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PCU3 Teletraining on LONG RANGE FORECASTING

PCU3 Teletraining on LONG RANGE FORECASTING. By Mike Halpert Climate Prediction Center. LRF Training Parts. Introduction (Audio VisitView presentation) Basis, Tools, Forecast Process (online tutorial) FORECAST CASE STUDY (this training)

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PCU3 Teletraining on LONG RANGE FORECASTING

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  1. PCU3 Teletraining onLONG RANGE FORECASTING By Mike Halpert Climate Prediction Center

  2. LRF Training Parts • Introduction (Audio VisitView presentation) • Basis, Tools, Forecast Process (online tutorial) • FORECAST CASE STUDY (this training) • Product interpretation, use in local office, and customer outreach (residence training on Climate Services Operations)

  3. Tele-training Objectives • Understand LRF techniques, product components, and skill • Understand challenges involved with making LRF • Gain ability to answer customer inquiries about LRF

  4. Tele-training Outline • Basics of LRF • Detail process involved in preparing LRF • Demonstrate forecast case study based on DJF 2004-2005 • Examine verification of forecasts

  5. Pre-test • Which of the following is not a main source of predictability for seasonal forecasts? (Circle the correct answer) • ENSO • Synoptic-scale features • Trends • Boundary Conditions (Soil moisture, Snow cover, etc.)

  6. Seasonal Outlook Schedule/Leads • Monthly, near mid-month CPC prepares a set of 13 outlooks for 3-month “seasons” for lead times ranging from ½ month, 1 ½ months, …, 12 ½ months. • Seasonal outlooks are prepared for average temperature and total accumulated precipitation. • Three categories are used (terciles): BELOW-, NEAR- and ABOVE-average (median) temperature (precipitation). Contours give the total probability of the indicated category. • Regions where no strong climate signals exist are designated as “EC”, for equal chances of each category (33.33%).

  7. Temperature Precipitation

  8. Interpretation of LRF Surface Outlook 33 40 B Northern GA Below: 44% Near: 33% Above: 23%

  9. 33 40 B Interpretation of LRF Surface Outlook 33 40 A Southern NV Below: 22% Near: 33% Above: 45% Northern GA Below: 44% Near: 33% Above: 23%

  10. 33 40 B Interpretation of LRF Surface Outlook Southern MN Below: 33% Near: 33% Above: 33% EC=Equal Chances Contours are labeled with the total probability for the indicated category. 33 40 EC A EC Southern NV Below: 22% Near: 33% Above: 45% Northern GA Below: 44% Near: 33% Above: 23% EC EC

  11. Official 90 day P forecast Central KY Below: 39% Near: 33% Above: 28% Central MD Below: 33% Near: 33% Above: 33% Southeast TX Below: 25% Near: 33% Above: 42%

  12. FACTORS INFLUENCING A CLIMATE FORECAST • Climate Change - trends • Natural Climate Variability – “organizes” weather El Niño-Southern Oscillation (ENSO) Mid-latitude Oscillation modes (NAO, AO, PNA, …) Land Surface Processes (Soil moisture, Snow cover, …) • Atmospheric Noise - unpredictable “climate” signals produced by chance through cumulative effects of weather. This is large in middle latitudes, small in the Tropics.

  13. FORECAST TOOLS • El Niño-Southern Oscillation (ENSO) • Long-term trends (Optimal Climate Normal [OCN]) • Other Statistical: Canonical Correlation Analysis (CCA) , Screened Multiple Linear Regression (SMLR), Constructed Analysis (CAS) • Dynamical Models: Coupled GCM, Ensembles

  14. ENSO SST, Anomaly 28 28 28oC is approximate SST threshold for deep tropical convection El Niño: eastward extension of 28oC across entire Pacific La Niña: westward retraction of 28oC isotherm to 170oE

  15. ENSO Tropical Rainfall El Niño Enhanced Convection La Niña suppressed convection SSTs > 28oC produce extension of tropical convection across east-central Pacific during JFM and MAM

  16. ENSO - Current Status (11/04) October 2004

  17. ENSO – Forecast (11/04)

  18. ENSO-based Objective Forecast

  19. Optimal Climate Normal (OCN) • OCN, as it is used as a tool at CPC is, quite simply, a measure of the trend. For a given station and season, the OCN forecast is the difference between the seasonal mean (median) temperature (precipitation) during the last 10 (15) years and the 30 year climatology. • The ‘Optimal’ in OCN refers to optimal number of years to use in the trend calculation to optimize skill when OCN is used to make forecasts. Very often this number, called k, is less than 30 years. When it is, the tool has value in making forecasts.

  20. OCN DJF 2004-05

  21. Canonical Correlation Analysis (CCA) • CCA is a statistical technique relating tropical Pacific Ocean sea-surface temperatures (SSTs), 700 hPa heights, (the predictors) and U.S. surface temperatures (T) and precipitation (P) (the predictands) • When CCA is developed, relationships are found between observed U.S. T and P for a given season, say, January-February-March (JFM) and the predictors for the prior four non-overlapping seasons, in this case, OND, JAS, AMJ and JFM of the prior year.

  22. CCA DJF 2004-05

  23. CFS DJF 2004-05 Outlook °C mm/month Coupled Forecast System – Ensemble average of 20 members from 11 October – 30 October 2004. Base period for climo is 1982-2003. Forecast skill in gray areas is less than 0.3

  24. International Research Institute (IRI) Multi-Model Forecast

  25. CDC Seasonal Forecast ToolBased on Tropical SSTs

  26. NORTH ATLANTIC OSCILLATION • A major source of intraseasonal variability during winter over the U. S., Atlantic and Europe. • Modulates the circulation pattern over the high latitudes, regulating the number and intensity of significant weather events affecting the U.S. • Currently there is no capability to forecast the seasonal phase of the NAO

  27. Historical NAO

  28. NAO-ENSO-T composites La Niña & NAO + Neutral & NAO + El Niño & NAO + Neutral & Neutral El Niño & Neutral La Niña & Neutral La Niña & NAO - Neutral & NAO - El Niño & NAO -

  29. Prognostic Map Discussion (PMD) • PMD is a text document that includes the following items : • Current atmospheric and oceanic conditions • El Nino Forecast • Tools used in temperature forecast • Tools used in precipitation forecast • Hyperlinked terminology

  30. Temperature Verification Verification Issued: 18NOV2004

  31. Regional Verification - Temperature

  32. Precipitation Verification Issued: 18NOV2004 Verification

  33. Regional Verification - Precipitation

  34. Summary Discussion What subjective weight would you give each tool when making LRF for DJF 2004-5? Place a colored mark at top of figure. Use red for highest weight, yellow for middle weight, blue for lowest weight.

  35. Summary Discussion Interpret the forecast to a customer in your CWA.

  36. Summary Discussion Verification Circle the region(s) that typically verify the best. Circle the region that verified the best during this past winter.

  37. Questions???

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