Convective Initiation and Flow Regimes of Severe Storms Across the Central High Plains Scott F. Blair National Weather Service Goodland, Kansas

Overview Goodland County Warning Area 19 Counties Served Overall Purpose  Spatial / Temporal Characteristics of Convective Initiation (CI)  Flow Regime Type Associated With Severe Convection Scope of Study  Limited to examine severe weather occurring within the GLD CWA  Determine any signals to better anticipate local severe weather traits

Central High Plains

Nebraska Kansas Oklahoma Wyoming Colorado New Mexico Central High Plains 2500 ft Cheyenne Ridge Raton Ridge Palmer Divide GLD CWA

Severe Weather Criteria - Defined 1” Diameter Hail  Remained consistent with current warning operations 50+ Knot WindsAll Tornadoes Severe Weather Climatology (1950 – 2006) CI / Flow Regime Event Investigations (1997 – 2006) Built Upon Defined Criteria

Severe Weather Climatology 1950 – 2006 Severe Reports

Severe Weather Climatology 1950 – 2006 Severe Reports

May, June, and July 82% Tornadoes 77% Hail 73% Wind 76% ALL Severe Weather Occurred May – July  Climatological Three-Month Maximum of Severe Weather  Ten-Year Period (1997–2006) Further Examined Severe Weather Climatology 1950 – 2006 Severe Reports

Convective Initiation  First 45 dBZ echo resolved in 0.5 degree reflectivity to represent initiation  Origin of deep moist convection ultimately producing 1 st severe report in GLD CWA  Unlimited domain for the origin of convective initiation  New convection (mergers, clusters, outflow) associated with original activity NOT used 45 dBZ Severe Wx

Convective Initiation Spatial Distribution 285 Event Cases May – July ( )

Convective Initiation Spatial Distribution 285 Event Cases May – July ( )

Convective Initiation Temporal Analysis 1900 – 2100 UTC Peak Initiation Period (65% Events) (1900 – 2300 UTC ~85% Events)

Convective Initiation vs. 1 st Severe  Temporal analysis parsed by CI and 1 st severe report / type from event day Convective Initiation 1 st Severe Report

Convective Initiation vs. 1 st Severe Peak CI Period: 1900 UTC – 2100 UTC Peak 1 st Hail Report Period: 2200 UTC – 0000 UTC Peak 1 st Tor Report Period: 2300 UTC – 0000 UTC Peak 1 st Wind Report Period: 2300 UTC – 0100 UTC  Large majority of cases exhibit strong diurnal preference in regards to time of CI and time of 1 st resultant severe type  Data suggests greatest operational concern with regards to CI and 1 st severe event between 1900 UTC and 0100 UTC

500 mb Flow Regimes Surrounding Upper Air Sites UtilizedData Stratified by 45 Degree Increments  Investigated 500 mb Flow for Each Event Day W NW N SW S ___________________________________________________________________________ Determine any signal that might exist with respect to the origin of severe convection per specific flow regime

500 mb Flow Regimes Distribution of Events: West (43%) Southwest (33%) Northwest (20%) Regime Distribution - Entire Study Period N S NW W SW Preferred flow regimes by month?

500 mb Flow Regimes

Flow Regimes N – 22.5 S – SW – W – NW

500 mb Flow Regimes Flow Regimes N – 22.5 S – SW – W – NW

Limitations  NCDC National Mosaic Reflectivity Imagery Radar data available every 30 minutes to 1 hour 2 km radar resolution  In-Depth Study Period Restricted to 10 Year Database  Study Domain Narrowed to Goodland CWA

Closing Remarks May, June, and July climatological three-month maximum of severe weather for GLD CWA ~ 285 CI event cases (1997 – 2006) Spatial distribution CI overall analogous with some clustering in identifiable topographical locations Temporal analysis established strong diurnal preference with regards to CI and 1 st resultant severe weather type Preferred flow regimes were favored in specific geographic locations Flow regimes tended to transition throughout the progression of months during the study period

Questions ??? Thank You ! Contact Information: Acknowledgements Albert Pietrycha (SOO – NWS GLD) NWS Goodland Resources