Matthew Vaughan, Brian Tang, and Lance Bosart Department of Atmospheric and Environmental Sciences University at Albany/SUNY Albany, NY NROW XV Nano-scale College South Auditorium Albany, New York Thursday 13 November 2014 Supported by the NOAA Collaborative Science, Technology and Applied Research Program

 CSTAR initiative to investigate severe convection with low predictive skill  Cooperation between SUNY-Albany and NWS offices at ALB, BGM, and PIT  Improve forecasting skill of severe convection by focusing study on environments with poor predictive skill

 Identify and evaluate poor forecast performance  Use forecasting performance as a proxy for predictability  Underlying assumption: If forecasters had trouble, the event had low predictability.

 Create Northeast domain to evaluate forecast skill  Plot SPC convective outlook contours over the domains.  Verify SLIGHT contours with storm reports  Sound familiar? Hitchens and Brooks (2012) evaluated SLIGHT contours over CONUS domain  MOD and HIGH contours were treated the same as SLIGHT

 Algorithm details  40-km grid spacing  Use 0600 UTC SLIGHT risk valid UTC  Plot all valid storm reports for forecast period  Every grid point <40km from report is designated: “hit” Legend: = False Alarm (grid) = Correct Hit (grid) = Missed report

 Analysis grid over the Northeast Legend: = False Alarm (grid) = Correct Hit (grid) = Missed report = Correct Hit (report) = Incorrect Hit (grid)

 For inclusion in the dataset, an event must meet 1 of 2 criteria:  Have a SLIGHT risk contour within the NE domain  Contain at least 20 reports within the domain Given a SLIGHT in NE, 20 reports = 55th percentile

 Event days = 1508  SLIGHT days = 1331  Events >20 reports without SLIGHT = 177

Low POD High FAR  Type 1  20+ reports;  Lowest 25 th percentile POD  Type 2  Highest 75 th percentile FA area  Lowest 25 th percentile severe report area Type 1Type 2 Type 3  No events meet Type 3 requirements as defined here

Type 1Type 2  N = 189 events  25 th POD percentile = 2.15%  All but 3 events have POD = 0  Median: 37 reports per event  Average: 50 reports per event  N = 66 events  All but 4 events have FAR > 95%  Median: 2.5 reports per event  Average: 3 reports per event

 0.5° Climate Forecast System Reanalysis (CFSR)  Chose morning (1200 UTC) for following analysis.  Type 1 centered on maximum report density  Type 2 centered at centroid of SLIGHT risk region  Chose largest of SLIGHT risk contours for composite center

Geopotential height (meters; contoured every 100 m), wind speed (knots; fill), and wind vector (knots; barbed) on the 250 hPa pressure surface. The red dot indicates event-composite center and the median location of the maximum report density. 250 hPaN=60

Geopotential height (meters; contoured every 40 m) and total wind(knots; barbed) on the 500 hPa pressure surface. The red dot indicates event-composite center and the median location of the maximum report density. 500 hPaN=60

Geopotential height (meters; contoured every 25 m), relative humidity (%; fill contoured every 5%) on the 700 hPa pressure surface. The red dot indicates event- composite center and the median location of the maximum report density. 700 hPaN=60

Geopotential height (meters; solid contour every 20 m), temperature (Celsius; dashed), and wind vector (knots; barbed) on the 850 hPa pressure surface. The red dot indicates event- composite center and the median location of the maximum report density. 850 hPaN=60

MSLP (hPa; contoured every 2 hPa), precipitable water (mm; fill), and total surface wind (knots; barbed). The red dot indicates event-composite center and the median location of the maximum report density. SurfaceN=60

hPa lapse rates (°C/km; contoured every.5 °C/km), MUCAPE (J/kg; fill), and hPa shear vector (knots; barbed). The red dot indicates event-composite center and the median location of the maximum report density. CAPE & ShearN=60

Geopotential height (meters; contoured every 100 m), wind speed (knots; fill), and wind vector (knots; barbed) on the 250 hPa pressure surface. The red dot indicates event-composite center and the median location of the centroid of the NE SLIGHT risk areas. 250 hPaN=32

Geopotential height (meters; contoured every 40 m) and total wind(knots; barbed) on the 500 hPa pressure surface. The red dot indicates event-composite center and the median location of the centroid of the NE SLIGHT risk areas. 500 hPaN=32

Geopotential height (meters; contoured every 25 m), relative humidity (%; fill contoured every 5%) on the 700 hPa pressure surface. The red dot indicates event- composite center and the median location of the centroid of the NE SLIGHT risk areas. 700 hPaN=32

Geopotential height (meters; solid contour every 20 m), temperature (Celsius; dashed), and wind vector (knots; barbed) on the 850 hPa pressure surface. The red dot indicates event- composite center and the median location of the centroid of the NE SLIGHT risk areas. 850 hPaN=32

MSLP (hPa; contoured every 2 hPa), precipitable water (mm; fill), and total surface wind (knots; barbed). The red dot indicates event-composite center and the median location of the centroid of the NE SLIGHT risk areas. SurfaceN=32

hPa lapse rates (°C/km; contoured every.5 °C/km), MUCAPE (J/kg; fill), and hPa shear vector (knots; barbed). The red dot indicates event-composite center and the median location of the centroid of the NE SLIGHT risk areas. CAPE & ShearN=32

 Assess variability in composites  Analyze deviation among cases and reassess compositing method  Compare Type 1 & Type 2 flow regimes to cases with good predictive skill scores  May extend comparison to events of similar scale  Expand composites  Investigate variables identified in Hurlbut and Cohen (2014)

 NE predictive skill  Flat POD, decreasing FAR, increasing CSI  Number of reports per event increasing  NE low predictive skill event climatology  Type 1: 5 median events per year (Trending up)  Type 2: 2 median events per year (Trending down)  Peak in warm season  Most cases with low predictive skill follow climatology except rare N-ly, S-ly flow

 Type 1 (Low POD)  Westerly Anticyclonic side of jet, relatively low humidity at 700 hPa, higher mid-level lapse rates  Type 2 (High FAR)  Westerly Anticyclonic side of jet, higher 700 hPa humidity, higher precipitable water values, more confluent 850 hPa flow