Subseasonal forecasting for Africa and tropical climate ... · PDF fileSubseasonal forecasting for Africa and tropical climate sensitive regions Wassila M. Thiaw Climate Prediction

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