Warm-Season Lake-/Sea-Breeze Severe Weather in the Northeast Patrick H. Wilson, Lance F. Bosart, and Daniel Keyser Department of Earth and Atmospheric Sciences, University at Albany, Albany, NY Thomas A. Wasula NOAA / National Weather Service, Albany, NY CSTAR-II Grant NA04NWS Ninth Northeast Regional Operational Workshop Albany, NY 8 November 2007

Research Goals  Investigate influence of thermodynamic and dynamical processes, along with physiographic effects, on lake-/sea-breeze severe weather events  Increase awareness and understanding of this phenomenon

Methodology  Warm season: April–October  Domain area shown by map  Selected cases from search of SPC archived storm data, along with input from NWS meteorologists, for 2000–2006  Verified from NCDC archived radar data

Methodology (continued)  Obtained 32 km-resolution NCEP/NARR gridded datasets for all cases to perform synoptic-scale analyses  Acquired 20 km-resolution RUC gridded datasets for three cases to perform mesoscale analyses  Collected soundings, radar data, satellite images, water temperature data, and surface observations  Classified cases into separate categories and conducted case study analyses

Case Classifications  Pure Case: mesoscale forcing primary; synoptic-scale forcing secondary  Mixed Case: mesoscale forcing and synoptic- scale forcing of similar importance  Null Case: convection suppressed by lake-/sea-breeze processes

Case List Cases chosen for RUC analysis highlighted  Pure Cases 9 August 2001 (Ontario) 6 July 2003 (Erie) 7 August 2005 (Chesapeake) 2 August 2006 (Ontario)  Mixed Cases 9 April 2001 (Erie) 19 April 2002 (Erie) 19 June 2002 (Atlantic) 24 July 2003 (Erie and Ontario) 1 August 2005 (Huron and Ontario) 5 August 2005 (Atlantic) 24 April 2006 (Chesapeake) 30 June 2006 (Erie and Ontario) 23 July 2006 (Erie and Ontario) 28 July 2006 (Atlantic)  Null Case 11 July 2006 (Atlantic)

Storm Formation Areas and Tracks: All Cases Legend Red: Storm Formation Areas Arrows: Storm Tracks Green: Null Case Area Pink: Tornado Risk Area

SPC Verification of Cases using Convective Outlook Reports for 2003–2006  Pure Cases (3) Slight Risk: 2, General Thunderstorms: 1  Mixed Cases (7) Slight Risk: 2, General Thunderstorms: 4, Nothing: 1  Null Case (1) Missed Null Area

Pure Case Example  2 August 2006 (Ontario)

1200 UTC 2 August 2006: 200 hPa NARR Analysis Pure

1200 UTC 2 August 2006: 500 hPa NARR Analysis Pure

1200 UTC 2 August 2006: Surface NARR Analysis Pure BUF

1200 UTC 2 August 2006: Sounding Parcel taken from lowest 500 m to determine CAPE Pure

1600 UTC 2 August 2006: 925 hPa RUC Analysis Pure

1600 UTC 2 August 2006: CAPE and 1000–700 hPa Wind Shear RUC Analysis Pure

1700 UTC 2 August 2006: Surface Observations Pure

1800 UTC 2 August 2006: NARR Cross-Section Analysis −3.5 −3.0 −2.5 −2.0 −1.5 −1.0 − Pure

1700 UTC 2 August 2006: Radar Pure

1800 UTC 2 August 2006: Radar Pure

1900 UTC 2 August 2006: Radar Pure

2000 UTC 2 August 2006: Radar Pure

2100 UTC 2 August 2006: Radar Pure

2200 UTC 2 August 2006: Radar Pure

2300 UTC 2 August 2006: Radar Pure

1702 UTC 2 August 2006: Visible Satellite Pure

1825 UTC 2 August 2006: Visible Satellite Pure

1902 UTC 2 August 2006: Visible Satellite Pure

2002 UTC 2 August 2006: Visible Satellite Pure

2125 UTC 2 August 2006: Visible Satellite Pure

2202 UTC 2 August 2006: Visible Satellite Pure

2302 UTC 2 August 2006: Visible Satellite Pure

2 August 2006: SPC Storm Reports Pure

Pure Case Conclusions  Ridge axis in place at surface or aloft  T > 30°C, T d > 20°C, CAPE > 1500 J kg −1  Placement and timing signal given by 925 hPa θ e -ridge axis (θ e > 335 K)  Tendency to become squall lines and to prefer valleys  Boundary intersections enhance convection  Occur most often during hottest months of summer

1800 UTC 6 July 2003 (Pure): MODIS Visible Satellite Questions?

Mixed Case Example  19 June 2002 (Atlantic)

1200 UTC 19 June 2002: 200 hPa NARR Analysis Mixed

1200 UTC 19 June 2002: 500 hPa NARR Analysis Mixed

1200 UTC 19 June 2002: Surface NARR Analysis Mixed WAL

1200 UTC 19 June 2002: Sounding Parcel taken from lowest 500 m to determine CAPE Mixed

1800 UTC 19 June 2002: 500 hPa Vorticity NARR Analysis Mixed −10 −8 −6 −4 −

1800 UTC 19 June 2002: 925 hPa RUC Analysis Mixed

1800 UTC 19 June 2002: CAPE and 1000–700 hPa Wind Shear RUC Analysis Mixed

1800 UTC 19 June 2002: Surface Observations Mixed

1800 UTC 19 June 2002: Radar Mixed

1900 UTC 19 June 2002: Radar Mixed

2000 UTC 19 June 2002: Radar Mixed

2100 UTC 19 June 2002: Radar Mixed

1732 UTC 19 June 2002: Visible Satellite Mixed

1902 UTC 19 June 2002: Visible Satellite Mixed

2002 UTC 19 June 2002: Visible Satellite Mixed

2132 UTC 19 June 2002: Visible Satellite Mixed

19 June 2002: SPC Storm Reports Mixed

Mixed Case Conclusions  Troughs generally in place at surface or aloft  20°C < T < 30°C, 10°C < T d < 20°C  Placement and timing signal given by 925 hPa θ e -ridge axis (320 K < θ e < 350 K)  Cyclonic vorticity and cyclonic vorticity advection important  Boundary intersections enhance convection  Occur most often during late spring, early autumn, and cooler portions of summer

Null Case Example  11 July 2006 (Atlantic)

1200 UTC 11 July 2006: 200 hPa NARR Analysis Null

1200 UTC 11 July 2006: 500 hPa NARR Analysis Null

1200 UTC 11 July 2006: Surface NARR Analysis Null OKX CHH

1200 UTC 11 July 2006: Sounding Parcel taken from lowest 500 m to determine CAPE Null

1200 UTC 11 July 2006: Sounding Parcel taken from lowest 500 m to determine CAPE Null

1500 UTC 11 July 2006: CAPE and 1000–700 hPa Wind Shear RUC Analysis Null

1500 UTC 11 July 2006: Surface Observations Null

1800 UTC 11 July 2006: Surface Observations Null

1800 UTC 11 July 2006: 925 hPa RUC Analysis Null

1600 UTC 11 July 2006: Radar Null

1700 UTC 11 July 2006: Radar Null

1800 UTC 11 July 2006: Radar Null

1900 UTC 11 July 2006: Radar Null

2000 UTC 11 July 2006: Radar Null

2100 UTC 11 July 2006: Radar Null

11 July 2006: SPC Storm Reports Null

24-hour Quantitative Precipitation Estimates ending at 1200 UTC 12 July Null

Null Case Conclusions  Convection forms from previous factors unrelated to effects of lake or sea breezes  Convection is suppressed as the marine boundary layer is too stable to maintain updrafts (less CAPE, more CIN)  Significant θ e difference between the contrasting air masses  Conditions for severe convection may be quite favorable aloft in the null region due to synoptic patterns  Key to these cases is boundary layer characteristics