMO,

UNDP and UNOCHA

• Served as the Outreach Center of Asian Institute

of Technology, 1986-1999

• Independent international foundation, July 1999

• Inter-governmental charter signed, February 2005

• Over 100 staffs, 19 nationalities

ADPC Organization ChartBoard of Trustees

23 Members 16 Countries

International Advisory

Council (IAC) 95 members

Executive Committee

Regional Consultative

Committee (RCC)32 Members

26 Countries

Urban Disaster Risk Management

(UDRM)

Public Health in Emergencies (PHE)

Disaster Management

Systems (DMS)

Office of the Executive Director (OED)

Climate Risk Management

(CRM)

Training Resource Group (TRG)

Severe thunderstorms

or Nor’westers

Favorable Synoptic conditions for Nor’westers• Presence of an active elongated trough of low over the Gangetic plains of north

India across north Bangladesh on the mean seal level pressure chart

• Presence of southerly low level jet with a pole ward meridional component in the lower tropospheric wind flow

• High magnitude of moisture in the humidity field intruding from the Bay of Bengal into Bangladesh and thereafter north India

• Presence of sub-tropical jet stream with strong vertical wind shear in the low to middle troposphere levels over Bangladesh and neighborhood

• Intrusion of high convective available potential energy (CAPE) from the Bay of Bengal into Bangladesh and presence of a low convective inhibition energy (CINE) regime.

• A pocket of strong warm temperature advection at 850 hpa and cold temperature advection at 300 hpa

S. No Date No of events /day Reported Station Reported Wind Speedkm/h

Wind Direction

(’ly)

Reported Time (UTC)

1 21.03.2009 1a Rajshahi 56 NW 1305-1308

1b Rangpur 41 NE 1535-1537

2

26.03.2009

1a 44 SW 09491b 52 W 09521c 44 W 09552 Rangpur 63 N 2259-2302

3 29.03.20091 65 - 11302a 46 NW 17562b M.M.O Dhaka 65 S 1800

4 30.03.2009 1 43 SW 1313

5

31.03.2009

1a 52 NW 1445-1447

1b 57 NW 14501c 74 NW 15081d 56 NW 1510-1513

1e 44 NW 15242a 56 NW 1730-1800

2b Cox’sbazar 46 N 1755-1757

6 02.04.2009 1 48 N 15457 06.04.2009 1 51 W 09158 08.04.2009 1 Sylhet 58 NW 2037-2040

9 09.04.2009 1 70 W 0858

10 17.04.20091a 51 E 1025 1b Hatiya 51 SE 1402 2 Rangpur 83 NW 1405-1408

3a Kutubdia 93 S 1414 3b Cox’sbazar 83 SWS 1436 4 81

N

1524

11 19.04.2009 1 Sylhet 70 W 1924 12 29.04.2009 1 Rangpur 67 E 1855-1856

13 01.05.2009 1 Sylhet 67 NW 1031-1033

2 46 NW 1725

2009 pre-monsoon

2009 pre-monsoon season

(29) NW

SE (2)

8) W

S (3)

NE (9

N (10)

E (3)

(4) SW

41 – 60 km/h ~ 41, 61 – 90 km/h ~ 27, 91 – 120 km/h ~ 2

2009 pre-monsoon season

CAPE

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1May

_00

2May

_00

3May

_00

5May

_00

6May

_00

9May

_00

10M

ay_0

0

11M

ay_0

0

13M

ay_0

0

15M

ay_0

0

16M

ay_0

0

18M

ay_0

0

24M

ay_0

0

25M

ay_0

0

26M

ay_0

0

29M

ay_0

0

31M

ay_0

0

Date/Time

CA

PE

(J/k

g)

Dhaka Guwahati Patna Agartala kolkata Ranchi

(b)

-3000

-2500

-2000

-1500

-1000

-500

0

500

1May

_00

2May

_00

3May

_00

5May

_00

6May

_00

9May

_00

10M

ay_0

0

11M

ay_0

0

13M

ay_0

0

15M

ay_0

0

16M

ay_0

0

18M

ay_0

0

24M

ay_0

0

25M

ay_0

0

26M

ay_0

0

29M

ay_0

0

Date/Time

CIN

E(J

/kg

)


(c)

CINE

LI

-20

-15

-10

-5

0

5

10

1May

_00

2May

_00

3May

_00

5May

_00

6May

_00

9May

_00

10M

ay_0

0

11M

ay_0

0

13M

ay_0

0

15M

ay_0

0

16M

ay_0

0

18M

ay_0

0

24M

ay_0

0

25M

ay_0

0

26M

ay_0

0

29M

ay_0

0

31M

ay_0

0

Date/Time

Lif

ted

Ind

ex


(c)

-25

-20

-15

-10

-5

0

5

10

15

1May

_00

2May

_00

3May

_00

5May

_00

6May

_00

9May

_00

10M

ay_0

11M

ay_0

13M

ay_0

15M

ay_0

16M

ay_0

18M

ay_0

24M

ay_0

25M

ay_0

26M

ay_0

29M

ay_0

31M

ay_0

Date/Time

Sh

ow

alte

r In

dex


(c)

SI

Threshold Value >1500

0 > (NEGATIVE)Week instability CAPE < 1000 J/kgModerate instability 1000 J/kg < CAPE < 2500 J/kgStrong instability CAPE > 2500 J/kg

Week instability CAPE < 1000 J/kgModerate instability 1000 J/kg < CAPE < 2500 J/kgStrong instability CAPE > 2500 J/kg

Very Stable atmospheric condition LI ≥ 6.0Stable condition - unlikely to form thunderstorms 1.0 < LI < 6.0Slightly Unstable - possible thunderstorms with mechanical lifting -2.0 < LI < 0.0Unstable - likely to form thunderstorms with strong mechanical lifting -6.0< LI < -2.0Very Unstable - likely to form severe thunderstorms with strong mechanical lifting LI < -6.0

Very Stable atmospheric condition LI ≥ 6.0Stable condition - unlikely to form thunderstorms 1.0 < LI < 6.0Slightly Unstable - possible thunderstorms with mechanical lifting -2.0 < LI < 0.0Unstable - likely to form thunderstorms with strong mechanical lifting -6.0< LI < -2.0Very Unstable - likely to form severe thunderstorms with strong mechanical lifting LI < -6.0

Possible showers or thunderstorms SI ≤ +3.0Possible severe convective activity SI ≤ -3.0Possible showers or thunderstorms SI ≤ +3.0Possible severe convective activity SI ≤ -3.0

0

10

20

30

40

50

60

70

80

90

100

1May

_00

2May

_00

3May

_00

5May

_00

6May

_00

9May

_00

10M

ay_0

0

11M

ay_0

0

13M

ay_0

0

15M

ay_0

0

16M

ay_0

0

18M

ay_0

0

24M

ay_0

0

25M

ay_0

0

26M

ay_0

0

29M

ay_0

0

31M

ay_0

0

Date/Time

To

tal T

ota

ls In

dex


(c)

TTI

0

200

400

600

800

1000

1200

1400

1May

_00

2May

_00

3May

_00

5May

_00

6May

_00

9May

_00

10M

ay_0

0

11M

ay_0

0

13M

ay_0

0

15M

ay_0

0

16M

ay_0

0

18M

ay_0

0

24M

ay_0

0

25M

ay_0

0

26M

ay_0

0

29M

ay_0

0

31M

ay_0

0

Date/Time

SW

EA

T In

dex

Dhaka Guwahati Patna Agartala Koltata Ranchi

(c)

SWEAT

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1May

_00

2May

_00

3May

_00

5May

_00

6May

_00

9May

_00

10M

ay_0

0

11M

ay_0

0

13M

ay_0

0

15M

ay_0

0

16M

ay_0

0

18M

ay_0

0

24M

ay_0

0

25M

ay_0

0

26M

ay_0

0

29M

ay_0

0

31M

ay_0

0

Date/Time

Bu

lk R

ich

ard

son

Nu

mb

er


(c)

BRN

Indicator of occurrence of thunderstorm TTI ≥ 40

Indicator of occurrence of thunderstorm with tornado intensity TTI ≥ 47

Indicator of occurrence of thunderstorm TTI ≥ 40

Indicator of occurrence of thunderstorm with tornado intensity TTI ≥ 47

Indicator for potential strong convectionSWEAT = +250

Indicator for potential severe thunderstormsSWEAT = +300

ndicator for potential tornados SWEAT = +400

Indicator for potential strong convectionSWEAT = +250

Indicator for potential severe thunderstormsSWEAT = +300

ndicator for potential tornados SWEAT = +400

Thunderstorms unlikely due to too much wind shear BRN < 10

Possibility of Supercells 10 < BRN < 45

Storms with multicells than supercellsBRN > 45

Thunderstorms unlikely due to too much wind shear BRN < 10

Possibility of Supercells 10 < BRN < 45

Storms with multicells than supercellsBRN > 45

Weather Research and Forecasting (WRF)• Developed by the Mesoscale and Microscale Meteorology Division of National Centre for Atmospheric Research (NCAR) of USA

• National Centre for Environment Prediction (NCEP) real time analysis (FNL) data as initial and lateral boundary conditions (LBCs) at six hourly intervals

Domain parameters & Model physics;

• Horizontal Resolution : 9 km• No. of grid point along X : 153• No. of grid point along Y : 139• No. of Vertical sigma levels : 27• Iterative Time step : 50 seconds • Integration scheme : 3rd order Runga-Kutta• mp_physics : WSM 3• Cumulus parameterization : Kain-Fritch scheme • Sf_sfclay_physics : Monin-Obukhov with

Carslon-Bolan viscous sub-layer option• Sf_surface_physics : Noah LSM• ra_lw_physics : RRTM• ra_sw_physics : Dudhia • Boundary layer parameterization : Yonsei University scheme

Date Model Simulated Time (UTC)

Observed Place Observed Wind Speed (km/h)

Observed Time (UTC)

Squall speed Nor’westers (41-60 km/h)

31 /03/2009 1900 Chittagong 56 1730

02/05/2009 0900 Dhaka 57 0505

2300 Cox's Bazar/Ctg 48 2251

05/05/2009 1400 Rangpur 59 1520

11/05/2009 1000 Dhaka 43 0945

18/05/2009 0500 Dhaka 44 0505

29/05/2009 0700 Dhaka 48 0737

31/05/2009 0900 Saidpur 52 0630

Light Nor'wester (61-90 km/h)

29/03/2009 1200 Dhaka 65 1130

1800 Dhaka 65 1800

01/05/2009 1100 Sylhet 67 1031

03/05/2009 0900 Dhaka 74 0836

13/05/2009 2000 Chittagong 63 2000

16/05/2009 0900 Chittagong 63 0922

Moderate Nor'wester (91-120 km/h)

17/04/2009 1600 Kutubdia 93 1414

11/05/2009 0900 Barrackpore, India 93 1240

S. No.

Parameter Squall speed Light Moderate

Obs. Model Obs. Model Obs. Model

1 Cloud Top Altitude (hPa) 150 110 102 115 120 100

2 Precipitation rate at surface (mm/h) 36 24 32 24 31 32

3 Direction of movement NWly NWly NNWly Wly WNWly NWly

4 Speed of movement (km/h) 53 51 52 46 59 75

5 Maximum wind speed at surface (m/s) 14 9 18 10 26 11

6 Length of squall line (km) 215 239 300 290 340 320

7 Altitude of Core pptn (hPa) N/A 830 N/A 800 N/A 750

8 Intensity of Core pptn (mg/kg) N/A 195 N/A 740 N/A 26

9 Updrafts speed (maximum) (cm/s) N/A 120 N/A 100 N/A 160

10 Downdrafts Speed (maximum) (cm/s) N/A 60 N/A 120 N/A 60

11 Liquid water Content (mg/kg) N/A 221 N/A 301 N/A 365

Composite Characteristics

Concluding Remarks….

• Convective indices at Patna, Ranchi, Guwahati and Agartala stations are good indicators for identifying possible thunderstorm days over Bangladesh as the systems initiate or conceive over West Bengal, Assam and Meghalaya regions.

• Some of the factors which are essential for triggering of Nor’westers such as low level moist southerly jet from the head Bay of Bengal, mid-trophospheric cold dry westerly trough, etc. are well simulated by the model.

• WRF-ARW model is able to simulate some salient features of thunderstorms with some temporal and spatial shifting.

Acknowledgement

• SAARC Meteorological Research Centre (SMRC)

• Bangladesh Meteorological Department (BMD)

• Dr. Someshwar Das and research team at SMRC

Tusen Takk

Mission• raising awareness and enhancing knowledge and skills-------------------------------------------------------------------------• strengthening sustainable institutional mechanisms-------------------------------------------------------------------------• facilitating exchange of information, experience and expertise-------------------------------------------------------------------------• developing and demonstrating innovative disaster risk reduction practices

• Mainstream Disaster Reduction in Development• Build and Strengthen Capacity• Facilitate Partnerships and Exchange of Experiences• Be recognized as a Proactive and Responsive

Regional Resource• Achieve Quality Service Through a Team Approach

Goals

ADPC HighlightsADPC Projects and Programs:• Longest serving regional center

globally• Proactive and responsive

regional resource center• 81 projects and programs across

Asia• Regional Early Warning Center

provides services to 27 countries in the region

Characteristics of severe thunderstorms over Bangladesh and neighborhood: Observations & WRF- ARW...

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