Verification of Probabilistic SPC Convective Outlooks from 2002–2023 Using Probabilistic Contingency Tables and Optical Flow Displacement.

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Bibliographic Details
Title:	Verification of Probabilistic SPC Convective Outlooks from 2002–2023 Using Probabilistic Contingency Tables and Optical Flow Displacement.
Authors:	Epstein, Miles¹ (AUTHOR) milesep@uw.edu, Anderson-Frey, Alex¹ (AUTHOR)
Source:	Weather & Forecasting. May2026, Vol. 41 Issue 5, p1-16. 16p.
Subjects:	Contingency tables, Motion estimation (Signal processing), United States. National Oceanic & Atmospheric Administration, Forecasting, Severe storms, Weather forecasting, Thunderstorms, Thunderstorm forecasting
Abstract:	The National Oceanic and Atmospheric Administration/National Weather Service's Storm Prediction Center issues daily Convective Outlooks outlining spatial risk levels for severe thunderstorms with up to eight days of lead time. Since 2002, categorical Outlooks area function of the hazard-specific (hail, wind, and tornado) probabilistic Outlooks, which forecast the probability that each of these hazards will occur at a severe level within 25 miles of a given point. We develop two methods for evaluating gridded probabilistic Day 1 Outlook fields against their associated Local Storm Reports (LSRs) and Practically Perfect Hindcasts (PPH; smoothed LSRs): probabilistic contingency tables and optical flow displacement. Probabilistic contingency tables reveal a trend toward underforecasting over the study period (2002–2023), strongest for wind. These results are based on storm coverage (using an imperfect storm report dataset) and do not reflect forecast intensity or user perception of forecasts. This finding highlights the nuanced considerations involved in issuing and verifying Convective Outlooks. Next, an optical flow displacement method demonstrates utility in depicting how an Outlook could be deformed to better match PPH. Analysis across this study period reveals small spatial biases in Outlooks on moderate- and high-risk days, most notably that hail Outlooks tend to be centered too far east while wind Outlooks tend to be centered too far west relative to PPH. These findings may help guide forecasters in issuing Convective Outlooks and act as a basis for future research on Convective Outlooks and thunderstorm dynamics. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
Abstract:	The National Oceanic and Atmospheric Administration/National Weather Service's Storm Prediction Center issues daily Convective Outlooks outlining spatial risk levels for severe thunderstorms with up to eight days of lead time. Since 2002, categorical Outlooks area function of the hazard-specific (hail, wind, and tornado) probabilistic Outlooks, which forecast the probability that each of these hazards will occur at a severe level within 25 miles of a given point. We develop two methods for evaluating gridded probabilistic Day 1 Outlook fields against their associated Local Storm Reports (LSRs) and Practically Perfect Hindcasts (PPH; smoothed LSRs): probabilistic contingency tables and optical flow displacement. Probabilistic contingency tables reveal a trend toward underforecasting over the study period (2002–2023), strongest for wind. These results are based on storm coverage (using an imperfect storm report dataset) and do not reflect forecast intensity or user perception of forecasts. This finding highlights the nuanced considerations involved in issuing and verifying Convective Outlooks. Next, an optical flow displacement method demonstrates utility in depicting how an Outlook could be deformed to better match PPH. Analysis across this study period reveals small spatial biases in Outlooks on moderate- and high-risk days, most notably that hail Outlooks tend to be centered too far east while wind Outlooks tend to be centered too far west relative to PPH. These findings may help guide forecasters in issuing Convective Outlooks and act as a basis for future research on Convective Outlooks and thunderstorm dynamics. [ABSTRACT FROM AUTHOR]
ISSN:	08828156
DOI:	10.1175/WAF-D-25-0085.1