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Cold season severe weather climatology

Cold season severe weather climatology . What is the impact of ENSO Cycle? Suzanne Fortin. Outline. Recent Annual Severe Weather Climatology Distribution of of Severe Events During the Cold Season Analysis of Severe Events and ENSO Cycle Significance of ENSO Cycle to Severe Incidence.

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Cold season severe weather climatology

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  1. Cold season severe weather climatology What is the impact of ENSO Cycle? Suzanne Fortin

  2. Outline • Recent Annual Severe Weather Climatology • Distribution of of Severe Events During the Cold Season • Analysis of Severe Events and ENSO Cycle • Significance of ENSO Cycle to Severe Incidence

  3. Recent Annual Climatology of Severe Weather

  4. Focus Upon Cold Season Severe • February 28, 2007 • Previous studies focused on yearly activity and ENSO phase (Mayes et al., 2006, Agee and Zurn-Birkhimer, 1998, Browning, 1998). • Situational awareness

  5. 50+ Year Climatology of Cold Season Severe

  6. ENSO Phases Since 1950 Warm (red) and cold (blue) episodes based on a threshold of +/- 0.5oC for the Oceanic Niño Index (ONI)

  7. Incidence of Severe Events during Cold Season for the ENSO Phases La Nina EL Nino Neutral

  8. Incidence of Severe Type Event during ENSO Phases

  9. Methodology Used compositing methodology developed by NWSH, CPC and NWS field Test of statistical significance performed on statistical analysis to determine if deviations from normal climatology are significant (90%)

  10. Results Concurrent 5 Months Prior Overall severe event incidence is more prevalent during cold phase of ENSO (La Nina) Mixed signal during late winter, with severe events occurring during both cold and warm phases of ENSO “Signal” that severe incidence in late winter greater when cold phase (1) or neutral phase (2) during late summer/early fall

  11. Summary • Scaled analysis to the past 30 years due to limited dataset prior to 1970s • Statistical analysis also showed severe weather frequency greater during warm phase (El Nino) of ENSO for certain periods • Study area limited to CWA, may need to expand to larger domain • Signal that severe weather frequency greater during cold season during concurrent cold phase of ENSO • Signal that severe weather frequency during later part of cold season greater if cold/neutral phase of ENSO during late summer/early fall

  12. Future Work • Compositing • Expansion of domain? • Analysis of specific severe type frequency

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