Significant Tornado Parameter (with CIN) Stats

Description: The Significant Tornado Parameter (with CIN), or STPC, is a multiple component index that is meant to highlight the coexistence of ingredients favoring right-moving supercells capable of producing EF2-EF5 tornadoes. The STPC Stats graph provides a climatological reference frame to better anticipate significant tornadoes and identify significant environmental parameters.

red horizontal line - current value of STPC with values indicated on the y-axis (dimensionless); line is color coded according to probability based on STPC listed in upper right

large green boxes - the bottom and top of the box represent the 25th and 75th percentile of STPC values, respectively, with the median value indicated by the horizontal line inside the box

whiskers on the green boxes- vertical lines spanning the 10th-25th percentile (below the box) and the 75th-90th percentile (above the box) of STPC values

white box in upper right - conditional probability of EF2-EF5 tornado given the existence of a supercell and the value of the current sounding's parameter (CAPE, LCL, ESRH, EBS, STP, or STPC); significance of values are color coded from lower to higher values ranging from white, to yellow, red, and pink

How to use box and whiskers: Compare the sounding's value of STPC (red horizontal line) with the box and whiskers to get an idea how your value relates to the tornadoes in the analysis dataset. Note that EF2 or greater tornadoes become more likely when STPC increases from 1 to 2 and higher, and they become less likely as STPC decreases from 1 to 0.

How to use probability of EF2 or greater tornado: Compare the probabilities of EF2+ tornadoes for each parameter by itself to the dataset's climatological value of 15% to get an idea of the relative significance of the parameter in anticipating EF2+ tornadoes. The probabilities based on the research dataset have not been thoroughly evaluated in a WFO warning environment, so USE WITH CAUTION. The relative significance may be more useful than the absolute value.

Other relevant notes: STP referenced in the probabilities is the same as STP (fixed), and it uses 0-1km SRH, SBCAPE, and no CIN. STPC uses effective SRH, MLCAPE, and MLCIN. STPC is tuned for MLCAPE > 1500 J/kg, ESRH > 150 m2/s2, EBWD > 20 m/s (40 kts), MLLCL < 1km, and MLCIN > -50 J/kg. The equation for STPC is:

STPC = (MLCAPE/1500 J kg-1) x (ESRH/150 m2 s-2) x (EBWD/20 m s-1) x [(2000 - MLLCL)/1000 m] [(200 + MLCIN)/150 J kg-1]

where the Effective Bulk Wind Difference (EBWD) contribution is capped at 30 m/s.