Multi-model operational Multi-model operational seasonal forecasts for seasonal forecasts for SADCSADC

Willem A. Willem A. LandmanLandmanAsmerom BerakiAsmerom BerakiCobus OlivierCobus OlivierFrancois Francois EngelbrechtEngelbrecht

Conformal-Cubic Conformal-Cubic Atmospheric Model Atmospheric Model (CCAM)(CCAM)

Runs performed on a computer cluster at the Runs performed on a computer cluster at the University of PretoriaUniversity of Pretoria

Climatological ensemble runs - 12hr LAF (5 Climatological ensemble runs - 12hr LAF (5 members)members)

Atmospheric initial conditions for climatological Atmospheric initial conditions for climatological runs obtained from NCEP reanalysis dataruns obtained from NCEP reanalysis data

Climatological simulations performed for the Climatological simulations performed for the period: 1979-2003. Lower boundary forcing from period: 1979-2003. Lower boundary forcing from AMIP SST and sea-iceAMIP SST and sea-ice

ECHAM4.5 at the SAWSECHAM4.5 at the SAWS

All runs performed on NEC SX-8All runs performed on NEC SX-8 Climatological (6 members) and operational ensemble Climatological (6 members) and operational ensemble

runs - 24hr LAFruns - 24hr LAF Atmospheric initial conditions from ECMWF (1979 to Atmospheric initial conditions from ECMWF (1979 to

1996) analysis1996) analysis Climatological dataset (1979-2003) constructed using Climatological dataset (1979-2003) constructed using

AMIP physics; model constrained by lower boundary AMIP physics; model constrained by lower boundary conditions generated from a high resolution AMIP2 conditions generated from a high resolution AMIP2 dataset for SST and sea-icedataset for SST and sea-ice

Operational set-up: persisted and forecast SSTs obtained Operational set-up: persisted and forecast SSTs obtained from a high resolution observed SST (optimum from a high resolution observed SST (optimum interpolation v-2) and IRI (mean) respectively (6 members interpolation v-2) and IRI (mean) respectively (6 members each)each)

12-member ensemble operational runs on 1812-member ensemble operational runs on 18 thth of each of each month for 6 consecutive months (i.e., 0-5 months lead-month for 6 consecutive months (i.e., 0-5 months lead-time)time)

First objective multi-model forecast

Old subjective consensus forecast

Combining algorithm:1. CPT downscaling2. Equal weights

Multi-model ensemble

Ensemble 1

(ECHAM4.5 at SAWS)

12 members

Ensemble 2

(CCAM at UP)

5 members

Ensemble 3

(CCM3.6 at IRI)

24 members

Ensemble 4

(CFS at CPC)

40 members

The current long-range forecast multi-model ensemble system of the South African Weather Service

New forecasting New forecasting systemsystem

UEA CRU data (0.5UEA CRU data (0.5° resolution)° resolution)– PrecipitationPrecipitation– Minimum temperaturesMinimum temperatures– Maximum temperatures Maximum temperatures

MOS using 850 hPa MOS using 850 hPa geopotential height fieldsgeopotential height fields– Domain: 10N-50S; 0-70EDomain: 10N-50S; 0-70E

Production date: from July 2008

DJF rainfall simulation DJF rainfall simulation skillskill

DJF 1999/2000 precip & DJF 1999/2000 precip & max temp PROBABILITY max temp PROBABILITY forecastsforecasts

Pre

cip M

ax T

A typical example of the format of the forecasts

Rainfall forecast issued in DecemberRainfall forecast issued in December

DMC and VACSDMC and VACS

DMCDMC– SAWS to compile draft document on SAWS to compile draft document on

modernizing the SARCOF processmodernizing the SARCOF process– DMC has been receiving MM forecasts DMC has been receiving MM forecasts

from SAWS since August 2008from SAWS since August 2008 MM work to be linked with VACSMM work to be linked with VACS

– Workshop in 2009 (will introduce Workshop in 2009 (will introduce product)product)

ENSO forecastENSO forecast

CCA (antecedent CCA (antecedent SST)SST)

ECHAM4.5-MOM3 ECHAM4.5-MOM3 (from Dave DeWitt)(from Dave DeWitt)

CFS (NCEP)CFS (NCEP)

Combining algorithm:1. CPT downscaling2. Equal weights

Multi-model ensemble(& verification statistics)

Ensemble 1

(ECHAM4.5 at SAWS)

12 members

Ensemble 2

(CCAM at UP)

5 members

Ensemble 3

(CCM3.6 at IRI)

24 members

Ensemble 4

(CFS at CPC)

40 members

The planned long-range forecast multi-model ensemble system of the South African Weather Service

Ensemble 5+6 (+7)

(GloSea4 at UKMO

and

CPTEC/COLA at INPE

(ECMWF?))