Subseasonal forecasting for Africa and tropical climate sensitive regions

Wassila M. Thiaw

Climate Prediction CenterNational Centers for Environmental Predictions

International TeamEndalkachew BekeleTom DiLibertoVadlamani KumarNicholas NovellaChalump OonariyaMiliaritiana Robjhon Acknowledgements: CFS Team, NMME Team

FEWSNET Food Security Outlooks

Source: FEWSNET

Regional Hazards Outlooks for Food Security Outlooks

Regional Hazards Outlooks Process

USAID begins humanitarian 

response planning

• Climate monitoring

• NWP tools – severe weather up to one week

• Subseasonal outlooks (week1, week2, week3, week4, monthly)

• Seasonal outlooks

Hazards Outlooks Basic Requirements

Approach to operational subseasonal forecasting

• Assess state of the MJO and forecasts– MJO active and projected to remain active

• MJO rainfall anomaly composites & NWP toolsGuidance to draw polygons of enhanced or suppressed

rainfall

Phase 4, 90% CI Phase 8, 90% CI

Phase 1, 90% CI Phase 5, 90% CI

MJO rainfall anomaly compositeMaritime Continent, DJF

NE Brazil, DJF

Phase 1, 90% CI Phase 5, 90% CI

Phase 1, 90% CI Phase 5, 90% CI

West Africa, JAS

East Africa, OND

MJO rainfall anomaly composite

Approach to operational subseasonal forecasting

• Assess state of the MJO and forecasts– MJO active and projected to remain active

• MJO rainfall anomaly composites & NWP toolsGuidance to draw polygons of enhanced or suppressed

rainfall

• NWP tools out to two weeks– Low and upper level winds– Low and mid‐level geopotential height– Mean sea level pressure – Ensemble precipitation forecasts

• Probability of exceedence• Bias corrected precipitation anomaly forecasts

Approach to operational subseasonal forecasting

• Assess state of the MJO and forecasts– MJO active and projected to remain active

• MJO rainfall anomaly composites & NWP toolsGuidance to draw polygons of enhanced or suppressed

rainfall

• NWP tools out to two weeks– Low and upper level winds– Low and mid‐level geopotential height– Mean sea level pressure – Ensemble precipitation forecasts

• Probability of exceedence• Bias corrected precipitation anomaly forecasts

• SST anomaly and SST tendency 

Week-1 Week-2

Week-1Verification

Week-2Verification

Example of week1 and week2 outlooks

Week1 Forecast verificationsHeidke Skill Score

Data•CFSv2 – 45 day hindcasts•NMME outputs, zero lead•TRMM

Methodology•Construct CFSv2 week1 to week4 P anomaly forecasts•Apply bias correction to the weekly forecasts•Obtain monthly CFSv2 forecasts•Calculate AC between forecasts and observations•Apply CCA correction to NMME forecasts•Evaluate NMME skill

CFS2 and NMME Subseasonal Forecast Skill

Week-1 Week-2

Week-3 Week-4

CFS2 Precipitation forecast skill

Week-1, with BC Week-2, with BC

Week-3, with BC

CFS2 Precipitation (bias corrected) forecast skill

Week-4, with BC

Week-1, with BC Week-2, with BC

Week-3, with BC

Precipitation (bias corrected) forecast skill

Regional Precipitation (bias corrected) forecast skill

Week‐2