Extended range prediction during 2013 season

Using Ensemble Prediction System based in CFSv2

AndGFSv2 forced with Bias corrected CFSv2 forecasted SST

Working group on Extended Range Prediction Ministry of Earth System Sciences, India

INITIAL CONDITION 10th June 2013

• Ocean and Atmospheric Initial conditions (IC) are obtained from NCEP.

• Technique was developed to perturb ICs to generate 11 members. (Abhilash et al., 2013)

• Model has been integrated for 45 days for each 11 ICs at five day intervals starting from 16th May (Eg: 16May, 21May, 26May, 31May, 05Jun........etc). Climatology has been calculated from 10-year hindcast.

• Bias correction in daily forecasted SST from CFSv2 for each lead time has been done by removing the daily mean bias for corresponding lead time (model climatology-observed climatology) from forecasted daily SST. (Sahai et al., 2013; Abhilash et al., 2013)

Strategy: Ensemble Prediction using CFS/GFSv2 (T126)

FORECAST FROM CFSv2(T126) And

Bias Corrected GFSv2(T126)Based on IC 10th June 2013

Daily evolution of rainfall and wind at 850hPaCFS forecast based on IC=10 June 2013

Daily evolution of rainfall and wind at 850hPaGFS forecast forced with bias corrected CFS forecasted SST

based on IC=10 June 2013

Daily evolution of vorticity at 850hPaCFS forecast based on IC=10 June 2013

Daily evolution of vorticity at 850hPaGFS forecast forced with bias corrected CFS forecasted SST

based on IC=10 June 2013

CFS forecast based on IC=10 June 2013

Actual Anomaly

GFSbc forecast based on IC=10 June 2013

Actual Anomaly

CFS-GFS Forecast Over Homogenous RegionsMZI, CEI, NEI, NWI & SPI

CFS

GFSbc

MISO monitoring and forecast for next 25 days

CFS GFSbc

Inferences from the present analysis

• Both CFSv2 and GFSbc show that rainfall over monsoon zone of India (MZI) would start to intensify from 13th Jun onwards. This intensification of rainfall is likely due to the formation of a system over BOB.

• Monsoon trough would be over MZI around 13th Jun both in CFSv2 and GFSbc.

• CFSv2 indicates more rainfall over main land of India during P1(11-15June), P2(16-20 Jun) and P4(26-30 Jun); while less rainfall is predicted during P3(21-25Jun). Positive anomalies are seen over west coast and MZI during P1(11-15June), P2(16-20 Jun) and P4(26-30 Jun).

• GFSbc indicates not much difference during P1. But the rainfaal pattern in P2-P4 are different from that of CFSv2.

• CFSv2 shows the above normal condition over MZI (during P1-P4), CEI (during P1, P2 and P4), NWI (during P2 and P3) and SPI (during P1, P2 and P4). Near normal conditions are seen over CEI (during P3), NEI (during P1-P3), NWI (during P4). Below normal conditions are seen over NEI (during P4), NWI (during P1) and SPI (during P3).

• GFSbc shows the above normal condition over MZI (during P1 and P2), CEI (during P1, P2 and P4), NWI (during P2 and P4) and SPI (during P1 and P3). Near normal conditions are seen over MZI (during P3 and P4), CEI (during P3), NEI (during P1-P4) and NWI (during P3). Below normal conditions are seen over NWI (during P1) and SPI (during P2 and P4).

Inferences from the present analysis

• Real time forecast for MISO shows a prominent northward propagation from both CFSv2 and GFSbc.

• However GFSbc shows faster propagation than that in CFSv2.

Inferences from the present analysis

Verification

Forecast of Monsoon Onset over Kerala Based on 16 May 2013: 29 May 2013

Onset date forecasts are obtained from

each 11 member of CFSv2 45 day forecast. Then

ensemble mean is given as the final

forecasted onset date.Y axis on each panel

is in mm/day for rainfall (bars) and m/s

for 850hPa wind(green line). Red

circle is the onset date and also written

at the top of each panel

Onset declared by IMD: 1st June 2013

NCEP/TRMMAnalysis

Wind (850hPa)and R/F

Verification

CFSv2 GFSbc

F/C from16May IC

F/C from16May IC

NCEP/TRMMAnalysis

Wind (850hPa)and R/F

Verification

CFSv2 GFSbc

F/C from26May IC

F/C from26May IC

CFS-GFS Verification Over Homogenous RegionsMZI, CEI, NEI, NWI & SPI

CFS, CEI

GFSbc , CEI

CFS, MZI

GFSbc, MZI

CFS, NEI

GFSbc , NEI

CFS, NWI

GFSbc, NWI

CFS, SPI

GFSbc, SPI

16 May IC 21 May IC

MISO F/C verification

(OBS is for 20 days only)

MISO F/C verification

26 May IC(OBS is for 15 days only)