On March 26,2017, SPC upgraded the severe weather risk to “Moderate” (4/5) across central/south-central Oklahoma and parts of far N Texas. With a 10% tor, 30% hatched wind, and 45% hatched hail, there was a significant chance that all severe hazards would occur in the risk area. Given the risk, SPC requested (and was granted) GOES Rapid Scan Mode for GOES-East from 1914Z to 0314Z. Additionally, GOES-16 mesoscale sector 1 was moved to cover the risk area from 1914Z to 0514Z, meaning 1-min imagery would be available.
The risk was in association with a strong shortwave trough moving across the southern Plains. The strengthening system is depicted in the three 2km GOES-16 water vapor channels (below) during the early afternoon of the 26th just prior to initiation. The upper system would act to deepen a surface low in western Oklahoma, drawing up moisture from the south. Storms would develop along the dryline from N Texas through central Oklahoma into North-central Oklahoma after 3 PM.
For comparison, below is the single, 4 km water vapor band from GOES-13 (East), which was operating in rapid scan mode (images available every 5-30 minutes).
A Tornado Watch was issued for much of Oklahoma prior to convective initiation at 2100 UTC. Storm initiation took place just after 2100 UTC, and was clearly observed, as it was occurring, in the GOES-16 0.64 um visible imagery. Below is a comparison between the GOES-16 visible data at 0.5 km, 1-min resolution vs GOES-13 (East) visible data at 1 km in rapid scan mode. Initiation took place during a 3-hourly GOES-East full disk scan, which led to a gap in imagery between 2045 and 2115 UTC. During the period shown (2030 – 2130 UTC), 61 images were captured from GOES-16 while 5 images were captured from GOES-13.
-Bill Line, NWS
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