Severe convection struck much of the central US on 5/7. EWP participants were monitoring the nearcast instability fields (forecasts and analyses), and noticed convection was developing along a sharp instability gradient. Participants noted that this has been a common theme with the nearcast during the week (convection developing along and moving with boundaries), as it does very well with picking up on moisture gradients and their movement. The loop below is hourly NearCast theta-e difference analyses (with 00 UTC forecast at end) with IR underlaid. Notice convection initiates along the boundary in Oklahoma and continues to develop northward along the instability gradient as depicted by NearCast. Negative values (blues to purples to reds) indicate greater instability.
The NearCast system is a Lagrangian model that dynamically projects GOES Sounder temperature and moisture retrieval data forward through space and time at multiple levels of the atmosphere. This provides forecasters with hourly, rapid updating, observation-based, 1-9 hour forecasts and analyses of the vertical moisture structure of the atmosphere. The sounder observes horizontal moisture boundaries particularly well, while the NearCast system preserves said boundaries in its analyses and forecasts. NearCast products can be loaded in AWIPS-II as past analyses leading into the most recent 9 hour forecast cycle, as is done with this loop.
- Bill Line
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