Model used by IMD for Genesis Prediction

[International Training Workshop on Tropical Cyclones Forecasting]

(ITWTCF)

S. D. Kotal

NWP Division, New Delhi

(03-14 August 2015)

Operational NWP Models at IMD

• GFS T574L64 (23 km)

• WRF (3DVAR - 27 km, 9km, 3 km)

• EPS (Ensemble track, strike probability)

• HWRF (27 KM, 9 KM)(Track, Intensity, Rainfall)

• GPP (Genesis Potential Parameter)

• SCIP (for cyclone intensity prediction)

• MME (for cyclone track)

• RI-Index (Rapid Intensification)

• Decay after landfall (Decay model)

NWP Model product from Other Centres

• NCMRWF

• ECMWF

• JMA

• NCEP GFS

• UKMO

Extended Range

• ECMWF (CFAN)

• IITM (CFS)

Genesis Probability

• NCEP Genesis probability (24h, 48h)

• CIRA Genesis probability (24h, 48h)

CYCLOGENESIS

CYCLONE ‘GIRI’

Limitation of models.

Variation of forecasts among NWP models.

Requirements are also different for different

forecast services.

Forecasters need more skillful, consensus, and

requirement based products.

Statistical post processing can add skill to

dynamical forecast.

Dynamical models provide very useful

guidance to operational forecasters:

NWP Model based Objective Cyclone Prediction System

(Dynamical-Statistical)

STEP-IV

Cyclogenesis

Prediction

Track

Prediction

Intensity

Prediction

Rapid Intensification

Decay after

Landfall

Decay Model

RI-Index

SCIP Model

Multimodel

Ensemble(MME)

Genesis Potential

Parameter(GPP)

STEP-I

STEP-II

STEP-III

STEP-V

GENESIS POTENTIAL

PARAMETER (GPP)

The GPP is defined as: (Natural Hazards, 2009, 50,389-402)

if ζ850 > 0, M > 0 and I > 0

= 0 if ζ850 ≤ 0, M ≤ 0 and I ≤ 0

Where , ζ850 = Low level relative vorticity (at 850 hPa) in 10-5 s-1

S = Vertical wind shear between 200 and 850 hPa (ms-1)

= Middle troposphere relative humidity

Where RH is the mean relative humidity between 700 and 500 hPa

I = (T850 – T500) °C = Middle-trpospheric instability (Temperature

difference between 850 hPa and 500 hPa)

30

]40[

RHM

S

xMxIGPP

850

Genesis potential parameter for developing versus non- developing systems:

GPP(x10-5)

T.No. 1.0 1.5 2.0 2.5 3.0

Developing 11.1 12.3 13.3 13.5 13.6

Non-Developing 3.4 4.2 4.6 2.7 -

0

2

4

6

8

10

12

14

16

1 1.5 2 2.5 3

T.No.

GPP

DevelopingNon-Developing

Threshold value

of GPP = 8.0

Applications of GPP

Area average GPP to identify the

potential of a system to intensify into a

Cyclonic Storm at the early stage of

development.

Grid point analysis of GPP to identify the

potential cyclogenesis zone over the North

Indian Sea.

THANE

Depression at 1200 UTC of 25 December 2011 (THANE)

Genesis Potential Parameter (THANE in 2011)

VIYARU

Grid point Analysis of Genesis Potential Parameter

(GPP) for cyclone VIYARU

Area average Genesis potential parameter (GPP)

PHAILIN

Grid Point Analysis of Genesis Potential

Parameter (GPP)

On 1 Oct. 2013: 168 hour forecast (7 days in advance) of GPP

valid for 00 UTC 08 October 2013 correctly indicated the location of

potential cyclogenesis zone, where Depression formed on that day.

Grid Point Analysis of Genesis Potential

Parameter (GPP)

On 3 Oct. 2013: 120 hour forecast (5 days in advance) of GPP

valid for 00 UTC 08 October 2013 correctly indicated the location of

potential cyclogenesis zone, where Depression formed on that day.

Grid Point Analysis of Genesis Potential

Parameter (GPP)

On 6 Oct. 2013: 48 hour forecast (2 days in advance) of GPP

valid for 00 UTC 08 October 2013 correctly indicated the location of

potential cyclogenesis zone, where Depression formed on that day.

Area average Genesis potential parameter (GPP) GPP Analysis and Forecast

(Initial stage=T.No.-1.0; based on 00UTC of 7.10.2013)

17.6

15.6

14

22.2

21.2

21.8

18

25.1

19.8 2

2.8

20.4

0

5

10

15

20

25

30

0 12 24 36 48 60 72 84 96 108 120

Lead Time (h)

GP

P

GPP Threshold GPP=8.0

GPP Analysis and Forecast

(Initial stage=T.No-1.5; based on 00UTC of 8.10.2013)

18.6

18.6

18.5 19

19

20.9

20.7

20.9

17

24.7 2

6

0

5

10

15

20

25

30

0 12 24 36 48 60 72 84 96 108 120

Lead Time(h)

GP

P

GPP Threshold GPP=8.0

GPP Analysis and Forecast

(Initial stage=T.No-2.0; based on 00UTC of 9.10.2013)

21.9

23.1

24.2 2

8.4

27.9

28.5

25.2

26.2

30.9

31.9

0

5

10

15

20

25

30

35

0 12 24 36 48 60 72 84 96 108

Lead Time(h)

GP

P

GPP Threshold GPP=8.0 Inference: Analysis and forecasts of

GPP show that GPP ≥ 8.0 (threshold

value for intensification into cyclone)

indicated its potentential to intensify

into a cyclone at early stages of

development (T.No. 1.0, 1.5, 2.0).

LEHAR

MADI

GPP Analysis and Forecast

(Initial stage=T. No. 1.0; based on 00UTC of 2.12.2013)

23.6

16.0 18

.8

26.3

20.7 24

.3 25.4

22.5 23.8

27.5

20.1

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0 12 24 36 48 60 72 84 96 108 120

Lead Time(h)

GP

P

GPP Threshold GPP=8.0

GPP Analysis and Forecast

(Initial stage=T.No 1.0; based on 00UTC of 3.12.2013)

17.2

12.0

17.6

18.2 19.2

16.6

20.6

17.3 18

.4

17.2 18

.4

0.0

5.0

10.0

15.0

20.0

25.0

0 12 24 36 48 60 72 84 96 108 120

Lead Time(h)

GP

P

GPP Threshold GPP=8.0

Area average Genesis potential parameter (GPP)

GPP Analysis and Forecast

(Initial stage=T.No 1.0; based on 00UTC of 4.12.2013)

17.6 19

.5 21.3

22.0

18.7

18.8 20

.2

18.9

18.4

15.6

18.7

0.0

5.0

10.0

15.0

20.0

25.0

0 12 24 36 48 60 72 84 96 108 120

Lead Time(h)

GP

P

GPP Threshold GPP=8.0

GPP Analysis and Forecast

(Initial stage=T.No 1.0; based on 00UTC of 5.12.2013)

18.0 20

.3 21.1 22

.8

27.3

24.8

19.4

19.1

15.0

14.9 18

.4

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0 12 24 36 48 60 72 84 96 108 120

Lead Time(h)

GPP

GPP Threshold GPP=8.0

HUDHUD

Grid point Analysis of Genesis Potential Parameter

(GPP) for cyclone HUDHUD

On 3 Oct. 2014: 96 hour forecast (4 days in advance) of GPP

valid for 12 UTC 07 October 2014 correctly indicated the

location of potential cyclogenesis zone, where Depression formed

on that day.

Grid Point Analysis of Genesis Potential

Parameter (GPP)

On 4 Oct. 2013: 72 hour forecast (3 days in advance) of GPP

valid for 12 UTC 07 October 2014 correctly indicated the

location of potential cyclogenesis zone, where Depression formed

on that day.

Grid Point Analysis of Genesis Potential

Parameter (GPP)

On 5 Oct. 2014: 48 hour forecast (2 days in advance) of GPP

valid for 12 UTC 07 October 2014 correctly indicated the

location of potential cyclogenesis zone, where Depression formed

on that day.

Grid Point Analysis of Genesis Potential

Parameter (GPP)

On 6 Oct. 2014: 24 hour forecast (1 days in advance) of GPP

valid for 12 UTC 07 October 2014 correctly indicated the

location of potential cyclogenesis zone, where Depression formed

on that day.

Grid Point Analysis and Forecasts of

Genesis Potential Parameter (GPP)

Grid Point Analysis and Forecasts of

Genesis Potential Parameter (GPP)

Area average Genesis potential parameter (GPP)

Inference: Analysis and forecasts of

GPP show that GPP ≥ 8.0 (threshold

value for intensification into cyclone)

indicated its potentential to intensify

into a cyclone at early stages of

development (T.No. 1.0, 1.5, 2.0).

GENESIS POTENTIAL PARAMETER

Based on 1200 UTC of 7 Oct 2014

0

5

10

15

20

25

0 24 48 72 96

Lead Time (h)

GP

P GPP

THRESHOLD

GPP based on 0000 UTC of

7 October 2014

Deep Depression over Bay of Bengal during

(5-8) November 2014

SUMMARY

Area average of GPP could predict the potential of the systems to

intensify into cyclonic storms at their early stages of development.

Grid point analysis shows that higher value of the GPP over a

region indicates higher potential zone of genesis.

The region with GPP value equal or greater than 30 is found to be

high potential zone for cyclogenesis.

The analysis and forecasts of the parameter affirm its usefulness as

a predictive signal (4-5 days in advance) for day to day monitoring of

cyclogenesis over the north Indian Sea.

Final official forecast is issued using all available inputs.