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

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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
• Climate Diagnostics and Prediction Workshop
• October 20, 2008
• Lincoln, NE

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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

• 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
  years 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

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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

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Conditional ClimatologyData

• 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

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How does ENSO phase impact tornado activity in
the Plains?
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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 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 ActivityLate Spring
through Summer
La Niña
Neutral
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

• 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
LN in
EN in
LN out
EN out
Neutral

• Background shading Mean 1950-2005
• Barbs Anomalies

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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
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
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
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
LN in
EN out
LN out
EN out
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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 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

• 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

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Thank you!
Questions? Email Barbara.Mayes_at_noaa.gov WFO
OAX [phone]

• 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-b
  in/Composites/printpage.pl

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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
LN in
EN in
LN out
EN out
Neutral

• Background shading Mean 1950-2005
• Vectors Anomalies

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