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The dryline is among the most important meteorological phenomena in the Great Plains because of its significance in tornadogenesis, severe weather, and consistent rainfall. Past research has extensively examined the dynamics of the dryline; however, recent meteorological research looks beyond dynamics and focuses on land-atmosphere interactions. This study focuses on how soil moisture, a surrogate for evapotranspiration, affects the climatological longitudinal positioning of the dryline, presenting a climatological study for the months of April-June during 2006-15 in the southern Great Plains. Here, drylines are defined as specific humidity gradients exceeding 3 g kg-1 (100 km)-1 that do not deviate more than 308 from a north-south orientation; they were found to occur on 33.4% of spring days, and the most favorable position was2100.98 at 0000 UTC. Specific humidity gradients ranged from 3.0 to 15.2 g kg-1 (100 km)-1, with an average value of 6.8 g kg-1 (100 km)-1. A relationship between the dryline longitudinal position and soil moisture was found; as soil moisture values increased, the dryline was located farther west, which suggests soil moisture may influence the longitudinal positioning of the dryline. There was also a relationship between the gradient of soil moisture and the intensity (specific humidity gradient) of the dryline, such that when longitudinal soil moisture gradients were strong (increasing from west to east), the dryline intensity increased. [ABSTRACT FROM AUTHOR]

Among the Storm Prediction Center's (SPC) probabilistic convective outlook products are forecasts specifically targeted at significant severe weather: tornadoes that produce EF2 or greater damage, wind gusts of at least 75 mi h−1, and hail with diameters of 2 in. or greater. During the period of 2005-15, for outlooks issued beginning on day 3 and through the final update to the day 1 forecast, the accuracy and skill of these significant severe outlooks are evaluated. To achieve this, criteria for the identification of significant severe weather events were developed, with a focus on determining days for which outlooks were not issued, but should have been based on the goals of the product. Results show that significant tornadoes and hail are generally well identified by outlooks, but significant wind events are underforecast. There exist differences between verification measures when calculating them based on 1) only those days for which outlooks were issued and 2) days with outlooks or missed events; specifically, there were improvements in the frequency of daily skillful forecasts when disregarding missed events. With the greatest number of missed events associated with significant wind events, forecasts for this hazard are identified as an area of future focus for the SPC. [ABSTRACT FROM AUTHOR]

The Storm Prediction Center issues four categorical convective outlooks with lead times as long as 48 h, the so-called day 3 outlook issued at 1200 UTC, and as short as 6 h, the day 1 outlook issued at 0600 UTC. Additionally, there are four outlooks issued during the 24-h target period (which begins at 1200 UTC on day 1) that serve as updates to the last outlook issued prior to the target period. These outlooks, issued daily, are evaluated over a relatively long period of record, 1999-2011, using standard verification measures to assess accuracy; practically perfect forecasts are used to assess skill. Results show a continual increase in the skill of all outlooks during the study period, and increases in the frequency at which these outlooks are skillful on an annual basis. [ABSTRACT FROM AUTHOR]