Recently, it was discovered that a code used to calculate neighborhood-based equitable threat scores (nETSs) in Squitieri and Gallus (2016) had an error in it (introduced during code modification). After correcting the code, the results in Squitieri and Gallus (2016) were recomputed. Within the original manuscript, Figs. 4–7, 12, and 14–21 were all affected by the error. After the correction was applied, the conclusions of the paper remained roughly the same, with one significant new finding, and one noticeable change in results (addressed below, with an update to all other figures provided in the online supplemental material).
The significant new finding was that moisture forecast accuracy within developing LLJs significantly correlated with mature MCS QPF skill for weakly forced cases (Fig. 1, bottom row). It can be concluded that improvements in forecasting LLJ-bearing moisture during the early stages of LLJ evolution may improve QPFs when MCSs become mature. Previously, Squitieri and Gallus (2016) had found noticeable correlations of LLJ forecast accuracy with MCS QPF skill for weakly forced events to be rare, with little to no statistical significance noted (Fig. 1, top row). Because forecasting weakly forced convective phenomena remains a challenge for forecasters and model developers alike, this new correlation is important to note.
As in Fig. 17 of Squitieri and Gallus (2016), but for Spearman rank correlations between the 6-h MCS QPF ETSs for 2–40-mm thresholds at 0600–1200 UTC and MAEs for the LLJ atmospheric water vapor content at 0300 UTC. (top) The older results before the corrections applied and (bottom) the newer results after the applied correction.
Citation: Weather and Forecasting 34, 2; 10.1175/WAF-D-19-0022.1
Regarding the other noticeable change in results, 0600–1200 UTC MCS QPF skill correlated more with 0600 and 0900 UTC LLJ potential temperature forecast accuracy for strongly forced cases before the correction. Now, MCS QPF skill at 0300–0900 and 0600–1200 UTC demonstrates more significant correlations with 0600 UTC LLJ potential temperature forecast accuracy (Fig. 2).
As in Fig. 19 of Squitieri and Gallus (2016), for type C cases only, correlating (a) 0000–0600 UTC 6-h MCS QPF ETSs with 0300 UTC LLJ potential temperature MAEs, (b) 0300–0900 UTC 6-h MCS QPF ETSs with 0600 UTC LLJ potential temperature MAEs, (c) 0600–1200 UTC 6-h MCS QPF ETSs with 0600 UTC LLJ potential temperature MAEs, and (d) 0600–1200 UTC 6-h MCS QPF ETSs with 0900 UTC LLJ potential temperature MAEs.
Citation: Weather and Forecasting 34, 2; 10.1175/WAF-D-19-0022.1
REFERENCE
Squitieri, B. J., and W. A. Gallus Jr., 2016: WRF forecasts of Great Plains nocturnal low-level jet driven MCSs. Part I: Correlation between low-level jet forecast accuracy and MCS precipitation forecast skill. Wea. Forecasting, 31, 1301–1323, https://doi.org/10.1175/WAF-D-15-0151.1.
