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Convective Season Synoptic Climatology by ENSO Phase in the North Central U.S. Barbara E. Mayes – WFO Omaha/Valley, NE Joshua M. Boustead – WFO Topeka, KS Jeffrey S. Boyne and Glenn R. Lussky – WFO La Crosse, WI Craig Cogil – WFO Des Moines, IA Richard S. Ryrholm – WFO Sioux Falls, SD

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convective season synoptic climatology by enso phase in the north central u s

Convective Season Synoptic Climatology by ENSO Phase in the North Central U.S.

Barbara E. Mayes – WFO Omaha/Valley, NE

Joshua M. Boustead – WFO Topeka, KS

Jeffrey S. Boyne and Glenn R. Lussky – WFO La Crosse, WI

Craig Cogil – WFO Des Moines, IA

Richard S. Ryrholm – WFO Sioux Falls, SD

Climate Diagnostics and Prediction Workshop

October 20, 2008

Lincoln, NE

NATIONAL WEATHER SERVICE

presentation outline
Presentation Outline
  • Study overview
    • Recap of conditional climatology phase
    • Creating synoptic composites
    • ENSO patterns
  • Results: Composite images
  • Conclusions and future work

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introduction
Introduction
  • Why care about climate?
    • Influence large-scale weather patterns
    • Predictable on longer time scales
  • Uses for compositing analysis of severe weather
    • Anticipate convective activity
      • Frequency/intensity
      • Type/mode
    • Answer media/public/EM question: “What will this year’s severe weather season be like?”
    • Allow meteorologists to prepare for active seasons via training, anticipation, situational awareness
  • Upcoming NWS product: 3-Month Outlook of Local ENSO Impacts
study overview
Study Overview
  • Conditional climatology
    • Investigated statistical relationship between ENSO phase and convective (tornadic) activity
      • Tornado days
      • Significant (F2+) tornadoes
    • Segmented data by NWS County Warning Area
      • Test methodology for upcoming climate product, 3-Month Outlook of Local ENSO Impacts
      • Can be utilized/applied readily by NWS offices
    • Answers “what” climatology changes occur
  • Composite synoptic environment
    • Having found statistical relationships between ENSO phase and tornado activity, investigating synoptic environment for differences among ENSO phases
    • Answers “why” the climatology changes
conditional climatology data
Conditional Climatology:Data
  • Severe weather data: NCDC Storm Data
    • 1950-2005
    • Tornado, hail, and wind data
      • Over 150,000 reports!
      • Utilized mainly tornado data
    • Issues with severe weather data
      • Population density
      • Increased reporting
  • Oceanic Niño Index (ONI): NOAA
    • Climate Prediction Center
    • 3-month running SST anomaly in Niño 3.4
      • 5 continual 3-month periods above 0.5 ºC = El Niño
      • 5 continual 3-month periods below 0.5 ºC = La Niña
la ni a north american perspective
La Niña: North American Perspective

Typical JFM weather patterns and anomalies during a moderate to strong

La Niña

  • Blocking high in the Gulf of Alaska
  • Variable jet speed
  • Increased storminess in central N. America
  • Cold air in AK/Canada spilling into the Plains
  • Warm and dry in the Southeastern U.S.
  • Wet in the Ohio Valley
  • Higher than average Atlantic hurricane activity

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el ni o north american perspective
El Niño: North American Perspective

Anomalous low in the Gulf of Alaska

Zonal jet stream

Wet in California

Cool and wet in the Southeastern U.S.

Dry in the Ohio Valley

Warm in the northern CONUS

Lower than average Atlantic hurricane activity

Typical JFM weather patterns and anomalies during a moderate to strong

El Niño

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impact of enso on tornado activity late spring through summer
Impact of ENSO on Tornado Activity:Late Spring through Summer

Neutral

La Niña

El Niño

  • ENSO phase during MJJ-SON seasons
  • Tornado activity during MAMJ:
    • Number of significant tornadoes
    • Number of tornado days
  • Reference: Mayes et al., 2007

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creating composites based on enso phase
Creating Composites Based on ENSO Phase
  • Sorted Mar-Apr-May-Jun (MAMJ) for all years 1950-2005 by ENSO phase
    • Based on ENSO phase during 3-month “seasons” overlapping MAMJ: JFM, FMA, MAM, AMJ, MJJ, JJA
    • Going into La Niña or El Niño if neutral at beginning of MAMJ and enter into phase during those months
    • Going out of La Niña or El Niño if in the phase at the beginning of MAMJ and neutral by the end of those months.
    • In La Niña or El Niño if in the same phase for all seasons covering MAMJ
    • Not included if transitioned from one phase to the opposite during MAMJ
  • Created composites for each of the 5 phases with NCEP/NCAR reanalysis data using NOAA Climate Diagnostics Center (CDC) Monthly/ Seasonal Climate Composites website

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300 hpa winds
300 hPa Winds

LN in

EN in

LN out

EN out

Neutral

  • Background shading: Mean 1950-2005
  • Barbs: Anomalies

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500 hpa height
500 hPa Height

LN in

EN in

LN out

EN out

Neutral

  • Background shading: Mean 1950-2005
  • Contours: Anomalies

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700 hpa temperature
700 hPa Temperature

LN in

EN in

LN out

EN out

Neutral

  • Background shading: Mean 1950-2005
  • Contours and vectors: Anomalies

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850 hpa dewpoint temperature
850 hPaDewpoint Temperature

EN in

LN in

EN out

LN out

  • Background shading: Mean 1950-2005
  • Contours and vectors: Anomalies

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mean sea level pressure
Mean Sea Level Pressure

LN in

EN in

LN out

EN out

Neutral

  • Background shading: Mean 1950-2005
  • Contours: Anomalies

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700 500 hpa lapse rates
700-500 hPa Lapse Rates

EN out

LN in

EN out

LN out

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conclusions for la ni a
Conclusions for La Niña
  • Features with La Niña (especially ongoing or developing) would enhance convection across the Plains:
    • Enhanced upper low in the West
    • Enhanced upper southwesterly flow
    • Enhanced southerly low-level jet
    • Favored dryline location pushing eastward into the Central Plains
    • Enhanced surface trough in lee of Rockies

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conclusions for el ni o
Conclusions for El Niño
  • Features with El Niño (especially with antecedent episode coming out) would suppress convection across the Plains:
    • Upper-level jet suppressed southward, zonal
    • Blocking/ridgy 500mb flow pattern
    • Decreased mid-level baroclinicity
    • Anomalous surface low in the southeast U.S. or anomalous surface high in the central Plains

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future steps
Future Steps
  • Continue investigating reanalysis dataset
    • Continue investigating convective “ingredients”
      • Shear (i.e. 0-6km bulk shear)
      • Instability (i.e. lifted index)
      • Vertical profiles/soundings
    • Verify significance of results
    • Create schematic diagrams
  • Examine 2006-08 in relationship to expected tornado climatology and synoptic-scale environment
thank you
Thank you!

Questions?

Email: Barbara.Mayes@noaa.gov

WFO OAX: (402) 359-5166

References

  • Mayes, B.E., C. Cogil, G.R. Lussky, J.S. Boyne, and R.S. Ryrholm, 2007: Tornado and severe weather climatology and predictability by ENSO phase in the north central U.S.:  A compositing study. Preprints of the 19th Conference on Climate Variability and Change, San Antonio, TX, Amer. Meteor. Soc.
  • Mayes, B.E., J.M. Boustead, C. Cogil, G.R. Lussky, J.S. Boyne, and R.S. Ryrholm, 2008: Synoptic-scale convective environment climatology by ENSO phase in the north central United States. Preprints of the 24th Conference on Severe Local Storms, Savannah, GA, Amer. Meteor. Soc.
  • Training and documentation for conditional climatology/compositing:http://www.weather.gov/om/csd/pds/pcu4/web/support/stats.htm
  • NOAA Climate Diagnostics Center Monthly/Seasonal Climate Composites: http://www.cdc.noaa.gov/cgi-bin/Composites/printpage.pl

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sounding anomalies
Sounding Anomalies
  • Solid line and right side vectors: La Niña in or going in
  • Dashed line and left side vectors: 1950-2005 mean
  • Point sounding at KOAX (Omaha, NE)
  • La Niña in or going in environment:
    • Stronger shear, particularly deep-layer
    • Perhaps a dry air anomaly at mid-levels and warm anomaly near the ground

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850 hpa winds
850 hPa Winds

LN in

EN in

LN out

EN out

Neutral

  • Background shading: Mean 1950-2005
  • Vectors: Anomalies

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